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LearningRoboticsUsingPython

TableofContents

LearningRoboticsUsingPythonCreditsAbouttheAuthorAbouttheReviewerswww.PacktPub.com

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PrefaceWhatthisbookcoversWhatyouneedforthisbookWhothisbookisforConventionsReaderfeedbackCustomersupport

DownloadingtheexamplecodeDownloadingthecolorimagesofthisbookErrataPiracyQuestions

1.IntroductiontoRoboticsWhatisarobot?

HistoryofthetermrobotModerndefinitionofarobot

Wheredorobotscomefrom?Whatcanwefindinarobot?

ThephysicalbodySensorsEffectorsControllers

Howdowebuildarobot?ReactivecontrolHierarchical(deliberative)controlHybridcontrol

Summary2.MechanicalDesignofaServiceRobot

TheRequirementsofaservicerobotRobotdrivemechanism

SelectionofmotorsandwheelsCalculationofRPMofmotorsCalculationofmotortorque

ThedesignsummaryRobotchassisdesign

InstallingLibreCAD,Blender,andMeshLabInstallingLibreCADInstallingBlenderInstallingMeshLab

Creatinga2DCADdrawingoftherobotusingLibreCADThebaseplatedesignBaseplatepoledesignWheel,motor,andmotorclampdesignCasterwheeldesignMiddleplatedesignTopplatedesign

Workingwitha3DmodeloftherobotusingBlenderPythonscriptinginBlenderIntroductiontoBlenderPythonAPIsPythonscriptoftherobotmodel

QuestionsSummary

3.WorkingwithRobotSimulationUsingROSandGazeboUnderstandingroboticsimulation

MathematicalmodelingoftherobotIntroductiontothedifferentialsteeringsystemandrobotkinematicsExplainingoftheforwardkinematicsequationInversekinematics

IntroductiontoROSandGazeboROSConcepts

TheROSfilesystemTheROSComputationGraphTheROScommunitylevel

InstallingROSIndigoonUbuntu14.04.2IntroducingcatkinCreatinganROSpackageHello_world_publisher.pyHello_world_subscriber.pyIntroducingGazeboInstallingGazeboTestingGazebowiththeROSinterfaceInstallingTurtleBotRobotpackagesonROSIndigoInstallingTurtleBotROSpackagesusingtheaptpackagemanagerinUbuntuSimulatingTurtleBotusingGazeboandROSCreatingtheGazebomodelfromTurtleBotpackagesWhatisarobotmodel,URDF,xacro,androbotstatepublisher?CreatingaChefBotdescriptionROSpackage

chefbot_base_gazebo.urdf.xacro

kinect.urdf.xacrochefbot_base.urdf.xacro

SimulatingChefBotandTurtleBotinahotelenvironmentQuestionsSummary

4.DesigningChefBotHardwareSpecificationsoftheChefBothardwareBlockdiagramoftherobot

MotorandencoderSelectingmotors,encoders,andwheelsfortherobot

MotordriverSelectingamotordriver/controller

InputpinsOutputpinsPowersupplypins

EmbeddedcontrollerboardUltrasonicsensors

SelectingtheultrasonicsensorInertialMeasurementUnitKinectCentralProcessingUnitSpeakers/micPowersupply/battery

WorkingoftheChefBothardwareQuestionsSummary

5.WorkingwithRoboticActuatorsandWheelEncodersInterfacingDCgearedmotorwithTivaCLaunchPad

DifferentialwheeledrobotInstallingtheEnergiaIDEInterfacingcode

InterfacingquadratureencoderwithTivaCLaunchpadProcessingencoderdataQuadratureencoderinterfacingcode

WorkingwithDynamixelactuatorsQuestionsSummary

6.WorkingwithRoboticSensorsWorkingwithultrasonicdistancesensors

InterfacingHC-SR04toTivaCLaunchPadWorkingofHC-SR04InterfacingcodeofTivaCLaunchPadInterfacingTivaCLaunchPadwithPython

WorkingwiththeIRproximitysensorWorkingwithInertialMeasurementUnit

InertialNavigationInterfacingMPU6050withTivaCLaunchPad

SettinguptheMPU6050libraryinEnergiaInterfacingcodeofEnergia

InterfacingMPU6050toLaunchpadwiththeDMPsupportusingEnergiaQuestionsSummary

7.ProgrammingVisionSensorsUsingPythonandROSListofroboticvisionsensorsandimageprocessinglibrariesIntroductiontoOpenCV,OpenNI,andPCL

WhatisOpenCV?InstallationofOpenCVfromsourcecodeinUbuntu14.04.2ReadinganddisplayinganimageusingthePython-OpenCVinterfaceCapturingfromwebcamera

WhatisOpenNIInstallingOpenNIinUbuntu14.04.2

WhatisPCL?ProgrammingKinectwithPythonusingROS,OpenCV,andOpenNI

HowtolaunchOpenNIdriverTheROSinterfaceofOpenCV

CreatingROSpackagewithOpenCVsupportDisplayingKinectimagesusingPython,ROS,andcv_bridge

WorkingwithPointCloudsusingKinect,ROS,OpenNI,andPCLOpeningdeviceandPointCloudgeneration

ConversionofPointCloudtolaserscandataWorkingwithSLAMusingROSandKinectQuestionsSummary

8.WorkingwithSpeechRecognitionandSynthesisUsingPythonandROSUnderstandingspeechrecognition

BlockdiagramofaspeechrecognitionsystemSpeechrecognitionlibraries

CMUSphinx/PocketSphinxJulius

WindowsSpeechSDKSpeechsynthesisSpeechsynthesislibraries

eSpeakFestival

WorkingwithspeechrecognitionandsynthesisinUbuntu14.04.2usingPythonSettingupPocketSphinxanditsPythonbindinginUbuntu14.04.2WorkingwithPocketSphinxPythonbindinginUbuntu14.04.2Output

Real-timespeechrecognitionusingPocketSphinx,GStreamer,andPythoninUbuntu14.04.2SpeechrecognitionusingJuliusandPythoninUbuntu14.04.2

InstallationofJuliusspeechrecognizerandPythonmodulePython-JuliusclientcodeImprovingspeechrecognitionaccuracyinPocketSphinxandJuliusSettingupeSpeakandFestivalinUbuntu14.04.2

WorkingwithspeechrecognitionandsynthesisinWindowsusingPythonInstallationoftheSpeechSDK

WorkingwithSpeechrecognitioninROSIndigoandPythonInstallationofthepocketsphinxpackageinROSIndigo

WorkingwithspeechsynthesisinROSIndigoandPythonQuestionsSummary

9.ApplyingArtificialIntelligencetoChefBotUsingPythonBlockdiagramofthecommunicationsysteminChefBotIntroductiontoAIML

IntroductiontoAIMLtagsIntroductiontoPyAIML

InstallingPyAIMLonUbuntu14.04.2InstallingPyAIMLfromsourcecode

WorkingwithAIMLandPythonLoadingasingleAIMLfilefromthecommand-lineargument

WorkingwithA.L.I.C.E.AIMLfilesLoadingAIMLfilesintomemoryLoadingAIMLfilesandsavingtheminbrainfilesLoadingAIMLandbrainfilesusingtheBootstrapmethod

IntegratingPyAIMLintoROSaiml_server.pyaiml_client.pyaiml_tts_client.pyaiml_speech_recog_client.pystart_chat.launchstart_tts_chat.launchstart_speech_chat.launch

QuestionsSummary

10.IntegrationofChefBotHardwareandInterfacingitintoROS,UsingPythonBuildingChefBothardwareConfiguringChefBotPCandsettingChefBotROSpackagesInterfacingChefBotsensorswithTivaCLaunchPad

EmbeddedcodeforChefBotWritingaROSPythondriverforChefBotUnderstandingChefBotROSlaunchfilesWorkingwithChefBotPythonnodesandlaunchfiles

WorkingwithSLAMonROStobuildthemapoftheroomWorkingwithROSlocalizationandnavigation

Questions

Summary11.DesigningaGUIforaRobotUsingQtandPython

InstallingQtonUbuntu14.04.2LTSWorkingwithPythonbindingsofQt

PyQtInstallingPyQtonUbuntu14.04.2LTS

PySideInstallingPySideonUbuntu14.04.2LTS

WorkingwithPyQtandPySideIntroducingQtDesignerQtsignalsandslotsConvertingaUIfileintoPythoncodeAddingaslotdefinitiontoPyQtcodeUpandrunningofHelloWorldGUIapplication

WorkingwithChefBot'scontrolGUIInstallingandworkingwithrqtinUbuntu14.04.2LTS

QuestionsSummary

12.TheCalibrationandTestingofChefBotTheCalibrationofXboxKinectusingROS

CalibratingtheKinectRGBcameraCalibratingtheKinectIRcamera

WheelodometrycalibrationErroranalysisofwheelodometryErrorcorrection

CalibratingtheMPU6050TestingoftherobotusingGUI

ProsandconsoftheROSnavigationQuestionsSummary

LearningRoboticsUsingPython

Allrightsreserved.Nopartofthisbookmaybereproduced,storedinaretrievalsystem,ortransmittedinanyformorbyanymeans,withoutthepriorwrittenpermissionofthepublisher,exceptinthecaseofbriefquotationsembeddedincriticalarticlesorreviews.

Everyefforthasbeenmadeinthepreparationofthisbooktoensuretheaccuracyoftheinformationpresented.However,theinformationcontainedinthisbookissoldwithoutwarranty,eitherexpressorimplied.NeithertheauthornorPacktPublishing,anditsdealersanddistributorswillbeheldliableforanydamagescausedorallegedtobecauseddirectlyorindirectlybythisbook.

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Firstpublished:May2015

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CoverimagebyJarekBlaminsky(<milak6@wp.pl>)

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LentinJoseph

Reviewers

AvkashChauhan

VladimirIakovlev

BlagojPetrushev

MarekSuppa

CommissioningEditor

RebeccaYoué

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RebeccaYoué

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AbouttheAuthorLentinJosephisanelectronicsengineer,roboticsenthusiast,machinevisionexpert,embeddedprogrammer,andthefounderandCEOofQboticsLabs(http://www.qboticslabs.com)inIndia.Hegothisbachelor'sdegreeinelectronicsandcommunicationengineeringattheFederalInstituteofScienceandTechnology(FISAT),Kerala.Inhisfinalyearengineeringproject,hecreatedasocialrobot,whichcaninteractwithpeople.Theprojectwasahugesuccessandgotmentionedinvisualandprintmedia.Themainfeatureofthisrobotwasthatitcouldcommunicatewithpeopleandreplyintelligently.Italsohassomeimage-processingcapabilities,suchasface,motion,andcolordetection.TheentireprojectwasimplementedusingthePythonprogramminglanguage.Hisinterestinrobotics,imageprocessing,andPythonbeganthisproject.

Aftergraduation,heworkedatastart-upcompanybasedonroboticsandimageprocessingfor3years.Inthemeantime,helearnedfamousroboticsoftwareplatforms—suchasRobotOperatingsystem(ROS),V-REP,andActin(aroboticsimulationtool)—andimageprocessinglibraries,suchasOpenCV,OpenNI,andPCL.Healsoknowsaboutrobot3Ddesigning,embeddedprogrammingonArduino,andStellarisLaunchpad.

After3yearsofworkexperience,hestartedanewcompanycalledQboticsLabs,whichismainlyfocusedonresearchtobuildgreatproductsindomainssuchaswearabletechnology,robotics,machinevision,greentechnology,andonlineeducation.Hemaintainsapersonalwebsite(http://www.lentinjoseph.com)andatechnologyblogcalledtechnolabsz(http://www.technolabsz.com).Hepublisheshisworksonhistechblog.HewasaspeakeratPyCon2013India,andhespokeonthetopicoflearningroboticsusingPython.

Iwouldliketodedicatethisbooktomyparentsbecausetheygavemetheinspirationtowriteit.Iwouldalsoliketoconveymyregardstomyfriendswhohelpedandinspiredmetowritethisbook.

IwouldliketothankMarekSuppaforhisvaluablecontributioninwritingChapter1,IntroductiontoRobotics,inadditiontoreviewingthisbook.

AbouttheReviewersAvkashChauhaniscurrentlyleadingateamofengineersatastart-upbasedinSanFrancisco,wherehisteamisbuildingabigdatamonitoringplatformusingmachinelearningandnewagemethodstoimprovebusinesscontinuityandgainmaximumadvantagefromtheplatformitself.HeisthefounderandprincipalofBigDataPerspective,withavisiontomaketheHadoopplatformaccessibletomainstreamenterprisesbysimplifyingitsadoption,customization,management,andsupport.BeforeBigDataPerspective,heworkedatPlatforaInc.,buildingbigdataanalyticssoftwarerunningnativelyonHadoop.Previously,heworkedfor8yearsatMicrosoft,buildingcloudandbigdataproductsandprovidingassistancetoenterprisepartnersworldwide.Avkashhasover15yearsofsoftwaredevelopmentexperienceincloudandbigdatadisciplines.Heisaprogrammeratheartinfull-stackdisciplineandhasthebusinessacumentoworkwithenterprises,meetingtheirneeds.Heispassionateabouttechnologyandenjoyssharinghisknowledgewithothersthroughvarioussocialmedia.Hehasalsowrittenafewbooksonbigdatadisciplineandisveryactiveinthetechsocialspace.Heisanaccomplishedauthor,blogger,technicalspeaker,andhelovestheoutdoors.

VladimirIakovlevisasoftwaredeveloper.Mostofthetime,hedevelopswebapplicationsusingPython,Clojure,andJavaScript.He'stheownerofafewsemi-popularopensourceprojects.HewasaspeakeratafewPython-relatedconferences.

Inhisfreetime,Vladimirlikestoplaywithelectronicdevices,suchasArduinoandPyBoard,andimage-processingdevices,suchasLeapMotion.Hehastriedtobuildsomerobots.Hehasalreadybuiltaroboticarm.

Currently,VladimirworksatUpwork,wherehedevelopswebapplications,mostlywithPython.

BlagojPetrushevisasoftwareengineerandconsultantbasedinSkopje,Macedonia.Hisworkrevolvesmainlyaroundbackends,datastores,andnetworkapplications.Amonghisinterestsaremachinelearning,NLP,dataanalysis,modelinganddatabases,anddistributedprogramming.

MarekSuppahasbeenplayingwith(kindof)smartmachinesforthepastfewyears,whicharepretentiouslycalledrobotsinsomepartsoftheworld.Rightnow,heleadsaroboticfootballteam,buildingtoolstohelpothersstartwithrobotsandsettingoffonanewventuretoseehowfarthecurrenttechnologywillletusmovetowardthegoalofcreatingarobotasitwasfirstdefined.

Iwouldliketothankeveryonewhosupportedthecreationofthisbook,whoeverandwherevertheymightbe.

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PrefaceLearningRoboticswithPythoncontainstwelvechaptersthatmainlyaimsathowtobuildanautonomousmobilerobotfromscratchandhowtoprogramitusingPython.Therobotmentionedinthisbookisaservicerobot,whichcanbeusedtoservefoodathome,hotels,andrestaurants.Fromthebeginningtoend,thisbookdiscussesthestep-by-stepprocedureonhowtobuildthisrobot.Thebookstartswiththebasicconceptsofroboticsandthenmovesontothe3Dmodelingandsimulationoftherobot.Afterthesuccessfulsimulationoftherobot,itdiscussesthehardwarecomponentsrequiredtobuildtherobotprototypeinordertocompletetherobotnavigation.

ThesoftwarepartofthisrobotismainlyimplementedusingthePythonprogramminglanguageandsoftwareframeworks,suchasRobotOperatingSystem(ROS),Open-CV,andsoon.YouwillunderstandtheapplicationofPythonfromtheaspectsofdesigningtherobottotherobot’suserinterface.TheGazebosimulatorisusedtosimulatetherobotandmachinevisionlibraries,suchasOpen-CVandOpenNI.PCLisusedtoprocessthe2Dand3Dimagedataoftherobot.Eachchapterispresentedwithanadequatetheorytounderstandtheapplicationaspect.Thebookisreviewedbyexpertsinthisfieldwhoarepassionateaboutrobotics.

WhatthisbookcoversChapter1,IntroductiontoRobotics,containsbasicconceptsandterminologiesofrobotics.Thischapterisamustforbeginnerswhoarejuststartingwithrobotics.

Chapter2,MechanicalDesignofaServiceRobot,discussesthe2Dand3DCADdesigningaspectoftherobotusingLibreCADandBlender(freesoftware).ThischapteralsodemonstrateshowtouseBlenderPythonAPIsinordertobuildthe3Dmodel.

Chapter3,WorkingwithRobotSimulationUsingROSandGazebo,takesyouthroughthesimulationoftheservicerobotusingGazeboandROS.

Chapter4,DesigningChefBotHardware,explainsthehardwaredesigningoftherobot,includingblockdiagramandhardwarecomponentsrequiredtobuildChefBot.

Chapter5,WorkingwithRoboticActuatorsandWheelEncoders,coversinterfacingofroboticactuatorsandwheelencodersusingTivaCLaunchPad.Italsomentionshigh-endsmartactuatorslikedynamixel.

Chapter6,WorkingwithRoboticSensors,discussesinterfacingofultrasonicdistancesensors,IRproximitysensors,andIMUusingTivaCLaunchPad.

Chapter7,ProgrammingVisionSensorsUsingPythonandROS,talksabouttheintroductiontoOpen-CV,OpenNI,andPCLlibrariesandinterfacingthesetoROSandprogrammingusingPython.

Chapter8,WorkingwithSpeechRecognitionandSynthesisUsingPythonandROS,discussesspeechrecognitionandsynthesisusingvariouslibrariesandinterfacingittoROSprogrammingusingPython.

Chapter9,ApplyingArtificialIntelligencetoChefBotUsingPython,coverstutorialstobuildaChatterBot.Thiscanbeusedtomaketherobotinteractive.

Chapter10,IntegrationofChefBotHardwareandInterfacingitintoROS,UsingPython,explorestutorialstointegratethecompletehardwareandessentialsoftwaresection.ItmainlydiscussesautonomousnavigationoftheservicerobotandhowtoprogramitusingROSandPython.

Chapter11,DesigningaGUIforaRobotUsingQtandPython,coverstutorialsonhowtobuildaGUIfortheuserwhooperatestherobotinatypicalrestaurant.TheGUIisbuiltusingQtandthePyQtPythonwrapper.

Chapter12,TheCalibrationandTestingofChefBot,explorestutorialsonhowtocalibrateandtesttherobotforthefinalrun.

WhatyouneedforthisbookThebookisallabouthowtobuildarobot.Tostartwiththisbook,youshouldhavesomehardware.Therobotcanbebuiltfromscratch,oryoucanbuyadifferential-driveconfigurationrobotwithanencoderfeedback.Youshouldbuyacontrollerboard,suchasTexasInstrumentsLaunchpad,forembeddedprocessing.Youshouldhaveatleastalaptop/netbookfortheentirerobotprocess.Inthisbook,wewilluseIntelNUCforrobotprocessing.It’sverycompactinsizeanddelivershighperformance.Forthe3Dvision,youshouldhave3Dsensors,suchaslaserscanner,Kinect,andAsusXtionPro.

Inthesoftwaresection,youshouldhaveagoodunderstandingonhowtoworkwithGNU/Linuxcommands.YoushouldalsohaveagoodknowledgeofPython.YoushouldinstallUbuntu14.04.2LTStoworkwiththeexamples.IfyouhaveknowledgeaboutROS,OpenCV,OpenNI,andPCL,itwillbeagreatadd-on.YouhavetoinstallROSIndigototesttheseexamples.

WhothisbookisforLearningRoboticswithPythonisagoodcompanionforentrepreneurswhowanttoexploretheserviceroboticsdomain,professionalswhowanttoimplementmorefeaturestotheirrobots,researcherswhowanttoexploremoreaboutrobotics,andhobbyistorstudentswhowanttolearnrobotics.Thebookfollowsastep-by-stepguidethatcanbeeasilyunderstoodbyanyone.

ConventionsInthisbook,youwillfindanumberofstylesoftextthatdistinguishbetweendifferentkindsofinformation.Herearesomeexamplesofthesestyles,andanexplanationoftheirmeaning.

Codewordsintext,databasetablenames,foldernames,filenames,fileextensions,pathnames,dummyURLs,userinput,andTwitterhandlesareshownasfollows:“Thefirstprocedureistocreateaworldfileandsaveitwiththe.worldfileextension.”

Ablockofcodeissetasfollows:

<xacro:includefilename=”$(find

chefbot_description)/urdf/chefbot_gazebo.urdf.xacro”/>

<xacro:includefilename=”$(find

chefbot_description)/urdf/chefbot_properties.urdf.xacro”/>

Anycommand-lineinputoroutputiswrittenasfollows:

$roslaunchchefbot_gazebochefbot_empty_world.launch

Newtermsandimportantwordsareshowninbold.Wordsthatyouseeonthescreen,inmenusordialogboxesforexample,appearinthetextlikethis:“wecancommandtherobottonavigatetosomepositiononthemapusingthe2DNavGoalbutton”.

Warningsorimportantnotesappearinaboxlikethis.

Tipsandtricksappearlikethis.

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Chapter1.IntroductiontoRoboticsIfyoureadanintroductorychapterinanytechnicalbook,youmayhavenoticedthatitprettymuchalwaysfollowsthesamestructure.Itbeginsbydescribinghowawesomethetopicis,whatagooddecisionitistostartreadingthebook,andhowyoushouldkeeponreadingbecausetherearemanyexcitingthingsawaitingyouinitsfurtherchapters.

Thischapterisnosuchchapter.Itstartswiththefollowingquote:

Roboticsisanart.

Although,suchastrongstatementdoesprobablydeservesomeexplanation,webelievethatafteryoufinishreadingthisbook(andbuildingyourownrobots!),nofurtherexplanationwillbeneeded.

Soifroboticsisanart,howdoesonelearnit?Toputitdifferently,whatarethedifferencesbetweenlearningtoplayamusicalinstrument,learningtopaint,learningtowrite,andlearningrobotics?Webelievethattherearenottoomanyofthem.Justasmusiciansneedtoplayontheirinstruments,paintersneedtoproducepaintings,andwritersneedtowritetheirtexts,roboticists(thetermweusetodescribepeoplewhobuildrobotics)needtobuildtheirrobots.Justasmusicians,painters,andwritersneedtolearnthejargonusedintheirtrades,roboticistsneedtofamiliarizethemselveswithafewbasictermsthattheymightrunintowhilereadingtutorials,researchingscientificliterature,andtalkingtootherroboticsenthusiasts.Also,justasanyartistneedstoknowatleastalittlebitaboutthehistoryoftheirrespectiveart,sodoesanygoodroboticistneedtoknowathingortwoaboutthehistoryofrobotics.That'swhyinthischapter,wewillcover:

Whatisarobot?Wheredorobotscomefrom?Whatcanwefindinarobot?Howdowebuildrobots?

Whatisarobot?Ratherthandefiningwhatarobotisrightaway,let'spauseforamomentanddiscusswhetherweneedtoansweraquestionlikethisafterall.Everybodyknowsthatarobotissomesortofamachinethatcanmovearoundanddependingonwhatmovieyousaworwhichbookyouread,itcaneitherhelphumansintheirday-to-daylifeormeantheendofhumanity.

It'sclearthatthereissomecontroversyandlotsofmisunderstandingsaboutrobotsandtheirroleinthepast,present,andthefuture.Inordertobetterunderstandthesituation,let'sfirstexaminecloselytheterm"robot"itself.Then,wewilltrytodefineitabitmoreformallytopreventanymisunderstandingorcontroversy.

HistoryofthetermrobotTheterm"robot"wasusedforthefirsttimebyKarelČapek,aCzechwriterinhisplayRossum'sUniversalRobots(R.U.R)thathewrotein1920,todenoteanartificialhumanmadeoutofsynthetic

organicmatter.Theserobots(robotiinCzech)weremadeinfactoriesandtheirpurposewastoreplacehumanworkers.Whiletheywereveryefficientandexecutedorderstheyweregivenperfectly,theylackedanyemotion.Itseemedthathumanswouldnotneedtoworkatallbecauserobotsseemedtobehappytoworkforthem.Thischangedafterawhileandarobotrevoltresultedinextinctionofthehumanrace.

R.U.Risquitedarkanddisturbing,butitdoesnotleavethefuturehopeless.Itwasconsideredquiteasuccessbackinthedayandwecertainlydorecommendyoutoreadit.Asitscopyrighthadalreadyexpiredinmanycountriesatthetimeofwritingthisbook,itshouldnotbeaproblemtofindaversiononline,whichisinthepublicdomain.

"Whenhe(YoungRossum)tookalookathumananatomyhesawimmediatelythatitwastoocomplexandthatagoodengineercouldsimplifyit.Soheundertooktoredesignanatomy,experimentingwithwhatwouldlenditselftoomissionorsimplification.Robotshaveaphenomenalmemory.Ifyouweretoreadthematwenty-volumeencyclopediatheycouldrepeatthecontentsinorder,buttheyneverthinkupanythingoriginal.They'dmakefineuniversityprofessors."

--KarelCapek,R.U.R.(Rossum'sUniversalRobots),1920

WhilemanyattributethetermrobottoKarelČapekashewrotetheplayinwhichitappearedforthefirsttime,therearesourcessuggestingthatitwasactuallyČapek'sbrotherJosefwhocameupwiththeterm(itseemsthattherewasanarticleinCzechdailyprintwrittenbyKarelČapekhimself,inwhichhewantstosettherecordstraightbytellingthisstory).Karelwantedtousethetermlaboři(fromLatinlabor,work),buthedidnotlikeit.Itseemedtooartificialtohim,soheaskedhisbrotherforadvice.JosefsuggestedrobotiandthatwaswhatKarelusedintheend.

Nowthatweknowwhenthetermrobotwasusedforthefirsttimeandwhoactuallycreatedit,let'sfindoutwheredoesitcomefrom.TheexplanationthatmanyuseisthatitcomesfromtheCzech

wordsrobotaandrobotník,whichliterallymeans"work"and"worker"respectively.However,thewordrobotaalsomeans"work"or"serflabor"inSlovak.Also,weshouldtakeintoaccountthatsomesourcessuggestthatbythetimeKarelwaswritingR.U.R,heandhisbrotheroftenvisitedhisfatherinasmallSlovakspatowncalledTrenčianskeTeplice.Therefore,itmightverywellbethatthetermrobotwasinspiredbytheusageoftheword"robota"inSlovaklanguage,whichiscoincidentally,thenativelanguageofoneoftheauthorsofthisbook.

WhetherthetermrobotcomesfromCzechorSlovak,thewordrobotamightbeamatterofnationalpride,butitdoesnotconcernustoomuch.Inbothcases,theliteralmeaningis"work","labor",or"hardwork"anditwasthepurposeoftheČapek'srobots.However,robotshaveevolveddramaticallyoverthepasthundredyears.Tosaythattheyareallaboutdoinghardworkwouldprobablybeanunderstatement.

So,let'strytodefinethenotionofarobotasweperceiveittoday.

ModerndefinitionofarobotWhenwetrytofindaprecisedefinitionofsometerm,ourfirststopisusuallysomesortofencyclopediaoradictionary.Let'strytodothisforthetermrobot.

OurfirststopwillbeEncyclopediaBritannica.Itsdefinitionofarobotisasfollows:

"Anyautomaticallyoperatedmachinethatreplaceshumaneffort,thoughitmightnotresemblehumanbeingsinappearanceorpreformfunctionsinahumanlikemanner."

Thisisquiteanicedefinition,buttherearequiteafewproblemswithit.

Firstofall,it'sabittoobroad.Bythisdefinition,awashingmachineshouldalsobeconsideredarobot.Itdoesoperateautomatically(well,mostofthemdo),itdoesreplacehumaneffort(althoughnotbychangingthesametasksahumanwoulddo),anditcertainlydoesnotresembleahuman.

Secondly,it'squitedifficulttoimaginewhatarobotactuallyisafterreadingthisdefinition.Withsuchabroaddefinition,therearewaytoomanythingsthatcanbeconsideredarobotandthisdefinitiondoesnotprovideuswithanyspecificfeatures.

ItturnsoutthatwhileEncyclopediaBritannica'sdefinitionofarobotdoesnotfitourneedswellenough,it'sactuallyoneofthebestonesthatonecanfind.Forexample,TheFreeDictionarydefinesarobotas"Amechanicaldevicethatsometimesresemblesahumanandiscapableofperformingavarietyofoftencomplexhumantasksoncommandorbybeingprogrammedinadvance."Thisisevenworsethanwhatwehadanditseemsthatawashingmachineshouldstillbeconsideredarobot.

Theinherentproblemwiththesedefinitionsisthattheytrytocapturevastamountofmachinesthatwecallrobotsthesedays.Theresultisthatit'sverydifficult,ifnotimpossible,tocomeupwithadefinitionthatwillbecomprehensiveenoughandnotincludeawashingmachineatthesametime.JohnEngelberger,founderoftheworld'sfirstroboticscompanyandindustrialrobotics(asweknowittoday)oncefamouslysaid,"Ican'tdefinearobot,butIknowonewhenIseeone."

So,isitevenpossibletodefinearobot?Maybenotingeneral.However,ifwelimitourselvesjusttothescopeofthisbook,theremaybeadefinitionthatwillsuitourneedswellenough.InherveryniceintroductorybookonthesubjectofroboticscalledTheRoboticsPrimer(whichwealsohighlyrecommend),MajaJ.Mataricusesthefollowingdefinition:

"Arobotisanautonomoussystemwhichexistsinthephysicalworld,cansenseitsenvironment,andcanactonittoachievesomegoals."

Atfirstsight,itmightnotseemlikeavastimprovementoverwhatwehavesofar,butlet'sdissectitpartbyparttoseewhetheritmeetsourneeds.

Thefirstpartsays,"Arobotisanautonomoussystem".Byautonomous,wemeanthatarobotmakesdecisionsonitsown—it'snotcontrolledbyahuman.Thisalreadyseemstobeanimprovementasitweedsoutanymachinethat'scontrolledbysomeone(suchasourfamouswashingmachine).Robotsthatwewilltalkaboutthroughoutthisbookmaysometimeshavesomesortofaremotefunction,whichallowsahumantocontrolitremotely,butthisfunctionalityisusuallybuilt-inassortofasafetymeasuresothatifsomethinggoeswrongandtherobot'sautonomoussystemsfailstobehaveaswewouldexpectthemto,it'sstillpossibletogettherobottosafetyanddiagnoseitsproblemsafterwards.However,themaingoalstillstaysthesame,thatis,tobuildrobotsthatcantakesomedirectionfromhumansandareabletoactandfunctionontheirown.

However,justbeinganautonomoussystemwillcertainlynotbeenoughforarobotinthisbook.Forinstance,wecanfindmanycomputerprogramsthatwecancallautonomoussystems(theyarenotcontrolledbyanindividualandmakedecisionsontheirown)andyetwedonotconsiderthemtoberobots.

Togetaroundthisobstacle,weneedtheotherpartofthesentencethatsays,"whichexistsinthephysicalworld".

Giventherecentadvancesinthefieldsofartificialintelligenceandmachinelearning,thereisnoshortageofcomputersystemsthatactontheirownandperformsomeworkforus,whichiswhatrobotsshouldbefor.Asaquitenotoriousexample,let'sconsiderspamfilters.Thesearecomputerprogramsthatreadeverye-mailthatreachesyoure-mailaddressanddecideswhetheryoumaywanttoreadit(andthatthee-mailisindeedlegitimate)orwhetherit'syetanotherexampleofanunwantede-mail.

Thereisnodoubtthatsuchasystemishelpful(ifyoudisagree,trytoreadsomeofthee-mailsinyourSpamfolder—Iamprettysureitwillbeaboringread).It'sestimatedthatover60percentofalle-mailtrafficin2014canbeattributedtospame-mails.Beingabletoautomaticallyfilterthemcansaveusalotofreadingtime.Also,asthereisanohumaninvolvedinthedecisionprocess(although,wecanhelpitbymarkingane-mailasspam),wecancallsuchasystemasautonomous.Still,wewillnotcallitatruerobot.Rather,wecallthem"softwarerobots"orjust"bots"(thefactthattheirnameisshortermaycomefromthefactthattheyareshortofthephysicalpartsoftruerobots).

Whilesoftwarerobotsaredefinitelyaninterestinggrouponitsown,it'sthephysicalworldinwhichrobotsoperatethatmakestheprocessofcreatingthemsoexcitinganddifficultatthesametime.

Whencreatingasoftwarerobot,youcancountonthefactthattheenvironmentitwillrunin(usuallytheoperatingsystem)willbequitestable(asin,nottoomanythingsmaychangeunexpectedly).However,whenyouarecreatingarealrobot,youcanneverbesure.

Thisiswhyarealrobotneedstoknowwhatishappeningintheenvironmentinwhichitoperates.Also,thisiswhythenextpartofthedefinitionsays,"cansenseitsenvironment".

Sensingwhatishappeningaroundarealrobotisarguablyitsmostimportantfeature.Tosensetheirsurroundingenvironments,robotsusuallyhavesensors.Thesearedevicesthatmeasurephysicalcharacteristicsoftheenvironmentandprovidethisinformationbacktotherobotsothatitcan,forinstance,reacttosuddenchangesoftemperature,humidity,orpressure.Thisisquiteabigdifferencefromsoftwarerobots.Whiletheyjustgettheinformationtheyneedinordertooperatesomewhatmagically,realrobotsneedtohaveasubsystemorsubsystemsthattakecareofobtainingthisinformation.Ifwelookatthedifferencesbetweenrobotsandhumans,wewillnotfindmany(inourveryhigh-levelview,ofcourse).Wecanthinkofsensoringsubsystemsasartificialreplacementsforhumanorgansthatprovidethissortofinformationtothebrain.

Oneimportantconsequenceofthisdefinitionisthatanythingthatdoesnotsenseitsenvironmentcannotbecalledarobot.Thisincludesanydevicesthatjust"driveblind"ormoveinarandomfashionbecausetheydonothaveanyinformationfromtheenvironmenttobasetheirbehavioron.

Anyroboticistwilltellyouthatrobotsareveryexcitingmachines.Manywillalsoarguethatwhatmakesthemsoexcitingisactuallytheirabilitytointeractwiththeoutsideworld(whichistomoveorotherwisechangetheenvironmenttheyarein).Withoutthis,theyarejustanotherstaticmachinethatmightbeuseful,butratherunexciting.

Ourdefinitionofarobotreflectsthisinitslastpartwhenitsays,"canactonittoachievesomegoals".

Actingontheenvironmentmightsoundlikeaverycomplextaskforarobot,butinthiscase,itjustmeanschangingtheworldinsome(evenveryslight)way.Wecallthesepartsofrobotsthatperformthisaseffectors.Ifwelookatourrobotvshumancomparison,effectorsaretheartificialequivalentsofhands,legs,andotherbodypartsthatallowittomove.Effectorsmakeuseofsomelower-levelsystemssuchasmotorsormusclesthatactuallycarryoutthemovement.Wecallthemactuators.Although,theartificialonesmayseemtofunctionsimilartothebiologicalones,acloserlookwillrevealthattheyareactuallyquitedifferent.

Youmayhavenoticedthatthispartisnotonlyaboutactingontherobot'senvironment,butalsoaboutachievingsomegoals.Whilemanyhobbyroboticistsbuildrobotsjustforthefunofit,mostrobotsarebuiltinordertocarryout(or,shouldwerathersay,tohelpwith)sometasks,suchasmovingheavypartsinafactoryorlocatingvictimsinareasaffectedbynaturaldisasters.

Aswesaidbefore,asystemoramachinethatbehavesrandomlyanddoesnotuseinformationfromitsenvironmentcannotreallybeconsideredarobot.However,howcanitusetheseinformationsomehow?Theeasiestthingtodoistodosomethinguseful,whichwecanrephraseastryingtoreachsomegoalthatweconsideruseful,whichinturnbringsusbacktoourdefinition.Agoalofarobot

doesnotnecessarilyneedtobesomethingascomplexandambitiousas"hardlaborforhuman".Itcaneasilybesomethingsimple,suchas"donotbumpintoobstacles"or"turnthelightswitchon".

Now,aswehaveatleastaslightideaofwhatarobotis,wecanmoveontobrieflydiscusswhererobotscomefrom,inotherwords,thehistoryofrobotics.

Wheredorobotscomefrom?Asthetitlesuggests,thispartofthechaptershouldbeaboutthehistoryofrobots.Wealreadyknowafewquiteimportantfacts,suchasthetermrobotwascoinedbyaCzechauthorKarelČapekin1920.Asitturnsout,therearemanymoreinterestingeventsthathappenedovertheyears,otherthanthisone.Inordertokeepthingsorganized,let'sstartfromthebeginning.

It'squitedifficulttopinpointaprecisedateinhistory,whichwecanmarkasthedateofbirthofthefirstrobot.Forone,wehaveestablishedquitearestrictivedefinitionofarobotpreviously;thus,wewillhavetowaituntilthe20thcenturytoactuallyseearobotinthepropersenseoftheword.Untilthen,let'satleastdiscussthehonorablementions.

Thefirstonethatcomesclosetoarobotisamechanicalbirdcalled"ThePigeon".ThiswaspostulatedbyaGreekmathematicianArchytasofTarentuminthe4thcenturyBCandwassupposedtobepropelledbysteam.Itcannotnotbeconsideredarobotbyourdefinition(notbeingabletosenseitsenvironmentalreadydisqualifiesit),butitcomesprettycloseforitsage.Overthefollowingcenturies,thereweremanyattemptstocreateautomaticmachines,suchasclocksmeasuringtimeusingtheflowofwater,life-sizedmechanicalfigures,orevenfirstprogrammablehumanoidrobots(itwasactuallyaboatwithfourautomaticmusiciansonit).Theproblemwithalltheseisthattheyareverydisputableasthereisverylittle(ornone)historicallytrustworthyinformationavailableaboutthesemachines.

ItwouldhavestayedlikethisforquitesometimeifitwasnotforLeonardoDaVinci'snotebooksthatwererediscoveredin1950s.Theycontainacompletedrawingofa1945humanoid(afancywordforamechanicaldevicethatresemblehumans),whichlookslikeanarmoredknight.Itseemsthatitwasdesignedsothatitcouldsitup,waveitsarms,moveitshead,andmostimportantly,amuseroyalty.Inthe18thcentury,followingtheamusementline,JacquesdeVaucansoncreatedthreeautomata:afluteplayerthatcouldplaytwelvesongs,atambourineplayer,andthemostfamousone,"TheDigestingDuck".Thisduckwascapableofmoving,quacking,flappingwings,oreveneatinganddigestingfood(notinawayyouwillprobablythink—itjustreleasedmatterstoredinahiddencompartment).Itwasanexampleof"movinganatomy"—modelinghumanoranimalanatomyusingmechanics.

Ourlistwillnotbecompleteifweomittedtheserobot-likedevicesthatcameaboutinthefollowingcentury.Manyofthemwereradio-controlled,suchasNikolaTesla'sboat,whichheshowcasedatMadisonSquareGardeninNewYork.Youcouldcommandittogoforward,stop,turnleftorright,turnitslightsonoroff,andevensubmerge.Allofthisdidnotseemtooimpressiveatthattimebecausethepressreportsattributeditto"mindcontrol".

Atthispoint,wehaveonceagainreachedthetimewhenthetermrobotwasusedforthefirsttime.Aswesaidmanytimesbefore,itwasin1920whenKarelČapekuseditinhisplay,R.U.R.Twodecadeslater,anotherveryimportanttermwascoined.IssacAsimovusedthetermroboticsforthefirsttimeinhisstory"Runaround"in1942.Asimovwrotemanyotherstoriesaboutrobotsandisconsideredtobeaprominentsci-fiauthorofhistime.

However,intheworldofrobotics,heisknownforhisthreelawsofrobotics:

Firstlaw:Arobotmaynotinjureahumanbeingorthroughinactionallowahumanbeingtocometoharm.SecondLaw:Arobotmustobeytheordersgiventoitbyhumanbeings,exceptwheresuchorderswouldconflictwiththefirstlaw.Thirdlaw:Arobotmustprotectitsownexistence,aslongassuchprotectiondoesnotconflictwiththefirstorsecondlaw.

Afterawhile,headdedazerothlaw:

Zerothlaw:Arobotmaynotharmhumanityorbyinactionallowhumanitytocometoharm.

Theselawssomehowreflectthefeelingspeoplehadaboutmachinestheycalledrobotsatthattime.Seeingenslavementbysomesortofintelligentmachineasarealpossibility,theselawsweresupposedtobesomesortofguidingprinciplesoneshouldatleastkeepinmind,ifnotdirectlyfollow,whendesigninganewintelligentmachine.Also,whilemanywereafraidoftherobotapocalypse,timehasshownthatit'sstillyettocome.Inorderforittotakeplace,machineswillneedtogetsomesortofintelligence,someabilitytothink,andactbasedontheirthoughts.Also,whilewecanseethatoverthecourseofhistory,themechanicalsideofrobotswentthroughsomedevelopment,theintelligencesimplywasnotthereyet.

Thiswaspartofthereasonwhyinthesummerof1956,agroupofverywisegentlemen(whichincludedMarvinMinsky,JohnMcCarthy,HerbertSimon,andAllanNewell)werelatercalledtobethefoundingfathersofthenewlyfoundedfieldofArtificialIntelligence.Itwasatthisveryeventwheretheygottogethertodiscusscreatingintelligenceinmachines(thus,thetermartificialintelligence).

Although,theirgoalswereveryambitious(somesourcesevenmentionthattheirideawastobuildthiswholemachineintelligenceduringthatsummer),ittookquiteawhileuntilsomeinterestingresultscouldbepresented.

OnesuchexampleisShakey,arobotbuiltbytheStanfordResearchInstitute(SRI)in1966.Itwasthefirstrobot(inourmodernsenseoftheword)capabletoreasonitsownactions.Therobotsbuiltbeforethisusuallyhadalltheactionstheycouldexecutepreprogrammed.Ontheotherhand,Shakeywasabletoanalyzeamorecomplexcommandandsplititintosmallerproblemsonhisown.ThefollowingimageofShakeyistakenfromhttps://en.wikipedia.org/wiki/File:ShakeyLivesHere.jpg:

Shakey,restingintheComputerHistoryMuseuminMountainView,California

Hishardwarewasquiteadvancedtoo.Hehadcollisiondetectors,sonarrangefinders,andatelevisioncamera.Heoperatedinasmallclosedenvironmentofrooms,whichwereusuallyfilledwithobstaclesofmanykinds.Inordertonavigatearoundtheseobstacles,itwasnecessarytofindawayaroundtheseobstacleswhilenotbumpingintosomething.Shakeydiditinaverystraightforwardway.

Atfirst,hecarefullyplannedhismovesaroundtheseobstaclesandslowly(thetechnologywasnotasadvancedbackthen)triedtomovearoundthem.Ofcourse,gettingfromastablepositiontomovementwouldn'tbepossiblewithoutsomeshakeymoves.TheproblemwasthatShakey'smovementsweremostlyofthisshakeynature,sohecouldnotbecalledanythingotherthanShakey.

ThelessonslearnedbytheresearcherswhoweretryingtoteachShakeyhowtonavigateinhisenvironmentturnedouttobeveryimportant.ItcomesasnosurprisethatoneoftheresultsoftheresearchonShakeyistheA*searchalgorithm(analgorithmthatcanveryefficientlyfindthebestpathbetweentwogoals).Thisisconsideredtobeoneofthemostfundamentalbuildingblocksnotonlyinthefieldofroboticsorartificialintelligence,butalsointhefieldofcomputerscienceasawhole.

Ourdiscussiononthehistoryofroboticscangoonandonforaverylongtime.Althoughonecandefinitelywriteabookonthistopic(asit'saveryinterestingone),it'snotthisbook;weshalltrytogetbacktothequestionwetriedtoanswer,whichwas:wheredorobotscomefrom?

Inanutshell,robotsevolvedfromtheverybasicmechanicalautomationthroughremotely-controlledobjectstodevicesorsystemsthatcanact(orevenadapt)ontheirowninordertoachievesomegoal.

Ifthissoundswaytoocomplicated,donotworry.Thetruthisthattobuildyourownrobot,youdonotreallyneedtodeeplyunderstandanyofthis.Thevastmajorityofrobotsyouwillencounterarebuiltfromsimplepartsthatarenotdifficulttounderstandwhenyouseethebigpicture.

So,let'sfigureouthowwewillbuildourownrobot.Let'sfindoutwhataretherobotsmadeof.

Whatcanwefindinarobot?Intheveryfirstpartofthischapter,wetriedtocomeupwithagood(modern)definitionofarobot.Itturnsoutthatthedefinitionwecameupwithdoesnotonlydescribearobotasweknowit(orwouldliketoknowit),butalsogivesussomegreatpointersastowhatpartscanwemostdefinitelyfindin(oron)arobot.Let'sseeourdefinitionagain:

"Arobotisanautonomoussystemwhichexistsinthephysicalworld,cansenseitsenvironment,andcanactonittoachievesomegoals."

So,whatwillthesemostimportantpartsbe?Hereiswhatwethinkshouldbeonthislist.

ThephysicalbodyItwillbehardforarobottoexistinthephysicalworldwithoutaphysicalbody.Whilethisobviouslyhasitsadvantages(havingarealworldrobotyoucanplaywithismuchmoreexcitingthanhavingacomputersimulation),thereisalsosomepricetobepaid.Forinstance,aphysicalrobotcanonlybeatoneplaceatatime,cannotreallychangeitsshape,anditsfunctionsarequitelimitedbyhowitsbodylooks.Asitsenvironmentwillbethephysicalworld,it'ssafetoassumethattherobotwillnotbetheonlyobjectinit.Thisalreadyposessomechallenges,suchasmakingsurethattherobotwon'trunintosomewall,object,human,orevenanotherrobot.Also,inordertodothis,therobotneedstobeable,asthedefinitionsays,tosenseitsenvironment.

SensorsWealreadydiscussedinquitesomedepthabouthowimportantarobot'ssensorsarebecausewithoutthem,hewouldbejustlost.Agoodquestiontoaskmightbe,"So,whatdoesarobotactuallysense?".Asinmanyotherplaces(inscienceandtechnology),itdependsonwhattherobot'spurposeandgoalinagivenenvironmentis,thedesignoftherobot,andtheamountofpoweritconsumes,andsoon.Agoodrobotdesignerandprogrammertriestotakeallthesedependenciesintoaccountsothatintheend,thefinalrobotcanhavetherightamountofinformationaboutitsenvironmenttofulfillitspurposeandreachitsgoals.

Oneimportantnotionwithregardstosensingisthatofastate.Astateofarobotbasicallymeansadescriptionofallitsparametersatanygiventime.Forinstance,ifweconsiderarobottohavesomesoundsensors(thankstowhichitcouldmeasurethenoiselevelinitsenvironment),butnowayoffiguringouthowmuchbatterypowerdoesithaveleft,wecancallitsstatepartially-observable.Ontheotherhand,ifithadasensorforeveryoutputoftherobotandeveryphysicalcharacteristicoftheenvironmenttherobotresidesin,wecancallsuchastatefullyobservable.

Nowthatweknowthestateoftherobotintheenvironment,ourrobotneedssomethingthatcanbeusedtoleavesomeeffectonitsenvironment.Somethinglikeaneffector.

Effectors

Wealreadytouched(albeitbriefly)onthetopicofeffectorswhenweweretryingtodecipherpartsofourdefinitionofarobot,sowealreadyknowthateffectorslettherobotdophysicalthingsandthesmallsubpartsofthem,actuators,areactuallythosethatdotheheavylifting.

Whatwedidnotmentionwasthat,historically,therearetwomainactivitieseffectorscanhelpwith:locomotionandmanipulation.

Ingeneral,locomotionmeansmovingaround:goingfrompointAtopointB.Thisisofgreatinterestinasubfieldofrobotics,whichiscalledmobilerobotics.Thisareaofresearchisconcernedwithallsortsofrobotsthatmoveintheair,underwater,orjustontheground.

Bymanipulation,wemeanaprocessofmovinganobjectfromoneplacetoanother.Thisprocessisofhugeinteresttomanipulatorrobotics,whichisconcernedmostlywithallsortsofroboticarmsthatinthevastmajorityofcases,areusedinindustry.

Justforthesakeofcompleteness,whatarethedifferenteffectorsourrobotscanmakeuseof?Amongthemostbasicones,itwilldefinitelybemotorsofallsortsalongwithsomewheelsthatwillallowtherobottomovearound.

Oncewehavedatafromtheenvironment,wecanalsoactonit.Thereisjustonepiecemissinghere:thelinkbetweenthem.

ControllersAfterall,wefinallycametotheconclusionofthiswholesystem.Ifitwasnotforcontrollers,arobotcouldnevereverbefullyautonomous.Thisistousedatafromsensorstodecidewhattodonextandthenexecutesomeactionsusingeffectors.Thismaylooklikeasimpledescription,butintheend,itturnsoutthatcontrollersarequitedifficulttogetright,especiallywhenyouareplayingwiththemforthefirsttime.

Formostmobilerobotsandvastmajorityofhobbyrobots,controllersareusuallymicroprocessorsthatareprogrammedinsomelow-levelprogramminglanguage.It'salsonotuncommonforarobottousemultiplecontrollers.However,whileitdefinitelyhelpstohaveabackupcontrollerreadyincaseyourmainonebrakesdownandgreattohaveamodularsysteminwhicheverythingisitsownmodule(andhasitsowncontroller),youdonotgetthisforfree.Thepriceyouhavetopayisthecommunicationbetweencontrollers,whichrequiresagooddealofexpertise.

Nowthatwehaveallthebuildingblocksforarobotready,weshouldatleastbrieflydiscussthewaysinwhichtheycanbeorganized.Thismightnotseemimportant,butitturnsoutthathavingagooddesignupfrontcansaveusalotofeffort,energy,andresources.So,let'sdiveintohowwecanputarobottogetherarchitecturally.

Howdowebuildarobot?Ifwetrytolookatthepartsofarobotfromthepreviouspartofthischapterinanabstractfashion,thereareessentiallythreeprocessestakingplace:sensing(donebysensors),acting(donebyeffectors),andthenplanning(ifthereisany,it'sdonebycontrollers).Dependingonhowweputthesethreeprocessestogether(astheyarethebuildingblockstheyarealsocalledprimitives),wecangetdifferentarchitectureswithdifferentproperties.Let'satleastsaysomethingaboutthethreeverybasicarchitectures(alsocalledparadigms).

ReactivecontrolReactivecontrolisprobablythesimplestarchitecture(orparadigm)onecanputtogetherwiththeprimitivesdescribedpreviously.Inthisparadigm,aswecanseeinthefollowingfigure,thereisnoplanningprocessinvolved.Thereisadirectconnectionbetweensensingandacting,whichmeansthatassoonassomesensorydatacomesin,theeffectorsactontheenvironmentinsomepredefinedway:

Justasthereflexesinyourbodydonotsendtheinformationaboutsomethinghappeningallthewayuptothebrain(whichwouldbequiteslow),butratherjusttothenearestspinalcordsothattheresponsecouldbefast,areactively-controlledrobotwillnothaveanycomplexcomputation,butfast,precomputedactionsthatwillbestoredsomewhere.

Hierarchical(deliberative)controlSupposeyouwereprogrammingachessplayingrobotwiththerulesofordinarychess,itwouldbeyourrobot'sturn,thenyourrobot'sopponent's,andsoon.It'sobviousthatinasettinglikethis,yourrobotdoesnotreallyneedtobeextremelyfast.However,itwillbegreatifitdidsomeplanningaboutthefuturesothatitcananticipatethefutureopponent'sturnsandthenadjustitsstrategy,basedontheopponent'scurrentturn.

Asetuplikethiswillbeperfectforhierarchical(ordeliberative)controlparadigm.Asyoucanseeinthefollowingfigure,theloopofplanning,acting,andsensingisclosed.Thus,thesystemcanactivelymovetowardsitsgoal,whateverthatmightbe:

HybridcontrolSofar,wediscussedcontrolparadigmsthatwaseitherfastbutnotveryflexible,orsmartbutquiteslow.Whatwewillreallyneedinmanycasesissomethinginbetween.Also,thisispreciselywhatahybridcontrolparadigmtriestooffer.

Howcanweusethisinareal-liferobot?Supposewewanttobuildaroboticwaiterthatwouldservedrinksinacoffeeshop(coincidentally,thatiswhatmostofthisbookisabout).Suchawaiterwoulddefinitelyneedtohaveitsowninternalrepresentationofthecoffeeshop(wherearethetablesandchairslocated,andsoon).Onceit'sgivenataskofdeliveringacupofcoffeetoagivencustomer,itwillhavetoplanitspathandthenmovealongsidethatpath.Aswecanexpectthiscoffeeshoptobequiteagoodone,theremaybeotherguestsinsidetoo.Wecannotletourrobotbumpintoanychairoratable,letalonecollidingwithacustomerrandomlywhileit'stryingtodelivercoffee.Forthis,weneedawelltunedreactivecontroller.

Thefollowingfigureshowstheschematicsofthehybridcontrolparadigm.Wecanseethattherobotatfirstplansitstask,butbreaksitdownitintoseriesofactionsthatcanbeexecutedbythereactiveparadigm.Oneinterestingthingtonotehereisthefactthatthesensorydataisavailabletoaidtheplanning(asitneedstodosomeplanning)andtheacting(asitdoesthereactivecontrol)partsofthesystem:

That'saboutit!Now,youknowwhatarobotis,whatmakesitarobot,whereitcamefrom,thepartsneededtocreatearobot,andhowyoucanarchitecturallyputittogether.It'sabouttimeyoubuildoneyourself!

SummaryInthischapter,youlearnedwhatarobotactuallyisandwherethistermcamefrom.Wedidourbesttodefinearobotasanautonomousmachinethatexistsinaphysicalworld,cansenseitsenvironment,andcanactonittoachievesomegoals.Wealsowentthroughabriefhistoryofthefieldofroboticsanddiscoveredthatmanyinterestingmachineswerebuiltpriortotheeraofrealrobots(fromourdefinition).Lateron,wediscussedthebasicbuildingblocksofarobot,thatis,effectors,sensors,andcontrollers,whichcanbecombinedinnumerousways.Finally,wedugabitdeeperintothearchitectureofcontrolsystemsthatareusefultokeepinmindwhendesigningarobot.

Inthenextchapter,wewillfinallyseesomerealrobotsalongwitharealprogramminglanguage.

Chapter2.MechanicalDesignofaServiceRobotThemainpurposeofthisbookistolearnroboticsbydesigningandbuildingrobotsandprogrammingitusingPython.Tolearnrobotics,wewillfirstlookathowtomechanicallydesignarobotfromscratch.Therobotthatwearegoingtobuildisusedasaservicerobotinhotelsandrestaurantstoservefoodanddrinks.

Inthischapter,wecanseevariousmechanicalcomponentsusedinthisrobot.Also,wecanseehowtoassembleitscomponents.WecandesignandassemblethepartsusingCADtoolandalsobuilda3Dmodelofrobotforsimulatingtherobot.

Theactualrobotdeployedinhotelsmaybebig,buthereweareintendingtobuildaminiatureversionofitonlyfortestingourtechnology.Ifyouareinterestedtobuildarobotfromscratch,thischapterisforyou.Ifyouarenotinterestedtobuildtherobot,youcanchoosesomeroboticplatformsalreadyavailableonthemarkettoworkwiththisbook.

Tobuildtherobotbody,wefirstneedtoknowtherequirementsofdesigningtherobot;aftergettingtherequirements,wecandesignitanddrawthemodelin2DCADtoolstomanufacturetherobotparts.Wecanalsodiscussthe3Dmodeltosimulatetherobotforthenextchapter.

TheRequirementsofaservicerobotBeforedesigninganyroboticsystem,thefirstprocedureistoidentifyitsrequirements.Thefollowingareasetofhardwarerequirementstobemetbythisrobot:

TherobotshouldhaveaprovisiontocarryfoodTherobotshouldbeabletocarryamaximumpayloadof5kgTherobotshouldtravelataspeedbetween0.25m/sand1m/sThegroundclearanceoftherobotshouldbegreaterthan3cmTherobotmustbeabletoworkfor2hourscontinuouslyTherobotshouldbeabletomoveandsupplyfoodtoanytableavoidingobstaclesTherobotheightshouldbebetween40cmand1meterTherobotshouldbeoflowcost

Now,wecanidentifythemechanicaldesignrequirementssuchaspayload,movingspeed,groundclearance,robotheight,andthecostoftherobot.Wewilldesignthebodyandselectcomponentsaccordingly.Let'sdiscusstherobotmechanismwecanusetomatchtheserequirements.

RobotdrivemechanismOneofthecosteffectivesolutionformobilerobotnavigationisdifferentialdrivesystems.It'soneofthesimplestdrivemechanismsforamobilerobotthatismainlyindentedforindoornavigation.Thedifferentialdriverobotconsistsoftwowheelsmountedonacommonaxiscontrolledbytwoseparatemotors.Therearetwosupportingwheelscalledcasterwheels.Itensuresstabilityandweightdistributionoftherobot.Thefollowingdiagramshowsatypicaldifferentialdrivesystem:

Differentialdrivesystem

Thenextstepistoselectthemechanicalcomponentsofthisrobotdrivesystem,thatis,mainlymotors,wheels,androbotchassis.Basedontherequirements,wewillfirstdiscusshowtoselectthemotor.

SelectionofmotorsandwheelsMotorsareselectedafterlookingattheirspecifications.SomeoftheimportantparametersformotorselectionaretorqueandRPM.Wecancomputethesevaluesfromthegivenrequirements.

CalculationofRPMofmotors

Assumetherequiredrobot'sspeedas0.35m/s.Wesawthespeedofrobotmustbewithin0.25m/sto1m/s,aspertherequirement.Takethediameterofthewheelas9cmbecauseaccordingtotherequirement,thegroundclearanceshouldbegreaterthan3cm.Usingthefollowingequation,wecancalculatetheRPMofmotors:

RPM=((60*Speed/(3.14*DiameterofWheel)

RPM=(60*0.35)/(3.14*0.09)=21/0.2826=74RPM

Youcanalsotakealookathttp://www.robotshop.com/blog/en/vehicle-speed-rpm-and-wheel-diameter-finder-9786forcomputation.

ThecalculatedRPMwith9cmdiameterwheeland0.35m/sspeedis74RPM.Wecanconsider80RPMasthestandardvalue.

Calculationofmotortorque

Let'scalculatethetorquerequiredtomovetherobot:

1. Noofwheels=Fourwheelsincludingtwocasterwheels.2. Noofmotors=Two.3. Let'sassumethecoefficientoffrictionis0.6andradiusofwheelis4.5cm.4. Taketotalweightofrobot=weightofrobot+payload=(W=mg)=(~100N+~50N)W=~

150N,whereastotalmass=15Kg5. Theweightactingonthefourwheelscanbewrittenas2*N1+2*N2=W,thatis,N1isthe

weightactingoneachcasterwheelandN2oneachmotorwheel.6. Assumethattherobotisstationary.Themaximumtorqueisrequiredwhentherobotstarts

moving.Itshouldalsoovercomefriction.7. Wecanwritethefrictionalforceasrobottorque=0untiltherobotmoves.Ifwegettherobot

torqueinthiscondition,wegetthemaximumtorqueasfollows:

µ*N*r-T=0,whereµisthecoefficientoffriction,Nistheaverageweightactingoneachwheel,ristheradiusofwheels,andTisthetorque.

N=W/4(assumingthattheweightoftherobotisequallydistributedonallthefourwheels)

Therefore,weget:

0.6*(150/4)*0.045-T=0

Hence,T=1.0125N-mor10.32Kg-cm

ThedesignsummaryAfterdesign,wecalculatedthefollowingvalues:

MotorRPM=80MotorTorque=10.32kg-cmWheeldiameter=9cm

RobotchassisdesignAftercomputingtherobot'smotorandwheelparameters,wecandesigntherobotchassisorrobot

body.Asrequired,therobotchassisshouldhaveaprovisiontoholdfood,itshouldbeabletowithstandupto5kgpayload,thegroundclearanceoftherobotshouldbegreaterthan3cmanditshouldbelowincost.Apartfromthis,therobotshouldhaveaprovisiontoplaceelectronicscomponentssuchasPersonalComputer(PC),sensors,andbattery.

Oneoftheeasiestdesignstosatisfytheserequirementsisatable-likedesign.TheTurtleBot(http://www.turtlebot.com/)designisakindoftable-likedesign.Ithasthreelayersinthechassis.ArobotplatformcalledRoombaisthedrivemechanismofthisplatform.TheRoombaplatformhasmotorsandsensorsinbuilt,sononeedtoworryaboutthedesigningofrobothardware.ThefollowingfigureshowstheTurtleBotrobotchassisdesign:

TurtleBotRobot

WewilldesignarobotsimilartoTurtleBotwithourownmovingplatformandcomponents.Ourdesignwillalsohaveathreelayerarchitecture.Let'sseewhatalltoolswewantbeforewestartdesigning.

Beforewestartdesigningtherobotchassis,weneedtoknowaboutComputer-aideddesign(CAD)tools.ThepopulartoolsavailableforCADare:

SolidWorks(http://www.solidworks.com/default.htm)AutoCAD(http://www.autodesk.com/products/autocad/overview)Maya(http://www.autodesk.com/products/maya/overview)Inventor(http://www.autodesk.com/products/inventor/overview)GoogleSketchUp(http://www.sketchup.com/)Blender(http://www.blender.org/download/)LibreCAD(http://librecad.org/cms/home.html)

Thechassisdesigncanbedesignedusinganysoftwareyouarecomfortablewith.Here,wewilldemonstratethe2DmodelinLibreCADandthe3DmodelinBlender.OneofthehighlightsoftheseapplicationsisthattheyarefreeandavailableforallOSplatforms.Wewillusea3DmeshviewingtoolcalledMeshLabtoviewandcheckthe3DmodeldesignanduseUbuntuasthemainoperatingsystem.Also,wecanseetheinstallationproceduresoftheseapplicationsinUbuntu14.04.2tostartthedesigningprocess.Wewillprovidetutoriallinkstoinstallapplicationsinotherplatformstoo.

InstallingLibreCAD,Blender,andMeshLabLibreCADisafree,opensource2DCADapplicationforWindows,OSX,andLinux.Blenderisafree,opensource3Dcomputergraphicssoftwareusedtocreate3Dmodels,animation,andvideogames.ItcomeswithaGPLlicenseasperwhichuserscanshare,modify,anddistributetheapplication.MeshLabisanopensource,portable,andextensiblesystemtoprocessandeditunstructured3Dtriangularmeshes.

ThefollowingarethelinkstoinstallLibreCADinWindows,Linux,andOSX:

Visithttp://librecad.org/cms/home.htmltodownloadLibreCADVisithttp://librecad.org/cms/home/from-source/linux.htmltobuildLibreCADfromsourceVisithttp://librecad.org/cms/home/installation/linux.htmltoinstallLibreCADinDebian/UbuntuVisithttp://librecad.org/cms/home/installation/rpm-packages.htmltoinstallLibreCADinFedoraVisithttp://librecad.org/cms/home/installation/osx.htmltoinstallLibreCADinOSXVisithttp://librecad.org/cms/home/installation/windows.htmltoinstallLibreCADinWindows

WecanfindthedocumentationonLibreCADatthefollowinglink:

http://wiki.librecad.org/index.php/Main_Page.

InstallingLibreCADTheinstallationprocedureforalloperatingsystemsisprovided.IfyouareanUbuntuuser,youcansimplyinstallitfromtheUbuntuSoftwareCentreaswell.

InstallingBlenderVisitthefollowingdownloadpagetoinstallBlenderforyourOSplatform:http://www.blender.org/download/.YoucanfindthelatestversionofBlenderhere.Also,youcanfindthelatestdocumentationonBlenderathttp://wiki.blender.org/.

IfyouareusingUbuntu/Linux,youcansimplyinstallBlenderviaUbuntuSoftwareCentre.

InstallingMeshLabMeshLabisavailableforallOSplatforms.ThefollowinglinkwillprovideyouthedownloadlinksofprebuiltbinariesandsourcecodeofMeshLab:

http://meshlab.sourceforge.net/

IfyouareanUbuntuuser,youcaninstallMeshLabfromanaptpackagemanagerusingthefollowingcommand:

$sudoapt-getinstallmeshlab

Creatinga2DCADdrawingoftherobotusingLibreCADWecantakealookatthebasicinterfaceofLibreCAD.ThefollowingscreenshotshowstheinterfaceofLibreCAD:

ACADtoolbarhasthenecessarycomponentstodrawamodel.ThefollowingscreenshotshowsthedetailedoverviewoftheCADtoolbar:

AdetaileddescriptionofLibreCADtoolsisavailableatthefollowinglink:

http://wiki.librecad.org/index.php/LibreCAD_users_Manual.

CommandBox:Thisisusedtodrawfiguresbyonlyusingcommands.Wecandrawdiagramswithouttouchinganytoolbar.Adetailedexplanationabouttheusageofthecommandboxcanbefoundat:

http://wiki.librecad.org/index.php/A_short_manual_for_use_from_the_command_line.LayerList:Thiswillhavelayersusedinthecurrentdrawing.Abasicconceptincomputer-aideddraftingistheuseoflayerstoorganizeadrawing.Adetailedexplanationoflayerscanbefoundat:

http://wiki.librecad.org/index.php/Layers.Block:Thisisagroupofentitiesandcanbeinsertedinthesamedrawingmorethanoncewithdifferentattributesatdifferentlocations,differentscale,androtationangle.AdetailedexplanationofBlockscanbefoundatthefollowinglink:

http://wiki.librecad.org/index.php/Blocks.AbsoluteZero:Thisistheoriginofthedrawing(0,0).

Now,startsketchingbysettingtheunitofdrawing.Setthedrawingunittocentimeter.OpenLibreCAD,navigatetoEdit|ApplicationPreference.SetUnitasCentimeters,asshowninthefollowingscreenshot:

Let'sstartwiththebaseplatedesign.Thebaseplatehasprovisionstoconnectmotors,placebattery,andcontrolboard.

ThebaseplatedesignThefollowingfigureshowstherobot'sbaseplate.Thisplateprovidesprovisionsfortwomotorsfordifferentialdriveandeachcasterwheelonthefrontandbackofthebaseplate.MotorsarementionedasM1andM2inthediagramandcasterwheelsarerepresentedasC1andC2.Italsoholdsfourpolestoconnecttothenextplates.PolesarerepresentedasP1-1,P1-2,P1-3,andP1-4.ThescrewsareindicatedasSandwewillusethesamescrewshere.Thereisaholeatthecentertobringthewiresfromthemotortothetopoftheplate.Theplateiscutontheleft-handsideandtheright-handsidesothatthewheelscanbeattachedtothemotor.Thedistancefromthecentertocasterwheelsismentionedas12.5cmandthedistancefromthecentertomotorsismentionedas5.5cm.Thecenterofpolesisat9cminlengthand9cminheightfromthecenter.Theholesofalltheplatesfollowthesamedimensions:

Thedimensionsarenotmarkedonthediagram;instead,it'smentionedinthefollowingtable:

Parts Dimension(cm)(LengthxHeight)(radius)

M1andM2 5x4

C1andC2 Radius=1.5

S(Screw) 0.15

P1-1,P1-2,P1-3,P1-4 Outerradius0.7,Height3.5

LeftandRightWheelSections 2.5x10

Baseplate Radius=15

Wecandiscussmoreaboutmotordimensionsandclampdimensionslater.

Baseplatepoledesign

Thebaseplatehasfourpolestoextendtothenextlayer.Thepolesare3.5cminlengthwitharadiusof0.7cm.Wecanextendtothenextplatebyattachinghollowtubestothepoles.Atthetopofthehollowtube,wewillinsertahardplastictomakeascrewhole.Thisholewillbeusefultoextendtothetoplayer.Thebaseplatepoleandthehollowtubesoneachpoleisshowninthefollowingfigure.Eachhollowtubearadiusof0.75cmandlengthof15cm:

Wheel,motor,andmotorclampdesignWehavetodecidethediameterofthewheelandcomputemotorrequirements.Here,weareusingatypicalmotorandwheelthatwecanuseifthedesignissuccessful:

Themotordesigncanvaryaccordingtothemotorselection;ifnecessary,thismotorcanbetakenasperthedesignandcanbechangedaftersimulation.TheXvalueinthemotordiagramcanvaryaccordingtothespeedandtorqueofmotors.Thisisthegearassemblyofmotor.

Thefollowingfigureshowsatypicalwheelthatwecanusewithadiameterof90cm.Thewheelwithadiameterof86.5mmwillbecome90mmafterplacingthegrip.

Themotorneedstobemountedonthebaseplate;tomount,weneedaclampwhichcanbescrewedontotheplateandalsoconnectthemotortotheclamp.Thefollowingfigureshowsatypicalclampwecanuseforthispurpose.It'sanL-shapedclamp,withwhichwecanmountthemotorononesideandfitanothersidetotheplate:

Casterwheeldesign

Casterwheelsneednothaveaspecialdesign;wecanuseanycasterwheelthatcantouchthegroundsimilartothewheels.Thefollowinglinkhasacollectionofcasterwheelsthatwecanuseforthisdesign:

http://www.pololu.com/category/45/pololu-ball-casters

MiddleplatedesignThedimensionofthisplateissameasthebaseplate,andthescrewsizeisalsosimilar:

Themiddleplatecanbeheldabovethehollowtubesfromthebaseplate.Thisarrangementisconnectedusinganotherhollowtubethatextendsfromthemiddleplate.Thetubefromthemiddleplatewillhaveascrewatthebottomtofixthetubefromthebaseplatetothemiddleplate,andahollowendtoconnectthetopplate.Thetopandsideviewofthetubeextendingfromthemiddleplateisshowninthefollowingfigure:

Thistubewillconnectthemiddleplatetothebaseplateandatthesametimeprovideaprovisiontoconnectthetopplate.

TopplatedesignThetopplateissimilartootherplates;ithasfoursmallpolesof3cm,similartothebaseplate.Thesepolescanbeplacedonthehollowtubesfromthemiddleplate.Thefourpolesareconnectedtotheplate,shownasfollows:

Afterthetopplatedesign,therobotchassisdesignisalmostfinished;let'sseethe3DmodelbuildingofthisrobotusingBlender.The3Dmodelisbuiltforsimulationpurposeandthe2Ddesignwebuildismainlyformanufacturingpurpose.

Workingwitha3DmodeloftherobotusingBlenderInthissection,wewilldesigna3Dmodeloftherobot.The3Dmodelismainlyusedforsimulationpurpose.ThemodelingwillbedoneusingBlender.Theversionmustbegreaterthan2.6becauseweonlytestedthetutorialsontheseversions.

Thefollowingscreenshotshowstheblenderworkspaceandtoolsthatcanbeusedtoworkwith3Dmodels:

ThemainreasonwhyweareusingBlenderhereissothatwecanmodeltherobotusingPythonscripts.BlenderhasaninbuiltPythoninterpreterandaPythonscripteditorforcodingpurpose.WearenotdiscussingabouttheuserinterfaceofBlenderhere.WecanfindagoodtutorialofBlenderonitswebsite.RefertothefollowinglinktolearnaboutBlender'suserinterface:

http://www.blender.org/support/tutorials/

Let'sstartcodinginBlenderusingPython.

PythonscriptinginBlender

BlenderismainlywritteninC,C++,andPython.UserscanwritetheirownPythonscriptandaccessallthefunctionalitiesofBlender.IfyouareanexpertinBlenderPythonAPIs,youcanmodeltheentirerobotusingaPythonscriptinsteadofmanualmodeling.

BlenderusesPython3.x.Blender.PythonAPIisgenerallystable,butsomeareasarestillbeingaddedtoandimproved.Refertohttp://www.blender.org/documentation/blender_python_api_2_69_7/forthedocumentationonBlenderPythonAPI.

Let'sdiscussBlenderPythonAPIsthatwewilluseinourrobotmodelscript.

IntroductiontoBlenderPythonAPIsPythonAPIsinBlendercandomostofthefunctionalitiesofBlender.ThemainjobsthatcanbedonebytheseAPIsareasfollows:

EditanydatainsideBlender,suchasscenes,meshes,particles,andsoonModifyuserpreference,keymaps,andthemesCreatenewBlendertoolsDrawthe3DviewusingOpenGLcommandsfromPython

BlenderprovidesthebpymoduletothePythoninterpreter.Thismodulecanbeimportedinascriptandgivesaccesstoblenderdata,classes,andfunctions;scriptsthatdealwithBlenderdatawillneedtoimportthismodule.ThemainPythonmoduleswewilluseinbpyare:

ContextAccess:ThisprovidesaccesstoBlenderuserinterfacefunctionsfromthe(bpy.context)script.DataAccess:ThisprovidesaccesstotheBlenderinternaldata(bpy.data).Operators:ThisprovidesPythonaccesstocallingoperators,whichincludesoperatorswritteninC,Python,orMacros(bpy.ops).

ForswitchingtoscriptinginBlender,weneedtochangethescreenlayoutofBlender.ThefollowingscreenshotshowstheoptionthathelpsyoutoswitchtoScriptinglayout:

AfterselectingtheScriptingtab,wecanseeatexteditorandPythonconsolewindowinBlender.Inthetexteditor,wecancodeusingBlenderAPIsandalsotryPythoncommandsviathePythonconsole.ClickontheNewbuttontocreateanewPythonscriptandnameitrobot.py.Now,wecandesignthe3DmodelofrobotusingonlyPythonscripts.Theupcomingsectionhasthecompletescripttodesignourrobotmodel.Wecandiscussthecodebeforerunningit.WehopeyouhavereadthePythonAPIsofBlenderfromtheirsite.ThecodeintheupcomingsectionissplitintosixPythonfunctionstodrawthreerobotplates,drawmotorsandwheels,drawfoursupporttubes,andexportintotheSTereoLithography(STL)3Dfileformatforsimulation.

PythonscriptoftherobotmodelThefollowingisthePythonscriptoftherobotmodelthatwewilldesign:.

1. BeforestartingPythonscriptinBlender,wemustimportthebpymodule.ThebpymodulecontainsallthefunctionalitiesofBlenderanditcanonlybeaccessedfrominsidetheBlenderapplication:

importbpy

2. Thisfollowingfunctionwilldrawthebaseplateoftherobot.Thisfunctionwilldrawacylinderwitharadiusof5cmandcutaportionfromtheoppositesidessothatmotorscanbeconnectedusingtheBooleanmodifierinsideBlender:

#Thisfunctionwilldrawbaseplate

defDraw_Base_Plate():

3. Thefollowingtwocommandswillcreatetwocubeswitharadiusof0.05meteroneithersideofthebaseplate.Thepurposeofthesecubesistocreateamodifierthatsubtractsthecubesfromthebaseplate.Soineffect,wewillgetabaseplatewithtwocuts.Aftercuttingthetwosides,wewilldeletethecubes:

bpy.ops.mesh.primitive_cube_add(radius=0.05,location=(0.175,0,0.09))

bpy.ops.mesh.primitive_cube_add(radius=0.05,location=(-0.175,0,0.09))

####################################################

#Addingbaseplate

bpy.ops.mesh.primitive_cylinder_add(radius=0.15,depth=0.005,location=

(0,0,0.09))

#Addingbooleandifferencemodifierfromfirstcube

bpy.ops.object.modifier_add(type='BOOLEAN')

bpy.context.object.modifiers["Boolean"].operation='DIFFERENCE'

bpy.context.object.modifiers["Boolean"].object=bpy.data.objects["Cube"]

bpy.ops.object.modifier_apply(modifier="Boolean")

######################################################

#Addingbooleandifferencemodifierfromsecondcube

bpy.ops.object.modifier_add(type='BOOLEAN')

bpy.context.object.modifiers["Boolean"].operation='DIFFERENCE'

bpy.context.object.modifiers["Boolean"].object=

bpy.data.objects["Cube.001"]

bpy.ops.object.modifier_apply(modifier="Boolean")

###############################################################################

###############################

#Deselectcylinderanddeletecubes

bpy.ops.object.select_pattern(pattern="Cube")

bpy.ops.object.select_pattern(pattern="Cube.001")

bpy.data.objects['Cylinder'].select=False

bpy.ops.object.delete(use_global=False)

4. Thefollowingfunctionwilldrawthemotorsandwheelsattachedtothebaseplate:

#Thisfunctionwilldrawmotorsandwheels

defDraw_Motors_Wheels():

5. Thefollowingcommandswilldrawacylinderwitharadiusof0.045and0.01meterindepthforthewheels.Aftercreatingthewheels,itwillberotatedandtranslatedintothecutportionofthebaseplate:

#CreatefirstWheel

(0,0,0.07))

#Rotate

bpy.context.object.rotation_euler[1]=1.5708

#Transalation

bpy.context.object.location[0]=0.135

#Createsecondwheel

(0,0,0.07))

#Rotate

#Transalation

bpy.context.object.location[0]=-0.135

6. Thefollowingcodewilladdtwodummymotorstothebaseplate.Thedimensionsofmotorsarementionedinthe2Ddesign.Themotorisbasicallyacylinderanditwillberotatedandplacedinthebaseplate:

#Addingmotors

(0.075,0,0.075))

(-0.075,0,0.075))

7. Thefollowingcodewilladdashafttothemotors,similartothemotormodel;theshaftisalsoacylinderanditwillberotatedandinsertedintothemotormodel:

#Addingmotorshaft

(0.12,0,0.075))

(-0.12,0,0.075))

###############################################################################

###############################

8. Thefollowingcodewilladdtwocasterwheelsonthebaseplate.Currently,weareaddingacylinderaswheel.Inthesimulation,wecanassignitasawheel:

#AddingCasterWheel

(0,0.125,0.065))

(0,-0.125,0.065))

9. ThefollowingcodewilladdadummyKinectsensor:

#AddingKinect

bpy.ops.mesh.primitive_cube_add(radius=0.04,location=(0,0,0.26))

10. Thisfunctionwilldrawthemiddleplateoftherobot:

#Drawmiddleplate

defDraw_Middle_Plate():

(0,0,0.22))

#Addingtopplate

defDraw_Top_Plate():

(0,0,0.37))

11. Thisfunctionwilldrawallthefoursupportinghollowtubesforallthethreeplates:

#Addingsupporttubes

defDraw_Support_Tubes():

###############################################################################

##############

#Cylinders

(0.09,0.09,0.23))

(-0.09,0.09,0.23))

(-0.09,-0.09,0.23))

(0.09,-0.09,0.23))

12. ThisfunctionwillexportthedesignedrobottoSTL.WehavetochangetheSTLfilepathbeforeexecutingthescript:

#ExportingintoSTL

defSave_to_STL():

bpy.ops.object.select_all(action='SELECT')

#bpy.ops.mesh.select_all(action='TOGGLE')

bpy.ops.export_mesh.stl(check_existing=True,

filepath="/home/lentin/Desktop/exported.stl",filter_glob="*.stl",ascii=False,

use_mesh_modifiers=True,axis_forward='Y',axis_up='Z',global_scale=1.0)

#Maincode

if__name__=="__main__":

Draw_Base_Plate()

Draw_Motors_Wheels()

Draw_Middle_Plate()

Draw_Top_Plate()

Draw_Support_Tubes()

Save_to_STL()

13. Afterenteringthecodeinthetexteditor,executethescriptbypressingtheRunScriptbutton,asshowninthefollowingscreenshot.Theoutput3Dmodelwillbeshownonthe3DviewofBlender.Also,ifwecheckthedesktop,wecanseetheexported.stlfileforthesimulation

purposes:

Theexported.stlfilecanbeopenedwithMeshLabandthefollowingisascreenshotofMeshLab:

Downloadingtheexamplecode

YoucandownloadtheexamplecodefilesforallPacktbooksyouhavepurchasedfromyouraccountathttp://www.packtpub.com.Ifyoupurchasedthisbookelsewhere,youcanvisithttp://www.packtpub.com/supportandregistertohavethefilese-maileddirectlytoyou.

Questions1. Whatisrobotmodelingandwhatareitsuses?2. Whatistheaimof2Drobotmodel?3. Whatistheaimof3Drobotmodel?4. WhatistheadvantageofPythonscriptingovermanualmodeling?

SummaryThischapterwasmainlyaimedatrobotmechanicaldesigning.Italsoincludedtherobotparametercalculationandrobotchassisdesign.Inrobotdesigning,wefirstneedtohavetheprerequisitesready.Onceit'sready,wecancalculatetherequirementsofthecomponentstobeusedintherobot.Afterthecomponentrequirementsaremet,wedesigntherobotchassisaccordingtothegivenrequirements.Therobotchassisdesigninvolves2Ddesignofallthepartsrequiredtobuildtherobot.After2Ddesigning,wesawhowtobuildthe3DrobotmodelusingBlenderandPythonscript.The3Dmodelwasbuiltusingthedimensionsthatweusedin2Ddrawing.WealsocoveredtheBlenderPythonscripttobuildtheentire3Dmodel.Inthischapter,wegotthedesignoftherobotthatcanbeusedtomanufactureit,andalsodevelopeda3Dmodelforsimulation.Inthenextchapter,wewilldiscussthesimulationofthisrobotmodelandsomepopularsimulationtools.

Chapter3.WorkingwithRobotSimulationUsingROSandGazeboInthelastchapter,welookedatthemechanicaldesigningofourrobotanddesignedits2Dand3Dmodels.Inthischapter,wewillsimulatetherobotthatwedesigned.Beforedivingintosimulation,wewilllookattheusesofrobotsimulation,advantages,disadvantages,andvariousroboticsoftwaresimulationtools.

Wewillalsodiscusskinematicsandthedynamicparametersoftherobotthatwillhelpyoutounderstandthefunctioningoftherobot.Afterdiscussingtheseconcepts,wewilldiscussthesoftwareplatformsthatareusedforthissimulation.WeareplanningtoperformthissimulationusingGazebowiththehelpofRobotOperatingSystem(ROS).AfterwediscussthebasicconceptsofROSandGazebo,wewillimplementtherobotkinematicanddynamicmodeloftherobotaccordingtotheGazebodescriptions.Finally,wewillsimulatetherobotinatypicalhotelenvironmentandtesttheautonomousnavigationabilityoftherobottoservefood.

UnderstandingroboticsimulationIngeneral,roboticsimulationisaprocessofdevelopingavirtualmodelcapableofemulatingthereal-worldprocess.Throughsimulation,wecancreateavirtualmodeloftherobotandtestitsdesignandprogrammingcode.

OneofthedefinitionsofsimulationaccordingtoSystemsSimulation:TheArtandScience,RobertE.Shannon,PrenticeHallis:

Itistheprocessofdesigningamodelofarealsystemandconductingexperimentswiththismodelforthepurposeofunderstandingthebehaviorofthesystemandforevaluatingvariousstrategiesfortheoperationofthesystem.Thusitiscriticalthatthemodebedesignedinsuchawaythatthemodelbehaviormimicstheresponsebehavioroftherealsystemtoeventsthattakeplaceovertime.

Theterm'smodelandsystemarekeycomponentsofourdefinitionofsimulation.Byamodelwemeanarepresentationofagroupofobjectsorideasinsomeformotherthanthatoftheentityitself.Byasystemwemeanagrouporcollectionofinterrelatedelementsthatcooperatetoaccomplishsomestatedobjective.

Roboticsimulatorsaresoftwareapplicationsthatcanmodeltherobotandrenderthevirtualenvironmentthatmimicstherealenvironmentoftherobot.Inourcase,theenvironmentisatypicalhotel/restaurantwithtablesandchairs.Wehavetomakethissamearrangementinsimulatorstotestitsworking.

ThefollowingfigureshowsarobotsimulatorcalledGazebo.ItalsoshowsarobotcalledTurtleBot,alongwithsomerandomobjects.YouwilllearnmoreaboutGazeboandTurtleBotintheupcomingsectionsofthischapter.

RobotsimulatorGazebo

Welookedattherequirementstobuildtherobotandthemechanicaldesignoftherobot.Thenextstepistosimulatethedesignprocess.Itallowsdeveloperstotesttheprogrammingcodeandvalidatethemechanicaldesignoftherobotaccordingtothedesignproposalrequest.Thevirtualmodeloftherobotcanbemodifiedwithoutanyadditionalcosts.

Oneofthemainadvantagesofperformingthesimulationprocessisthatwecanbuildavirtualprototypeofacomplexrobotwithlesscostthatbehavessimilartotheactualdesignoftherobot,andtestthevirtualrobotuntilitmeetsthespecifications.Thedisadvantageisthat,usingsimulators,wecannotcovertheentirescenariothatmayoccurintherealworld.

Theadvantagesofsimulationare:

LowcosttobuildarobotfromscratchTheactualrobotcodecanbetestedwiththesimulatedrobotThedesignoftherobotcanbemodifiedwithoutanycostAnypartoftherobotcanbetestedIfit'sacomplexproject,thentherobotcanbesimulatedinstagesAcompletesimulationcandeterminewhethertherobotmeetsthespecificationsAlmostallsimulationsoftwarearecompatiblewithawiderangeofprogramminglanguages

Someofthedisadvantageare:

Intherealworld,theremaybemoreparametersthanthevirtualworld;wecan'tmodelalltheseparametersinsimulationAllsimulationprogramssimulatewhattheyareprogrammedtosimulate

Let'stakealookatsomeofthelatestroboticsimulatorapplications:

Gazebo:Thisisamultirobotsimulatorwithsupportformanysensors.Thesoftwareis

compatiblewithROS.It'safreeandopensourcesimulatorusedextensivelyforroboticresearch.TheofficialwebsiteofGazeboiswww.gazebosim.org.V-REP:Thisisoneofthemostadvanced3DsimulatorsforindustrialrobotsdesignedbyCoppeliaRobotics.Thistoolofferssupportforawiderangeofprogramminglanguages,includingC/C++,Python,Java,Lua,Matlab,andUrbi.Thissimulatorhasbuilt-insupporttodevelopalgorithmsinordertosimulateautomationscenarios.Theplatformisusedineducationaswellbyengineers.TheofficialwebsiteofV-REPishttp://www.coppeliarobotics.com/.Webots:Thisisa3DsimulationplatformdevelopedbyCyberboticsandisusedinserviceandindustrialrobotsimulations.ThistoolofferssupportforWindows,Linux,andAppleplatforms.It'soneofthemostcommonsimulationsoftwareusedineducationorforresearchpurposes.Anyrobotcanbemodeled,programmed,andsimulatedinC,C++,Java,Python,Matlab,orURBI.ThissoftwareiscompatiblewithexternallibrariessuchasOpenSourceComputerVision(OpenCV).RoboLogix:Thisisa3DindustrialsimulationsoftwaredevelopedbyLogicDesign.TheRoboLogixplatformwasdesignedtoemulatereal-worldroboticsapplicationswithfive-axisindustrialrobot.Theprograminstalledontherobotcanbedevelopedandtestedinawiderangeofpracticalapplications.Theplatformofferssupportforawiderangeofindustrialrobots,includingABB,Fanuc,andKawasaki.

Beforeperformingthesimulation,let'scheckhowtherobotworksandwhatisthemathbehindthis.

MathematicalmodelingoftherobotTheimportantpartofamobilerobotisitssteeringsystem.Thiswillhelptherobottonavigateintheenvironment.Wewillusethedifferentialdrivemodeltoreducethecomplexity,cost,andsizeoftherobot.Adifferential-driverobotconsistsoftwomainwheelsmountedonacommonaxiscontrolledbyseparatemotors.Adifferentialdrivesystem/steeringsystemisanonholonomicsystem,whichmeansithasconstraintsontheposechange.Acarisanexampleofanonholonomicsystem,asitcannotchangeitspositionwithoutchangingitspose.Let'slookathowourrobotworksandhowwemodeltherobotintermsofitsmathematics.

Introductiontothedifferentialsteeringsystemandrobotkinematics

Robotkinematicsisthestudyofthemathematicsofmotionwithoutconsideringtheforcesthataffectmotion.Itmainlydealswiththegeometricrelationshipsthatgovernthesystem.Robotdynamicsisthestudyofmotioninwhichalltheforcesaremodeled.

Amobilerobotorvehiclehassixdegreesoffreedom(DOF)expressedbythepose(x,y,z,roll,pitch,andyaw).Itconsistsofposition(x,y,z)andattitude(roll,pitch,andyaw).Rollreferstosidewiserotation,pitchreferstoforwardandbackwardrotation,andyaw(calledtheheadingororientation)referstothedirectioninwhichtherobotmovesinthex-yplane.Thedifferential-driverobotmovesfromx-yintheplane,sothe2Dposeconsistsmainlyofx,y,andθ,whereθistheheadoftherobotthatpointsintheforwarddirectionoftherobot.Thismuchinformationissufficienttodescribeadifferentialrobotpose.

Theposeoftherobotinx,y,andθintheglobalcoordinatesystem

Inadifferential-driverobot,themotioncanbecontrolledbyadjustingthevelocityoftwoindependentlycontrolledmotorsontheleft-handsideandtheright-handside,thatis,V-leftandV-rightrespectively.Thefollowingfigureshowsacoupleofpopulardifferentialdriverobotsavailableonthemarket:

iRobot,Roomba,andPioneer3DX

Theforwardkinematicsequationsforarobotwithadifferential-drivesystemareusedtosolvethefollowingproblem:

Ifrobotisstandinginaposition(x,y,θ)attimet,determinethepose(x',y',θ')att+δtgiventhecontrolparametersV-leftandV-right.

Thistechniquecanbeusedintherobottofollowaparticulartrajectory.

Explainingoftheforwardkinematicsequation

Wecanstartbyformulatingasolutionforforwardkinematics.Thefollowingfigureisanillustrationofoneofthewheelsoftherobot:

AsinglewheeloftherobotrotatingalongthelocalYaxis

Themotionaroundtheyaxisisknownasroll;everythingelsecanbeconsideredasslip.Let'sassumethatnoslipoccursinthiscase.Whenthewheelcompletesonefullrotation,thecantermovesatadistanceof2πr,whereristheradiusofthewheel.Wewillassumethatthemovementistwo-dimensional.Thismeansthatthesurfaceisflatandeven.

Whentherobotisabouttoperformarollingmotion,therobotmustrotatearoundapointthatliesalongitscommonleftandrightwheelaxes.ThepointthattherobotrotatesaroundisknownasICC-InstantaneousCenterofCurvature(ICC).Thefollowingdiagramshowsthewheelconfigurationofdifferential-drivewithICC:

Wheelconfigurationforarobotwithdifferential-drive

Thecentralconceptforthederivationofthekinematicequationistheωangularvelocityoftherobot.EachwheelontherobotrotatesaroundICCalongacirclewithawheelradiusofr.

Thespeedofthewheelisv=2πr/T,whereTisthetimetakentocompleteonefullturnaroundICC.Theωangularvelocityisdefinedas2π/Tandtypicallyhastheunitradians(ordegrees)persecond.Combiningtheequationsforvandwyieldsω=2π/T.

Adetailedmodelofthedifferential-drivesystemisshowninthefollowingfigure:

Ifweapplythepreviousequationinbothwheels,theresultwillbethesame,thatis,ω:

Where,RisthedistancebetweenICCandthemidpointofthewheelaxisandlisthelengthofthewheelaxis.AftersolvingωandR,wegetthefollowingresult:

Thepreviousequationisusefulforsolvingtheforwardkinematicsproblem.Supposetherobotmoveswithanangularvelocityofωforδtseconds,itcanchangetherobot'sorientationorwhereitisheadingto:

Where,thecenterofICCrotationisgivenbybasictrigonometryas:

RotatingtherobotωδtdegreesaroundICC

Givenastartingposition(x,y),thenewposition(x',y')canbecomputedusingthe2Drotationmatrix.TherotationaroundICCwithangularvelocityωforδtsecondsyieldsthefollowingpositionatt+δttime:

Thenewpose(x',y',andθ')canbecomputedfromequations(6)and(8),givenω,δt,andR.

ωcanbecomputedfromequation(5);VrandVlareoftendifficulttomeasureaccurately.Insteadofmeasuringthevelocity,therotationofeachwheelcanbemeasuredusingasensorcalledwheelencoders.Thedatafromthewheelencodersistherobot'sodometryvalues.Thesesensorsaremountedonthewheelaxesanddeliverbinarysignalsforeachstepthewheelrotates(eachstepmaybeintheorderof0.1mm).Thesesignalsarefedtoacountersuchthatvδtisthedistancetravelledfromtimettot+δt.Wecanwrite:

n*step=vδt

Fromthis,wecancomputev:

Ifweinsertequation(9)inequations(3)and(4),wegetthefollowingresult:

Here,nlandnraretheencodercountsoftheleftandrightwheels.VlandVrarethespeedoftheleftandrightwheelsrespectively.Thus,therobotstandsinpose(x,y,θ)andmovesnlandnrcountsduringatimestepδt;thenewpose(x',y',θ')isgivenby:

where,

Thederivedkinematicequationdependsmainlyonthedesignandgeometryoftherobot.Differentdesignscanleadtodifferentequations.

Inversekinematics

Theforwardkinematicsequationprovidesanupdatedposeatagivenwheelspeed.Wecannowthinkabouttheinverseproblem.

Standinpose(x,y,θ)attimetanddeterminetheV-leftandV-rightcontrolparameterssuchthattheposeattimet+δtis(x',y',θ').

Indifferential-drive,thisproblemmaynothaveasolutionbecausethiskindofrobotcan'tbemovedtoanyposebysimplysettingthewheelvelocity.It'sbecauseoftherobotconstraintscallednonholonomicrobotsthatthisproblemcanbesolved,becausethesekindsofrobotscanmovetoanypose.

Innonholonomicrobots,therearesomewaystoincreasetheconstrainedmobilityifweallowadifferentsequence(V-left,V-right).Ifweinsertvaluesfromequations(12)to(15),wecanidentifysomespecialcasesofcontrol:

IfV-right=V-left=>nr=nl=>R=∞,ωδT=0=>:Thismeanstherobotmovesinastraightlineandθremainsthesame

IfV-right=-V-left=>nr=-nl=>R=0,ωδt=2nl*step/land =>x'=x,y'=y,θ'=θ+ωδt=>:ThismeanstherobotrotatesinthepositionaroundICC,thatis,anyθisreachable,while(x,y)remainsunchanged

Combiningtheseoperations,thefollowingalgorithmcanbeusedtoreachanytargetposefromthestartingpose:

1. Rotateuntiltherobot'sorientationcoincideswiththelinefromthestartingpositiontothetargetposition,V-right=-V-left=V-rot.

2. Drivestraightuntiltherobot'spositioncoincideswiththetargetposition,V-right=V-left=V-ahead.

3. Rotateuntiltherobot'sorientationcoincideswiththetargetorientation,V-right=-V-left=V-rot.

where,V-rotandV-aheadcanbechosenarbitrarily.

Refertohttp://www8.cs.umu.se/~thomash/reports/KinematicsEquationsForDifferentialDriveAndArticulatedSteeringUMINF-11.19.pdfformoreinformationonkinematicsequations.

Wecanswitchtothedetailsoftoolsweareusingtosimulatethisrobot.Understandingthekinematicsoftherobotwillhelpyoutobuildthesimulationoftherobot.Italsohelpsyoutowritethesoftwarefortherobot.Thetoolswewilluseforthesimulationare:

RobotOperatingSystem(ROS)Gazebo

Thesearesomeofthepopulartoolsavailableforroboticsprogrammingandsimulation.Let'slookatthefeaturesandashortintroductionofROSandGazebo.Later,wewilldiscusshowtoperformsimulationusingthesetools.

IntroductiontoROSandGazeboROSisasoftwareframeworkforwritingrobotsoftware.ThemainaimofROSistoreusetheroboticsoftwareacrosstheglobe.ROSconsistsofacollectionoftools,libraries,andconventionsthataimtosimplifythetaskofcreatingcomplexandrobustrobotbehavioracrossawidevarietyofroboticplatforms.

TheofficialdefinitionofROSis:

ROSisanopen-source,meta-operatingsystemforyourrobot.Itprovidestheservicesyouwouldexpectfromanoperatingsystem,includinghardwareabstraction,low-leveldevicecontrol,implementationofcommonly-usedfunctionality,message-passingbetweenprocesses,andpackagemanagement.Italsoprovidestoolsandlibrariesforobtaining,building,writing,andrunningcodeacrossmultiplecomputers.ROSissimilarinsomerespectsto'robotframeworks,suchasPlayer,YARP,Orocos,CARMEN,Orca,MOOS,andMicrosoftRoboticsStudio.

Refertohttp://wiki.ros.org/ROS/IntroductionformoreinformationonROS.

SomeofthemainfeaturesofROSare:

DistributedFramework:ROSisadistributedframeworkthatcanrunonmultiplemachines,sothecomputationoftherobotcanbedividedoverdifferentmachines.Itcanreducetheonboardprocessingoftherobot.Codereuse:ThemaingoalofROSistoreusecode.Codereuseenablesthegrowthofagoodresearchanddevelopmentcommunityaroundtheworld.ROSexecutablesarecallednodes.TheseexecutablescanbegroupedintoasingleentitycalledROSpackages.Agroupofpackagesiscalledastackandthesestackscanbesharedanddistributed.Languageindependence:TheROSframeworkcanbeprogrammedusingpopularlanguages(suchasPython,C++,andLisp).ThenodescanbewritteninanylanguageandcancommunicatethroughROSwithoutanyissues.Easytesting:ROShasabuilt-inunit/integrationtestframeworkcalledrostesttotestROSpackages.Scaling:ROSisappropriateforlargeruntimesystemsandforlargedevelopmentprocesses.FreeandOpenSource:ThesourcecodeofROSisopenandit'sabsolutelyfreetouse.ThecorepartofROSislicensedunderBSDlicenseanditcanbereusedincommercialandclosedsourceproducts.

SomeofthemainconceptsofROSarediscussedintheupcomingsection.

ROSConcepts

TherearemainlythreelevelsofROS:

TheROSfilesystemTheROSComputationGraphTheROScommunity

TheROSfilesystem

TheROSfilesystemmainlycovershowROSfilesareorganizedonthedisk.Themaintermswehavetounderstandare:

Packages:ROSpackagesarethemainunitofanROSsoftwareframework.AROSpackagemaycontainexecutables,ROS-dependentlibrary,configurationfiles,andsoon.ROSpackagescanbereusedandshared.PackageManifests:Themanifests(package.xml)filewillhaveallthedetailsofthepackages,includingname,description,license,anddependencies.Message(msg)types:Messagedescriptionsarestoredinthemsgfolderinapackage.ROSmessagesaredatastructuresforsendingdatathroughROS.Messagedefinitionsarestoredinafilewiththe.msgextension.Service(srv)types:Servicedescriptionsarestoredinthesrvfolderwiththe.srvextension.ThesrvfilesdefinetherequestandresponsedatastructureforserviceinROS.

TheROSComputationGraph

TheROSComputationGraphisthepeer-to-peernetworkoftheROSprocessthatprocessesdatatogether.ThebasicconceptsofROSComputationGrapharenodes,ROSMaster,parameterserver,

messages,andservices.

Nodes:Theseareprocessesthatperformcomputation.Forexample,onenodeofarobotpublishestheodometrydataoftherobot,anothernodepublishesthelaserscannerdata,andsoon.AnROSnodeiswrittenwiththehelpofanROSclientlibrary(suchasroscppandrospy).Wewilllookatthislibraryduringthesamplenodecreation.ROSMaster:ThisprovidesnameregistrationandalookupfortherestoftheComputationGraph.Withoutstartingthemaster,nodeswillnotfindeachothernorsendmessages.Parameterserver:Thisallowsdatatobestoredinacentrallocation.Messages:Nodescommunicatewitheachotherbypassingmessages.Amessageissimplyadatastructurecomprisingoftypedfields.Thiswillsupportdatatypes,suchasinteger,floatingpoint,Boolean,andsoon.Topics:NodesexchangedataintheformofmessagesviaROStransportsystemwithaspecificnamecalledtopics.Topicisthenameusedtoidentifythecontentofthemessage.Anodeinterestedinacertainkindofdatawillsubscribetotheappropriatetopic.Ingeneral,publishersandsubscribersarenotawareofeachother'sexistence.Theideaistodecoupletheproductionofinformationfromitsconsumption.Logically,onecanthinkofatopicasastronglytypedmessagebus.Eachbushasanameandanyonecanconnecttothebustosendorreceivemessagesaslongastheyaretherighttype.Services:Thepublish/subscribemodelisaveryflexiblecommunicationparadigm,butitsmany-to-many,one-waytransportisnotappropriateforrequest/replyinteractions,whichareoftenrequiredinadistributedsystem.Request/replyisdoneviaservices,whicharedefinedbyapairofmessagestructures:onefortherequestandoneforthereply.Aprovidingnodeoffersaserviceunderanameandaclientusestheservicebysendingtherequestmessageandawaitingthereply.ROSclientlibrariesgenerallypresentthisinteractiontotheprogrammerasifitwerearemoteprocedurecall.Bags:TheseareformatstosaveandplaybacktheROSmessagedata.Bagsareanimportantmechanismtostoredata(suchassensordata)thatcanbedifficulttocollect,butit'snecessarytodevelopandtestalgorithms.

TheROSMasteractsasanameserviceintheROSComputationGraph.ItstorestopicsandservicesregistrationinformationforROSnodes.NodescommunicatewiththeMastertoreporttheirregistrationinformation.AsthesenodescommunicatewiththeMaster,theycanreceiveinformationaboutotherregisterednodesandmakeconnectionsasappropriate.Themasterwillalsomakecallbackstothesenodeswhenthisregistrationinformationchanges,whichallowsnodestodynamicallycreateconnectionsasnewnodesarerun.

Nodesconnecttoothernodesdirectly;theMasteronlyprovidesthelookupinformation,muchlikeaDNSserver.Nodesthatsubscribetoatopicwillrequestconnectionsfromnodesthatpublishthattopicandwillestablishthatconnectionoveranagreeduponconnectionprotocol.ThemostcommonprotocolusedinanROSiscalledTCPROS,whichusesstandardTCP/IPsockets.

ThefollowingfigureshowshowtopicsandserviceworksbetweennodesandMaster:

TheROScommunitylevel

TheROScommunitylevelconceptsareROSresourcesthatenableseparatecommunitiestoexchangesoftwareandknowledge.Theseresourcesinclude:

Distributions:ROSDistributionsarecollectionsofversionedstacksthatyoucaninstall.DistributionsplayasimilarroletoLinuxdistributions:theymakeiteasiertoinstallsoftwareandmaintainconsistentversionsofit.Repositories:ROSreliesonafederatednetworkofcoderepositories,wheredifferentinstitutionscandevelopandreleasetheirownrobotsoftwarecomponents.TheROSWiki:ThisisthemainforumtodocumentinformationaboutROS.Anyonecansignupforanaccountandcontributetheirowndocumentation,providecorrectionsorupdates,writetutorials,andsoon.MailingLists:Theros-usersmailinglististheprimarycommunicationchannelaboutnewupdatestoROS.ThisisalsoaforumtoaskquestionsabouttheROSsoftware.

ThereareenoughconceptstobediscussedaboutROS;youcanrefertotheROSofficialwebsiteatwww.ros.orgformoreinformation.Now,wewilllookattheinstallationprocedureofROS.

InstallingROSIndigoonUbuntu14.04.2Asperourpreviousdiscussion,weknowthatROSisametaoperatingsystemtobeinstalledonahostsystem.ROSiscompletelysupportedonUbuntu/LinuxandintheexperimentalstagesonWindowsandOSX.SomeofthelatestROSdistributionsare:

Distribution ReleasedDate

ROSIndigoIgloo July22,2014

ROSHydroMedusa September4,2013

ROSGroovyGalapagos December31,2012

WewilldiscusstheinstallationprocedureofthelatestdistributionofROScalledIndigoIglooonUbuntu14.04.2LTS.ROSIndigoIgloowillbeprimarilytargetedattheUbuntu14.04LTS.IfyouareaWindowsorOSXuser,youcanpreferablyinstallUbuntuinaVirtualBoxapplicationandinstallROSonit.ThelinktodownloadVirtualBoxishttps://www.virtualbox.org/wiki/Downloads.

Theinstallationinstructionsareasfollows:

1. ConfigureyourUbunturepositoriestoallowrestricted,universe,andmultiversedownloadable.WecanconfigureitusingUbuntu'sSoftware&Updatetool.WecangetthisbytoolbysimplysearchingontheUbuntuUnitysearchmenuandtickthefollowingoptions,asshowninthefollowingscreenshot:

Ubuntu'sSoftwareandUpdatetool

2. SetupyoursystemtoacceptROSpackagesfrompackages.ros.org.ROSIndigoissupportedonlyonUbuntu13.10andUbuntu14.04.Thefollowingcommandwillstorepackages.ros.orgtoUbuntu'saptrepositorylist:

$sudosh-c'echo"debhttp://packages.ros.org/ros/ubuntutrustymain">

/etc/apt/sources.list.d/ros-latest.list'

3. Next,wehavetoaddapt-keys.Theapt-keyisusedtomanagethelistofkeysusedbyapttoauthenticatethepackages.Packagesthathavebeenauthenticatedusingthesekeyswillbeconsideredtrusted.Thefollowingcommandwilladdapt-keysforROSpackages:

$wgethttps://raw.githubusercontent.com/ros/rosdistro/master/ros.key-O-|

sudoapt-keyadd-

4. Afteraddingapt-keys,wehavetoupdatetheUbuntupackageindex.ThefollowingcommandwilladdandupdatetheROSpackagesalongwiththeUbuntupackages:

$sudoapt-getupdate

5. AfterupdatingtheROSpackages,wecaninstallthepackages.ThefollowingcommandwillinstallthenecessarytoolsandlibrariesofROS:

$sudoapt-getinstallros-indigo-desktop-full

6. Wemayneedtoinstalladditionalpackagesevenafterthedesktop-fullinstallation;eachadditionalinstallationwillbementionedintheappropriatesection.Thedesktop-fullinstallwilltakesometime.AftertheinstallationofROS,youarealmostdone.Thenextstepistoinitializerosdep,whichenablesyoutoeasilyinstallthesystemdependenciesforROSsourcepackagesyouwanttocompileandisrequiredtorunsomecorecomponentsinROS:

$sudorosdepinit

$rosdepupdate

7. ToaccesstheROStoolsandcommandsonthecurrentbashshell,wecanaddROSenvironmentalvariablestothe.bashrcfile.Thiswillexecuteinthebeginningofeachbashsession.ThefollowingisacommandtoaddtheROSvariableto.bashrc:

echo"source/opt/ros/indigo/setup.bash">>~/.bashrc

Thefollowingcommandwillexecutethe.bashrcscriptonthecurrentshelltogeneratethechangeinthecurrentshell:

source~/.bashrc

8. Oneoftheusefultoolstoinstallisrosinstall.Thistoolhastobeinstalledseparately.ItenablesyoutoeasilydownloadmanysourcetreesfortheROSpackagewithonecommand:

$sudoapt-getinstallpython-rosinstall

AftertheinstallationofROS,wewilldiscusshowtocreateasamplepackageinROS.Beforecreatingapackage,wehavetobuildanROSworkspace.ThepackagesarecreatedintheROSworkspace.Wewillusethecatkinbuildsystem,asetoftoolstobuildpackagesinROS.Thecatkinbuildsystemgeneratesexecutableorsharedlibrariesfromthesourcecode.ROSIndigousesthecatkinbuildsystemtobuildpackages.Let'sseewhatcatkinis.

Introducingcatkin

CatkinistheofficialbuildsystemofROS.Beforecatkin,ROSusedtherosbuildsystemtobuildpackages.ItsreplacementiscatkinonthelatestROSversion.CatkincombinesCMakemacrosand

PythonscriptstoprovidethesameCMakenormalworkflow.Catkinprovidesabetterdistributionofpackages,bettercross-compilation,andbetterportabilitythantherosbuildsystem.Formoreinformation,refertowiki.ros.org/catkin.

Catkinworkspaceisafolderwhereyoucanmodify,build,andinstallcatkinpackages.

Let'scheckhowtocreateanROScatkinworkspace.

Thefollowingcommandwillcreateaparentdirectorycalledcatkin_wsandasubfoldercalledsrc:

$mkdir-p~/catkin_ws/src

Switchdirectorytothesrcfolderusingthefollowingcommand.Wewillcreateourpackagesinthesrcfolder:

$cd~/catkin_ws/src

Initializethecatkinworkspaceusingthefollowingcommand:

$catkin_init_workspace

Afteryouinitializethecatkinworkspace,youcansimplybuildthepackage(evenifthereisnosourcefile)usingthefollowingcommand:

$cd~/catkin_ws/

$catkin_make

Thecatkin_makecommandisusedtobuildpackagesinsidethesrcdirectory.Afterbuildingthepackages,wewillseeabuildanddevelfolderincatkin_ws.Theexecutablesarestoredinthebuildfolderandinthedevelfolder,thereareshellscriptfilestoaddtotheworkspaceontheROSenvironment.

CreatinganROSpackage

Inthissection,wewillseehowtocreateasamplepackagethatcontainstwoPythonnodes.OneofthenodesisusedtopublishaHelloWorldmessageonatopic,andtheothernodewillsubscribetothistopic.

AcatkinROSpackagecanbecreatedusingthecatkin_create_pkgcommandinROS.

Thepackageiscreatedinsidethesrcfolderthatwecreatedduringthecreationofworkspace.Beforecreatingpackages,switchtothesrcfolderusingthefollowingcommand:

$cd~/catkin_ws/src

Thefollowingcommandwillcreateahello_worldpackagewithstd_msgsdependencies,whichcontainstandardmessagedefinitions.TherospyisthePythonclientlibraryforROS:

$catkin_create_pkghello_worldstd_msgsrospy

Thisisthemessagewegetafterthesuccessfulcreation:

Createdfilehello_world/package.xml

Createdfilehello_world/CMakeLists.txt

Createdfolderhello_world/src

Successfullycreatedfilesin/home/lentin/catkin_ws/src/hello_world.Pleaseadjust

thevaluesinpackage.xml.

Afterthesuccessfulcreationofthehello_worldpackage,weneedtoaddtwoPythonnodesorscriptstodemonstratethesubscribingandpublishingoftopics.

First,createafoldernamedscriptsinthehello_worldpackageusingthefollowingcommand:

$mkdirscripts

Switchtothescriptsfolderandcreateascriptnamedhello_world_publisher.pyandanotherscriptcalledhello_world_subscriber.pytopublishandsubscribetothehelloworldmessage.Thefollowingsectioncoversthecodeandexplanationofthesescriptsornodes:

Hello_world_publisher.py

Thehello_world_publisher.pynodebasicallypublishesagreetingmessagecalledhelloworldtoatopic/hello_pub.Thegreetingmessageispublishedtothetopicattherateof10Hz.

Thestepbystepexplanationofthiscodeisasfollows:

1. WeneedtoimportrospyifwearewritinganROSPythonnode.ItcontainsPythonAPI'stointeractwithROStopics,services,andsoon.

2. Tosendthehelloworldmessage,wehavetoimportaStringdatatypefromthestd_msgspackage.Ithasamessagedefinitionforstandarddatatypes.Wecanimportusingthefollowingcommand:

#!/usr/bin/envpython

importrospy

fromstd_msgs.msgimportString

3. Thefollowinglineofcodecreatesapublisherobjecttoatopiccalledhello_pub.ThedatatypeisStringandqueue_sizeis10.Ifthesubscriberisnotfastenoughtoreceivethedata,wecanusethequeue_sizeoptiontoadjustit:

deftalker():

pub=rospy.Publisher('hello_pub',String,queue_size=10)

4. ThefollowinglineofcodeismandatoryforallROSPythonnodes.Itinitializesandassignsanametothenode.Thenodecannotbelauncheduntilitgetsaname.Itcancommunicatewithothernodesusingitsname.Iftwonodesarerunningwiththesamenodename,onewillshutdown.Ifwewanttorunbothnodes,usetheanonymous=Trueflagasshownhere:

rospy.init_node('hello_world_publisher',anonymous=True)

5. Thefollowinglinecreatesarateobjectcalledr.Usingasleep()methodintheRateobject,wecanupdatetheloopinadesiredrate.Here,wearegivenatrate10:

r=rospy.Rate(10)#10hz

6. Thefollowingloopwillcheckwhetherrospyconstructstherospy.is_shutdown()flag.Then,itexecutestheloop.IfweclickonCtr+C,thisloopwillexit.

Insidetheloop,ahelloworldmessageisprintedontheterminalandpublishedonthehello_pubtopicwitharateof10Hz:

whilenotrospy.is_shutdown():

str="helloworld%s"%rospy.get_time()

rospy.loginfo(str)

pub.publish(str)

r.sleep()

7. InadditiontothestandardPython__main__check,thefollowingcodecatchesarospy.ROSInterruptExceptionexception,whichcanbethrownbytherospy.sleep()method,andtherospy.Rate.sleep()method,whenCtrl+Cisclickedonoryournodeisotherwiseshutdown.Thereasonthisexceptionisraisedissothatyoudon'taccidentallycontinueexecutingcodeafterthesleep()method:

if__name__=='__main__':

talker()

exceptrospy.ROSInterruptException:pass

Afterpublishingthetopic,wewillseehowtosubscribeit.Thefollowingsectioncoversthecodetosubscribethehello_pubtopic.

Hello_world_subscriber.py

Thesubscribercodeisasfollows:

importrospy

Thefollowingcodeisacallbackfunctionthatisexecutedwhenamessagereachesthehello_pubtopic.Thedatavariablecontainsthemessagefromthetopicanditwillprintusingrospy.loginfo():

defcallback(data):

rospy.loginfo(rospy.get_caller_id()+"Iheard%s",data.data)

Thefollowingsectionwillstartthenodewithahello_world_subscribernameandstartsubscribingtothe/hello_pubtopic.

1. ThedatatypeofthemessageisStringandwhenamessagearrivesonthistopic,amethodcalledcallbackwillbecalled:

deflistener():

rospy.init_node('hello_world_subscriber',anonymous=True)

rospy.Subscriber("hello_pub",String,callback)

2. Thiswillkeepyournodefromexitinguntilthenodeisshutdown:

rospy.spin()

3. ThefollowingisthemaincheckofthePythoncode.Themainsectionwillcallthelistener()method,whichwillsubscribetothe/hello_pubtopic:

listener()

4. AftersavingtwoPythonnodes,youneedtochangethepermissiontoexecutableusingthechmodcommands:

chmod+xhello_world_publisher.py

chmod+xhello_world_subscriber.py

5. Afterchangingthefilepermission,buildthepackageusingthecatkin_makecommand:

cd~/catkin_ws

catkin_make

6. FollowingcommandaddsthecurrentROSworkspacepathinallterminalsothatwecanaccesstheROSpackagesinsidethisworkspace:

echo"source~/catkin_ws/devel/setup.bash">>~/.bashrc

source~/.bashrc

Thefollowingistheoutputofthesubscriberandpublishernodes:

1. First,weneedtorunroscorebeforestartingthenodes.TheroscorecommandorROSmasterisneededtocommunicatebetweennodes.So,thefirstcommandis:

$roscore

2. Afterexecutingroscore,runeachnodeusingthefollowingcommands.3. Thefollowingcommandwillrunthepublisher:

$rosrunhello_worldhello_world_publisher.py

4. Thefollowingcommandwillrunthesubscribernode.Thisnodesubscribestothehello_pubtopic,asshowninthefollowingscreenshot:

$rosrunhello_worldhello_world_subscriber.py

WecoveredsomebasicsofROS.Now,wewillseewhatisGazeboisandhowwecanworkwithGazebousingROS.

IntroducingGazebo

Gazeboisafreeandopensourcerobotsimulatorinwhichwecantestalgorithms,designrobots,andperformregressiontestingusingrealisticscenarios.Gazebocanaccuratelyandefficientlysimulateapopulationofrobotsincomplexindoorandoutdoorenvironments.Gazeboisbuiltinarobustphysicsenginewithhighqualitygraphicsandaconvenientprogrammaticandgraphicalinterface.

ThefeaturesofGazeboareasfollows:

Dynamicsimulation:GazebocansimulatedynamicsofarobotusingaphysicsenginesuchasOpenDynamicsEngine(ODE).(http://opende.sourceforge.net/),Bullet(http://bulletphysics.org/wordpress/),Simbody(https://simtk.org/home/simbody/),andDART(http://dartsim.github.io/).Advanced3DGraphics:Gazeboprovideshighqualityrendering,lighting,shadows,andtexturingusingtheOGREframework(http://www.ogre3d.org/).Sensorssupport:Gazebosupportsawiderangeofsensors,includinglaserrangefinders,kinectstylesensors,2D/3Dcamera,andsoon.Wecansimulateeitherwithnoiseorwithoutnoise.Plug-in:Wecandevelopcustompluginsfortherobot,sensor,andenvironmentalcontrol.PluginscanaccessGazebo'sAPI.RobotModels:Gazeboprovidesmodelsforpopularrobots,suchasPR2,Pioneer2DX,iRobotCreate,andTurtleBot.Wecanalsobuildcustommodelsofrobots.TCP//IPTransport:WecanrunsimulationonaremotemachineandaGazebointerface

throughasocket-basedmessagepassingservice.CloudSimulation:WecanrunsimulationontheCloudserverusingtheCloudSimframework(http://cloudsim.io/).CommandLineTools:Extensivecommand-linetoolsareusedtocheckandlogsimulation.

InstallingGazebo

GazebocanbeinstalledasastandaloneapplicationoranintegratedapplicationalongwithROS.Inthischapter,wewilluseGazeboalongwithROSforsimulationandtotestourwrittencodeusingtheROSframework.

IfyouwanttotrythelatestGazebosimulatorindependently,youcanfollowtheproceduregivenathttp://gazebosim.org/download.

ToworkwithGazeboandROS,wedon'tneedtoinstallitseparatelybecauseGazeboisbuilt-inalongwiththeROSdesktop-fullinstallation.

TheROSpackageintegratesGazebowithROSnamedgazebo_ros_pkgs,whichhascreatedwrappersaroundastandaloneGazebo.ThispackageprovidesthenecessaryinterfacetosimulatearobotinGazebousingROSmessageservices.

ThecompleteGazebo_ros_pkgscanbeinstalledinROSIndigousingthefollowingcommand:

$sudoapt-getinstallros-indigo-gazebo-ros-pkgsros-indigo-gazebo-ros-control

TestingGazebowiththeROSinterface

AssumingthattheROSenvironmentisproperlysetup,wecanstartroscorebeforestartingGazebousingthefollowingcommand:

$roscore

ThefollowingcommandwillrunGazebousingROS:

$rosrungazebo_rosgazebo

Gazeboisrunningastwoexecutables,thatis,theGazeboserverandtheGazeboclient.TheGazeboserverwillexecutethesimulationprocessandtheGazeboclientcanbetheGazeboGUI.Usingthepreviouscommand,theGazeboclientandserverwillruninparallel.

TheGazeboGUIisshowninthefollowingscreenshot:

AfterstartingGazebo,wewillseethefollowingtopicsgenerated.Usingtherostopiccommand,wewillfindthefollowinglistoftopics:

$rostopiclist

/gazebo/link_states

/gazebo/model_states

/gazebo/parameter_descriptions

/gazebo/parameter_updates

/gazebo/set_link_state

/gazebo/set_model_state

Wecanruntheserverandclientseparatelyusingthefollowingcommand:

RuntheGazeboserverusingthefollowingcommand:

$rosrungazebo_rosgzserver

RuntheGazeboclientusingthefollowingcommand:

$rosrungazebo_rosgzclient

WehaveinstalledthebasicpackagesofGazeboinROS.Ifyouarenotplanningtobuildthehardwareforthisrobot,thealternativeplanistobuyanotherrobotcalledTurtleBot(http://store.clearpathrobotics.com/products/turtlebot-2).Now,wewillseehowtoinstalltheTurtleBotstackonROS.

InstallingTurtleBotRobotpackagesonROSIndigo

TheTurtleBotinstallationprocedurefromitssourceismentionedathttp://wiki.ros.org/Robots/TurtleBot.

ThefollowingisaquickproceduretoinstalltheTurtleBotstackanditsdependenciesfromtheaptpackagemanager:

1. First,youneedtoinstallthesynapticpackagemanagerusingthefollowingcommand.Synapticisagraphicalpackagemanagementprogramforapt.Itprovidesthesamefeaturesastheapt-getcommand-lineutilitywithaGUIfrontendbasedonGTK+:

$sudoapt-getinstallsynaptic

2. Aftertheinstallationofthesynapticpackagemanager,openitandfilteritssearchesusingtheros-indigo-roconkeyword.

3. Installallthepackageslistedonsynaptic,asshowninthefollowingscreenshot:

Rocon,alsoknownasroboticsinconcert,isadependencyoftheTurtleBotstack.ThispackagemainlyaimstobringROStomultirobotdevicetablets.Youcanreadmoreaboutroconathttp://wiki.ros.org/rocon.

Aftertheinstallationofrocon,weneedtoinstallanotherdependencycalledthekobukipackage.KobukiisasimilarroboticmobileplatformfromYujinRobots(http://wiki.ros.org/kobuki).TurtleBotpackagesaredependentonthesepackages.

Theros-indigo-kobukipackagecanbeinstalledusingsynaptic,suchastheroconpackage.The

followingisascreenshotoftheinstallation:

FollowingisthestepbystepproceduretobuildandinstallTurtleBot'slatestROSpackagesfromthesourcecodeinROSIndigo.Thedependenciesforinstallingthesepackagesarealreadymetinthepreviousprocedure.

1. Createafoldercalledturtlebotinthehomefolderusingthefollowingcommand:

$mkdir~/turtlebot

2. Switchthedirectorytoturtlebotusingthefollowingcommand:

$cd~/turtlebot

3. DownloadthelatestsourcecodeofTurtleBotusingthefollowingcommand:

$wstoolinitsrc-j5

https://raw.github.com/yujinrobot/yujin_tools/master/rosinstalls/indigo/turtleb

ot.rosinstall

4. Installallthedependenciesofthesourcecodeusingthefollowingcommand:

$rosdepinstall--from-pathssrc-i-y

5. Buildthesourcecodeusing:

$catkin_make

6. ToaccessTurtleBotpackagesfromallterminals,wehavetoaddsource

~/turtlebot/devel/setup.bashcommandtothe.bashrcfile.Thefollowingcommandwilldothisjob:

$echo"source~/turtlebot/devel/setup.bash">>~/.bashrc

7. Thiscommandwillexecutethe.bashrcfile:

$source~/.bashrc

InstallingTurtleBotROSpackagesusingtheaptpackagemanagerinUbuntu

IfyouwanttoinstallTurtleBotpackageswithoutcompilingsourcecode,wecanuseaptpackagemanager.ThefollowingisthecommandtoinstallTurtleBotpackagesinROS:

$sudoapt-getinstallros-indigo-turtlebotros-indigo-turtlebot-appsros-indigo-

turtlebot-interactionsros-indigo-turtlebot-simulatorros-indigo-kobuki-ftdiros-

indigo-rocon-remocon

Let'scheckhowtosimulateTurtleBotinGazeboandmovetherobotonanemptyenvironment.

SimulatingTurtleBotusingGazeboandROS

TheTurtleBotsimulatorpackagecontainstheturtlebot_gazebopackagestosimulateTurtleBotonGazebo.

AfterthesuccessfulinstallationoftheTurtleBotpackage,wecanenterthefollowingcommandtobringuptheTurtleBotsimulationusingROSandGazebo:

$roslaunchturtlebot_gazeboturtlebot_empty_world.launch

Onanotherterminal,runthefollowingcommand.ThiswillexecuteaPythonscripttocontrolTurtleBotusingakeyboard;thisiscalledkeyboardteleoperation:

$roslaunchturtlebot_teleopkeyboard_teleop.launch

Followingisthescreenshotoftheoutput:

Thetop-leftterminalexecutesthesimulationcommandandthebottom-leftwindowexecutestheteleopcommand.

Wecanmovearoundtherobotwithkeyboardteleoperationusingthekeysmentionedonthescreen.Wecanalsomonitorthevaluesfromthemodelusingtherostopicscommand.Wecanviewthecurrenttopicsusingthefollowingcommand:

$rostopiclist

Itpublishesallthevaluesfromthesensors,suchasthekinectsensor,theodometryvaluesfromwheelencoders,theIMUsensorvalueforodometry,andGazebo'sstatevalues.

WewillusethecloneoftheTurtleBotpackageinwhichtherobotmodelandsimulationparametersaredifferent.Wecanperformthiscloningformostofthemobilerobotthathasadifferentialsteeringsystem.WewillcreatethepackagesforourrobotbycloningtheTurtleBotcode.Wewillnameourcustomrobotaschefbotinsteadofturtlebot,andallourpackageswillbenamedaccordingtothis.

CreatingtheGazebomodelfromTurtleBotpackages

InTurtleBotpackages,thesimulationandkinematicmodelsareimplementedusingtwopackages,thatis,turtlebot_gazeboandturtlebot_description.Theturtlebot_gazebopackagehasfilestolaunchsimulationinGazebo.Theturtlebot_descriptionpackagecontainstheGazeboandthekinematicmodeloftherobot.

Wecustomizedandreusedtheturtlebotpackagesandrecreatedthesamepackagesforourrobot.Wenamedourrobotaschefbot;wecancreatechefbot_gazebo,whichcontainsthesimulationlaunchfiles.ThelaunchfilesinROSareakindofanXMLfileinwhichwecanlaunchmultiplenodesandsetmultipleparametersbyrunningasinglefile.Torunthelaunchfile,wehavetousetheroslaunchcommand.

WecancheckouttheimplementedROSpackagesofChefBotathttp://wiki.ros.org/roslaunchforreference.

ThefollowingcommandclonesthecompleteROSpackagesoftheChefBot:

$gitclonehttps://github.com/qboticslabs/Chefbot_ROS_pkg.git

Thechefbot_descriptionpackagecontainsthekinematicmodelandtheGazebomodeloftherobot.Thefollowingfigureshowsthevariousfilesinthesetwopackages:

TheChefbot_descriptionandtheChefbot_Gazebopackage

Switchtocatkin_ws,whichwecreatedtodevelopROSpackages.Inthesrcfolder,firstcreateafoldercalledchefbot.Then,wecancreateallthepackagesofChefBotinit,usingthefollowingcommands:

$cd~/catkin_ws/src

$mkdirchefbot

$cdchefbot

Thechefbot_gazebocanbecreatedusingthefollowingcommandwiththerequireddependencies:

$catkin_create_pkgchefbot_gazebodepthimage_to_laserscandiagnostic_aggregator

gazebo_roskobuki_gazebo_pluginsrobot_pose_ekfrobot_state_publisherxacro

yocs_cmd_vel_muxcreate_gazebo_pluginscreate_descriptioncreate_drivercreate_node

Aftercreatingthepackage,youcancopythetwofoldersinchefbot_gazebofromthesourcecodeofthechapterthatcanbedownloadedfromthePacktPublishingwebsite.Thiscodeisadaptedfromtheturtlebot_gazebopackage;youcanalsorefertoitscodeforfurtherreference.

Hereistheexplanationofeachfileusage.First,wediscussedthechefbot_gazebopackage.Inthelaunchfolder,therearelaunchfilesforeachfunctionality:

chefbot_empty_world.launch:ThisfilewilllaunchtheChefBotmodelinGazebowithanemptyworld,wheretheworldisaGazebofilecontaininginformationabouttherobotenvironment.chefbot_playground.launch:ThisfilewilllaunchtheChefbotmodelinGazebo.ThesimulatedGazeboenvironmentcontainssomerandomobjectslikecylindersandboxes.gmapping_demo.launch:ThisfilewillstartSimultaneousLocalizationAndMapping(SLAM).UsingSLAM,wecanmaptheenvironmentandstoreitforfutureuse.Inourcase,wecanmapahotelenvironmentusingthispackage.Wewilldiscussmoreongmappingintheupcomingchapter.FormoreinformationonSLAM,refertohttp://wiki.ros.org/gmapping.amcl_demo.launch:AMCLstandsforAdaptiveMonteCarloLocalization(http://wiki.ros.org/amcl).Aftermappingtheenvironment,therobotcanautonomouslynavigatebylocalizingitselfonthemapandalsobygivingthefeedbackfromwheels.Thefeedbackfromtherobotiscalledodometry.ThelocalizationalgorithmAMCLandthenavigationalgorithm,suchaspathplanningisperformedinthislaunchfile.chefbot_base.launch.xml:ThisXMLfilewillparseanxacrofilecalledchefbot_circles_kinect.urdf.xacrotoURDFpresentinthechefbot_descriptionfolder.AfterconvertingthexacrofiletoURDF,itwillgeneratetherobotmodelequivalenttoROS.WewilllearnmoreaboutURDFandxacroafterthissection.

AftergeneratingtherobotmodelinURDF,thisfilewillgeneratetheGazebo-compatiblemodelfromtheURDFrobotdescription.Also,itwillstartavelocitymuxernodethatwillprioritizethecommandvelocityoftherobot.Anexampleofcommandvelocityistheteleoperationbykeyboardorjoystick.Accordingtothepriorityassigned,thecommandvelocitywillreachtherobot.Let'sdiscussmoreonURDFandxacrotogetaclearpictureofthedescriptionoftherobot.

Whatisarobotmodel,URDF,xacro,androbotstatepublisher?

RobotmodelinROScontainspackagestomodelthevariousaspectsoftherobot,whichisspecifiedintheXMLRobotDescriptionFormat(URDF).ThecorepackageofthisstackisURDF,whichparsesURDFfilesandconstructsanobjectmodeloftherobot.

UnifiedRobotDescriptionFormat(URDF)isanXMLspecificationtodescribethemodelofarobot.WecanrepresentthefollowingfeaturesoftherobotusingURDF:

ThekinematicanddynamicdescriptionoftherobotThevisualrepresentationoftherobotThecollisionmodeloftherobot

Thedescriptionoftherobotconsistsofasetoflink(part),elements,andasetofjointelements,whichconnecttheselinkstogether.Atypicalrobotdescriptionisshowninthefollowingcode:

<robotname="chefbot">

</robot>

ItwillbegoodifyourefertothefollowinglinksformoreinformationonURDF:

http://wiki.ros.org/urdf

http://wiki.ros.org/urdf/Tutorials

Xacro(XMLMacros)isanXMLmacrolanguage.Withxacro,wecancreateshorterandreadableXMLfiles.WecanusexacroalongwithURDFtosimplifytheURDFfile.Ifweaddxacrotourdf,wehavetocalltheadditionalparsernodetoconvertxacrotourdf.

Thefollowinglinkcangiveyoumoreideaaboutxacro:

http://wiki.ros.org/xacro

robot_state_publisherallowsyoutopublishthestateoftherobottotf(http://wiki.ros.org/tf).Oncethestategetspublished,it'savailabletoallthecomponentsinthesystemthatalsousetf.Thepackagetakesthejointanglesoftherobotasinputandpublishesthe3Dposesoftherobotlinksusingthekinematictreemodeloftherobot.ThepackagecanbeusedasalibraryandasanROSnode.Thispackagehasbeenwelltestedandthecodeisstable.Nomajorchangesareplannedinthenearfuture.

Worldfiles:TheserepresenttheenvironmentofGazebo,whichhavetobeloadedalongwiththerobot.Theempty.worldandplayground.worldworldfilesareincludedinthelaunchfiles,soitwillloadwhenGazebostarts.CMakeList.txtandpackage.xml:Thesefilesarecreatedduringthecreationofpackage.CmakeList.txtfilehelpstobuildthenodesorlibrarieswithinapackageandthepackage.xmlfileholdsthelistofallthedependenciesofthispackage.

CreatingaChefBotdescriptionROSpackage

Thechefbot_descriptionpackagecontainstheurdfmodelofourrobot.Beforecreatingthis

packagebyyourown,youcangothroughthedownloadedpackagesofChefBot.Itcanhelpyoutospeeduptheprocess.

Let'scheckhowtocreatethechefbot_descriptionpackage.Followingprocedurewillguideyouincreatingthispackage:

1. First,weneedtoswitchtothechefbotfolderinthesrcfolder:

$cd~/catkin_ws/src/chefbot

2. Thefollowingcommandwillcreatetherobotdescriptionpackagealongwithdependencies,suchasurdf,xacro,andthedescriptionpackageofKobuki,andcreatemobilerobots:

$catkin_create_pkgchefbot_descriptionurdfxacrokobuki_description

create_description

3. Copythemeshes,urdf,androbotsfoldersfromthedownloadedsourcetothepackagefolder.Themeshfolderholdsthe3Dpartsoftherobotandtheurdffoldercontainstheurdfdescriptionandthesensorsoftherobot.Theentirerobotmodelisdividedintoasetofxacrofilesforeasierdebuggingandbetterreadability.

Let'sseethefunctionalityofeachfilesinsidethispackage.Youcanreferthedownloadedsourcecodeforcheckingthesefiles,andyoucanalsocopythesefilesfromthedownloadedfilestothenewlycreatedfolder.Thefunctionalityofeachurdffolderisasfollows:

chefbot_base.urdf.xacro:Thisxacrorepresentsthekinematicmodeloftheentirerobot.ItmodelstheentirejointsoftherobotusingtheURDFtags.Thejointincludestwowheels,twocasterwheels,gyrosensors,andsoon.The3Dkinectsensorisnotmodeledinthisfile.Itwillalsoattachmeshestoeachlinks.ThisfileisreusedfromtheKobukimobile-basedpackage.chefbot_base_gazebo.urdf.xacro:ThisistheGazebomodelrepresentationofeachlinkoftherobot.Itincludestheactuatordefinition,sensordefinitions,theparametersettingofthedifferentialrobot,andsoon.Gazebousesthisvaluetoperformthesimulation.Therobotparameterscanchangebychangingthevaluesinthisfile.chefbot_gazebo.urdf.xacro:ThepreviousGazebourdfdoesnothavethedefinitionsofthe3Dsensorkinect.Thisfilestartsthekinect_openniGazeboplugintosimulatethekinectsensorontherobot.chefbot_library.urdf.xacro:Thisfileincludesallthexacrofilesandsensorsoftherobot.Thissinglefilecanlaunchallthedescriptionsoftherobot.chefbot_properties.urdf.xacro:Thisfileincludesthe3Dkinectsensorpositionontherobotmodel.common_properties.urdf.xacro:Thisfilecontainspropertiesofmeshessuchascolor.kinect.urdf.xacro:ThisfilecontainstheGazeboparameterofkinectandispresentinsidethesensorsfolder.Thisfileisincludedinthechefbot_gazebo.urdf.xacroandchefbot_properties.urdf.xacrofilestosetthekinectparameters.chefbot_circles_kinect_urdf.xacro:Thisfileisinsidetherobotfolder.Itincludesthechefbot_library.urdf.xacrofile,whichwillloadalltherobotdescriptionfilesneededtostartthesimulation.

Inthemeshesfolder,wemainlyhavethewheelandthebodyoftherobot,the3DmodelpartsofChefBot.

SimilartoTurtleBot,wecanlaunchtheChefBotsimulationusingthefollowingcommand:

Whenweexecutethiscommand,launchfileswillexecuteintheorder,asshowninthefollowingscreenshot:

Wehavealreadyseenthefunctionalityofeachfile.Theimportantfilesweneedtodiscussare:

chefbot_gazebo.urdf.xacro

kinect.urdf.xacro

chefbot_base.urdf.xacro

chefbot_base_gazebo.urdf.xacro

Let'stakealookatchefbot_base_gazebo.urdf.xacro.Theactualfiledefinitionisprettylong,sowewillonlydiscusstheimportantparts.

BeforediscussingGazebodefinitions,wecanrefertotheGazebotagsparametersmentionedinURDF.ThevarioustagsthatcanbeusedintheURDFcanbefoundathttp://osrf-distributions.s3.amazonaws.com/sdformat/api/1.5.html.

TheGazebodefinitionforeachlinkismentionedinURDFas<gazebo></gazebo>.ThefollowingURDFdefinitionsforindividualjointsoftherobotaremodeledusingtheGazeboparameters.Thejointsincludewheeljointsandcasterwheeljoints.Themu1andmu2parametersarecoefficientsoffriction.Kpandkdindicatethedynamicalstiffnessanddampingofajoint.MinDepthistheminimumallowabledepthbeforethecontactcorrectionimpulseisapplied.MaxVelisthemaximumcontactcorrectionvelocitytruncationterm:

<?xmlversion="1.0"?>

<robotname="kobuki_sim"xmlns:xacro="http://ros.org/wiki/xacro">

<xacro:macroname="kobuki_sim">

<gazeboreference="wheel_left_link">

</gazebo>

<gazeboreference="wheel_right_link">

</gazebo>

<gazeboreference="caster_front_link">

</gazebo>

<gazeboreference="caster_back_link">

</gazebo>

ThefollowingsectionisusedfortheInertialMeasurementUnit(IMU)sensorintherobot(http://en.wikipedia.org/wiki/Inertial_measurement_unit)modeledinGazebo.ThemainuseofIMUintherobotistogenerateagoododometryvalue:

<gazeboreference="gyro_link">

<sensortype="imu"name="imu">

<always_on>true</always_on>

<update_rate>50</update_rate>

<visualize>false</visualize>

<noise>

<type>gaussian</type>

<rate>

<bias_mean>0.0</bias_mean>

<bias_stddev>0.0</bias_stddev>

</rate>

<accel><!--notusedinthepluginandrealrobot,henceusingtutorial

values-->

<bias_mean>0.1</bias_mean>

<bias_stddev>0.001</bias_stddev>

</accel>

</noise>

</imu>

</sensor>

</gazebo>

Thedifferential-drivecontrollerpluginforGazeboisgiveninthefollowingcode.WewillreusetheKobukidifferential-drivepluginforthedrivesystem.Wewillalsomentionthemainmeasurementsoftherobot,suchasthewheelseparation,wheeldiameter,torqueofthemotor,andsoon,inthissection.Thissectionwillalsoincludethecliffsensor,whichwillnotbeusedinourmodel.Wemayignorethissectionifwedon'twanttouseit:

<pluginname="kobuki_controller"filename="libgazebo_ros_kobuki.so">

<publish_tf>1</publish_tf>

<left_wheel_joint_name>wheel_left_joint</left_wheel_joint_name>

<right_wheel_joint_name>wheel_right_joint</right_wheel_joint_name>

<wheel_separation>.30</wheel_separation>

<wheel_diameter>0.09</wheel_diameter>

<velocity_command_timeout>0.6</velocity_command_timeout>

<cliff_sensor_left_name>cliff_sensor_left</cliff_sensor_left_name>

<cliff_sensor_center_name>cliff_sensor_front</cliff_sensor_center_name>

<cliff_sensor_right_name>cliff_sensor_right</cliff_sensor_right_name>

<cliff_detection_threshold>0.04</cliff_detection_threshold>

<bumper_name>bumpers</bumper_name>

<imu_name>imu</imu_name>

</plugin>

</gazebo>

kinect.urdf.xacro

Thisfilemainlyhasthedefinitionsofjointsandlinksofthekinectsensor.Thisfilealsoincludestwolaunchfiles:

<xacro:includefilename="$(find

chefbot_description)/urdf/chefbot_gazebo.urdf.xacro"/>

<xacro:includefilename="$(find

chefbot_description)/urdf/chefbot_properties.urdf.xacro"/>

Thechefbot_gazebo.urdf.xacrofileconsistsofthekinectpluginforGazebo.WewillreusethispluginfromTurtleBot.Thekinectpluginisactuallythelibgazebo_ros_openni_kinect.sofile;wecanalsodefinetheparametersofKinect,asshowninthefollowingcode:

<pluginname="kinect_camera_controller"

filename="libgazebo_ros_openni_kinect.so">

<cameraName>camera</cameraName>

<imageTopicName>rgb/image_raw</imageTopicName>

<depthImageTopicName>depth/image_raw</depthImageTopicName>

<pointCloudTopicName>depth/points</pointCloudTopicName>

<cameraInfoTopicName>rgb/camera_info</cameraInfoTopicName>

<depthImageCameraInfoTopicName>depth/camera_info</depthImageCameraInfoTopicName>

<frameName>camera_depth_optical_frame</frameName>

<distortion_k1>0.0</distortion_k1>

<distortion_t1>0.0</distortion_t1>

<distortion_t2>0.0</distortion_t2>

</plugin>

chefbot_base.urdf.xacro

Thisfiledefinesthelinksandjointsoftherobotandalsoincludesthechefbot_gazebo.urdf.xacrofile.Thejointsoftherobotarewheels,casterwheels,andsoon.HereistheXMLdefinitionofthebodyoftherobot,thewheeloftherobot,andthecasterwheeloftherobot.

Thebaselinkoftherobotincludestherobotbody,excludingthewheels.Wecanexporttherobotbodymeshfromtheblenderandexportittothe.DAEextensionusingMeshLab(http://en.wikipedia.org/wiki/COLLADA).Thebasejointisafixedtype.Thereisnomovementonthebaseplate.Wecandefinethecollisionprofileandinertiaforeachlinkoftherobot.ThesefilesarereusedfromTurtleBot,asshowninthefollowingcode:

<xacro:macroname="kobuki">

<linkname="base_footprint"/>

Baselinkissetatthebottomofthebasemould.

Thisisdonetobecompatiblewiththewaybaselink

wasconfiguredforturtlebot1.Referto

https://github.com/turtlebot/turtlebot/issues/40

Toputthebaselinkatthemoreoftusedwheel

axis,setthez-distancefromthebase_footprint

to0.352.

<jointname="base_joint"type="fixed">

<originxyz="000.0102"rpy="000"/>

<parentlink="base_footprint"/>

<childlink="base_link"/>

</joint>

<linkname="base_link">

<meshfilename="package://chefbot_description/meshes/base_plate.dae"/>

</geometry>

<originxyz="0.0010-0.034"rpy="00${M_PI/2}"/>

</visual>

<cylinderlength="0.10938"radius="0.178"/>

</geometry>

<originxyz="0.000.05949"rpy="000"/>

</collision>

<originxyz="0.0100"/>

<massvalue="2.4"/>

<!--Kobuki'sinertiatensorisapproximatedbyacylinderwithhomogeneous

massdistribution

Moredetails:

http://en.wikipedia.org/wiki/List_of_moment_of_inertia_tensors

m=2.4kg;h=0.09m;r=0.175m

ixx=1/12*m*(3*r^2+h^2)

iyy=1/12*m*(3*r^2+h^2)

izz=1/2*m*r^2

<inertiaixx="0.019995"ixy="0.0"ixz="0.0"

iyy="0.019995"iyz="0.0"

izz="0.03675"/>

</inertial>

</link>

<!--Oneofthewheeljointisgivenbelow.Thekindofjointusedhereisa

continuousjoint.-->

<jointname="wheel_left_joint"type="continuous">

<parentlink="base_link"/>

<childlink="wheel_left_link"/>

<originxyz="0${0.28/2}0.026"rpy="${-M_PI/2}00"/>

<axisxyz="001"/>

</joint>

<linkname="wheel_left_link">

<meshfilename="package://chefbot_description/meshes/wheel.dae"/>

</geometry>

<originxyz="000"rpy="000"/>

</visual>

<cylinderlength="0.0206"radius="0.0352"/>

</geometry>

<originrpy="000"xyz="000"/>

</collision>

<massvalue="0.01"/>

<originxyz="000"/>

<inertiaixx="0.001"ixy="0.0"ixz="0.0"

iyy="0.001"iyz="0.0"

izz="0.001"/>

</inertial>

</link>

SimulatingChefBotandTurtleBotinahotelenvironmentAfterdiscussingeachfile,wecantrythesimulationoftworobotsinahotelenvironment.Theproceduresandscreenshotsofthesimulationareasfollows.

SimilartoTurtleBot,wecanstartChefBotusingthefollowingcommands:

ItwillshowtherobotinGazebo,asshowninthefollowingscreenshot:

WecanexitGazeboandstartbuildingthehotelenvironmentfortherobot.

Thefirstprocedureistocreateaworldfileandsaveitwiththe.worldfileextension.Atypicalhotelenvironmentwithnineblock-liketablesisshowninthefollowingscreenshot.YoucantakeanemptyGazeboworldusingthefollowingcommandandmakeanenvironmentusingthebasicshapesavailableinGazebo:

1. Startroscoreusingthefollowingcommand:

$roscore

2. StartGazebowithanemptyworldusingthefollowingcommand:

$rosrungazebo_rosgazebo

3. Nowwehavecreatedanenvironment,asshowninthefollowingscreenshot,andsaveditasempty.world.

4. Copyempty.worldtotheworldfolderinthechefbot_decriptionpackage.Starttherobotwiththisenvironmentusingthefollowingcommand:

ThiswillbringthesameenvironmentthatwecreatedbeforealongwithChefBot.TheprocedureremainsthesameforTurtleBot.

Insteadofchefbot_description,wehavetocopytheturtlebot_descriptionfolderforTurtleBotusers:

1. Startthegmappinglaunchfiletostartmappingthisarea.Wecanusethefollowingcommandtolaunchthegmappingprocess:

$roslaunchchefbot_gazebogmapping_demo.launch

2. InTurtleBot,usethefollowingcommand:

$roslaunchturtlebot_gazebogmapping_demo.launch

3. Itwillstartthegmappingprocessandifwewanttoviewthemappingprocess,startrviz,atoolinROStovisualizesensordata(http://wiki.ros.org/rviz).ThecommandisthesameasitwasforTurtleBot:

$roslaunchturtlebot_rviz_launchersview_navigation.launch

Thescreenshotofrvizisasfollows:

Tocreateamapoftheroom,wehavetostartthekeyboardteleoperation:

1. Usingthekeyboardteleoperationfunction,wecanmovetherobotusingthekeyboardsothatitcanmaptheentirearea:

$roslaunchturtlebot_teleopkeyboard_teleop.launch

2. ThecommandissameforTurtleBot.Acompletemapofthesurroundingisshowninthefollowingscreenshot:

3. Afterbuildingthemap,wecansavethenamehotel_worldusingthefollowingcommand:

$rosrunmap_servermap_saver-f~/hotel_world

ThecommandissameforTurtleBot4. Aftersavingthemap,exitalltheotherapplicationsthatarecurrentlyinuse.5. Afterthemapisgenerated,thenextstepisautonomousnavigationandthelocalizationofthe

robotusingthebuiltmap.6. StartGazebousingthefollowingcommand:

7. InTurtleBot,usethefollowingcommand:

$roslaunchturtlebotbot_gazebochefbot_empty_world.launch

8. StarttheamcldemoinChefBot.Notethepathbecauseitmayvaryforeachuser.9. ForChefBot,usethefollowingcommands:

$roslaunchchefbot_gazeboamcl_demo.launch

map_file:=/home/lentin/hotel_world.yaml

10. ForTurtleBot,usethefollowingcommands:

$roslaunchturtlebot_gazeboamcl_demo.launch

map_file:=/home/lentin/hotel_world.yaml

11. Startrvizusingthefollowingcommand.Thisisthesameforbothrobots:

$roslaunchturtlebot_rviz_launchersview_navigation.launch

Nowwecancommandtherobottonavigatetoapositiononthemapusingthe2DNavGoalbutton.Clickonthisbuttonandselectapositionthatisnearatable.Afterclickingonthisposition,itwillplanthepathtothatpointandnavigatetothatposition,asshowninthefollowingscreenshot:

Therobotcanavoidobstaclesandalsoplantheshortestpathtothegoalposition.Afterseveralruns,wefoundthattherobotworksperfectlyifthemapwebuildwasaccurate.Themapbuildingprocedurecanbefine-tunedusingtheinstructionsat(http://wiki.ros.org/costmap_2d).Foranapplicationsuchasservingfood,itrequiresprettygoodaccuracyinthemap,sothattherobotcandeliverfoodtothecorrectposition.

Questions1. Whatisrobotsimulationandwhatarethepopularrobotsimulators?2. WhatisROSandGazebo?3. WhatistherobotmodelinROS?4. WhatisgmappingandAMCL?

SummaryInthischapter,youlearnedhowtosimulateacustomrobotcalledChefBot.Wediscussedthedesignofthetherobotinthepreviouschapter.Aftertherobotdesign,wemovedontosimulatetherobotinavirtualenvironmenttotestthedesignoftherobot,andcheckedwhetheritmetourspecifications.Inthischapter,youlearnedaboutsimulationandvarioussimulatorapplicationsusedinindustry,research,andeducationindetail.Afterthat,wediscussedhowtheROSframeworkandGazebosimulatorwasusedtoperformthesimulatorwork.Wealsocreatedasamplehello_worldpackageusingROS.WeinstalledtheTurtleBotstackandcreatedROSpackagesfromtheTurtleBotstack.Finally,wesimulatedtherobotandperformedgmappingandautonomousnavigationinahotelenvironment.Wegottoknowthattheaccuracyofthesimulationdependsonthemap,andthattherobotwillworkbetterinsimulationifthegeneratedmapisperfect.

Chapter4.DesigningChefBotHardwareInthischapter,wewilldiscussthedesignandworkingofChefBothardwareandselectionofitshardwarecomponents.Inthepreviouschapter,wedesignedandsimulatedthebasicrobotframeworkinahotelenvironmentusingGazeboandROS,andtestedvariousmeasurementslikerobotbodymass,motortorque,wheeldiameter,andsoon.Also,wetestedtheautonomousnavigationcapabilityofChefBotinahotelenvironment.

Toachievethisgoalinhardware,weneedtoselectallhardwarecomponentsandfindhowtointerconnectallthesecomponents.Weknowthatthemainfunctionalityofthisrobotisnavigation;thisrobotwillhavetheabilitytonavigatefromthestartpositiontotheendpositionwithoutanycollisionwithitssurroundings.Wewilldiscussthedifferentsensorsandhardwarecomponentsrequiredtoachievethisgoal.Wewillseeablockdiagramrepresentationanditsexplanation,andalsodiscussthemainworkingoftherobot.Finally,weneedtoselectthecomponentsrequiredtobuildtherobot.Wecanalsoseetheonlinestoreswherewecanpurchasethesecomponents.

IfyouhaveaTurtleBot,youmayskipthischapterbecauseitisonlyforthosewhoneedtocreatetherobothardware.Let'sseewhatspecificationswehavetomeetinthehardwaredesign.Therobothardwaremainlyincludesrobotchassis,sensors,actuators,controllerboards,andPC.

SpecificationsoftheChefBothardwareInthissection,wewilldiscussingsomeoftheimportantspecificationsthatwementionedinChapter2,MechanicalDesignofaServiceRobot.Thefinalrobotprototypewillmeetthefollowingspecifications:

Simpleandcosteffectiverobotchassisdesign:Therobotchassisdesignshouldbesimpleandcosteffective.Autonomousnavigationfunctionality:Therobotshouldautonomouslynavigateanditshouldcontainnecessarysensorsfordoingthis.LongBatterylife:Therobotshouldhavealongbatterylifeinordertoworkcontinuously.Theworkingtimeshouldbegreaterthan1hour.Obstacleavoidance:Therobotshouldbeabletoavoidstaticanddynamicobjectsinthesurroundings.

Therobothardwaredesignshouldmeetthesespecifications.Let'slookatoneofthepossiblewaysofinterconnectingthecomponentsinthisrobot.Thenextsectionshowstheblockdiagramofarobotandexplainsit.

BlockdiagramoftherobotTherobot'smovementiscontrolledbytwoDirectCurrent(DC)gearmotorswithanencoder.Thetwomotorsaredrivenusingamotordriver.Themotordriverisinterfacedintoanembeddedcontrollerboard,whichwillsendcommandstothemotordrivertocontrolthemotormovements.Theencoderofthemotorisinterfacedintothecontrollerboardforcountingthenumberofrotationsofthemotorshaft.Thisdataistheodometrydatafromtherobot.Thereareultrasonicsensors,whichareinterfacedintothecontrollerboardforsensingtheobstaclesandmeasuringthedistancefromtheobstacles.ThereisanIMUsensortoimproveodometrycalculation.TheembeddedcontrollerboardisinterfacedintoaPC,whichdoesallthehigh-endprocessingintherobot.VisionandsoundsensorsareinterfacedintothePCandWi-Fiisattachedforremoteoperations.

Eachblockoftherobotisexplainedinthefollowingdiagram:

RobotHardwareblockDiagram

MotorandencoderTherobotthatwearegoingtodesignisadifferentialdriverobotwithtwowheels,sowerequiretwomotorsforitslocomotion.Eachmotorconsistsofquadratureencoders(http://letsmakerobots.com/node/24031)togetthemotorrotationfeedback.

Thequadratureencoderwillgiveafeedbackoftherotationofthemotorassquarepulses;wecandecodethepulsetogetthenumberofticksoftheencoder,whichcanbeusedforfeedback.Ifweknowthewheeldiameterandthenumberofticksofthemotor,wecancomputethedisplacementandtheangleoftherobotthattraversed.Thiscomputationisveryusefulfornavigationoftherobot.

Selectingmotors,encoders,andwheelsfortherobot

Fromthesimulation,wegotanideaabouttherobotparameters.Onthesimulationparameters,wementionedthatthemotortorqueneededtodrivetherobotis18kg-cm,butthecalculatedtorqueislessthanthis;weareselectingahightorquemotorforbetterperformance.OneoftheeconomicalmotorsthatwemightconsiderusingisfromPololu.WecanselectahightorqueDCgearmotorwithanencoderworkingat12VDCandhavingspeedof80RPMaccordingtoourdesign.Wearechoosingthefollowingmotorforthedrivesysteminthisrobot:

http://www.pololu.com/product/1447

Thefollowingfigureshowstheimageoftheselectedmotorforthisrobot.Themotorcomeswithanintegratedquadratureencoderwitharesolutionof64countsperrevolutionofthemotorshaft,whichcorrespondsto8400countsperrevolutionofthegearbox'soutputshaft.

DCGearmotorwithencoderandwheel

Thismotorhas6pinswithdifferentcolors.Thepindescriptionofthismotorisgiveninthefollowingtable:

Color Function

Red Motorpower(connectstoonemotorterminal)

Black Motorpower(connectstotheothermotorterminal)

Green EncoderGND

Blue EncoderVcc(3.5V-20V)

Yellow EncoderAoutput

White EncoderBoutput

Accordingtoourdesign,wechoseawheeldiameterof90mm.Pololuprovidesa90mmwheel,whichisavailableathttp://www.pololu.com/product/1439.Theprecedingfigureshowedthemotorassembledwiththiswheel.

Theotherconnectorsneededtoconnectthemotorsandwheelstogetherareavailableasfollows:

Themountinghubrequiredtomountthewheeltothemotorshaftisavailableathttp://www.pololu.com/product/1083TheL-bracketforthemotortomountonrobotchassisisavailableathttp://www.pololu.com/product/1084

MotordriverAmotordriverormotorcontrollerisacircuitthatcancontrolthespeedofthemotor.Controllingmotorsmeansthatwecancontrolthevoltageacrossthemotorandcanalsocontrolthedirectionandspeedofthemotor.Motorscanrotateclockwiseorcounterclockwise,ifwechangethepolarityofmotorterminal.

H-bridgecircuitsarecommonlyusedinmotorcontrollers.H-bridgeisanelectroniccircuitthatcanapplyvoltageineitherdirectionofload.Ithashighcurrenthandlingpropertiesandcanchangethedirectionofcurrentflow.

ThefollowingscreenshotshowsabasicH-bridgecircuitusingswitches:

HBridgecircuit

Thedirectionofthemotor,dependingonthefourswitches,isgivenasfollows:

S1 S2 S3 S4 Result

1 0 0 1 Motormovesright

0 1 1 0 Motormovesleft

0 0 0 0 Motorfreeruns

0 1 0 1 Motorbrakes

1 0 1 0 Motorbrakes

1 1 0 0 Motorshootsthrough

WehaveseenthebasicsofanH-bridgecircuitonthemotordrivercircuit.Now,wecanselectoneofthemotordriversforourapplicationanddiscusshowitworks.

Selectingamotordriver/controller

TherearesomemotordriversavailablewithPololu,whicharecompatiblewiththeselectedmotor.Thefollowingfigureshowsoneofthemotordriversthatwewilluseinourrobot:

DualVNH2SP30MotorDriverCarrierMD03A

Thismotordriverisavailableathttp://www.pololu.com/product/708.

Thisdrivercandrivetwomotorswithacombinedmaximumcurrentratingof30A,andcontainstwointegratedICfordrivingeachofthemotors.Thepindescriptionofthisdriverisgivenintheupcomingsections.

Inputpins

Thefollowingpinsaretheinputpinsofthemotordriver,bywhichwecancontrolmainlythemotorspeedanddirection:

PinName Function

1DIAG/EN,2DIAG/EN Thismonitorsthefaultconditionofmotordriver1and2.Innormaloperation,itwillremaindisconnected.

1INa,1INb,2INa,2INb

Thesepinswillcontrolthedirectionofmotor1and2inthefollowingmanner:

IfINA=INB=0,motorwillbreakIfINA=1,INB=0,motorwillrotateclockwiseIfINA=0,INB=1,motorrotatecounterclockwiseIfINA=INB=1,motorwillbreak

1PWM,2PWM Thiswillcontrolthespeedofmotor1and2byrapidlyturningthemonandoff.

1CS,2CS Thisisthecurrentsensingpinforeachmotor.

Outputpins

Theoutputpinsofthemotordriverwilldrivethetwomotors.Thefollowingaretheoutputpins:

PinName Function

OUT1A,OUT1B Thesepinsconnecttomotor1powerterminals

OUT2A,OUT2B Thesepinsconnecttomotor2powerterminals

Powersupplypins

Thefollowingarethepowersupplypins:

Pinname Function

VIN(+),GND(-) Thesearethesupplypinsofthetwomotors.Thevoltagerangesfrom5.5Vto16V.

+5VIN,GND(-) Thisisthesupplyofmotordriver.Thevoltageshouldbe5V.

EmbeddedcontrollerboardControllerboardsaretypicallyI/Oboards,whichcansendcontrolsignalsintheformofdigital

pulsestotheH-Bridge/motordriverboardandcanreceiveinputsfromsensorssuchasultrasonicandIRsensors.Wecanalsointerfacemotorencoderstothecontrolboardforthemotorfeedback.

ThemainfunctionalitiesofLaunchpadinthisrobotare:

InterfacingthemotordriverandencoderInterfacingtheultrasonicsoundsensorSendingandreceivingsensorvaluestoPCandfromPC

WewilldealwithI/Oboardsandinterfacingwithdifferentcomponentsintheupcomingchapters.SomeofthepopularI/OboardsareArduino(arduino.cc)andTivaCLaunchPad(http://www.ti.com/tool/EK-TM4C123GXL)byTexasInstruments.WeareselectingTivaCLaunchPadoverArduinobecauseoffollowingfactors:

TivaCLaunchPadhasamicrocontrollerbasedon32-bitARMCortex-M4with256KBFlashmemory,32KBSRAM,and80MHzoperation;however,mostoftheArduinoboardsrunbelowthisspecification.Outstandingprocessingperformance,combinedwithfastinterrupthandling.12Timers.16PWMOutputs.Twoquadratureencoderinputs.EightUniversalAsynchronousReceiver/Transmitter(UART).5VtolerantGeneral-PurposeInput/Output(GPIO).LowcostandsizecomparedtoArduinoboards.EasyprogrammableinterfaceIDEcalledEnergia(http://energia.nu/).ThecodewritteninEnergiaisArduinoboardcompatible.

ThefollowingimageshowstheTexasInstrument'sTivaCLaunchPad:

TivaCLaunchpad

ThepinoutofTexasInstrumentLaunchpadseriesisgivenathttp://energia.nu/pin-maps/guide_stellarislaunchpad/.ThispinoutiscompatiblewithalltheLaunchpadseries.ThisisalsousedwhileprogramminginEnergiaIDE.

UltrasonicsensorsUltrasonicsensorsarealsocalledpingsensors,andaremainlyusedtomeasuretherobot'sdistancefromanobject.Themainapplicationofpingsensorsistoavoidobstacles.Theultrasonicsensorsendshighfrequencysoundwavesandevaluatestheechoesthatarereceivedfromtheobject.Thesensorwillcalculatethedelaybetweensendingandreceivingtheecho,andfromthat,determineitsdistancefromanobject.

Inourrobot,collision-freenavigationisanimportantaspect,otherwisetherewillbedamagetotherobot.Youwillseeafigureshowinganultrasonicsensorinthenextsection.Thissensorcanbeemployedonthesidesofarobottodetectcollisiononthesidesandbackoftherobot.Thekinectisalsomainlyusedforobstacledetectionandcollisionavoidance.Theaccuracyofkinectcanonlybeexpectedfrom0.8m,sothatdistanceinbetween0.8mcanbedetectedusingultrasonicsensor.Itisactuallyanadd-ontoourrobotforincreasingcollisionavoidanceanddetection.

Selectingtheultrasonicsensor

OneofthepopularandcheapultrasonicsensorsavailableisHC-SR04.Weareselectingthissensorforourrobotbecauseofthefollowingfactors:

Rangeofdetectionisfrom2cmto4mWorkingvoltageis5VWorkingcurrentisverylowtypically15mA

Wecanusethissensorforaccuratedetectionofobstacles;italsoworkswith5V.HereistheimageofHC-SR04anditspinout:

Ultrasonicsoundsensor

Thepinsanddescriptionaregivenasfollows:

Pins Function

Vcc,GND Thesearethesupplypinsofultrasonicsensor.Normally,weneedtoapply5Vforanormaloperation.

Trig Thisistheinputpinofthesensor.Weneedtoapplyapulsewithaparticulardurationtothispintosendtheultrasonicsoundwaves.

Echo Thisistheoutputpinofthesensor.Itwillgenerateapulseonthispinwithatimeduration,accordingtothedelayinreceivingthetriggeredpulse.

InertialMeasurementUnitWewilluseInertialMeasurementUnit(IMU)inthisrobottogetagoodestimateoftheodometryvalueandtherobotpose.Theodometryvaluescomputedfromtheencoderalonemaynotbesufficientforefficientnavigation,itcouldcontainerrors.Tocompensateforerrorsduringtherobot'smovement,wewilluseIMUinthisrobot.WeareselectingMPU6050forIMUbecauseoffollowingreasons:

InMPU6050,theaccelerometerandgyroscopeareintegratedonasinglechipItprovideshighaccuracyandsensitivityThereisprovisiontointerfacemagnetometerforbetterIMUperformanceThebreakoutboardofMPU6050isverycheapTheMPU6050candirectlyinterfacetoLaunchpad,bothare3.3Vcompatibleandsoftwarelibrariesarealsoavailableforeasierinterfacing

ThefollowingfigureshowsthebreakoutboardofMPU6050:

Thepinsandtheirdescriptionsaregivenasfollows:

Pins Functions

VDD,GND Supplyvoltage2.3V-3.4V

INT Thispinwillgenerateaninterruptwhendatacomestothedevicebuffer

SCL,SDA SerialDataLine (SDA)andSerialClockLine (SCL)areusedforI2Ccommunication

ASCL,ASDA AuxiliaryI2CforcommunicationwithMagnetometer

Wecanpurchasethebreakoutboardfromhttps://www.sparkfun.com/products/11028.

KinectKinectisa3Dvisionsensor,mainlyusedin3Dvisionapplicationandmotiongaming.Weareusingkinectfor3Dvision.Usingkinect,therobotwillgetthe3Dimageofitssurroundings.The3Dimagesareconvertedtofinerpointscalledpointcloud.Thepointclouddatawillhaveall3Dparametersofthesurrounding.

Themainuseofkinectontherobotistomockthefunctionalityofalaserscanner.ThelaserscannerdataisessentialforanalgorithmcalledSLAM,usedforbuildingamapoftheenvironment.Thelaserscannerisaverycostlydevice,soinsteadofbuyinganexpensivelaserscanner,wecanconvertakinectintoavirtuallaserscanner.AnotheralternativetokinectisAsusXtionPRO(http://www.asus.com/Multimedia/Xtion_PRO/).Thiswillsupportthesamesoftwarewrittenforkinect.Thepointcloudtolaserdataconversionisdoneonthesoftware,sononeedtochangethehardwareparts.Aftergeneratingamapoftheenvironment,therobotcannavigateitssurroundings.

Thefollowingimageshowsthevariouspartsofakinectsensor:

Kinect

ThekinectmainlyhasanIRcameraandIRprojectorandalsohasanRGBcamera.TheIRcameraandprojectorgeneratesthe3Dpointcloudofthesurroundings.Italsohasamicarrayandmotorizedtiltformovingthekinectupanddown.

Wecanpurchasekinectfromhttp://www.amazon.co.uk/Xbox-360-Kinect-Sensor-Adventures/dp/B0036DDW2G.

CentralProcessingUnitTherobotismainlycontrolledbyitsnavigationalalgorithmthatisrunningonitsPC.WecanchoosealaptoporminiPCornetbookfortheprocessing.Recently,IntellaunchedaminicomputercalledIntelNextUnitofComputing(NUC).Ithasanultrasmallformfactor(smallsize),islightweight,andhasagoodcomputingprocessorwithIntelCeleron,Corei3,orCorei5.Itcansupportupto16GBofRAMandhasintegratedWi-Fi/Bluetooth.WearechoosingIntelNUCbecauseofitsperformance,ultrasmallformfactor,andlightweight.Wearenotgoingforapopularboard,suchasRaspberryPi(http://www.raspberrypi.org/)orBeagleBone(http://beagleboard.org/)becausewerequirehighcomputingpowerinthiscase,whichcannotbeprovidedbytheseboards.

TheNUCweareusingisIntelDN2820FYKH.Herearethespecificationsofthiscomputer:

IntelCeleronDualCoreprocessorwith2.39GHz4GBRAM500GBharddiskIntelintegratedgraphicsHeadphone/microphonejack12Vsupply

ThefollowingimageshowstheIntelNUCminicomputer:

IntelNUCDN2820FYKH

WecanpurchaseNUCfromhttp://goo.gl/Quzi7a.

Speakers/micThemainfunctionoftherobotisautonomousnavigation.Weareaddinganadditionalfeatureinwhichtherobotcaninteractwithusersthroughspeech.Therobotcanbegivencommandsusingvoiceandcanspeaktotheuserusingatexttospeech(TTS)engine,whichcanconverttexttospeechformat.Amicrophoneandspeakersareessentialforthisapplication.Thereisnoparticularselectionforthishardware.IfthespeakerandmicareUSBcompatible,thenitwillbegreat.AnotheralternativeisaBluetoothheadset.

Powersupply/batteryOneoftheimportanthardwarecomponentisthepowersupply.Wesawinthespecificationthattherobothastoworkformorethan1hour;itwillbegoodifthesupplyvoltageofthebatteryiscommontothecomponents.Also,ifthesizeandweightofthebatteryisless,itwillnotaffecttherobot'spayload.Anotherconcernisthatthemaximumcurrentneededfortheentirecircuitshouldnotexceedthebattery'smaximumcurrent,whichitcansource.Themaximumvoltageandcurrent

distributionofeachpartofthecircuitisasfollows:

Components Maximumcurrent(Ampere)

IntelNUCPC 12V,3A

Kinect 12V,1A

Motors 12V,0.7A

Motordriver,Ultrasonicsensor,IMU,Speakers 5V,<0.5A

Tomeetthesespecifications,weareselectinga12V,9AHLi-Polymerbatteryforouroperation.Thisbatterycanalsosourcemaximumcurrentupto5Ampere.

Thefollowingimageshowsourselectedbatteryforthisrobot:

Wecanbuythefollowingbatteryfromhttp://goo.gl/Clzk6I.

WorkingoftheChefBothardwareWecanexplaintheworkingoftheChefBothardwareusingthefollowingblockdiagram.Thisimprovedversionofourfirstblockdiagrammentionsthevoltageofeachcomponentanditsinterconnection:

ThemainaimofthischapterwastodesignthehardwareforChefBot,whichincludedfindingtheappropriatehardwarecomponentsandfindingtheinterconnectionbetweeneachpart.Themainfunctionalityofthisrobotistoperformautonomousnavigation.Thehardwaredesignofrobotisoptimizedforautonomousnavigation.

Therobotdriveisbasedondifferentialdrivesystem,whichconsistsoftwomotorsandtwowheels.Therearecasterwheelsforsupportingthemainwheels.Thesetwomotorscanmovetherobotinanyposeina2Dplanebyadjustingtheirvelocitiesanddirection.

Forcontrollingthevelocityanddirectionofthewheels,wehavetointerfaceamotorcontroller,whichcandothesefunctions.Themotordriverwechoseshouldabletocontroltwomotorsatatimeandchangethedirectionandspeed.

ThemotordriverpinsareinterfacedtoamicrocontrollerboardcalledTivaCLaunchPad,whichcansendthecommandstochangethedirectionandspeedofthemotor.ThemotordriverisinterfacedintoLaunchpadwiththehelpofalevelshifter.Thelevelshifterisacircuit,whichcanshiftvoltage

levelsfrom3.3Vto5Vandviceversa.Weareusingalevelshifterbecausethemotordriverisoperatingat5Vlevel,buttheLaunchpadisoperatingat3.3V.

Eachmotorhasarotationfeedbacksensorcalledtheencoder,whichcanbeusedtoestimatetherobot'sposition.TheencodersareinterfacedintotheLaunchpadalongwiththelevelshifter.

OthersensorsinterfacedintoLaunchpadincludeultrasonicsoundsensorandIMU.Ultrasonicsoundsensorcandetectobjectsthatarecloseby,butcannotbedetectedbythekinectsensor.IMUisusedalongwiththeencoders,togetagoodrobotposeestimation.

AllsensorvaluesarereceivedontheLaunchpadandsenttoPCviaUSB.TheLaunchpadrunsafirmwarecodethatcanreceiveallsensorvaluesandsendtothePC.

ThePCisinterfacedtokinect,Launchpad,Speaker,andMic.ThePChasROSrunningonitanditwillreceivekinectdataandconvertedtodataequivalenttolaserscanner.ThisdatacanbeusedtobuildthemapoftheenvironmentusingSLAM.Thespeaker/micisusedforcommunicationbetweentheuserandrobot.ThespeedcommandsgeneratedinROSnodesaresenttoLaunchpad.LaunchpadwillthenprocessthespeedcommandsandsendappropriatePWMvaluestothemotordrivercircuit.

Afterdesigninganddiscussingtheworkingoftherobothardware,wewilldiscussthedetailedinterfacingofeachcomponentandthefirmwarecodingnecessaryfortheinterfacing.

Questions1. Whatisrobothardwaredesigningallabout?2. WhatisH-bridgeandwhatareitsfunctions?3. Whicharethecomponentsessentialfortherobotnavigationalgorithm?4. Whatisthecriteriathathastobekeptinmindwhileselectingroboticcomponents?5. WhatarethemainapplicationsofKinectonthisrobot?

SummaryInthischapter,wehaveseenthefeaturesoftherobotthatwearegoingtodesign.Themainfeatureofthisrobotisautonomousnavigation.Therobotcannavigateinitssurroundingbyanalyzingsensorreadings.Wewentthroughtherobotblockdiagraminwhichwediscussedtheroleofeachblock,andwethenselectedappropriatecomponentsthatsatisfytheserequirements.Thischapteralsosuggestedsomeeconomicalcomponentstobuildthisrobot.Inthenextchapter,wewillfindoutmoreaboutactuatorsandtheirinterfacingthatweusingonthisrobot.

Chapter5.WorkingwithRoboticActuatorsandWheelEncodersInthischapter,wewillcover:

InterfacingaDCGearedmotorwithTivaCLaunchPadInterfacingaquadratureencoderwithTivaCLaunchPadExplanationofinterfacingcodeInterfacingDynamixelactuators

Inthepreviouschapter,wehavediscussedtheselectionofhardwarecomponentsneededtobuildourrobot.Oneoftheimportantcomponentsinrobothardwareistheactuator.Actuatorsprovidemobilitytotherobot.Inthischapter,weareconcentratingonthedifferenttypesofactuatorsthatwearegoingtouseinthisrobotandhowtheycanbeinterfacedwithTivaCLaunchPad,whichisa32-bitARMmicrocontrollerboardfromTexasInstrumentthatworksat80MHz.ThefirstactuatorthatwearegoingtodiscussisaDCgearedmotorwithanencoder.ADCgearedmotorworksusingdirectcurrent,andhasgearreductiontoreducetheshaftspeedandincreasethetorqueofthefinalshaft.Thesekindofmotorsareveryeconomicandwecanusethiskindofmotorinourrobotprototype.

Inthefirstsectionofthischapter,wewilldealwiththedesignofourrobotdrivesystem.TheDrivesystemofourrobotconsistsoftwoDCgearedmotorswithencodersandamotordriver.ThemotordriveriscontrolledbyTivaCLaunchPad.WewillseeinterfacingofmotordriverandquadratureencoderwithTivaCLaunchpad.

Inthelastsection,wewillexploresomeofthelatestactuatorswhichcanreplacetheexistingDCgearedmotorwithencoder.Ifthedesiredrobotneedsmorepayloadandaccuracy,wehaveswitchtothesekindofactuators.

InterfacingDCgearedmotorwithTivaCLaunchPadInthepreviouschapter,weselectedaDCgearedmotorwithanencoderfromPololuandtheembeddedboardfromTexasInstrumentscalledTivaCLaunchPad.WeneedthefollowingcomponentstointerfacethemotorwithLaunchpad:

TwoPololumetalgearmotors37Dx57Lmmwith64countperrevolutionencoderPololuwheel90x10mmandamatchinghubPololudualVNH2SP30motordrivercarrierMD03AAsealedleadacid/LithiumIonbatteryof12VAlogiclevelconvertorof3.3Vto5Vhttps://www.sparkfun.com/products/11978.ATivaCLaunchPadanditscompatibleinterfacingwires

ThefollowingfigureshowstheinterfacingcircuitoftwomotorsusingPololuH-Bridge:

Motorinterfacingcircuit

TointerfacewithLaunchpad,wehavetoconnectalevelshifterboardinbetweenthesetwo.Themotordriverworksin5VbuttheLaunchpadworksin3.3V,sowehavetoconnectalevelshifter,asshowninthefollowingfigure:

Levelshiftercircuit

ThetwogearedDCmotorsareconnectedtoOUT1A,OUT1B,andOUT2A,OUT2Bofthemotordriver.VIN(+)andGND(-)arethesupplyvoltagesofthemotor.TheseDCmotorscanworkwith12Voltsupply,sowegive12Voltastheinputvoltage.Themotordriverwillsupportaninputvoltage

rangeof5.5Vto16V.

Thecontrolsignals/inputpinsofmotordriversareontheleft-handsideofthedriver.Thefirstpinis1DIAG/EN,inmostcasesweleavethispindisconnected.Thesepinsareexternallypulledhighinthedriverboarditself.ThemainuseofthispinistoenableordisabletheH-bridgechip.ItisalsousedtomonitorthefaultyconditionoftheH-bridgeIC.Pins1INAand1INBcontrolthedirectionofrotationofthemotor.The1PWMpinwillswitchthemotortoONandOFFstate.WeachievespeedcontrolusingPWMpins.TheCSpinwillsensetheoutputcurrent.Itwilloutput0.13VoltsperAmpereoftheoutputcurrent.TheVINandGNDpinsgivethesameinputvoltagethatwesuppliedtothemotor.Wearenotusingthesepinshere.The+5V(IN)andGNDpinsarethesupplyforthemotordriverIC.Thesupplytothemotordriverandmotorsisdifferent.

Thefollowingtableshowsthetruthtableoftheinputandoutputcombinations:

INA INB DIAGA/ENA DIAGB/ENB OUTA OUTB CS Operatingmode

1 1 1 1 H H HighImp BraketoVcc

1 0 1 1 H L Isense=Iout/K Clockwise(CW)

0 1 1 1 L H Isense=Iout/K Counterclockwise(CCW)

0 0 1 1 L L HighImp BrakertoGND

ThevalueDIAG/ENpinsarealwayshighbecausethispinisexternallypulledhighinthedriverboarditself.Usingthesesignalcombinations,wecanmovetherobotinanydirectionandbyadjustingthePWMSignal,wecanadjustthespeedofthemotortoo.ThisisthebasiclogicbehindcontrollingaDCmotorusinganH-bridgecircuit.

WhileinterfacingmotortoLaunchpad,wemayrequirealevelshifter.ThisisbecausetheoutputpinsofLaunchpadcanonlysupply3.3Voltbutthemotordriverneeds5Vtotrigger;so,wehavetoconnect3.3Vtoa5Vlogiclevelconvertortostartworking.

Thetwomotorsworkinadifferentialdrivemechanism.Thefollowingsectiondiscussesdifferentialdriveanditsoperation.

DifferentialwheeledrobotTherobotwehavedesignedisadifferentialwheeledrobot.Inadifferentialwheeledrobot,themovementisbasedontwoseparatelydrivenwheelsplacedoneithersideoftherobot'sbody.Itcanchangeitsdirectionbychangingtherelativerateofrotationofitswheels,andhence,doesn'trequireadditionalsteeringmotion.Tobalancetherobot,afreeturningwheelorcasterwheelsmaybeadded.

Thefollowingfigureshowsatypicalrepresentationofdifferentialdrive:

Ifthetwomotorsaremovinginthesamedirection,therobotwillmoveforwardorbackward.Ifonemotorhasmorespeedthantheother,thentherobotturnstotheslowermotorside;sototurnleft,stoptheleftmotorandmovetherightmotor.Thefollowingfigureshowshowweconnectthetwomotorsinourrobot.Thetwomotorsaremountedontheoppositesidesofthebaseplateandweputtwocastersinfrontandbackoftherobotinordertobalanceit:

Topviewofrobotbase

Next,wecanprogramthemotorcontrollerusingLaunchpadaccordingtothetruthtabledata.ProgrammingisdoneusinganIDEcalledEnergia(http://energia.nu/).WeareprogrammingLaunchpadusingalanguagecalledWiring(http://wiring.org.co/).

InstallingtheEnergiaIDEWecandownloadthelatestversionofEnergiafromthefollowinglink:

http://energia.nu/download/

WewilldiscusstheinstallationproceduremainlyonUbuntu14.04.2,64-bit.TheEnergiaversionthatwewilluseis0101E0013:

1. DownloadEnergiaforLinux64-bitfromtheabovelink.2. ExtracttheEnergiacompressedfileintotheHomefolderoftheuser.3. AddrulestosetreadandwritepermissiontoTivaCLaunchPad.Thisisessentialforwriting

firmwaretoLaunchpad.ThefollowingcommandwilladdpermissionforUSBdevice:

$echo'ATTRS{idVendor}=="1cbe",ATTRS{idProduct}=="00fd",GROUP="users",

MODE="0660"'|\

sudotee/etc/udev/rules.d/99-tiva-launchpad.rules

4. Afterenteringthecommand,plugLaunchpadtoPC.5. StartEnergiausingthefollowingcommandinsidethefolder:

$./energia

ThefollowingscreenshotshowstheEnergiaIDE:

6. Now,selecttheboardbynavigatingtoTools|Boards|Launchpad(TivaC)w/tm4c123(80MHz)asshowninthefollowingscreenshot:

7. Then,selecttheSerialPortbynavigatingtoTools|SerialPort|/dev/ttyACM0asshowninthefollowingscreenshot:

8. Compilethecodeusingthecompilebutton.Thescreenshotofasuccessfulcompilationisgivenhere:

9. Aftersuccessfulcompilation,uploadthecodeintotheboardbyclickingontheUploadbutton.Theuploadedcodewasanemptycodewhichperformsnooperations.

Iftheuploadingissuccessful,thefollowingmessagewillbeshown:

UsethefollowingtutorialtoinstallEnergiaonMacOSXandWindows:

Refertohttp://energia.nu/Guide_MacOSX.htmlforMacOSXRefertohttp://energia.nu/Guide_Windows.htmlforWindows

InterfacingcodeThefollowingcodecanbeusedtotestthetwomotorsindifferentialdriveconfiguration.Thiscodecanmovetherobotforwardfor5secondsandbackwardfor5seconds.Then,itmovestherobottotheleftfor5secondsandrightfor5seconds.Aftereachmovement,therobotwillstopfor1second.

Atthebeginningofthecode,wedefinepinsforINA,INB,andPWMofthetwomotorsasfollows:

///LeftMotorPins

#defineINA_112

#defineINB_113

#definePWM_1PC_6

///RightMotorPins

#defineINA_25

#defineINB_26

#definePWM_2PC_5

ThepinoutforLaunchpadisgivenat:

http://energia.nu/pin-maps/guide_tm4c123launchpad/

Thefollowingcodeshowsthefivefunctionstomovetherobotforward,backward,leftandright.Thefifthfunctionistostoptherobot.WewillusethedigitalWrite()functiontowriteadigitalvaluetoapin.ThefirstargumentofdigitalWrite()isthepinnumberandsecondargumentisthevaluetobewrittentothepin.ThevaluecanbeHIGHorLOW.WewillusetheanalogWrite()functiontowriteaPWMvaluetoapin.ThefirstargumentofthisfunctionisthepinnumberandsecondisthePWMvalue.Therangeofthisvalueisfrom0-255.AthighPWM,themotordriverwillswitchfastandhavemorespeed.AtlowPWM,switchinginsidethemotordriverwillbeslow,sothemotorwillalsobeslow.Currently,wearerunningatfullspeed.

voidmove_forward()

//SettingCWrotationtoandLeftMotorandCCWtoRightMotor

//LeftMotor

digitalWrite(INA_1,HIGH);

digitalWrite(INB_1,LOW);

analogWrite(PWM_1,255);

//RightMotor

digitalWrite(INA_2,LOW);

digitalWrite(INB_2,HIGH);

///////////////////////////////////////////////////////

voidmove_left()

//LeftMotor

//RightMotor

//////////////////////////////////////////////////////

voidmove_right()

//LeftMotor

//RightMotor

////////////////////////////////////////////////////////

voidstop()

//LeftMotor

//RightMotor

/////////////////////////////////////////////////

voidmove_backward()

//LeftMotor

//RightMotor

WefirstsettheINA,INBpinsofthetwomotortotheOUTPUTmode,sothatwecanwriteHIGHorLOWvaluestothesepins.ThefunctionpinMode()isusedtosetthemodeoftheI/Opin.ThefirstargumentofpinMode()isthepinnumberandsecondargumentisthemode.Wecansetapinasinputoroutput.Tosetapinasoutput,giveOUTPUTargumentasthesecondargument;tosetitasinput,giveINPUTasthesecondargumentasshowninfollowingcode.ThereisnoneedtosetthePWMpinastheoutputbecauseanalogWrite()writesthePWMsignalwithoutsettingpinMode():

voidsetup()

//SettingLeftMotorpinasOUTPUT

pinMode(INA_1,OUTPUT);

pinMode(INB_1,OUTPUT);

pinMode(PWM_1,OUTPUT);

//SettingRightMotorpinasOUTPUT

pinMode(INA_2,OUTPUT);

pinMode(INB_2,OUTPUT);

pinMode(PWM_2,OUTPUT);

Thefollowingsnippetisthemainloopofthecode.Itwillcalleachfunction,moveforward(),move_backward(),move_left(),andmove_right()for5seconds.Aftercallingeachfunction,therobotstopsfor1second.

voidloop()

//Moveforwardfor5sec

move_forward();

delay(5000);

//Stopfor1sec

stop();

delay(1000);

//Movebackwardfor5sec

move_backward();

delay(5000);

//Stopfor1sec

stop();

delay(1000);

//Moveleftfor5sec

move_left();

delay(5000);

//Stopfor1sec

stop();

delay(1000);

//Moverightfor5sec

move_right();

delay(5000);

//Stopfor1sec

stop();

delay(1000);

InterfacingquadratureencoderwithTivaCLaunchpadThewheelencoderisasensorattachedtothemotortosensethenumberofrotationsofthewheel.Ifweknowthenumberofrotations,wecancomputethedisplacement,velocity,acceleration,andangleofthewheel.

Forthisrobot,wehavechosenamotorwithanin-builtencoder.Thisencoderisaquadraturetype,whichcansenseboththedirectionandspeedofthemotor.Encodersusedifferenttypesofsensors,suchasopticalandhallsensors,todetecttheseparameters.ThisencoderusesHalleffecttosensetherotation.Thequadratureencoderhastwochannels,namelyChannelAandChannelB.Eachchannelwillgeneratedigitalsignalswithninetydegreephaseshift.Thefollowingfigureshowsthewaveformofatypicalquadratureencoder:

Quadratureencoderwaveforms

Ifthemotorrotatesclockwise,ChannelAwillleadChannelB,andifthemotorrotatescounterclockwise,ChannelBwillleadChannelA.Thisreadingwillbeusefultosensethedirectionofrotationofthemotor.Thefollowingsectiondiscusseshowwecantranslatetheencoderoutputtousefulmeasurementslikedisplacementandvelocity.

ProcessingencoderdataEncoderdataisatwochannelpulseoutwith90degreeoutofphase.Usingthisdata,wecanfindthedirectionofrotationandhowmanytimesthemotorhasrotated,andtherebyfindthedisplacementandvelocity.

Someofthetermsthatspecifyencoderresolutionarepulsesperrevolution(PPR)orlinesperrevolution(LPR)andcountsperrevolution(CPR).PPRspecifieshowmanyelectricalpulses(0to1transitions)therewillbeduringonerevolutionofamotor'sfinalshaft.SomemanufacturersusethenameCPRinsteadofPPR.Becauseeachpulsewillcontaintwoedges(risingandfalling)andthere

aretwopulsechannels(AandB)witha90degreephaseshift,thetotalnumberofedgeswillbefourtimesthenumberofPPR.Mostquadraturereceiversusethesocalled4Xdecodingtocountalltheedgesfromanencoder'sAandBchannelsyielding4XresolutioncomparedtotherawPPRvalue.

Inourmotor,PololuspecifiesthattheCPRis64forthemotorshaft,whichcorrespondsto8400CPRofthegearbox'soutputshaft.Ineffect,weget8400countsfromthegearboxoutputshaftwhenthemotor'sfinalshaftcompletesonerevolution.Thefollowingfigureshowshowwecancomputethecountfromtheencoderpulses:

Encoderwaveformwithcountwaveform

Inthisencoderspecification,theygivethecountperrevolution;itiscalculatedbytheencoderchanneledgetransitions.Onepulseofanencoderchannelcorrespondstofourcounts.Sotoget8400countsinourmotor,thePPRwillbe8400/4=2100.Fromtheprecedingfigure,wewillbeabletocalculatethenumberofcountsinonerevolution,butwealsoneedtosensethedirectionofthemovement.Thisisbecauseirrespectiveofwhethertherobotmovesforwardorbackward,thecountsthatwegetwillbesame;sosensingthedirectionisimportantinordertodecodethesignal.Thefollowingfigureshowshowwecandecodetheencoderpulses:

Ifweobservethecodepattern,wecanunderstandthatitfollowsthe2-bitGraycode.AGraycodeisencodingofnumbers,suchthatadjacentnumbershaveasingledigitdifferingby1.Graycodes(http://en.wikipedia.org/wiki/Gray_code)arecommonlyusedinrotaryencodersforefficientcoding.

Wecanpredictthedirectionofrotationofamotorbystatetransitions.Thestatetransitiontableisgiveninthefollowingfigure:

State Clockwisetransition Counterclockwisetransition

0,0 0,1to0,0 1,0to0,0

1,0 0,0to1,0 1,1to1,0

1,1 1,0to1,1 0,1to1,1

0,1 1,1to0,1 0,0to0,1

Itwillbemoreconvenientifwerepresentitinastatetransitiondiagram:

AftergettingthisGraycode,wecanprocessthepulsesusingamicrocontroller.Thechannelpinsofthemotorhavetobeconnectedtotheinterruptpinsofthemicrocontroller.Sowhenthechannelhasedgetransitions,itwillgenerateaninterruptortriggerinthepins,andifanyinterruptsarrivesinthatpin,aninterruptserviceroutineorsimplyafunctionwillbeexecutedinsidethemicrocontrollerprogram.Itcanreadthecurrentstateofthetwopins.Accordingtothecurrentstateofpinsandpreviousvalues,wecandeterminethedirectionofrotationandcandecidewhetherwehavetoincrementordecrementthecount.Thisisthebasiclogicofencoderhandling.

Aftergettingthecount,wecancalculatetheangleofrotation(indegrees)usingAngle=(CountValue/CPR)*360.Here,ifwesubstituteCPRwith8400,theequationbecomesAngle=0.04285*CountValue,thatis,forturningonedegree,24countshavetobereceivedor6encodedchannelpulseshavetocome.

ThefollowingfigureshowstheinterfacingcircuitofonemotorencoderwithTivaCLaunchPad:

InterfacingMotorencoderwithTivaCLaunchpad

Themaximumlevelofoutputpulseisbetween0Vto5Vfromtheencoder.Inthiscase,wecandirectlyinterfacetheencoderwithLaunchpadbecauseitcanreceiveinputofupto5V,orwecanusea3.3Vto5Vlevelshifterlikeweusedformotordriverinterfacingearlier.

Inthenextsection,wewillwriteacodeinEnergiatotestthequadratureencodersignal.Weneedtocheckwhetherwegetapropercountfromencoder.

QuadratureencoderinterfacingcodeThiscodewillprintthecountoftheleftandrightmotorencoderviaaserialport.Thetwoencodersarein2Xdecodingscheme,sowewillget4200CPR.Inthefirstsectionofthecode,wearedefiningpinsfortwochanneloutputsoftwoencodersandwearedeclaringthecountvariablefortwoencoders.Theencodervariableusesavolatilekeywordbeforethevariabledatatype.

ThemainuseofvolatileisthatthevariablewithvolatilekeywordwillbestoredintheRAM,whereasnormalvariablesareinCPUregisters.Encodervalueswillchangeveryquickly,sousinganordinaryvariablewillnotbeaccurate.Inordertogetaccuracy,wewillusevolatileforencodervariables,asfollows:

//Encoderpinsdefinition

//Leftencoder

#defineLeft_Encoder_PinA31

#defineLeft_Encoder_PinB32

volatilelongLeft_Encoder_Ticks=0;

//Variabletoreadcurrentstateofleftencoderpin

volatileboolLeftEncoderBSet;

//RightEncoder

#defineRight_Encoder_PinA33

#defineRight_Encoder_PinB34

volatilelongRight_Encoder_Ticks=0;

//Variabletoreadcurrentstateofrightencoderpin

volatileboolRightEncoderBSet;

Thefollowingcodesnippetisthedefinitionofthesetup()function.Inwiringlanguage,setup()isabuilt-infunctionusedforinitializationandforone-timeexecutionofvariablesandfunctions.Insidesetup(),weinitializetheserialdatacommunicationwithabaudrateof115200andcallauser-definedfunctionSetupEncoders()toinitializepinsoftheencoders.Theserialdatacommunicationismainlydonetochecktheencodercountviatheserialterminal.

voidsetup()

//InitSerialportwith115200buadrate

Serial.begin(115200);

SetupEncoders();

ThedefinitionofSetupEncoders()isgiveninthecodethatfollows.Toreceivetheencoderpulse,weneedtwopinsinLaunchpadastheinput.ConfiguretheencoderpinstoLaunchpadastheinputandactivateitspull-upresistor.TheattachInterrupt()functionwillconfigureoneoftheencoderpinsasaninterrupt.TheattachInterrupt()functionhasthreearguments.Firstargumentisthepinnumber,secondargumentistheInterruptServiceRoutine(ISR),andthethirdargumentistheinterruptcondition,thatis,theconditioninwhichtheinterrupthastofireISR.Inthiscode,weareconfiguringPinAoftheleftandrightencoderpinsastheinterrupt;itcallstheISRwhenthereisariseinthepulse.

voidSetupEncoders()

//Quadratureencoders

//Leftencoder

pinMode(Left_Encoder_PinA,INPUT_PULLUP);

//setspinAasinput

pinMode(Left_Encoder_PinB,INPUT_PULLUP);

//setspinBasinput

attachInterrupt(Left_Encoder_PinA,do_Left_Encoder,RISING);

//Rightencoder

pinMode(Right_Encoder_PinA,INPUT_PULLUP);

//setspinAasinput

pinMode(Right_Encoder_PinB,INPUT_PULLUP);

//setspinBasinput

attachInterrupt(Right_Encoder_PinA,do_Right_Encoder,RISING);

Thefollowingcodeisthebuilt-inloop()functioninwiringlanguage.Theloop()functionisaninfiniteloopwhereweputourmaincode.Inthiscode,wecalltheUpdate_Encoders()functiontoprinttheencodervaluecontinuouslythroughserialterminal.

voidloop()

Update_Encoders();

ThefollowingcodeisthefunctiondefinitionoftheUpdate_Encoders()function.Itprintstwoencodervaluesinalinewithastartingcharacter"e",andthevaluesareseparatedbytabspaces.TheSerial.print()functionisabuilt-infunctionthatwillprintthecharacter/stringgivenastheargument.

voidUpdate_Encoders()

Serial.print("e");

Serial.print("\t");

Serial.print(Left_Encoder_Ticks);

Serial.print("\t");

Serial.print(Right_Encoder_Ticks);

Serial.print("\n");

ThefollowingcodeistheISRdefinitionoftheleftandrightencoders.Whenarisingedgeisdetectedoneachofthepins,oneoftheISRswillbecalled.ThecurrentinterruptpinsarePinAofeachoftheencoders.Aftergettingtheinterrupt,wecanassumethattherisingPinAhasahighervaluestate,sothereisnoneedtoreadthatpin.ReadPinBofboththeencodersandstorethepinstatetoLeftEncoderBSetorRightEncoderBSet.ThecurrentstateiscomparedtothepreviousstateofPinBandcandetectthedirectionanddecidewhetherthecounthastobeincrementedordecrementedaccordingtothestatetransitiontable.

voiddo_Left_Encoder()

LeftEncoderBSet=digitalRead(Left_Encoder_PinB);

//readtheinputpin

Left_Encoder_Ticks-=LeftEncoderBSet?-1:+1;

voiddo_Right_Encoder()

RightEncoderBSet=digitalRead(Right_Encoder_PinB);

//readtheinputpin

Right_Encoder_Ticks+=RightEncoderBSet?-1:+1;

UploadthesketchandviewtheoutputusingtheserialmonitorinEnergia.NavigatetoTools|Serial

monitor.Movethetwomotorsmanuallyandyoucanseethecountchanging.Setthebaudrateintheserialmonitor,whichisthesameasinitializedinthecode;inthiscase,itis115200.

Theoutputwilllooklikethis:

Ifwewanttoupgradetherobottohighaccuracyandpayload,wehavetothinkabouthighqualityactuatorssuchasDynamixel.Dynamixelsareintelligentactuators,whichhavein-builtPIDcontrolandmonitoringoftheservoandencoderparameters,suchastorque,position,andsoon.

WorkingwithDynamixelactuatorsDynamixelisakindofnetworkedactuatorforrobotsdevelopedbyKoreanmanufactureROBOTIS.Itiswidelyusedbycompanies,universities,andhobbyistsduetoitsversatileexpansioncapability,powerfeedbackfunction,position,speed,internaltemperature,inputvoltage,andsoon.

TheDynamixelservoscanbeconnectedinadaisychain;itisamethodofconnectingdeviceinaserialfashion,thatis,connectingonedevicetoanotherthroughtheconnecteddevices,andcancontrolalltheconnectedservosfromonecontroller.DynamixelservoscommunicateviaRS485orTTL.ThelistofavailableDynamixelservosisgivenathttp://www.robotis.com/xe/dynamixel_en.

TheinterfacingofDynamixelisveryeasy.DynamixelcomeswithacontrollercalledUSB2Dyanmixel,whichwillconvertUSBtoDynamixelcompatibleTTL/RS485levels.ThefollowingfigureshowstheinterfacingdiagramofDynamixel:

ROBOTISprovidesDynamixelSDKforaccessingmotorregisters;wecanreadandwritevaluestoDynamixelregistersandretrievedatasuchasposition,temperature,voltage,andsoon.

TheinstructionstosetUSB2DynamixelandDynamixelSDKaregivenatsupport.robotis.com/en/.

DynamixelcanbeprogramedusingPythonlibraries.OneofthePythonlibrariesforhandlingDynamixelservosispydynamixel.ThispackageisavailableforWindowsandLinux.PydynamixelwillsupportRX,MX,andEXseriesservos.

WecandownloadthepydynamixelPythonpackagefromhttps://pypi.python.org/pypi/dynamixel/.

Downloadthepackageandextractittothehomefolder.Openaterminal/DOSpromptandexecutethefollowingcommand:

sudopythonsetup.pyinstall

Afterinstallingthepackage,wecantrythefollowingPythonexample,whichwilldetecttheservoattachedtotheUSB2Dynamixelandwritesomerandompositiontotheservo.ThisexamplewillworkwithRXandMXservos.

ThefollowingcodewillimportthenecessaryPythonmodulesrequiredforthisexample.ThisincludesDynamixelPythonmodulestoo:

importos

importdynamixel

importtime

importrandom

ThefollowingcodedefinesthemainparametersneededforDynamixelcommunicationparameters.ThenServosvariabledenotednumberofDynamixelservosconnectedtothebus.TheportNamevariableindicatestheserialportofUSB2DynamixeltowhichDynamixelservosareconnected.ThebaudRatevariableisthecommunicationspeedofUSB2DynamixelandDynamixel.

#ThenumberofDynamixelsonourbus.

nServos=1

#Setyourserialportaccordingly.

ifos.name=="posix":

portName="/dev/ttyUSB0"

portName="COM6"

#DefaultbaudrateoftheUSB2Dynamixeldevice.

baudRate=1000000

ThefollowingcodeistheDynamixelPythonfunctiontoconnecttoDynamixelservos.Ifitisconnected,theprogramwillprintitandscanthecommunicationbustofindthenumberofservosstartingfromID1to255.TheServoIDistheidentificationofeachservo.WearegivennServosas1,soitwillstopscanningaftergettingoneservoonthebus:

#Connecttotheserialport

print"Connectingtoserialport",portName,'...',

serial=dynamixel.serial_stream.SerialStream(port=portName,baudrate=baudRate,

timeout=1)

print"Connected!"

net=dynamixel.dynamixel_network.DynamixelNetwork(serial)

net.scan(1,nServos)

ThefollowingcodewillappendtheDynamixelIDandtheservoobjecttothemyActuatorslist.Wecanwriteservovaluestoeachservousingservoidandservoobject.WecanusethemyActuatorslistforfurtherprocessing:

#Alisttoholdthedynamixels

myActuators=list()

printmyActuators

Thiswillcreatealistforstoringdynamixelactuatorsdetails.

print"ScanningforDynamixels...",

fordyninnet.get_dynamixels():

printdyn.id,

myActuators.append(net[dyn.id])

print"...Done"

Thefollowingcodewillwriterandompositionsfrom450to600toeachDynamixelactuatorthatisavailableonthebus.TherangeofpositionsinDynamixelis0to1023.Thiswillsettheservoparameterssuchasspeed,torque,torque_limt,max_torque,andsoon:

#Setthedefaultspeedandtorque

foractuatorinmyActuators:

actuator.moving_speed=50

actuator.synchronized=True

actuator.torque_enable=True

actuator.torque_limit=800

actuator.max_torque=800

Thefollowingcodewillprintthecurrentpositionofthecurrentactuator:

#Movetheservosrandomlyandprintouttheircurrentpositions

whileTrue:

actuator.goal_position=random.randrange(450,600)

net.synchronize()

Thefollowingcodewillreadalldatafromactuators:

actuator.read_all()

time.sleep(0.01)

printactuator.cache[dynamixel.defs.REGISTER['Id']],

actuator.cache[dynamixel.defs.REGISTER['CurrentPosition']]

time.sleep(2)

Questions1. WhatistheH-Bridgecircuit?2. Whatisaquadratureencoder?3. Whatisthe4Xencodingscheme?4. Howdowecalculatedisplacementfromencoderdata?5. WhatarethefeaturesoftheDynamixelactuator?

SummaryInthischapterwehavediscussedtheinterfacingofmotorthatweareusinginourrobot.WehaveseenmotorandencoderinterfacingwithacontrollerboardcalledTivaCLaunchPad.Wehavediscussedthecontrollercodeforinterfacingmotorandencoder.Inthefuture,iftherobotrequireshighaccuracyandtorque,wehaveseenDynamixelservosthatcansubstitutecurrentDCmotors.Inthenextchapter,wewillseedifferentkindsofsensorsthatcanbeusedinrobotsanditsinterfacing.

Chapter6.WorkingwithRoboticSensorsInthepreviouschapter,wehaveseentheinterfacingofsomeactuatorsforourservicerobot.Thenextimportantsectionthatweneedtocoverisabouttheroboticsensorsusedinthisrobot.

Weareusingsensorsinthisrobottofindthedistancefromanobstacle,togettherobotodometrydata,andforroboticvisionandacoustics.

Thesensorsareultrasonicdistancesensors,orIRproximitysensorsareusedtodetecttheobstaclesandtoavoidcollisions.ThevisionsensorssuchasKinecttoacquire3Ddataoftheenvironment,forvisualodometry;objectdetection,forcollisionavoidance;andaudiodevicessuchasspeakersandmics,forspeechrecognitionandsynthesis.

Inthischapter,wearenotincludingvisionandaudiosensorsinterfacingbecauseintheupcomingchapterwewilldiscussthemandtheirinterfacingindetail.

WorkingwithultrasonicdistancesensorsOneofthemostimportantfeaturesofamobilerobotisnavigation.Anidealnavigationmeansarobotcanplanitspathfromitscurrentpositiontothedestinationandcanmovewithoutanyobstacles.Weuseultrasonicdistancesensorsinthisrobotfordetectingobjectsincloseproximitythatcan'tbedetectedusingtheKinectsensor.AcombinationofKinectandultrasonicsoundsensorsprovidesidealcollisionavoidanceforthisrobot.

Ultrasonicdistancesensorsworkinthefollowingmanner.Thetransmitterwillsendanultrasonicsoundwhichisnotaudibletohumanears.Aftersendinganultrasonicwave,itwillwaitforanechoofthetransmittedwave.Ifthereisnoecho,itmeanstherearenoobstaclesinfrontoftherobot.Ifthereceivingsensorreceivesanecho,apulsewillbegeneratedonthereceiver,anditcancalculatethetotaltimethewavewilltaketotraveltotheobjectandreturntothereceiversensors.Ifwegetthistime,wecancomputethedistancetotheobstacleusingthefollowingformula:

SpeedofSound*TimePassed/2=DistancefromObject.

Here,thespeedofsoundcanbetakenas340m/s.

Mostoftheultrasonicrangesensorshaveadistancerangefrom2cmto400cm.Inthisrobot,weuseasensormodulecalledHC-SR04.WecanseehowtointerfaceHC-SR04withTivaCLaunchPadtogetthedistancefromtheobstacles.

InterfacingHC-SR04toTivaCLaunchPadThefollowingfigureistheinterfacingcircuitoftheHC-SR04ultrasonicsoundsensorwithTivaCLaunchPad:

InterfacingdiagramofLaunchpadandHC-SR04

Theworkingvoltageoftheultrasonicsensoris5Vandtheinput/outputofthissensorisalso5Volt,soweneedalevelshifterontheTrigandEchopinsfortheinterfacingintothe3.3VlevelLaunchpad.Inthelevelshifter,weneedtoapplyhighvoltage,thatis,5Volt,andlowvoltage,thatis,3.3Volt,asshowninthefigure,toswitchfromoneleveltoanotherlevel.TrigandEchopinsareconnectedonthehighvoltagesideofthelevelshifterandthelowvoltagesidepinsareconnectedtoLaunchpad.TheTrigpinandEchopinareconnectedtothe10thand9thpinsofLaunchpad.Afterinterfacingthesensor,wecanseehowtoprogramthetwoI/Opins.

WorkingofHC-SR04

Thetimingdiagramofwaveformoneachpinisshowninthefollowingdiagram.Weneedtoapplyashort10µspulsetothetriggerinputtostarttherangingandthenthemodulewillsendoutaneightcycleburstofultrasoundat40KHzandraiseitsecho.Theechoisadistanceobjectthatispulsewidthandtherangeinproportion.Youcancalculatetherangethroughthetimeintervalbetweensendingtriggersignalsandreceivingechosignalsusingthefollowingformula:

Range=highleveltimeofechopinoutput*velocity(340M/S)/2.

Itwillbebettertouseadelayof60msbeforeeachtrigger,toavoidoverlappingbetweenthetriggerandecho:

InterfacingcodeofTivaCLaunchPad

ThefollowingEnergiacodeforLaunchpadreadsvaluesfromtheultrasoundsensorandmonitorsthevaluesthroughaserialport.

ThefollowingcodedefinesthepinsinLaunchpadtohandleultrasonicechoandtriggerpinsandalsodefinesvariablesforthedurationofthepulseandthedistanceincentimeters:

constintecho=9,Trig=10;

longduration,cm;

Thefollowingcodesnippetisthesetup()function.Thesetup()functioniscalledwhenasketch/codestarts.Usethistoinitializevariables,pinmodes,startusinglibraries,andsoon.Thesetupfunctionwillonlyrunonce,aftereachpoweruporresetoftheLaunchpadboard.Insidesetup(),weinitializeserialcommunicationwithabaudrateof115200andsetupthemodeofultrasonichandlingpinsbycallingafunctionSetupUltrasonic();

voidsetup()

SetupUltrasonic();

Thefollowingisthesetupfunctionfortheultrasonicsensor;itwillconfiguretheTriggerpinasOUTPUTandtheEchopinasINPUT.ThepinMode()functionisusedtosetthepinasINPUTorOUTPUT.

voidSetupUltrasonic()

pinMode(Trig,OUTPUT);

pinMode(echo,INPUT);

Aftercreatingasetup()function,whichinitializesandsetstheinitialvalues,theloop()functiondoespreciselywhatitsnamesuggests,andloopsconsecutively,allowingyourprogramtochangeandrespond.UseittoactivelycontroltheLaunchpadboard.

Themainloopofthisisinthefollowingcode.ThisfunctionisaninfiniteloopandcallstheUpdate_Ultra_Sonic()functiontoupdateandprinttheultrasonicreadingsthroughaserialport:

voidloop()

Update_Ultra_Sonic();

delay(200);

ThefollowingcodeisthedefinitionoftheUpdate_Ultra_Sonic()function.Thisfunctionwilldothefollowingoperations.First,itwilltakethetriggerpintotheLOWstatefor2microsecondsandHIGHfor10microseconds.After10microseconds,itwillagainreturnthepintotheLOWstate.Thisisaccordingtothetimingdiagram.Wealreadysawthat10µsisthetriggerpulsewidth.

Aftertriggeringwith10µs,wehavetoreadthetimedurationfromtheEchopin.Thetimedurationisthetimetakenforthesoundtotravelfromthesensortotheobjectandfromtheobjecttothesensorreceiver.WecanreadthepulsedurationbyusingthepulseIn()function.Aftergettingthetimeduration,wecanconvertthetimeintocentimetersbyusingthemicrosecondsToCentimeters()function,asshowninthefollowingcode:

voidUpdate_Ultra_Sonic()

digitalWrite(Trig,LOW);

delayMicroseconds(2);

digitalWrite(Trig,HIGH);

delayMicroseconds(10);

digitalWrite(Trig,LOW);

duration=pulseIn(echo,HIGH);

//convertthetimeintoadistance

cm=microsecondsToCentimeters(duration);

//Sendingthroughserialport

Serial.print("distance=");

Serial.print("\t");

Serial.print(cm);

Serial.print("\n");

Thefollowingcodeistheconversionfunctionfrommicrosecondstodistanceincentimeters.Thespeedofsoundis340m/s,thatis,29microsecondspercentimeter.Sowegetthetotaldistancebydividingthetotalmicrosecondsby29/2:

longmicrosecondsToCentimeters(longmicroseconds)

returnmicroseconds/29/2;

Afteruploadingthecode,opentheserialmonitorfromtheEnergiamenuunderTools|SerialMonitorandchangethebaudrateinto115200.Youcanseethevaluesfromtheultrasonicsensor,likethis:

Outputoftheenergiaserialmonitor

InterfacingTivaCLaunchPadwithPython

Inthissection,wecanseehowtoconnectTivaCLaunchPadwithPythontoreceivedatafromLaunchpad.

ThePySerialmodulecanbeusedforinterfacingLaunchpadtoPython.ThedetaileddocumentationofPySerialanditsinstallationprocedureforWindow,Linux,andOSXisonthefollowinglink:

http://pyserial.sourceforge.net/pyserial.html

PySerialisavailableintheUbuntupackagemanageranditcanbeeasilyinstalledinUbuntuusingthefollowingcommandinterminal:

$sudoapt-getinstallpython-serial

Afterinstallingthepython-serialpackage,wecanwriteapythoncodetointerfaceLaunchpad.Theinterfacingcodeisgiveninfollowingsection.

Thefollowingcodeimportsthepythonserialmoduleandthesysmodule.TheserialmodulehandlestheserialportsofLaunchpadandperformsoperationssuchasreading,writing,andsoon.Thesysmoduleprovidesaccesstosomevariablesusedormaintainedbytheinterpreterandtofunctionsthatinteractstronglywiththeinterpreter.Itisalwaysavailable:

importserial

importsys

WhenweplugLaunchpadtothecomputer,thedeviceregistersontheOSasavirtualserialport.InUbuntu,thedevicenamelookslike/dev/ttyACMx.Wherexcanbeanumber,ifthereisonlyonedevice,itwillprobablybe0.TointeractwiththeLaunchpad,weneedtohandlethisdevicefileonly.

Thefollowingcodewilltrytoopentheserialport/dev/ttyACM0ofLaunchpadwithabaudrateof115200.Ifitfails,itwillprintUnabletoopenserialport.

ser=serial.Serial('/dev/ttyACM0',115200)

except:

print"Unabletoopenserialport"

Thefollowingcodewillreadtheserialdatauntiltheserialcharacterbecomesanewline('\n')andprintsitontheterminal.IfwepressCtrl+Conthekeyboard,toquittheprogram,itwillexitbycallingsys.exit(0).

whileTrue:

line=ser.readline()

printline

except:

print"Unabletoreadfromdevice"

sys.exit(0)

Aftersavingthefile,changethepermissionofthefiletoexecutableusingthefollowingcommand:

$sudochmod+Xscript_name

$./script_name

Theoutputofthescriptwilllooklikethis:

WorkingwiththeIRproximitysensorInfraredsensorsareanothermethodtofindobstaclesandthedistancefromtherobot.Theprincipleofinfrareddistancesensorsisbasedontheinfraredlightthatisreflectedfromasurfacewhenhittinganobstacle.AnIRreceiverwillcapturethereflectedlightandthevoltageismeasuredbasedontheamountoflightreceived.

OneofthepopularIRrangesensorsisSharpGP2D12,theproductlinkisasfollows:

http://www.robotshop.com/en/sharp-gp2y0a21yk0f-ir-range-sensor.html

ThefollowingfigureshowstheSharpGP2D12sensor:

ThesensorsendsoutabeamofIRlightandusestriangulationtomeasurethedistance.ThedetectionrangeoftheGP2D12isbetween10cmand80cm.Thebeamis6cmwideatadistanceof80cm.ThetransmissionandreflectionoftheIRlightsensorisillustratedinthefollowingfigure:

OntheleftofthesensorisanIRtransmitter,whichcontinuouslysendsIRradiation,afterhittingintosomeobjects,theIRlightwillreflectanditwillbereceivedbytheIRreceiver.TheinterfacingcircuitoftheIRsensorisshownhere:

TheanalogoutpinVocanbeconnectedtotheADCpinofLaunchpad.TheinterfacingcodeoftheSharpdistancesensorwiththeTivaCLaunchpadisgivenfurtherinthissection.Inthiscode,weselectthe18thpinofLaunchpadandsetittotheADCmodeandreadthevoltagelevelsfromtheSharpdistancesensor.TherangeequationoftheGP2D12IRsensorisgivenasfollows:

Range=(6787/(Volt-3))–4

Here,VoltistheanalogvoltagevaluefromADCoftheVoutpin.

Inthisfirstsectionofthecode,wesetthe18thpinofTivaCLaunchPadastheinputpinandstartaserialcommunicationatabaudrateof115200:

intIR_SENSOR=18;//SensorisconnectedtotheanalogA3

intintSensorResult=0;//Sensorresult

floatfltSensorCalc=0;//Calculatedvalue

voidsetup()

Serial.begin(115200);//Setupcommunicationwithcomputertopresentresults

serialmonitor

Inthefollowingsectionofcode,thecontrollercontinuouslyreadstheanalogpinandconvertsittothedistancevalueincentimeters:

voidloop()

//readthevaluefromtheirsensor

intSensorResult=analogRead(IR_SENSOR);//Getsensorvalue

//Calculatedistanceincmaccordingtotherangeequation

fltSensorCalc=(6787.0/(intSensorResult-3.0))-4.0;

Serial.print(fltSensorCalc);//Senddistancetocomputer

Serial.println("cm");//Addcmtoresult

delay(200);//Wait

ThisisthebasiccodetointerfaceaSharpdistancesensor.TherearesomedrawbackswiththeIRsensors.Someofthemareasfollows:

Wecan'tusethemindirectorindirectsunlight,soit'sdifficulttousetheminanoutdoorrobotTheymaynotworkifanobjectisreflectiveTherangeequationonlyworkswithintherange

Inthenextsection,wecandiscussIMUanditsinterfacingwithTivaCLaunchPad.IMUcangivetheodometrydataanditcanbeusedastheinputtonavigationalgorithms.

WorkingwithInertialMeasurementUnitAnInertialMeasurementUnit(IMU)isanelectronicdevicethatmeasuresvelocity,orientation,andgravitationalforcesusingacombinationofaccelerometers,gyroscopes,andmagnetometers.AnIMUhasalotofapplicationsinrobotics;someoftheapplicationsareinbalancingofUnmannedAerialVehicles(UAVs)androbotnavigation.

Inthissection,wediscusstheroleofIMUinmobilerobotnavigationandsomeofthelatestIMUsonthemarketanditsinterfacingwithLaunchpad.

InertialNavigationAnIMUprovidesaccelerationandorientationrelativetoinertialspace,ifyouknowtheinitialposition,velocity,andorientation,youcancalculatethevelocitybyintegratingthesensedaccelerationandthesecondintegrationgivestheposition.Togetthecorrectdirectionoftherobot,theorientationoftherobotisrequired;thiscanbeobtainedbyintegratingsensedangularvelocityfromgyroscope.

Thefollowingfigureillustratesaninertialnavigationsystem,whichwillconvertIMUvaluestoodometricdata:

ThevalueswegetfromtheIMUareconvertedintonavigationalinformationusingnavigationequationsandfeedingintoestimationfilterssuchastheKalmanfilter.TheKalmanfilterisanalgorithmthatestimatesthestateofasystemfromthemeasureddata(http://en.wikipedia.org/wiki/Kalman_filter).ThedatafromInertialNavigationSystem(INS)willhavesomedriftbecauseoftheerrorfromtheaccelerometerandgyroscope.Tolimitthedrift,anINSisusuallyaidedbyothersensorsthatprovidedirectmeasurementsoftheintegratedquantities.Basedonthemeasurementsandsensorerrormodels,theKalmanfilterestimateserrorsinthenavigationequationsandallthecoloredsensors'errors.ThefollowingfigureshowsadiagramofanaidedinertialnavigationsystemusingtheKalmanfilter:

Alongwiththemotorencoders,thevaluefromtheIMUcanbetakenastheodometervalueanditcanbeusedfordeadreckoning,theprocessoffindingthecurrentpositionofamovingobjectbyusingapreviouslydeterminedposition.

Inthenextsection,wearegoingtoseeoneofthemostpopularIMUsfromInvenSensecalledMPU6050.

InterfacingMPU6050withTivaCLaunchPadTheMPU-6000/MPU-6050familyofpartsaretheworld'sfirstandonly6-axismotiontrackingdevicesdesignedforthelowpower,lowcost,andhighperformancerequirementsofsmartphones,tablets,wearablesensors,androbotics.

TheMPU-6000/6050devicescombinea3-axisgyroscopeand3-axisaccelerometeronthesilicondietogetherwithanonboarddigitalmotionprocessorcapableofprocessingcomplex9-axismotionfusionalgorithms.ThefollowingfigureshowsthesystemdiagramofMPU6050andbreakoutofMPU6050:

ThebreakoutboardofMPU6050isshowninthefollowingfigureanditcanbepurchasedfromthefollowinglink:

https://www.sparkfun.com/products/110286

TheconnectionfromLaunchpadtoMPU6050isgiveninthefollowingtable.Theremainingpinscanbeleftdisconnected:

Launchpadpins MPU6050pins

+3.3V VCC/VDD

GND GND

PD0 SCL

PD1 SDA

ThefollowingfigureshowstheinterfacingdiagramofMPU6050andTivaCLaunchpad:

TheMPU6050andLaunchpadcommunicateusingtheI2Cprotocol,thesupplyvoltageis3.3VoltanditistakenfromLaunchpad.

SettinguptheMPU6050libraryinEnergia

TheinterfacingcodeofEnergiaisdiscussedinthissection.Theinterfacingcodeusesthehttps://github.com/jrowberg/i2cdevlib/zipball/masterlibraryforinterfacingMPU6050.

DownloadtheZIPfilefromtheprecedinglinkandnavigatetoPreferencefromFile|PreferenceinEnergia,asshowninthefollowingscreenshot:

GotoSketchbooklocationunderPreferences,asseenintheprecedingscreenshot,andcreateafoldercalledlibraries.ExtractthefilesinsidetheArduinofolderinsidetheZIPfiletothesketchbook/librarieslocation.TheArduinopackagesinthisrepositoryarealsocompatiblewithLaunchpad.TheextractedfilescontaintheI2Cdev,Wire,andMPU6050packagesthatarerequiredfortheinterfacingoftheMPU6050sensor.Thereareothersensorspackagesthatarepresentinthelibrariesfolderbutwearenotusingthemnow.

TheprecedingprocedureisdoneinUbuntu,butitisthesameforWindowsandMacOSX.

InterfacingcodeofEnergiaThiscodeisusedtoreadtherawvaluefromMPU6050toLaunchpad,itusesaMPU6050third-partylibrarythatiscompatiblewithEnergiaIDE.Thefollowingaretheexplanationsofeachblockofthecode.

Inthisfirstsectionofcode,weincludethenecessaryheadersforinterfacingMPU6050toLaunchpadsuchas12C,WireandtheMPU6050libraryandcreateanobjectofMPU6050withthenameaccelgyro.TheMPU6050.hlibrarycontainsaclassnamedMPU6050tosendandreceivedatatoandfromthesensor:

#include"Wire.h"

#include"I2Cdev.h"

#include"MPU6050.h"

MPU6050accelgyro;

Inthefollowingsection,westarttheI2CandserialcommunicationtocommunicatewithMPU6050andprintsensorvaluesthroughtheserialport.Theserialcommunicationbaudrateis115200andSetup_MPU6050()isthecustomfunctiontoinitializetheMPU6050communication:

voidsetup()

Setup_MPU6050();

ThefollowingsectionisthedefinitionoftheSetup_MPU6050()function.TheWirelibraryallowsyoutocommunicatewiththeI2Cdevices.MPU6050cancommunicateusingI2C.TheWire.begin()functionwillstarttheI2CcommunicationbetweenMPU6050andLaunchpad;also,itwillinitializetheMPU6050deviceusingtheinitialize()methoddefinedintheMPU6050class.Ifeverythingissuccessful,itwillprintconnectionsuccessful,otherwiseitwillprintconnectionfailed:

voidSetup_MPU6050()

Wire.begin();

//initializedevice

Serial.println("InitializingI2Cdevices...");

accelgyro.initialize();

//verifyconnection

Serial.println("Testingdeviceconnections...");

Serial.println(accelgyro.testConnection()?"MPU6050connectionsuccessful":

"MPU6050connectionfailed");

Thefollowingcodeistheloop()function,whichcontinuouslyreadsthesensorvalueandprintsitsvaluesthroughtheserialport:TheUpdate_MPU6050()customfunctionisresponsibleforprintingtheupdatedvaluefromMPU6050:

voidloop()

//UpdateMPU6050

Update_MPU6050();

ThedefinitionofUpdate_MPU6050()isgivenasfollows.Itdeclaressixvariablestohandletheaccelerometerandgyroscopevaluein3-axis.ThegetMotion6()functionintheMPU6050classisresponsibleforreadingthenewvaluesfromthesensor.Afterreading,itwillprintviatheserialport:

voidUpdate_MPU6050()

int16_tax,ay,az;

int16_tgx,gy,gz;

//readrawaccel/gyromeasurementsfromdevice

accelgyro.getMotion6(&ax,&ay,&az,&gx,&gy,&gz);

//displaytab-separatedaccel/gyrox/y/zvalues

Serial.print("i");Serial.print("\t");

Serial.print(ax);Serial.print("\t");

Serial.print(ay);Serial.print("\t");

Serial.print(az);Serial.print("\t");

Serial.print(gx);Serial.print("\t");

Serial.print(gy);Serial.print("\t");

Serial.println(gz);

Serial.print("\n");

Theoutputfromtheserialmonitorisshownhere:

Wecanreadthesevaluesusingthepythoncodethatweusedforultrasonic.Thefollowingisthescreenshotoftheterminalwhenwerunthepythonscript:

InterfacingMPU6050toLaunchpadwiththeDMPsupportusingEnergiaInthissection,wewillseetheinterfacingcodeofMPU6050byactivatingDMP,whichcangiveusdirectorientationvaluesinquaternionoryaw,pitch,androll.Thisvaluecanbedirectlyappliedtoourroboticapplicationtoo.

ThefollowingsectionofcodeimportsallthenecessaryheaderfilestointerfaceandcreateanMPU6050objectlikethepreviouscode:

#include"Wire.h"

#include"I2Cdev.h"

#include"MPU6050_6Axis_MotionApps20.h"

//CreatingMPU6050Object

MPU6050accelgyro(0x68);

ThefollowingcodeinitializesanddeclaresvariablestohandleDMP:

//DMPoptions

//SettrueifDMPinitializationwassuccessful

booldmpReady=false;

//HoldsactualinterruptstatusbytefromMPU

uint8_tmpuIntStatus;

//returnstatusaftereachdeviceoperation

uint8_tdevStatus;

//ExpectedDMPpacketsize

uint16_tpacketSize;

//countofallbytescurrentlyinFIFO

uint16_tfifoCount;

//FIFOstoratebuffer

uint8_tfifoBuffer[64];

//Outputformatwillbeinquaternion

#defineOUTPUT_READABLE_QUATERNION

Thefollowingcodedeclaresvariousvariablestohandleorientationvariables:

//quaternionvariable

Quaternionq;

Thefollowingfunctionisaninterruptserviceroutine,whichiscalledwhenMPU6050INT pingeneratesaninterrupt:

//InterruptdetectionroutineforDMPhandling

volatileboolmpuInterrupt=false;

//indicateswhetherMPUinterruptpinhasgonehigh

voiddmpDataReady(){

mpuInterrupt=true;

Thefollowingcodeisthedefinitionofthesetup()function.Itinitializestheserialportwithabaudrateof115200andcallstheSetup_MPU6050()function:

voidsetup()

Setup_MPU6050();

ThefollowingcodeisthedefinitionoftheSetup_MPU6050()function.ItwillinitializeMPU6050andcheckswhetherit'sinitializedornot.Ifit'sinitialized,itwillinitializeDMPbycallingtheSetup_MPU6050_DMP()function:

voidSetup_MPU6050()

Wire.begin();

//initializedevice

Serial.println("InitializingI2Cdevices...");

accelgyro.initialize();

//verifyconnection

Serial.println("Testingdeviceconnections...");

Serial.println(accelgyro.testConnection()?"MPU6050connectionsuccessful":

"MPU6050connectionfailed");

//InitializeDMPinMPU6050

Setup_MPU6050_DMP();

ThefollowingcodeisthedefinitionoftheSetup_MPU6050_DMP()function.ItinitializesDMPandsetsoffsetinthreeaxis.IfDMPisinitialized,itwillstartfunctioningandconfigurethePF_0/PUSH2pinasaninterrupt.WhenthedataisreadyontheMPU6050buffer,aninterruptwillbegenerated,whichwillreadvaluesfromthebus:

//SetupMPU6050DMP

voidSetup_MPU6050_DMP()

//DMPInitialization

devStatus=accelgyro.dmpInitialize();

accelgyro.setXGyroOffset(220);

accelgyro.setXGyroOffset(-85);

if(devStatus==0){

accelgyro.setDMPEnabled(true);

pinMode(PUSH2,INPUT_PULLUP);

attachInterrupt(PUSH2,dmpDataReady,RISING);

mpuIntStatus=accelgyro.getIntStatus();

dmpReady=true;

packetSize=accelgyro.dmpGetFIFOPacketSize();

//Donothing

Thefollowingcodeisthedefinitiontheoftheloop()function.ItwillcallUpdate_MPU6050(),whichwillreadbuffervaluesandprintitontheserialterminal:

voidloop()

//UpdateMPU6050

Update_MPU6050();

ThisisthedefinitionofUpdate_MPU6050(),whichwillcalltheUpdate_MPU6050_DMP()function:

voidUpdate_MPU6050()

Update_MPU6050_DMP();

ThefollowingfunctionreadsfromtheFIFOregisterofMPU6050andthequaternionvaluegetsprintedontheserialterminal:

//UpdateMPU6050DMPfunctions

voidUpdate_MPU6050_DMP()

//DMPProcessing

if(!dmpReady)return;

while(!mpuInterrupt&&fifoCount<packetSize)

mpuInterrupt=false;

mpuIntStatus=accelgyro.getIntStatus();

//getcurrentFIFOcount

fifoCount=accelgyro.getFIFOCount();

if((mpuIntStatus&0x10)||fifoCount>512){

//resetsowecancontinuecleanly

accelgyro.resetFIFO();

elseif(mpuIntStatus&0x02){

//waitforcorrectavailabledatalength,shouldbeaVERYshortwait

while(fifoCount<packetSize)fifoCount=accelgyro.getFIFOCount();

//readapacketfromFIFO

accelgyro.getFIFOBytes(fifoBuffer,packetSize);

//trackFIFOcounthereincasethereis>1packetavailable

//(thisletsusimmediatelyreadmorewithoutwaitingforaninterrupt)

fifoCount-=packetSize;

#ifdefOUTPUT_READABLE_QUATERNION

//displayquaternionvaluesineasymatrixform:wxyz

accelgyro.dmpGetQuaternion(&q,fifoBuffer);

Serial.print("i");Serial.print("\t");

Serial.print(q.x);Serial.print("\t");

Serial.print(q.y);Serial.print("\t");

Serial.print(q.z);Serial.print("\t");

Serial.print(q.w);

Serial.print("\n");

#endif

Theoutputfromtheserialmonitorisshowninthefollowingscreenshot.Theserialmonitorshowsthequaternionvaluesofx,y,z,andwstartingwithan"i"character:

WecanalsousethePythonscripttoviewthesevalues.TheoutputofthePythonscriptisshowninthefollowingscreenshot:

Inthenextchapters,wewillseesomeofthevisionandaudiosensorsthatcanbeusedonthisrobotanditsinterfacingwithPython.

Questions1. Whatareultrasonicsensorsandhowdotheywork?2. Howdoyoucalculatedistancefromtheultrasonicsensor?3. WhatistheIRproximitysensorandhowdoesitwork?4. HowdoyoucalculatedistancefromtheIRsensor?5. WhatisIMUandhowdoyougettheodometricdata?6. WhatistheAidedInertialNavigationsystem?7. WhatarethemainfeaturesofMPU6050?

SummaryInthischapter,wehaveseensomeroboticsensors,whichcanbeusedinourrobot.Thesensorswediscussedareultrasonicdistancesensors,IRproximitysensors,andIMUs.Thesethreesensorshelpinthenavigationoftherobot.WealsodiscussedthebasiccodetointerfacethesesensorstoTivaCLaunchPad.WewillseemoreonvisionandaudiosensorsinterfacingusingPythoninthenextchapter.

Chapter7.ProgrammingVisionSensorsUsingPythonandROSInthepreviouschapter,wehaveseensomeoftheroboticsensorsusedinourrobotanditsinterfacingwiththeLaunchpadboard.Inthischapter,wewillmainlydiscussvisionsensorsanditsinterfaceusedinourrobot.

Therobotwearedesigningwillhavea3DsensorandwecaninterfaceitwithvisionlibrariessuchasOpenCV,OpenNI,andPointCloudLibrary(PCL).Someoftheapplicationsofthe3Dvisionsensorinourrobotareautonomousnavigation,obstacleavoidance,objectdetection,peopletracking,andsoon.

WewillalsodiscusstheinterfacingofvisionsensorsandimageprocessinglibrarieswithROS.Inthelastsectionofthechapter,wewillseeanavigationalalgorithmforourrobotcalledSLAM(SimultaneousLocalizationandMapping)anditsimplementationusinga3Dsensor,ROS,andimageprocessinglibraries.

Inthefirstsection,wewillseesome2Dand3Dvisionsensorsavailableonthemarketthatwewilluseinourrobot.

ListofroboticvisionsensorsandimageprocessinglibrariesA2Dvisionsensororanordinarycameradelivers2Dimageframesofthesurroundings,whereasa3Dvisionsensordelivers2Dimageframesandanadditionalparametercalleddepthofeachimagepoint.Wecanfindthex,y,andzdistanceofeachpointfromthe3Dsensorwithrespecttothesensoraxis.

Therearequiteafewvisionsensorsavailableonthemarket.Someofthe2Dand3Dvisionsensorsthatcanbeusedinourrobotarementionedinthischapter.

Thefollowingfigureshowsthelatest2DvisionsensorcalledPixy/CMUcam5(http://www.cmucam.org/),whichisabletodetectcolorobjectswithhighspeedandaccuracyandcanbeinterfacedtoanArduinoboard.Pixycanbeusedforfastobjectdetectionandtheusercanteachwhichobjectitneedstotrack.PixymodulehasaCMOSsensorandNXP(http://www.nxp.com/)processorforimageprocessing:

Pixy/CMUCam5

Thecommonlyavailable2Dvisionsensorsarewebcams.TheycontainaCMOSsensorandUSBinterface,butthereisnoinbuiltprocessingfortheobjectdetection.ThefollowingimageshowsapopularwebcamfromLogitechthatcancapturepicturesofupto5megapixelresolutionandHDvideos:

LogitechHDCam

Wecantakealookatsomeofthe3Dvisionsensorsavailableonthemarket.SomeofthepopularsensorsareKinect,AsusXtionPro,andCarmine.

Kinect

Kinectisa3DvisionsensorusedalongwiththeMicrosoftXbox360gameconsole.ItmainlycontainsanRGBcamera,aninfraredprojector,adepthsensor,amicrophonearray,andamotorfortilt.TheRGBanddepthcameracaptureimagesataresolutionof640x480at30Hz.TheRGBcameracaptures2Dcolorimages,whereasthedepthcameracapturesmonochromedepthimages.Kinecthasadepthsensingrangefrom0.8mto4m.

SomeoftheapplicationsofKinectare3Dmotioncapture,skeletontracking,facerecognition,andvoicerecognition.

KinectcanbeinterfacedtoPCusingtheUSB2.0interfaceandprogrammedusingKinectSDK,OpenNI,andOpenCV.KinectSDKisonlyavailableforWindowsplatformsandisdevelopedandsuppliedbyMicrosoft.Theothertwolibrariesareopensourceandavailableforallplatforms.TheKinectweareusinghereisthefirstversion;thelatestversionsofKinectonlysupportKinectSDKrunningonWindows.

AsusXtionPro

AsusXtionProisa3DsensordesignedforPC-basedmotionsensingapplications.XtionProisonlyfor3Dsensinganditdoesn'thaveanysoundsensingfacilities.IthasaninfraredprojectorandamonochromeCMOSsensortocapturetheinfrareddata.XtionProcommunicatestothePCviatheUSB2.0interface.XtioncanbepoweredfromtheUSBitselfandcancalculateasensedepthfrom0.8mto3.5mfromthesensor.

TheapplicationsofKinectandXtionProarethesameexceptforvoicerecognition.ItwillworkinWindows,Linux,andMac.WecandevelopapplicationsinXtionProusingOpenNIandOpenCV.

PrimeSenseCarmine

ThePrimeSenseteamdevelopedtheMicrosoftKinect3Dvisionsystem.Later,theydevelopedtheirown3DvisionsensorcalledCarmine.ThetechnologybehindCarmineissimilartoKinect.ItworkswithanIRprojectorandadepthimageCMOSsensor.ThefollowingfigureshowstheblockdiagramofCarmine:

Carmineblockdiagram

SimilartoKinect,CarminehasanRGBCMOSsensor,adepthimageCMOS,andanIRlightsource.Italsohasanarrayofmicrophonesforvoicerecognition.AllsensorsareinterfacedinSystemOn

Chip(SOC).InterfacingandpoweringisperformedthroughUSB.

CarminecancaptureRGBanddepthframesin640x480resolutionandcansensedepthfrom0.35mto3.5m.ComparedtoKinect,theadvantagesaresmallpowerconsumption,smallformfactor,andgooddepthsensingrange.

CarminecanbeinterfacedtoaPCanditwillsupportWindows,Linux,Mac,andAndroidplatforms.CarmineissupportedbyOpenNI;developerscanprogramthedeviceusingOpenNIanditswrapperlibraries.

AppleIncboughtPrimeSenseinNovember2013.YoucanbuyCarmineatthefollowinglink:

http://www.amazon.com/dp/B00KO908MM?psc=1

IntroductiontoOpenCV,OpenNI,andPCLLet'sdiscussaboutthesoftwareframeworksandlibrariesthatweareusinginourrobots.First,wecandiscussOpenCV.Thisisoneofthelibrariesthatwearegoingtouseinthisrobotforobjectdetectionandotherimageprocessingfunctionalities.

WhatisOpenCV?OpenCVisanopensourceBSD-licensedcomputervisionbasedlibrarythatincludeshundredsofcomputervisionalgorithms.Thelibrary,mainlyaimedforreal-timecomputervision,wasdevelopedbyIntelRussiaresearch,andisnowactivelysupportedbyItseez(http://itseez.com/).

OpenCVlogo

OpenCViswrittenmainlyinCandC++anditsprimaryinterfaceisinC++.ItalsohasgoodinterfacesinPython,Java,Matlab/OctaveandwrappersinotherlanguagessuchasC#andRuby.

InthenewversionofOpenCV,thereissupportforCUDAandOpenCLtogetGPUacceleration(http://www.nvidia.com/object/cuda_home_new.html).

OpenCVwillrunonmostoftheOSplatforms(suchasWindows,Linux,MacOSX,Android,FreeBSD,OpenBSD,iOS,andBlackberry).

InUbuntu,OpenCV,andPython,wrappersarealreadyinstalledwhenweinstalltheros-indigo-desktop-fullpackage.Ifthispackageisnotinstalled,thenwecaninstalltheOpenCVlibrary,ROSinterface,andPythoninterfaceofOpenCVusingthefollowingcommand:

$sudoapt-getinstallros-indigo-vision-opencv

IfyouwanttoinstallonlytheOpenCVPythonwrapper,thenusethefollowingcommand:

$sudoapt-getinstallpython-opencv

IfyouwanttotryOpenCVinWindows,youcantrythefollowinglink:

http://docs.opencv.org/doc/tutorials/introduction/windows_install/windows_install.html

ThefollowinglinkwillguideyouthroughtheinstallationprocessofOpenCVonMacOSX:

http://jjyap.wordpress.com/2014/05/24/installing-opencv-2-4-9-on-mac-osx-with-python-support/

ThemainapplicationsofOpenCVareinthefieldof:

ObjectdetectionGesturerecognitionHuman-computerinteractionMobileroboticsMotiontrackingFacialrecognition

NowwecanseehowtoinstallOpenCVinUbuntu14.04.2fromsourcecode.

InstallationofOpenCVfromsourcecodeinUbuntu14.04.2

WecaninstallOpenCVfromsourcecodeinLinuxbasedonthefollowingdocumentationofOpenCV:

http://docs.opencv.org/doc/tutorials/introduction/linux_install/linux_install.html

AftertheinstallationofOpenCV,wecantrysomeexamplesusingthePythonwrappersofOpenCV.

ReadinganddisplayinganimageusingthePython-OpenCVinterface

Thefirstexamplewillloadanimageingrayscaleanddisplayitonscreen.

Inthefollowingsectionofcode,wewillimportthenumpymoduleforimagearraymanipulationandthecv2moduleistheOpenCVwrapperforPythoninwhichwecanaccessOpenCVPythonAPIs.NumPyisanextensiontothePythonprogramminglanguage,addingsupportforlargemultidimensionalarraysandmatricesalongwithalargelibraryofhigh-levelmathematicalfunctionstooperateonthesearrays(https://pypi.python.org/pypi/numpy):

importnumpyasnp

importcv2

Thefollowingfunctionwillreadtherobot.jpgimageandloadthisimageingrayscale.Thefirstargumentofthecv2.imread()functionisthenameoftheimageandthenextargumentisaflagthatspecifiesthecolortypeoftheloadedimage.Iftheflagis>0,theimagereturnsathreechannelRGBcolorimage,iftheflag=0,theloadedimagewillbeagrayscaleimage,andiftheflagis<0,itwillreturnthesameimageasloaded:

img=cv2.imread('robot.jpg',0)

Thefollowingsectionofcodewillshowthereadimageusingtheimshow()function.Thecv2.waitKey(0)functionisakeyboardbindingfunction.Itsargumentistimeinmilliseconds.Ifit's0,itwillwaitindefinitelyforakeystroke:

cv2.imshow('image',img)

cv2.waitKey(0)

Thecv2.destroyAllWindows()functionsimplydestroysallthewindowswecreated:

cv2.destroyAllWindows()

Savetheprecedingcodewithanamecalledimage_read.pyandcopyaJPGfilewithrobot.jpgasitsname.Executethecodeusingthefollowingcommand:

$pythonimage_read.py

Theoutputwillloadanimageingrayscalebecauseweused0asthevalueintheimread()function:

Thefollowingexamplewilltrytoopenwebcam.Theprogramwillquitwhentheuserpressesanybutton.

Capturingfromwebcamera

Thefollowingcodewillcapturethewebcamhavingdevicename/dev/video0or/dev/video1.

WeneedtoimportthefollowingmodulesifweareusingOpenCVAPI's:

importnumpyasnp

importcv2

ThefollowingfunctionwillcreateaVideoCaptureobject.TheVideoCaptureclassisusedtocapture

videosfromvideofilesorcameras.TheinitializationargumentsoftheVideoCaptureclassistheindexofacameraoranameofavideofile.Deviceindexisjustanumbertospecifythecamera.Thefirstcameraindexis0havingdevicename/dev/video0;that'swhyweuse0here:

cap=cv2.VideoCapture(0)

ThefollowingsectionofcodeisloopedtoreadimageframesfromtheVideoCaptureobjectandshowseachframe.Itwillquitwhenanykeyispressed:

while(True):

#Captureframe-by-frame

ret,frame=cap.read()

#Displaytheresultingframe

cv2.imshow('frame',frame)

ifcv2.waitKey(10):

Thefollowingisascreenshotoftheprogramoutput:

YoucanexploremoreOpenCV-Pythontutorialsfromthefollowinglink:

http://opencv-python-tutroals.readthedocs.org/en/latest/py_tutorials/py_tutorials.html

Inthenextsection,wewilllookatOpenNIlibraryanditsapplication.

WhatisOpenNIOpenNIisaMultilanguage,cross-platformframeworkthatdefinesAPI'stowriteapplicationsusingNaturalinteraction(NI).Naturalinteractionisdefinedintermsofexperience.Itmeans,peoplenaturallycommunicatethroughgestures,expressions,movements,anddiscovertheworldbylookingaroundandmanipulatingphysicalstuff.

OpenNIAPI'sarecomposedofasetofinterfacestowriteNIapplications.Thefollowingfigureshowsathree-layeredviewoftheOpenNIlibrary:

Thetoplayerrepresentstheapplicationlayerthatimplementsnaturalinteraction-basedapplication.ThemiddlelayeristheOpenNIlayeranditwillprovidecommunicationinterfacesthatinteractwithsensorsandmiddlewarecomponentsthatanalyzethedatafromthesensor.Middlewarecanbeusedforfullbodyanalysis,handpointanalysis,gesturedetection,andsoon.OneoftheexamplesofmiddlelayerisNITE,whichcandetectgestureandskeleton.

Thebottomlayershowsthehardwaredevicesthatcapturevisualsandaudioelementsofthescene.Itincludes3Dsensors,RGBcameras,anIRcamera,andamicrophone.

OpenNIiscross-platformandhasbeensuccessfullycompiledanddeployedonLinux,MacOSX,andWindows.

Inthenextsection,wewillseehowwetoinstallOpenNIinUbuntu14.04.2.

InstallingOpenNIinUbuntu14.04.2

WecaninstalltheOpenNIlibraryalongwithROSpackages.ROSisalreadyinterfacedwithOpenNI,butthecompleteinstallationofros-indigo-desktop-fullmaynotinstallOpenNIpackages;weneedtoinstallitfromthepackagemanager.

Thefollowingistheinstallationcommand:

$sudoapt-getinstallros-indigo-openni-launch

ThesourcecodeandlatestbuildofOpenNIforWindows,Linux,andMacOSXisavailableatthefollowinglink:

http://structure.io/openni

Inthenextsection,wewillseehowtoinstallPCL.

WhatisPCL?PCLisalargescale,openprojectfor2D/3Dimage,andPointCloudprocessing.ThePCLframeworkcontainsnumerousalgorithmsincludedtoperformfiltering,featureestimation,surfacereconstruction,registration,modelfitting,andsegmentation.Usingthesemethods,wecanprocessPointCloudandextractkeydescriptorstorecognizeobjectsintheworldbasedontheirgeometricappearanceandcreatesurfacesfromthePointCloudsandvisualizethem.

PCLlogo

PCLisreleasedundertheBSDlicense.It'sopensource,andfreeforcommercial,orresearchuse.PCLiscross-platformandhasbeensuccessfullycompiledanddeployedonLinux,MacOSX,Windows,andAndroid/iOS.

YoucandownloadPCLatthefollowinglink:

http://pointclouds.org/downloads/

PCLisalreadyintegratedintoROS.ThePCLlibraryanditsROSinterfacewillinstallalongwithROSfulldesktopinstallation.Inthepreviouschapter,wediscussedhowtoinstallROSfulldesktopinstallation.PCListhe3DprocessingbackboneofROS.RefertothefollowinglinkfordetailsontheROS-PCLpackage:

http://wiki.ros.org/pcl.

ProgrammingKinectwithPythonusingROS,OpenCV,andOpenNILet'slookathowwecaninterfaceandworkwiththeKinectsensorinROS.ROSisbundledwithOpenNIdriver,whichcanfetchRGBandthedepthimageofKinect.ThispackagecanbeusedforMicrosoftKinect,PrimeSenseCarmine,AsusXtionPro,andProLive.

Thisdrivermainlypublishesrawdepth,RGB,andIRimagestreams.Theopenni_launchpackagewillinstallpackagessuchasopenni_cameraandopenni_launch.Theopenni_camerapackageistheKinectdriverthatpublishesrawdataandsensorinformation,whereastheopenni_launchpackagecontainsROSlaunchfiles.It'sbasicallyanXMLfilethatlaunchesmultiplenodesatatimeandpublishesdatasuchaspointclouds.

HowtolaunchOpenNIdriverThefollowingcommandwillopentheOpenNIdeviceandloadallnodeletstoconvertrawdepth/RGB/IRstreamstodepthimages,disparityimages,andpointclouds.TheROSnodeletpackageisdesignedtoprovideawaytorunmultiplealgorithmsinthesameprocesswithzerocopytransportbetweenalgorithms.

$roslaunchopenni_launchopenni.launch

YoucanviewtheRGBimageusingaROStoolcalledimage_view

$rosrunimage_viewimage_viewimage:=/camera/rgb/image_color

Inthenextsection,wewillseehowtointerfacetheseimagestoOpenCVforimageprocessing.

TheROSinterfaceofOpenCVROSisintegratedintomanylibraries.OpenCVisalsointegratedintoROSmainlyforimageprocessing.Thevision_opencvROSstackincludesthecompleteOpenCVlibraryandinterfacetoROS.

Thevision_opencvprovidesseveralpackages:

cv_bridge:ThiscontainstheCvBridgeclass;thisclassconvertsfromROSimagemessagestoOpenCVimagedatatypeandviceversaimage_geometry:Thiscontainsacollectionofmethodstohandleimageandpixelgeometry

ThefollowingdiagramshowshowOpenCVisinterfacedtoROS:

OpenCV-ROSinterfacing

TheimagedatatypeofOpenCVareIplImageandMat.IfwewanttoworkwithOpenCVinROS,wehavetoconvertIplImageorMattoROSImagemessages.TheROSpackagevision_opencvhastheCvBridgeclass;thisclasscanconvertIplImagetoROSimageandviceversa.

ThefollowingsectionshowshowtocreateaROSpackage;thispackagecontainsnodetosubscribeRGB,depthimage,processtheRGBimagetodetectedges,anddisplayallimagesafterconvertingtoanimagetypeequivalenttoOpenCV.

CreatingROSpackagewithOpenCVsupport

Wecancreateapackagecalledsample_opencv_pkgwiththefollowingdependencies,thatis,sensor_msgs,cv_bridge,rospy,andstd_msgs.Thesensor_msgsdependencydefinesmessagesforcommonlyusedsensors,includingcamerasandscanninglaserrangefinders;cv_bridgeistheOpenCVinterfaceofROS.

ThefollowingcommandwillcreatetheROSpackagewiththeprecedingdependencies:

$catkin-create-pkgsample_opencv_pkgsensor_msgscv_bridgerospystd_msgs

Aftercreatingthepackage,createascriptsfolderinsidethepackageandsavethecodeinthementionedinthenextsection.

DisplayingKinectimagesusingPython,ROS,andcv_bridge

ThefirstsectionofthePythoncodeisgivenbelow.Itmainlyincludesimportingofrospy,sys,cv2,

sensor_msgs,cv_bridge,andthenumpymodule.Thesensor_msgsdependencyimportstheROSdatatypeofImageandCameraInfo.Thecv_bridgemoduleimportstheCvBridgeclassforconvertingROSimagedatatypetotheOpenCVdatatypeandviceversa:

importrospy

importsys

importcv2

importcv2.cvascv

fromsensor_msgs.msgimportImage,CameraInfo

fromcv_bridgeimportCvBridge,CvBridgeError

importnumpyasnp

ThefollowingsectionofcodeisaclassdefinitioninPythontodemonstrateCvBridgefunctions.TheclassisnamedascvBridgeDemo:

classcvBridgeDemo():

def__init__(self):

self.node_name="cv_bridge_demo"

#Initializetherosnode

rospy.init_node(self.node_name)

#Whatwedoduringshutdown

rospy.on_shutdown(self.cleanup)

#CreatetheOpenCVdisplaywindowfortheRGBimage

self.cv_window_name=self.node_name

cv.NamedWindow(self.cv_window_name,cv.CV_WINDOW_NORMAL)

cv.MoveWindow(self.cv_window_name,25,75)

#Andoneforthedepthimage

cv.NamedWindow("DepthImage",cv.CV_WINDOW_NORMAL)

cv.MoveWindow("DepthImage",25,350)

#Createthecv_bridgeobject

self.bridge=CvBridge()

#Subscribetothecameraimageanddepthtopicsandset

#theappropriatecallbacks

self.image_sub=rospy.Subscriber("/camera/rgb/image_color",Image,

self.image_callback)

self.depth_sub=rospy.Subscriber("/camera/depth/image_raw",Image,

self.depth_callback)

rospy.loginfo("Waitingforimagetopics...")

ThefollowingcodegivesacallbackfunctionofthecolorimagefromKinect.Whenacolorimagecomesonthe/camera/rgb/image_colortopic,itwillcallthisfunction.Thisfunctionwillprocessthecolorframeforedgedetectionandshowtheedgedetectedandrawcolorimage:

defimage_callback(self,ros_image):

#Usecv_bridge()toconverttheROSimagetoOpenCVformat

frame=self.bridge.imgmsg_to_cv(ros_image,"bgr8")

exceptCvBridgeError,e:

printe

#ConverttheimagetoaNumpyarraysincemostcv2functions

#requireNumpyarrays.

frame=np.array(frame,dtype=np.uint8)

#Processtheframeusingtheprocess_image()function

display_image=self.process_image(frame)

#Displaytheimage.

cv2.imshow(self.node_name,display_image)

#Processanykeyboardcommands

self.keystroke=cv.WaitKey(5)

if32<=self.keystrokeandself.keystroke<128:

cc=chr(self.keystroke).lower()

ifcc=='q':

#Theuserhaspresstheqkey,soexit

rospy.signal_shutdown("Userhitqkeytoquit.")

ThefollowingcodegivesacallbackfunctionofthedepthimagefromKinect.Whenadepthimagecomesonthe/camera/depth/raw_imagetopic,itwillcallthisfunction.Thisfunctionwillshowtherawdepthimage:

defdepth_callback(self,ros_image):

#Usecv_bridge()toconverttheROSimagetoOpenCVformat

#Thedepthimageisasingle-channelfloat32image

depth_image=self.bridge.imgmsg_to_cv(ros_image,"32FC1")

exceptCvBridgeError,e:

printe

#ConvertthedepthimagetoaNumpyarraysincemostcv2functions

#requireNumpyarrays.

depth_array=np.array(depth_image,dtype=np.float32)

#Normalizethedepthimagetofallbetween0(black)and1(white)

cv2.normalize(depth_array,depth_array,0,1,cv2.NORM_MINMAX)

#Processthedepthimage

depth_display_image=self.process_depth_image(depth_array)

#Displaytheresult

cv2.imshow("DepthImage",depth_display_image)

Thefollowingfunctioniscalledprocess_image(),whichwillconvertthecolorimagetograyscale,thenblurtheimage,andfindtheedgesusingthecannyedgefilter:

defprocess_image(self,frame):

#Converttograyscale

grey=cv2.cvtColor(frame,cv.CV_BGR2GRAY)

#Blurtheimage

grey=cv2.blur(grey,(7,7))

#ComputeedgesusingtheCannyedgefilter

edges=cv2.Canny(grey,15.0,30.0)

returnedges

Thefollowingfunctioniscalledprocess_depth_image().Itsimplyreturnsthedepthframe:

defprocess_depth_image(self,frame):

#Justreturntherawimageforthisdemo

returnframe

Thisfunctionwillclosetheimagewindowwhenthenodeshutsdown:

defcleanup(self):

print"Shuttingdownvisionnode."

cv2.destroyAllWindows()

Thefollowingcodeisthemain()function.ItwillinitializethecvBridgeDemo()classandcalltherosspin()function:

defmain(args):

cvBridgeDemo()

rospy.spin()

exceptKeyboardInterrupt:

print"Shuttingdownvisionnode."

cv.DestroyAllWindows()

main(sys.argv)

Savetheprecedingcodetocv_bridge_demo.pyandchangethepermissionofthenodeusingthefollowingcommand.Thenodeisonlyvisibletotherosruncommandifwegiveitexecutablepermission.

$chmod+Xcv_bridge_demo.py

Thefollowingarethecommandstostartthedriverandnode.StarttheKinectdriverusingthefollowingcommand:

Runthenodeusingthefollowingcommand:

$rosrunsample_opencv_pkgcv_bridge_demo.py

Thefollowingisthescreenshotoftheoutput:

RGB,depth,andedgeimages

WorkingwithPointCloudsusingKinect,ROS,OpenNI,andPCLAPointCloudisadatastructureusedtorepresentacollectionofmultidimensionalpointsandiscommonlyusedtorepresent3Ddata.Ina3DPointCloud,thepointsusuallyrepresentthex,y,andzgeometriccoordinatesofanunderlyingsampledsurface.Whenthecolorinformationispresent,thePointCloudbecomes4D.

PointCloudscanbeacquiredfromhardwaresensors(suchasstereocameras,3Dscanners,ortime-of-flightcameras).Itcanbegeneratedfromacomputerprogramsynthetically.PCLsupportstheOpenNI3Dinterfacesnatively;thusitcanacquireandprocessdatafromdevices(suchasPrimeSensor's3Dcameras,MicrosoftKinect,orAsusXTionPRO).

PCLwillbeinstalledalongwiththeROSindigofulldesktopinstallation.Let'sseehowwecangenerateandvisualizePointCloudinRViz,adatavisualizationtoolinROS.

OpeningdeviceandPointCloudgenerationOpenanewterminalandlaunchtheROSOpenNIdriveralongwiththePointCloudgeneratornodesusingthefollowingcommand:

roslaunchopenni_launchopenni.launch

ThiscommandwillactivatetheKinectdriverandprocesstherawdataintoconvenientoutputslikePointCloud.

WewilluseRViz3DvisualizationtooltoviewPointClouds.

ThefollowingcommandwillstarttheRViztool:

$rosrunrvizrviz

SettheRVizoptionsforFixedFrame(atthetopoftheDisplayspanelunderGlobalOptions)tocamera_link.

Ontheleft-handsideoftheRVizpanel,clickontheAddbuttonandchoosethePointCloud2displayoption.Setitstopicto/camera/depth/points.

ChangeColorTransformerofPointCloud2toAxisColor.

ThefollowingfigureshowsascreenshotofRVizPointClouddata.Inthisscreenshot,thenearobjectismarkedinredandthefarobjectismarkedinvioletandblue.TheobjectinfrontofKinectisrepresentedascylinderandcube:

PointCloudofarobot

ConversionofPointCloudtolaserscandataWeareusingKinectinthisrobotforreplicatingthefunctionofexpensivelaserrangescanner.KinectcandeliverPointClouddatawhichcontainsthedepthofeachpointofsurrounding.ThePointClouddataisprocessedandconvertedtodataequivalenttoalaserscannerusingtheROSdepthimage_to_laserscanpackage.ThemainfunctionofthispackageistosliceasectionofthePointClouddataandconvertittoalaserscanequivalentdatatype.ThePointcloud2datatypeissensor_msgs/PointCloud2andforthelaserscanner,thedatatypeissensor_msgs/LaserScan.Thispackagewillperformthisprocessingandfakethelaserscanner.ThelaserscanneroutputcanbeviewedusingRViz.Inordertoruntheconversion,wehavetostarttheconvertornodeletsthatwillperformthisoperation.Wehavetospecifythisinourlaunchfiletostarttheconversion.Thefollowingistherequiredcodeinthelaunchfiletostartthedepthimage_to_laserscanconversion:

<nodepkg="nodelet"type="nodelet"name="laserscan_nodelet_manager"

args="manager"/>

<nodepkg="nodelet"type="nodelet"name="depthimage_to_laserscan"

args="loaddepthimage_to_laserscan/DepthImageToLaserScanNodelet

laserscan_nodelet_manager">

<paramname="scan_height"value="10"/>

<paramname="output_frame_id"value="/camera_depth_frame"/>

<paramname="range_min"value="0.45"/>

<remapfrom="image"to="/camera/depth/image_raw"/>

<remapfrom="scan"to="/scan"/>

</node>

Alongwithstartingthenodelet,weneedtosetcertainparametersofthenodeletforbetterconversion.Refertohttp://wiki.ros.org/depthimage_to_laserscanforadetailedexplanationofeachparameter.

Thelaserscanoftheprecedingviewisshowninthefollowingscreenshot.Toviewthelaserscan,addtheLaserScanoption.ThisissimilartohowweaddthePointCloud2optionandchangetheTopicvalueofLaserScanto/scan:

WorkingwithSLAMusingROSandKinectThemainaimofdeployingvisionsensorsinourrobotistodetectobjectsandperformrobotnavigationinanenvironment.SLAMisatechniqueusedinmobilerobotsandvehiclestobuildupamapofanunknownenvironmentorupdateamapwithinaknownenvironmentbytrackingthecurrentlocationofarobot.

Mapsareusedtoplantherobottrajectoryandtonavigatethroughthispath.Usingmaps,therobotwillgetanideaabouttheenvironment.Themaintwochallengesinmobilerobotnavigationaremappingandlocalization.

Mappinginvolvesgeneratingaprofileofobstaclesaroundtherobot.Throughmapping,therobotwillunderstandhowtheworldlooks.Localizationistheprocessofestimatingaposeoftherobotrelativetothemapwebuild.

SLAMfetchesdatafromdifferentsensorsandusesittobuildmaps.The2D/3DvisionsensorcanbeusedasaninputtoSLAM.The2Dvisionsensorssuchaslaserrangefindersand3DsensorssuchasKinectaremainlyusedasaninputforaSLAMalgorithm.

ROSisintegratedintoaSLAMlibraryusingOpenSlam(http://openslam.org/gmapping.html).Thegmappingpackageprovideslaser-basedSLAMasanodecalledslam_gmapping.Thiscancreatea2Dmapfromthelaserandposedatacollectedbyamobilerobot.

Thegmappingpackageisavailableathttp://wiki.ros.org/gmapping.

Touseslam_gmapping,youwillneedamobilerobotthatprovidesodometrydataandisequippedwithahorizontallymounted,fixed,laserrangefinder.Theslam_gmappingnodewillattempttotransformeachincomingscanintotheodom(odometry)tfframe.

Theslam_gmappingnodetakesinsensor_msgs/LaserScanmessagesandbuildsamap(nav_msgs/OccupancyGrid).ThemapcanberetrievedviaaROStopicorservice.

Thefollowingcodecanbeusedtomakeamapfromarobotwithalaserpublishingscansonthebase_scantopic:

$rosrungmappingslam_gmappingscan:=base_scan

Questions1. Whatare3Dsensorsandhowaretheydifferentfromordinarycams?2. Whatarethemainfeaturesofaroboticoperatingsystem?3. WhataretheapplicationsofOpenCV,OpenNI,andPCL?4. WhatisSLAM?5. WhatisRGB-DSLAMandhowdoesitwork?

SummaryInthischapter,wesawvisionsensorstobeusedinourrobot.WeusedKinectinourrobotanddiscussedOpenCV,OpenNI,PCLandtheirapplication.WealsodiscussedtheroleofvisionsensorsinrobotnavigationandapopularSLAMtechniqueanditsapplicationusingROS.Inthenextchapter,wewilldiscussspeechprocessingandsynthesistobeusedinthisrobot.

Chapter8.WorkingwithSpeechRecognitionandSynthesisUsingPythonandROSInthischapter,wewillmainlydiscussthefollowingtopics:

Introducingspeechrecognition,synthesis,andvariousspeechprocessingframeworksWorkingwithspeechrecognitionandsynthesisusingPythoninUbuntu/Linux,WindowsandMacOSXWorkingwithspeechrecognitionandsynthesispackagesinROSusingPython

Iftherobotsareabletorecognizeandrespondthewayhumanbeingscommunicate,thentherobot-humaninteractionwillbemuchmoreeasierandeffectivethananyothermethod.However,extractingspeechparameterssuchasmeaning,pitch,duration,andintensityfromhumanspeechisaverytoughtask.Researchersfoundnumerouswaystosolvethisproblem.Now,therearesomealgorithmsthataredoingagoodjobinspeechprocessing.

Inthischapter,wewilldiscusstheapplicationsofspeechrecognitionandsynthesisinourrobotandalsolookatsomeofthelibrariestoperformspeechrecognitionandsynthesis.

Themainobjectiveofspeechsynthesisandrecognitionsysteminthisrobotistomaketherobot-humaninteractioneasier.Ifarobothastheseabilities,itcancommunicatewiththesurroundingpeopleandtheycanaskvariousquestionsaboutthefoodandthecostofeachitem.Thespeechrecognitionandsynthesisfunctionalitycanbeaddedusingtheframeworkthatwewilldiscussinthischapter.

Inthefirstsectionofthischapter,youwilllearnaboutthestepsinvolvedinspeechrecognitionandsynthesis.

UnderstandingspeechrecognitionSpeechrecognitionbasicallymeanstalkingtoacomputerandmakingitrecognizewhatwearesayinginrealtime.Itconvertsnaturalspokenlanguagetodigitalformatthatcanbeunderstoodbyacomputer.Wearemainlydiscussingtheconversionofspeech-to-textprocesshere.Usingthespeechrecognitionsystem,therobotwillrecordthesentenceorwordcommandedbytheuser.Thetextwillbepassedtoanotherprogramandtheprogramwilldecidewhichactionithastoexecute.Wecantakealookattheblockdiagramofthespeechrecognitionsystemthatexplainshowitworks.

BlockdiagramofaspeechrecognitionsystemThefollowingisablockdiagramofatypicalspeechrecognitionsystem.Wecanseeeachblockandunderstandhowaspeechsignalisconvertedtotext:

Speechrecognitionsystemblockdiagram

ThespeechsignalisreceivedthroughamicrophoneandwillbeconvertedtoadigitalformatsuchasPCM(PulseCodeModulation)bythesoundcardinsidethePC.ThisdigitalformatcanbeprocessedbythesoftwareinsidethePC.Inaspeechrecognitionprocess,thefirstphaseistoextractthespeechfeaturesfromthedigitalsoundformat.

Inthespeechrecognitionsystem,thefollowingarethecommoncomponents:

Featureextraction:Inthisprocess,therawdigitalsoundisconvertedtosoundfeaturevectors,whichcarryinformationofsoundsandsuppresstheirrelevantsourcesofsound.Thesoundfeaturevectorscanbemathematicallyrepresentedasavectorwithrespecttotime.Aftergettingthesoundfeaturevectors,theywillbedecodedtotextfromalistofpossiblestringsandselectedaccordingtoitsprobability.Acousticmodel:Thefirststageofdecodingisacousticmodels.Acousticmodelsaretrainedstatisticalmodelsandarecapableofpredictingtheelementaryunitsofspeechcalledphonemesaftergettingthesoundfeaturevectors.PopularacousticmodelinginspeechrecognitionisHMM(HiddenMarkovModels)andanotherhybridapproachistouseartificialneuralnetworks.Lexicon:Alexicon(alsoknownasdictionary)containsthephoneticscriptofwordsthatweuseintrainingtheacousticmodel.Languagemodel:Thisprovidesastructuretothestreamofwordsthatisdetectedaccordingtotheindividualwordprobability.Thelanguagemodelistrainedusinglargeamountsoftrainingtext(whichincludesthetextusedtotraintheacousticmodel).Ithelpstoestimatetheprobabilities

andfindtheappropriateworddetected.Searchalgorithm:Thisisusedtofindthemostprobablesequenceofwordsinthesoundvectorswiththehelpofthelanguagemodelandlexicon.Recognizedwords:Theoutputofthesearchalgorithmisalistofwordsthathasthehighestprobabilityforgivensoundvectors.

SpeechrecognitionlibrariesThefollowingaresomegoodandpopularimplementationsofspeechrecognitionalgorithmsintheformoflibraries.

CMUSphinx/PocketSphinx

SphinxisagroupofspeechrecognitiontoolsdevelopedbyCarnegieMellonUniversity.Theentirelibraryisopensourceanditcomeswithacousticmodelsandsampleapplications.Theacousticmodeltrainerimprovestheaccuracyofdetection.Itallowsyoutocompileitslanguagemodelandprovidesalexiconcalledcmudict.ThecurrentSphinxversionis4.TheSphinxversioncustomizedforanembeddedsystemiscalledPocketSphinx.It'salightweightspeechrecognitionenginethatwillworkondesktopaswellasonmobiledevices.SphinxlibrariesareavailableforWindows,Linux,andMacOSX.

TherearePythonmodulesavailabletohandlePocketSphinxAPIsfromPython.ThefollowingistheofficialwebsiteofCMUSphinx:

http://cmusphinx.sourceforge.net/

Julius

ThisisahighperformanceandcontinuousspeechrecognitionlibrarybasedonHMMandcandetectcontinuousstreamofwordsorN-grams.It'sanopensourcelibrarythatisabletoworkinrealtime.TherearePythonmodulestohandleJuliusfunctionsfromPython.JuliusisavailableinWindows,Linux,andMacOSX.TheofficialwebsiteofJuliusis:

http://julius.sourceforge.jp/en_index.php

WindowsSpeechSDKMicrosoftprovidesaSDKtohandlespeechrecognitionandsynthesisoperation.SDKcontainsAPIstohandlespeech-relatedprocessingthatcanbeembeddedinsidetheMicrosoftapplication.TheSDKonlyworksonWindowsandithassomeportsforPythonlikethePySpeechmodule.ThesespeechAPIsarecomparativelyaccuratethanotheropensourcetools.

SpeechsynthesisSpeechsynthesisistheprocessofconvertingtextdatatospeech.Thefollowingblockdiagramshowstheprocessinvolvedinconvertingtexttospeech:

Blockdiagramofspeechsynthesisprocess

Formoredetails,refertopage6ofSpokenLanguageProcessing,X.Huang,A.Acero,H.-W.Hon,PrenticeHallPTR,publishedin2001.

Letustakealookatthespeechsynthesisstages:

Textanalysis:Intextanalysis,thetexttobeconvertedtospeechwillcheckforthestructureoftext,linguisticanalysis,andtextnormalizationtoconvertnumbersandabbreviationstowordsPhoneticanalysis:Inphoneticanalysis,eachindividualtextdatacalledgraphemeisconvertedtoanindividualindivisiblesequenceofsoundcalledphonemeProsodicanalysis:Inprosodicanalysis,theprosodyofspeech(suchasrhythm,stress,andintonationsofspeech)addedtothebasicsoundmakesitmorerealisticSpeechsynthesis:Thisunitfinallybindstheshortunitsofspeechandproducesthefinalspeechsignal

SpeechsynthesislibrariesLet'snowdiscussabitaboutthevariousspeechsynthesislibraries.

eSpeak

eSpeakisanopensourcelightweightspeechsynthesizermainlyforEnglishlanguageanditwillalsosupportseveralotherlanguages.UsingeSpeak,wecanchangethevoicesanditscharacteristics.eSpeakhasthemoduletoaccessitsAPIsfromPython.eSpeakworksmainlyinWindowsandLinuxandit'salsocompatiblewithMacOSX.TheofficialwebsiteofeSpeakisasfollows:

http://espeak.sourceforge.net/

Festival

FestivalisanopensourceandfreespeechsynthesizerdevelopedbyCentreofSpeechTechnologyResearch(CSTR)andiswrittencompletelyinC++.ItprovideaccesstotheAPIsfromShellintheformofcommandsandalsoinC++,Java,andPython.Ithasmultilanguagesupport(suchasEnglishandSpanish).FestivalmainlysupportsLinux-basedplatform.ThecodecanalsobebuiltinWindowsandMacOSX.ThefollowingistheofficialwebsiteoftheFestivalspeechsynthesissystem:

http://www.cstr.ed.ac.uk/projects/festival/

WorkingwithspeechrecognitionandsynthesisinUbuntu14.04.2usingPythonInthissection,wewilldiscussPythoninterfacingwithPocketSphinx,Julius,andMicrosoftSpeechSDKandspeechsynthesisframeworkssuchaseSpeakandFestival.Let'sstartwithspeechrecognitionlibrariesandtheirinstallationprocedures.

SettingupPocketSphinxanditsPythonbindinginUbuntu14.04.2ThefollowingpackagesarerequiredtoinstallPocketSphinxanditsPythonbindings:

python-pocketsphinx

pocketsphinx-hmm-wsj1

pocketsphinx-lm-wsj

Thepackagescanbeinstalledusingtheapt-getcommand.ThefollowingcommandsareusedtoinstallPocketSphinxanditsPythoninterface.

InstallingPocketSphinxinUbuntucanbedoneeitherthroughsourcecodeorbypackagemanagers.Here,wewillinstallPocketSphinxusingthepackagemanager:

ThefollowingcommandwillinstallHMMofPocketSphinx:

$sudoapt-getinstallpocketsphinx-hmm-wsj1

ThefollowingcommandwillinstallLMofPocketSphinx:

$sudoapt-getinstallpocketsphinx-lm-wsj

ThefollowingcommandwillinstallthePythonextensionofPocketSphinx:

$sudoapt-getinstallpython-pocketsphinx

Oncewearedonewiththeinstallation,wecanworkwithPythonscriptingforspeechrecognition.

WorkingwithPocketSphinxPythonbindinginUbuntu14.04.2ThefollowingisthecodetoperformspeechrecognitionusingPocketSphinxandPython.Thefollowingcodedemonstrateshowwecandecodethespeechrecognitionfromawavefile:

importsys

#InUbuntu14.04.2,thepocketsphinxmoduleshowserrorinfirstimportandwill

workforthesecondimport.Thefollowingcodeisatemporaryfixtohandlethat

importpocketsphinx

except:

importpocketsphinx

TheprecedingcodewillimportthepocketsphinxPythonmoduleandPythonsysmodule.Thesysmodulecontainfunctionsthatcanbecalledduringprogramruntime.Inthiscode,wewillusethesysmoduletogetthewavefilenamefromthecommand-lineargument:

hmdir="/usr/share/pocketsphinx/model/hmm/en_US/hub4wsj_sc_8k"

lmdir="/usr/share/pocketsphinx/model/lm/en_US/hub4.5000.DMP"

dictd="/usr/share/pocketsphinx/model/lm/en_US/cmu07a.dic"

Thehmdir,lmdirn,anddictdvariablesholdthepathofHMM,LM(LanguageModel),anddictionaryofPocketSphinx:

#Receivingwavefilenamefromcommandlineargument

wavfile=sys.argv[1]

ThefollowingcodewillpassHMM,LM,andthedictionarypathofPocketSphinxtoPocketSphinx'sDecoderclass.Readanddecodethewavefile.Intheend,itwillprintthedetectedtext:

speechRec=pocketsphinx.Decoder(hmm=hmdir,lm=lmdir,dict=dictd)

wavFile=file(wavfile,'rb')

speechRec.decode_raw(wavFile)

result=speechRec.get_hyp()

print"\n\n\nDetectedtext:>",result

print"\n\n\n"

OutputTheprecedingcodecanberunusingthefollowingcommand:

$python<code_name.py><wave_file_name.wav>

Thefollowingisascreenshotoftheoutput.Thedetectedtextwasnotthecontentonthewavefile.ThedetectionaccuracywiththedefaultacousticmodelandLMislow;wehavetotrainanewmodeloradaptanexistingmodeltoimproveaccuracy:

Thepreviousmethodwediscussedwasanofflinerecognition;inthenextsection,wewillseehowtoperformreal-timespeechrecognitionusingPocketSphinx,GStreamer,andPython.Inthisapproach,real-timespeechdatacomesthroughtheGStreamerframeworkandisdecodedusingPocketSphinx.ToworkwiththeGStreamerPocketSphinxinterface,installthefollowingpackages:

ThefollowingcommandwillinstalltheGStreamerpluginforPocketSphinx:

$sudoapt-getinstallgstreamer0.10-pocketsphinx

ThefollowingpackagewillinstalltheGStreamerPythonbinding.ItwillenableyoutouseGStreamerAPIsfromPython:

$sudoapt-getinstallpython-gst0.10

ThefollowingpackagewillinstalltheGStreamerplugintogetinformationfromGConf:

$sudoapt-getinstallgstreamer0.10-gconf

Real-timespeechrecognitionusingPocketSphinx,GStreamer,andPythoninUbuntu14.04.2Thefollowingisthecodeforreal-timespeechrecognitionusingGStreamer:

#ThefollowingmodulesneedtoimportbeforehandlinggstreamerAPI's

importgobject

importsys

importpygst

pygst.require('0.10')

gobject.threads_init()

importgst

#Moduletohandlekeyboardinterruptsignal

importsignal

#Keyboardsignalhandlingroutine

defsignal_handle(signal,frame):

print"YoupressedCtrl+C"

sys.exit(0)

#ImplementationofSpeechrecognitionclass

classSpeech_Recog(object):

#Initializinggstreamerpipelineandpocketsphinxelement

def__init__(self):

self.init_gst()

#Thisfunctionwillinitializegstreamerpipeline

definit_gst(self):

#Thefollowingcodecreateagstreamerpipelinewithpipelinedescription.The

requireddescriptorsneededforthecodeisgivenasparameters.

self.pipeline=gst.parse_launch('gconfaudiosrc!audioconvert!

audioresample'

+'!vadername=vadauto-threshold=true'

+'!pocketsphinxname=asr!fakesink')

#Accessingpocketsphinxelementfromgstreamerpipeline

asr=self.pipeline.get_by_name('asr')

#Connectingtoasr_resultfunctionwhenaspeechtotextconversionis

completed

asr.connect('result',self.asr_result)

#Usercanmentionlmanddictforaccuratedetection

#asr.set_property('lm','/home/user/mylanguagemodel.lm')

#asr.set_property('dict','/home/user/mylanguagemodel.dic')

#Thisoptionwillsetalloptionsareconfiguredwellandcanstartrecognition

asr.set_property('configured',True)

#PausingtheGStreamerpipelineatfirst.

self.pipeline.set_state(gst.STATE_PAUSED)

#Definitionofasr_result

defasr_result(self,asr,text,uttid):

#Printingthedetectedtext

print"DetectedText=>",text

#Thisfunctionwillstart/stopSpeechrecognitionoperation

defstart_recognition(self):

#VADER-VoiceActivityDEtectoR,whichhelpswhenthespeechstartandwhen

itsends.CreatingVADERobjectandsetthepropertysilenttoFalse,sonospeech

willdetecteduntilkeypress

vader=self.pipeline.get_by_name('vad')

vader.set_property('silent',False)

#Waitingforakeypresstostartrecognition

raw_input("Pressanykeytostartrecognition:>")

#Startplayingthepipeline

self.pipeline.set_state(gst.STATE_PLAYING)

#Waitingforstoppingtherecognition

raw_input("Pressanykeytostoprecognition:>")

vader=self.pipeline.get_by_name('vad')

#SettingsilentpropertyofVADERtoTrue

vader.set_property('silent',True)

#PausingGStreamerpipeline

self.pipeline.set_state(gst.STATE_PAUSED)

#CreatinganobjectofSpeech_Recog()class

app_object=Speech_Recog()

#Assignkeyboardinterrupthandler

signal.signal(signal.SIGINT,signal_handle)

whileTrue:

#CallingSpeechrecognitionroutine

app_object.start_recognition()

Thecodecanbesimplyexecutedusingthefollowingcommand:

$python<code_name.py>

Thefollowingisthescreenshotoftheoutputwindow:

Pressanykeytostartrecognition;afterthis,wecantalkanditwillbeconvertedandprintedontheterminalwindow.Tostopdetection,pressanykeyanditwillpausetheGStreamerpipeline.

OneoftheotherspeechrecognitiontoolisJulius.WewillseehowtoinstallitandworkwithitusingPython.

SpeechrecognitionusingJuliusandPythoninUbuntu14.04.2Inthissection,wewillseehowtoinstallthespeechrecognitionsystemofJuliusandhowtoconnectittoPython.Therequiredpackages(suchasJuliusandaudiotools)areavailableinUbuntu'spackagemanager,butwealsoneedtodownloadandinstallthePythonwrapperseparately.Let'sstartwiththerequiredcomponentsfortheinstallation.

InstallationofJuliusspeechrecognizerandPythonmoduleThefollowingaretheinstructionstoinstallJuliusandPythonbindinginUbuntu14.04.2:

ThefollowingcommandwillinstallthespeechrecognitionsystemofJulius:

$sudoapt-getinstalljulius

Thefollowingcommandwillinstallpadsp(thepulseaudiotool).ItmaybenecessarytoruntheJuliusspeechrecognizerinUbuntu14.04.2:

$sudoapt-getinstallpulseaudio-utils

ThefollowingcommandwillinstalltheOSSproxydaemontoemulatetheOSSsounddeviceandstreamthroughtheALSAdevice.Itwillemulatethe/dev/dspdeviceinUbuntuandstreamthroughALSA.Juliusneedsthe/dev/dspdeviceforitsfunctioning:

$sudoapt-getinstallosspd-alsa

ReloadtheALSAprocesstobindosspdtoalsa:

$sudoalsaforce-reload

Toinstallpyjulius,thePythonextensionforJulius,youneedtoinstallthesetuptoolsinPython.

1. Toinstallthesetuptools,thebestoptionistodownloadascriptfromthesetuptoolswebsite;it'saglobalscriptthatcanbeusedinanyOS.Thescriptcanbedownloadedfromthefollowinglinkusingthewgettool:

$wgethttps://bootstrap.pypa.io/ez_setup.py

$sudopythonez_setup.py

2. Theinstallationdetailsofsetuptoolsismentionedathttps://pypi.python.org/pypi/setuptools3. Aftertheinstallationofsetuptools,downloadpyjuliusfrom

https://pypi.python.org/pypi/pyjulius/0.34. Extracttheachieveandinstallationpackageusingthefollowingcommand:

$sudopythonsetup.pyinstall

5. Aftertheinstallationofpyjulius,installademooftheJuliustool,whichcontainsHMM,LM,anddictionaryofafewwords.DownloadtheJuliusquick-startfilesusingthefollowingcommand:

$wgethttp://www.repository.voxforge1.org/downloads/software/julius-3.5.2-

quickstart-linux.tgz

6. Extractthefilesandrunthecommandfromthefolder.7. Executethefollowingcommandintheextractedfolder.Itwillstartthespeechrecognitioninthe

commandline:

$padspjulius-inputmic-Cjulian.jconf

8. Toexitspeechrecognition,clickonCTRL+C.9. ToconnecttoPython,enterthefollowingcommand:

$padspjulius-module-inputmic-Cjulian.jconf

ThiscommandwillstartaJuliusserver.Thisserverlistenstoclients.IfwewanttouseJuliusAPIsfromPython,weneedtoconnecttoaserverusingaclientcodeasgiveninthefollowingsections.ThePythoncodeisaclientthatconnectstotheJuliusserverandprintstherecognizedtext.

Python-JuliusclientcodeThefollowingcodeisaPythonclientoftheJuliusspeechrecognitionserverthatwestartedusingthepreviouscommand.Afterconnectingtothisserver,itwilltriggerspeech-to-textconversionandfetchtheconvertedtextandprintonterminal:

importsys

#Importingpujuliusmodule

importpyjulius

#ItanimplementationofFIFO(FirstInFirstOut)queuesuitableformultithreaded

programming.

importQueue

#InitializeJuliusClientobjectwithlocalhostipanddefaultportof10500and

tryingtoconnectserver.

client=pyjulius.Client('localhost',10500)

client.connect()

#Whentheclientrunsbeforeexecutingtheserveritwillcauseaconnectionerror.

exceptpyjulius.ConnectionError:

print'Startjuliusasmodulefirst!'

sys.exit(1)

#Startlisteningtotheserver

client.start()

while1:

#Fetchingrecognitionresultfromserver

result=client.results.get(False)

exceptQueue.Empty:

continue

printresult

exceptKeyboardInterrupt:

print'Exiting...'

client.stop()#sendthestopsignal

client.join()#waitforthethreadtodie

client.disconnect()#disconnectfromjulius

AfterconnectingtoJuliusserver,thePythonclientwilllistentoserverandprinttheoutputfromtheserver.

Theacousticmodelsweusedintheprecedingprogramsarealreadytrained,buttheymaynotgiveaccurateresultsforourspeech.Toimprovetheaccuracyinthepreviousspeechrecognitionengines,weneedtotrainnewlanguageandacousticmodelsandcreateadictionaryorwecanadapttheexistinglanguagemodelusingourvoice.Themethodtoimproveaccuracyisbeyondthescopeofthischapter,sosomelinkstotrainoradaptbothPocketSphinxandJuliusaregiven.

ImprovingspeechrecognitionaccuracyinPocketSphinxandJuliusThefollowinglinkisusedtoadapttheexistingacousticmodeltoourvoiceforPocketSphinx:

http://cmusphinx.sourceforge.net/wiki/tutorialadapt

Juliusaccuracycanbeimprovedbywritingrecognitiongrammar.ThefollowinglinkgivesanideaabouthowtowriterecognitiongrammarinJulius:

http://julius.sourceforge.jp/en_index.php?q=en_grammar.html

Inthenextsection,wewillseehowtoconnectPythonandspeechsynthesislibraries.WewillworkwiththeeSpeakandFestivallibrarieshere.Thesearetwopopular,free,andeffectivespeechsynthesizersavailableinalltheOSplatforms.ThereareprecompiledbinariesavailableinUbuntuintheformofpackages.

SettingupeSpeakandFestivalinUbuntu14.04.2eSpeakandFestivalarespeechsynthesizersavailableintheUbuntu/Linuxplatform.TheseapplicationscanbeinstalledfromthesoftwarepackagerepositoryofUbuntu.ThefollowingaretheinstructionsandcommandstoinstallthesepackagesinUbuntu.

1. ThefollowingcommandswillinstalltheeSpeakapplicationanditswrapperforPython.WecanusethiswrapperinourprogramandaccesseSpeakAPIs:

$sudoapt-getinstallespeak

$sudoapt-getinstallpython-espeak

2. ThefollowingcommandwillinstalltheFestivaltext-to-speechengine.Festivalhassomepackagedependencies;alldependencieswillbeautomaticallyinstalledusingthiscommand:

$sudoapt-getinstallfestival

3. AftertheinstallationoftheFestivalapplication,wecandownloadandinstallPythonbindingsforFestival.

4. DownloadPythonbindingsusingthefollowingcommand.Weneedthesvntool(ApacheSubversion)todownloadthispackage.Subversionisafreesoftwareversioningandrevisioncontrolsystem:

$svncheckouthttp://pyfestival.googlecode.com/svn/trunk/pyfestival-read-only

5. Afterthedownloadingprocessiscomplete,switchtothepyfestival-read-onlyfolderandyoucaninstallthispackageusingthefollowingcommand:

HereisthecodetoworkwithPythonandeSpeak.Asyouwillsee,it'sveryeasytoworkwithPythonbindingforeSpeak.WeneedtowriteonlytwolinesofcodetosynthesizespeechusingPython:

fromespeakimportespeak

espeak.synth("HelloWorld")

ThiscodewillimporttheeSpeak-Pythonwrappermoduleandcallthesynthfunctioninthewrappermodule.Thesynthfunctionwillsynthesizethetextgivenasargument.

ThefollowingcodeshowshowtosynthesizespeechusingPythonandFestival:

importfestival

festival.say("HelloWorld")

TheprecedingcodewillimporttheFestival-PythonwrappermoduleandcallthesayfunctionintheFestivalmodule.Itwillsynthesizethetextasspeech.

WorkingwithspeechrecognitionandsynthesisinWindowsusingPythonInWindows,therearemanytoolsandframeworkstoperformspeechrecognitionandsynthesis.Thespeechrecognitionlibraries,namely,PocketSphinxandJuliusthatwediscussedwillalsobesupportedinWindows.MicrosoftalsoprovidesSAPI(SpeechApplicationProgrammingInterface),asetofAPIsthatallowsyoutousespeechrecognitionandsynthesisfromcode.TheseAPIsareeithershippedwithanoperatingsystemorwithMicrosoftSpeechSDK.

Inthissection,wewilldemonstratehowtoconnectPythonandMicrosoftSpeechSDKtoperformspeechrecognitionandsynthesis.ThisprocedurewillworkinWindows8,Windows7,32,and64bit.

InstallationoftheSpeechSDKThefollowingisthestep-by-stepproceduretoinstallSpeechSDKandthePythonwrapperofSpeechSDK:

1. DownloadSpeechSDKfromhttp://www.microsoft.com/en-in/download/details.aspx?id=272262. DownloadandinstallActiveStatePython2.7bitfrom

http://www.activestate.com/activepython/downloads3. DownloadandinstallPythonwrapperfortheWindowsSpeechSDKfrom

https://pypi.python.org/pypi/speech/.Currently,thisprojectisnotactive,butitwillworkfineinWindows7and8

4. Installthepackageusingthefollowingcommand:

pythonsetup.pyinstall

5. ThecodetodospeechrecognitionusingPythonisverysimpleandit'sgiveninthefollowingcode:

importspeech

result=speech.input("Speak")

printresult

Inthiscode,weimportthespeechmodule.Whenweimportthespeechmodule,thespeechrecognitionpanelofWindowswillpopup.Itwillbeinoffstatefirstandweneedtoturnitontoperformtherecognition.TherecognizedtextwillbeprintedonthePythoncommandline.

Next,wecanlookatthespeechsynthesisusingPython.Similartothespeechrecognitionprocess,it'sveryeasytoperformthespeechmodule.Thiscanbeusedtoperformspeechsynthesis.Hereisthecode:

importspeech

speech.say("HelloWorld")

Inthiscode,speech.say()isthemethodtoconverttexttospeech.

Wehaveseensomeofthespeechrecognitionandsynthesisplatforms.Now,wecantakealookathowwecanintegratespeechrecognitionandsynthesisinROS.ThefollowingsectiondiscussestheintegrationofspeechrecognitionandsynthesisonROS.

WorkingwithSpeechrecognitioninROSIndigoandPythonComparedtootherspeechrecognitionmethods,oneoftheeasiestandeffectivemethodstoimplementrealtimespeechrecognitionisPocketSphinxandGStreamerpipeline.WediscussedPocketSphinx,GStreameranditsinterfacingwithPythonpreviously.Next,wecanseeaROSpackagecalledpocketsphinxthatusestheGStreamerpocketsphinxinterfacetoperformspeechrecognition.ThepocketsphinxROSpackageisavailableintheROSrepository.Youwillgetthepackageinformationatthefollowinglink

http://wiki.ros.org/pocketsphinx

InstallationofthepocketsphinxpackageinROSIndigoToinstallthepocketsphinxpackage,firstswitchtothecatkinworkspacesourcefolder.

1. Downloadthesourcecodeofthepocketsphinxpackageusingthefollowingcommand:

$gitclonehttps://github.com/mikeferguson/pocketsphinx

2. Executethecatkin_makecommandfromthecatkinworkspacefoldertobuildthepackage3. Startthespeechrecognizerdemousingthefollowingcommand.Therobotcupdemohassome

basiccommandstodrivetherobot.Wecanchangethecommandbyadaptingacousticandlanguagemodels:

$roslaunchpocketsphinxrobocup.launch

4. Subscribeto/recognizer/outputusingthefollowingcommand:

$rostopicecho/recognizer/output

Thefollowingisthescreenshotoftheoutput:

ThisTopiccanbesubscribedandthecommandcanbeprocessedinsomeothernodes.Inthenextsection,wewillseehowtosynthesizespeechusingROSandPython.

WorkingwithspeechsynthesisinROSIndigoandPythonInROS,therearesomeROSpackagesthatperformspeechsynthesis.Here,wewilldiscussoneROSpackage.ThispackageusesFestivalasthebackend.Thepackagenameissound_play.Ithasnodesandlaunchscriptsthatenablespeechsynthesis.Weneedtoperformthefollowingstepsforspeechsynthesis:

1. Wecaninstallthesound_playpackageusingthefollowingcommand:

$sudoapt-getinstallros-indigo-sound-play

2. Aftertheinstallationofpackage,wehavetocreateasampleROSpackagetointeractwiththesound-playnode.ThefollowingisthecommandtocreateasamplepackageinROSwiththesound-playpackageasdependency:

$catkin_create_pkgsample_ttsrospyroscppsound_playstd_msgs

3. Wehavetocreateasound_playpythonclientcodeforsendingtexttosoundplayservernode.Thisclientwillsendthetextthatneedstobeconvertedtospeechtothesound_playservernode.TheclientwillsendthetexttoconverttospeechinaTopiccalled/robotsound.ThesoundplaynodeinthesoundplaypackagewillsubscribetothisTopicandconvertthestringfromTopictospeech.

4. Createafolderinsidethissample_ttspackagenamedscriptsandcreatethefollowingcodeinthescriptsfolderandnameittest.py.Thecodesnippetsoftest.pyisgiven.

5. Thefollowingcodewillimporttherospyandsound_playmodules.ThisscriptwillactasaSoundClient,whichwillconnecttothesound_playserverandsynthesizethespeech:

importroslib;roslib.load_manifest('sample_tts')

importrospy,os,sys

fromsound_play.msgimportSoundRequest

fromsound_play.libsoundplayimportSoundClient

6. Thiscodewillinitializethesoundplay_testnodeandcreateanobjectofSoundClient:

rospy.init_node('soundplay_test',anonymous=True)

soundhandle=SoundClient()

rospy.sleep(1)

soundhandle.stopAll()

7. Thiscodewillcallafunctiontosynthesizethespeech.Itcanbeusedtosynthesizespeechinanypackagethatincludessound_playasdependency.

print'StartingTTS'

soundhandle.say('Helloworld!')

rospy.sleep(3)

s=soundhandle.voiceSound("HelloWorld")

s.play()

rospy.sleep(3)

8. Thefollowingcommandstartsthesoundplayserver:

$roslaunchsound_playsoundplay_node.launch

9. Thefollowingcommandwillstartthetestscriptforspeechsynthesis:

$rosrunsample_ttstest.py

Questions1. Whatarethebasicproceduresinvolvedinconvertingspeechtotext?2. Whatisthefunctionoftheacousticmodelandlanguagemodelinspeechrecognition?3. Whatarethebasicproceduresinvolvedinconvertingtexttospeech?4. Whataretheproceduresinvolvedinphoneticanalysisandprosodicanalysis?5. HowcanweimprovetherecognitionaccuracyofSphinxandJulius?

SummaryThemainaimofthischapterwastodiscussspeechrecognitionandsynthesisandhowwecanimplementitonourrobot.Byaddingspeechfunctionalitiesinourrobot,wecanmaketherobotmoreinteractivethanbefore.Wesawwhataretheprocessesinvolvedinthespeechrecognitionandsynthesisprocess.Wealsosawtheblockdiagramoftheseprocessesandthefunctionsofeachblock.Afterdiscussingtheblocks,wesawsomeinterestingspeechrecognitionframeworks(suchasSphinx/PocketSphinx,Julius,andWindowsSpeechSDKandsynthesislibrariessuchaseSpeakandFestival).Afterdiscussingtheselibraries,wediscussedandworkedwiththePythoninterfacingofeachlibrary.Towardstheendofthischapter,wediscussedandworkedwiththeROSpackagesthatperformspeechrecognitionandsynthesisfunctionalities.

Chapter9.ApplyingArtificialIntelligencetoChefBotUsingPythonInthepreviouschapter,wehavediscussedandimplementedspeechrecognitionandspeechsynthesisusingPythonandROS.Inthischapter,wewilldiscusshowtoapplyAItoChefBottocommunicatewithpeopleintelligently,likeahuman.Actually,thesefeaturesareadd-onsinChefBot,whichcanincreasehuman-robotinteractionandmaketherobotresembleahumanfoodsupplier.Inthischapter,wewillmainlycoverthefollowingtopics:

BlockdiagramofChefBot'scommunicationsystemIntroductiontoAIMLandPyAIMLInterfacingChefBot'sAImoduletoROS

AI(ArtificialIntelligence)canbedefinedastheintelligentbehaviorexhibitedbycomputersormachines.UsingAI,wecancreateavirtualintelligenceinmachinestoperformaspecifictasklikeahuman.Inthischapter,wewilluseasimplemethodtoapplyAItotherobot.Thisintelligencewillworkusingpatternmatchingandsearchingalgorithms.Theinput-outputdialogpatternsbetweentheuserandrobotarestoredinfilescalledArtificialIntelligenceMarkupLanguage(AIML)andwewillinterpretthesestoredpatternsusingaPythonmodulecalledPyAIML.TheusercanstoredesiredpatternsinAIMLfilesandtheinterpretermodulewillsearchforappropriateresponsefromthedataset.Wecandevelopourownpatterndatasetforourrobotsimplybywritinglogicalpatterns.Inonesectionofthischapter,wewillseehowtowriteAIMLtagsandpatternsinarobot.Inthefirstsection,wewilldiscusswherewewilluseAIinChefBot.

BlockdiagramofthecommunicationsysteminChefBotThefollowingblockdiagramshowshowChefBotcommunicatesandinteractswithhumansusingspeech:

Robotcommunicationblockdiagram

Therobotcanconverthumanspeechtotextusingthespeechrecognitionsystemandcanconverttextualdatatospeechusingspeechsynthesis.Wehavealreadydiscussedtheseprocessesinthepreviouschapter.TheAIwewilldiscusshereiscontainedinbetweenthesetwoblocks.Afterreceivingthetextdatafromaspeechtotextconversionstage,itissenttotheAIMLinterpreter.TheAIMLinterpreterretrievesthemostmeaningfulreplyfromtheAIMLdataset.Thedatasetoftherobotcanbeanything,suchasfooddetails,casualtalks,andsoon.TheusercanwriteanykindofpatterninAIMLfiles.InthecaseofChefBot,theusercanaskaboutfooddetailsorcancommandtherobottodosomething.Therobotcommandsystemcheckswhethertheconvertedtextisacommandtotherobot.Ifit'sacommand,itisdirectlysenttothehardwarenodestoexecute.TheoutputtextfromAIMLwillbeconvertedtospeechusingatext-to-speechsystem.Also,wecanputanLCDdisplaytoshowtheresultofspeechintheformofananimatedface.Allthesefeaturesenhancetherobot'sinteraction.BeforewediscussthePythoninterpreterforAIML,wewilldiscussAIMLandAIMLtagsindetail.

IntroductiontoAIMLAIMLfilesareasubsetofExtensibleMark-upLanguage(XML)thatcanstoredifferenttextpatternsintheformoftags.AIMLwasdevelopedbytheAlicebotfreesoftwarecommunity(http://www.alicebot.org/).AIMLismainlyusedtoimplementChatbots,anaturallanguagesoftwareagentinwhichausercanaskquestionstotherobotanditcangiveanintelligentreply.ThissametechniqueisusedinChefBot.Usingspeechrecognition,therobotgetsinputtextfromtheuserandanAIMLinterpreter;asoftwareprogramthatcaninterpretAIMLfilesandretrieveanintelligentreplyfromtheAIMLdataset.Thereplywillbeconvertedtospeech.AIMLfilesmainlyconsistofvarioustags.HereareasetofcommonlyusedAIMLtags.

IntroductiontoAIMLtagsAIMLfilesconsistofasetofcommonlyusedAIMLtags.Let'stakealookatthem.

The<aiml>tag:EachAIMLcodebeginswiththistagandisclosedusingthe</aiml>tag.Thistagalsoconsistsofattributessuchastheversionandencodingschemeofthefile.TheAIMLfilecanparseevenwithouttheseattributes,butthiswillbeusefulinbigprojects.TheversionattributecorrespondstothecurrentversionofAIMLthatwewilluse.Theencodingattributeisthetypeofcharacterencodingwewilluseinthisfile.ThefollowingcodesnippetshowsanexampleusageofAIMLtags:

<aimlversion="1.0.1"encoding="UTF-8">

</aiml>

The<category>tag:ThebasicknowledgeblocksofAIMLarecalledcategories.Eachcategoryblockconsistsoftwosections.Oneistheuserinputintheformofasentenceandtheotherisacorrespondingresponsetouserinputwhichcomesfromrobot.Thecategorytagisrepresentedusingtheopening<category>tagandtheclosingtagisrepresentedusingthe</category>tag.Thesecategoriesmustbeinsidethe<aiml>and</aiml>tags.Thecategorytagsconsistoftwotags,namely,the<pattern>tagandthe<template>tag.Theinputgivenbyusersisinsidethe<pattern>tagandtheanswersareinthe<template>tag.Forexample,lookatthisfollowingconversation:

User:Howareyou?

Robot:Iamfine.

Inthisconversation,theuserdialogwillbeinthe<pattern>tagandtherobot'sresponsewillbeinthe<template>tag.ThefollowingcodeshowstherepresentationoftheprecedingdialogsintheAIMLformat:

<pattern>HOWAREYOU</pattern>

<template>IAMFINE</template>

</category>

</aiml>

Weneedtosavethisfileinthe.aimlor.xmlformat.

The<pattern>tag:Thepatterntagcomprisesofpossibleuserinputs.Therewillbeonlyone<pattern>taginacategoryblock.The<pattern>tagwillbethefirstelementofthe<category>tagand,inthe<pattern>tag,wordsareseparatedbysinglespaces.Thesentencein<pattern>tagmayhavewordsorwildcardssuchas"*"or"_",whichcanreplaceastringinthisposition.Intheprecedingexample,the<pattern>HOWAREYOU</pattern>codeindicatesthepossibleuserinputinthiscategory.

The<template>tag:The<template>tagcomprisesofpossibleanswersfortheuserinput.The<template>tagwillbewithinthe<category>tagandwillbeplacedafterthe<pattern>tag.The<template>tagcansaveaparticularansweroritcantriggerprograms.Also,wecangiveconditionalformofanswerstoo.Intheprecedingcode,the<template>tagsentence:"IAMFINE"willbetheanswerforthe"HOWAREYOU"pattern.Wecaninsertadditionaltagsinthe<template>tag.Thefollowingtagsareusedinthe<template>tag:

The<starindex="n"/>tag:Thistagisusedtoextractapartoftheusertextinputsentence.Thenindexindicateswhichfragmentoftexthastobeextractedandtakenfromtheentiresentence:

<starindex="1"/>:Thisindicatesthefirstfragmentofasentence<starindex="2"/>:Thisindicatesthesecondfragmentofasentence

Themainapplicationofthistagistoextractandstorethetextfromuserinput.Thefollowingisadialogbetweentherobotandtheuser.Thewildcardcanbeanything,suchasanameorsomethingelse.Usingthistag,wecanextractthiswildcardportionanduseitintheansweringsection:

User:Mynameis*

Robot:Nicetomeetyou*

So,iftheusersays,"MynameisLentin",thentherobotwillreply,"NicetomeetyouLentin".Thiskindofconversationisonlypossibleusingthe<star>tagandwildcardssuchas"*".ThecompleteAIMLexampleusingthestartagisasfollows:

<pattern>MYNAMEIS*</pattern>

NICETOMEETYOU<star/>

</template>

</category>

<pattern>MEETOURGUEST*AND*</pattern>

NICETOMEETYOU<starindex="1"/>AND<starindex="2"/>.

</template>

</category>

</aiml>

IfweloadthisexampletotheAIMLinterpreter,wewillgetthefollowingreplywhenwegivethefollowinginput:

USER:MYNAMEISLENTIN

ROBOT:NICETOMEETYOULENTIN

Thepreviousconversationusesonewildcardandthefollowingconversationwillusebothwildcards:

USER:MEETOURGUESTTOMANDJOSEPH

ROBOT:NICETOMEETYOUTOMANDJOSEPH

Here,thenameis"TOM",theindexnumberis"1",and"JOSEPH"isindexedas"2".

The<srai>tag:Usingthe<srai>tag,wecantargetmultiplepatternsfromasingle<template>tag.Usingthe<srai>tag,theAIMLinterpretercansearchrecursivelyfortheanswerthatisreplacingthecurrenttemplatetextwiththetemplatetextofanotherpattern.Thefollowingcodeisanexampleoftheusageofthe<srai>tag:

<pattern>WHATISAROBOT?</pattern>

AROBOTISAMACHINEMAINLYDESIGNEDFOREXECUTINGREPEATEDTASKWITHSPEEDAND

PRECISION.

</template>

</category>

<pattern>DOYOUKNOWWHATA*IS?</pattern>

<srai>WHATISA<star/></srai>

</template>

</category>

</aiml>

Whenauseraskstherobot,"DOYOUKNOWWHATAROBOTIS",itwillgotothesecondcategorytemplateandextractthewildcardsectionfromuserinput,"ROBOT"andputthecompletesentence,"WHATISAROBOT",andputitinthe<srai>tag.The<srai>tagcancallthepatterncalled"WHATISAROBOT"andfilltheoutputofthistemplatetotheactualtemplatetext.

FormoreAIMLtags,youcanrefertohttp://www.alicebot.org/documentation/aiml-reference.html.

AfterdiscussingAIMLfilesandtags,wewilldiscussthePythonAIMLinterpretertodecodeAIMLfiles.TheAIMLinterpretercanretrievethetemplatetextfromuserinput.WewilluseaPythonmodulecalledPyAIMLtointerpretAIMLfiles.Let'sdiscussmoreaboutPyAIML.

IntroductiontoPyAIMLPyAIMLisanopensourcePythonAIMLinterpreterwrittencompletelyinpurePythonwithoutusinganythird-partydependencies.ThemodulewillreadallthepatternsofAIMLfrommemoryandbuildadirectedpatterntree.Thebacktrackingdepth-firstsearchalgorithmisimplementedinthismoduleforpatternmatching.

Now,wecancheckwhetherwecaninstallPyAIMLonoursystem.ThePyAIMLmodulecanbeinstalledonLinux,Windows,andMacOSX.ThereareprebuiltbinariesofPyAIMLavailableonUbuntuandthesourcecodeofthismoduleisalsoavailableonGitHub.Currently,weareworkingwithPythonversion2.7,oranythinglessthan2.8,toinstallPyAIML.

InstallingPyAIMLonUbuntu14.04.2PyAIMLcanbeinstalledonUbuntuusingtheapt-getcommand.ThebinariesareavailableontheUbuntupackagerepositories.ThePythonversionweareworkingwithis2.7.6andthePyAIMLversionweareinstallingis0.86.ThefollowingcommandwillinstallPyAIMLonUbuntu14.04.2:

$sudoapt-getinstallpython-aiml

YoushouldinstallGittogetthesourcecode.Also,youshouldhavePythonversion2.7orgreaterthan2.7andlessthan2.8.Werequirethelatestversionofthemoduleifweareperformingtheinstallationviasourcecode.

InstallingPyAIMLfromsourcecodeWecanretrievethesourcecodemoduleusingthefollowinggitcommand:

$gitclonegit://pyaiml.git.sourceforge.net/gitroot/pyaiml/pyaiml

Aftercloningthecode,changethedirectorytoacloneddirectorynamedpyaiml:

$cdpyaiml

Installthemoduleusingthefollowingcommand:

WorkingwithAIMLandPythonTocheckwhetherthemoduleisproperlyinstalledonyourmachine,openaPythonIDLEandimporttheaimlmodule:

>>>importaiml

Ifthemoduleisimportedcorrectly,itwillnotshowanyerrorandcomestothenextline.Then,wecanconfirmthattheinstallationiscorrect.

ThemostimportantclasswearehandlingintheaimlmoduleisKernel().WearemainlyusingthisclasstolearnfromAIMLfilesandgetaresponsefromtheAIMLdatasettouserinput.Thefollowinglinewillcreateanobjectoftheaiml.Kernel()class:

>>>mybot=aiml.Kernel()

AftercreatingtheKernel()object,wecanassigntherobotnameusingthefollowingcommand.WewillassignChefbotasthenameforthisrobot:

>>>mybot.setBotPredicate("name","Chefbot")

ThenextstepistolearnAIMLfiles.WecanloadeitherasingleAIMLfileoragroupofAIMLfiles.ToloadasingleAIMLfile,wecanusethefollowingcommand.Notethatthesample.aimlfilemustbeinthecurrentpath:

>>>mybot.learn('sample.aiml')

Theprecedingcommandwillloadthesample.aimlfileintomemoryandtheoutputisasfollows:

Loadingsample.aiml...done(0.01seconds)s

IfyouwanttolearnmorethanoneAIML,it'sbettertouseanAIML/XMLfile,forexample,thestartup.xmlfilecanloadallotherAIMLfiles.Wewillseehowstartup.xmlworksinthenextsection.Tolearnstartup.xml,usethefollowingcommand:

>>>mybot.learn("startup.xml")

Afteryoulearnstartup.xml,let'striggerapatterninstartup.xmlcalled"LOADAIMLB".Whenwecallthispattern,itwillrespondbylearningallAIMLfilesandprinttheresponseinstringafterlearningeachAIMLfile:

>>>mybot.respond("loadaimlb")

AfterlearningAIMLfiles,wecanstartinputtingtexttothekernelobjectandretrievetheintelligenttextusingthefollowingcode:

>>>whileTrue:printk.respond(raw_input(">"))

ThecompletePythoncodetoloadoneAIMLfileandgetaresponsefromtheAIMLdatasetisgiven

inthecodesnippetinthefollowingsection.WecanpasstheAIMLfileasacommand-lineargument.

LoadingasingleAIMLfilefromthecommand-lineargumentWecanloadasingleAIMLfileusingthefollowingcode:

importaiml

importsys

mybot=aiml.Kernel()

mybot.learn(sys.argv[1])

whileTrue:

printmybot.respond(raw_input("Enterinput>"))

ThefollowingisthesampleAIMLfilerequiredtoloadinthiscode.Savethefollowingcodewiththenamesample.aiml:

<pattern>HOWAREYOU</pattern>

<template>IAMFINE</template>

</category>

</aiml>

Savethecodeaschatbot.pyandchangethepermissionofthecodeusingthefollowingcommand:

$chmod+xchatbot.py

Executethecodeusingthefollowingcommand:

$./chatbotsample.aiml

Itwillgiveyouthefollowingresult:

PressCtrl+Ctoquitthedialog.WecancheckwhethereachAIMLexamplewepreviouslydiscussedcanbetestedusingthisexample.

IfthereismorethanoneXMLfile,wecanusethefollowingcodetoloadalltheAIMLfilesintomemory.Let'sdownloadsomeAIMLdatasetfromtheArtificialLinguisticInternetComputer

Entity(A.L.I.C.E)robotandloaditusingPyAIML.

WorkingwithA.L.I.C.E.AIMLfilesTheAIMLfilesofA.L.I.C.E.chatterarefreelyavailableathttps://code.google.com/p/aiml-en-us-foundation-alice/.

ExtracttheAIMLfilestoafolderonthedesktoporinthehomedirectoryandcopystartup.xmltotheseAIMLfiles.Thisstartup.xmlfilewillloadalltheotherAIMLfilesintomemory.Thefollowingcodeisanexampleofatypicalstartup.xmlfile:

<aimlversion="1.0">

<pattern>LOADAIMLB</pattern>

</template>

</category>

</aiml>

TheprecedingXMLfilewilllearnalltheAIMLfileswhenwecalltheLOADAIMLBpattern.

LoadingAIMLfilesintomemoryThefollowingcodewillloadalltheAIMLfilesintomemory:

importaiml

importsys

importos

#Changethecurrentpathtoyouraimlfilespath

os.chdir('/home/lentin/Desktop/aiml-files')

mybot=aiml.Kernel()

#Learnstartup.xml

mybot.learn('startup.xml')

#CallingloadaimlbforloadingallAIMLfiles

mybot.respond('loadaimlb')

whileTrue:

Youwillgetthefollowingoutput:

LoadingAIMLfileswilltakesometime.Toavoidinitialloadingtime,wecandumptheAIMLpatternsloadedinthememoryandsavethemtobrainfiles.Loadingbrainfileswillsaveinitialloadingtime.

LoadingAIMLfilesandsavingtheminbrainfilesThefollowingcodewillloadAIMLfilesandsavetheminbrainfiles:

importaiml

importsys

importos

mybot=aiml.Kernel()

mybot.learn('startup.xml')

mybot.respond('loadaimlb')

#Savingloadedpatternsintoabrainfile

mybot.saveBrain('standard.brn')

whileTrue:

Youwillgetthefollowingoutput:

IfwewanttoinitializetherobotfromthebrainfileorAIMLfiles,abetterwayistousethebootstrap()methodinsidetheKernel()class.Thebootstrap()methodtakesthebrainfileorAIMLfilesandsomecommandasargument.Thecodeforloadingthebrainfileifitexistsisinthefollowingsection;otherwise,loaditfromAIMLandsaveanewbrainfile.Afterthisprocessiscomplete,respondfromtheloadeddataset.

LoadingAIMLandbrainfilesusingtheBootstrapmethodThefollowingcodewillloadAIMLfilesandbrainfilesusingtheBootstrapmethod:

importaiml

importsys

importos

#Changingcurrentdirectorytothepathofaimlfiles

#Thispathwillchangeaccordingtoyourlocationofaimlfiles

mybot=aiml.Kernel()

#Ifthereisabrainfilenamedstandard.brn,Kernel()willinitializeusing

bootstrap()method

ifos.path.isfile("standard.brn"):

mybot.bootstrap(brainFile="standard.brn")

#Ifthereisnotbrainfile,loadallAIMLfilesandsaveanewbrain

mybot.bootstrap(learnFiles="startup.xml",commands="loadaimlb")

mybot.saveBrain("standard.brn")

#ThisloopaskforresponsefromuserandprinttheoutputfromKernel()object

whileTrue:

IntegratingPyAIMLintoROSInthissection,wearegoingtodevelopROSPythonnodeswhichcanhandleAIMLfiles.WeareusingthePythoncodethatwedevelopedintheprecedingsection.TheROSversionwearegoingtouseisIndigoandtheUbuntuversionwewilluseis14.04.2.WealreadydiscussedtheinterfacingofspeechrecognitionandspeechsynthesisinROSandalsodiscussedthePythoncodetointerfaceAIMLfiles.Inthissection,wewillmakeapackageinROStohandleAIMLfiles.Currently,therearenoactivepackagesinROSrepositoriesthatcanhandleAIMLfiles.Wewillbuildourownpackageusingthecodethatwedevelop.

CreateaROSpackageusingthefollowingdependencies.Herethesound_playpackageisusedforspeechsynthesis:

$catkin_create_pkgros_aimlrospystd_msgssound_play

Createascriptsfolderinsidetheros_aimlpackageandcreatethefollowingPythonfilesinit.CreateafoldercalleddataandcopytheALICEAIMLdatasetwehavealreadydownloadedtothisfolder.

aiml_server.pyThefollowingcodeactsasanAIMLserverinwhichanAIMLclientcansenduserinputtotheserverthroughthe/chattertopicandretrievetheAIMLoutputresponsethroughthe/responsetopic:

importrospy

importaiml

importos

importsys

rospy.init_node('aiml_server')

mybot=aiml.Kernel()

#CreatingaROSpublisherforthe/responsetopic

response_publisher=rospy.Publisher('response',String,queue_size=10)

#FunctiontoloadAIMLfilesusingbootstrap()method

defload_aiml(xml_file):

#Getthepathofaimldataset.Wehavetomentionthispathonlaunchfileasa

rosparameter

data_path=rospy.get_param("aiml_path")

os.chdir(data_path)

ifos.path.isfile("standard.brn"):

mybot.bootstrap(brainFile="standard.brn")

mybot.bootstrap(learnFiles=xml_file,commands="loadaimlb")

mybot.saveBrain("standard.brn")

#Callbackfunctionof/chattertopic.Itwillreceiveinputfromuserandfeedto

respond()methodofKernel()object.andprinttheresults

defcallback(data):

input=data.data

response=mybot.respond(input)

rospy.loginfo("Iheard::%s",data.data)

rospy.loginfo("Ispoke::%s",response)

response_publisher.publish(response)

#Methodtocreatesubscriberin/chattertopic

deflistener():

rospy.loginfo("StartingROSAIMLServer")

rospy.Subscriber("chatter",String,callback)

#spin()simplykeepspythonfromexitinguntilthisnodeisstopped

rospy.spin()

load_aiml('startup.xml')

listener()

aiml_client.pyThisisasimpleclientcodethatwillsenduserinputtakenfromthekeyboardtotheAIMLserver.Theuserinputissendthroughthe/chattertopic:

importrospy

#Creatingapublisherforchattertopic

pub=rospy.Publisher('chatter',String,queue_size=10)

rospy.init_node('aiml_client')

whilenotrospy.is_shutdown():

#Receivingtextinputfromuser

input=raw_input("Enteryourtext:>")

#Publishingtochattertopic

pub.publish(input)

r.sleep()

aiml_tts_client.pyThisclientwilltranscribetheresponsefromaiml_serverandconvertittospeech.Thiscodeisadaptedfromtheclientcode,aswediscussedinthepreviouschapterforspeechsynthesis,aswediscussedinthepreviouschapter.Wewillusethesound_playpackagetoperformTTS:

importrospy,os,sys

fromsound_play.msgimportSoundRequest

fromsound_play.libsoundplayimportSoundClient

rospy.init_node('aiml_soundplay_client',anonymous=True)

soundhandle=SoundClient()

rospy.sleep(1)

soundhandle.stopAll()

print'StartingTTS'

#Callbackmethodtoreceivetextfrom/responsetopicandconverttospeech

defget_response(data):

response=data.data

rospy.loginfo("Response::%s",response)

soundhandle.say(response)

#Methodtocreateasubscriberfor/responsetopic.

deflistener():

rospy.loginfo("Startinglisteningtoresponse")

rospy.Subscriber("response",String,get_response,queue_size=10)

rospy.spin()

listener()

aiml_speech_recog_client.pyThisclientcansendthespeechtotextdatatotheAIMLserverinsteadoftypingonthekeyboard.Beforerunningthiscode,wehavetolaunchthePocketSphinxspeechrecognizer.Wecanseehowtorunthiscodeafterdiscussingit:

importrospy

rospy.init_node('aiml_speech_recog_client')

pub=rospy.Publisher('chatter',String,queue_size=10)

#Theoutputofpocketsphinxpackageissendingconvertedtextto/recognizer/output

topic.Thefollowingfunctionisthecallbackofthistopic.Thetextwillreceive

andsendthrough/chattertopic,whichisreceivedbyAIMLserver

defget_speech(data):

speech_text=data.data

rospy.loginfo("Isaid::%s",speech_text)

pub.publish(speech_text)

#Creatingasubscriberforpocketsphinxoutputtopic/recognizer/output

deflistener():

rospy.loginfo("StartingSpeechRecognition")

rospy.Subscriber("/recognizer/output",String,get_speech)

rospy.spin()

listener()

Let'sseehowthesenodescommunicatewiththeAIMLserver:

Aftercreatingallthescriptsinthescriptsfolder,createanotherfoldercalledlaunchintheros_aimlpackagetostorethelaunchfiles.Ithelpstolaunchallthenodesinasinglerun.Createthefollowinglaunchfilesinthelaunchfolder.

start_chat.launchThislaunchfilewilllaunchaiml_server.pyandaiml_client.py,inwhichtheuserwillreceivetheinputastextandtheresponseastext.Theaiml_pathROSparameterhastomentiontheminthelaunchfile:

<paramname="aiml_path"value="/home/lentin/catkin_ws/src/ros_aiml/data"/>

<nodename="aiml_server"pkg="ros_aiml"type="aiml_server.py"output="screen">

</node>

<nodename="aiml_client"pkg="ros_aiml"type="aiml_client.py"output="screen">

</node>

</launch>

start_tts_chat.launchThislaunchfilewilllaunchthetextinputandspeechsynthesisoftheAIMLresponse:

</node>

<includefile="$(findsound_play)/soundplay_node.launch">

</include>

<nodename="aiml_tts"pkg="ros_aiml"type="aiml_tts_client.py"output="screen">

</node>

<nodename="aiml_client"pkg="ros_aiml"type="aiml_client.py"output="screen">

</node>

</launch>

start_speech_chat.launchThisfilewilllaunchthespeechrecognitionclient,synthesisclient,andAIMLserver.Thiswillnotlaunchpocketsphinx;weneedtolaunchitseparately.Thislaunchfileenablesyoutoreceivetextinputfromthespeechrecognizerandconverttheresponsetospeechtoo:

</node>

<includefile="$(findsound_play)/soundplay_node.launch"></include>

<nodename="aiml_tts"pkg="ros_aiml"type="aiml_tts_client.py"output="screen">

</node>

<nodename="aiml_speech_recog"pkg="ros_aiml"type="aiml_speech_recog_client.py"

output="screen">

</node>

</launch>

Aftercreatingallthelaunchfiles,changethepermissionofallthelaunchfilesusingthefollowingcommand,whichwehavetoexecuteinthelaunchfolder:

$chmod+x*.launch

Thefolderstructureofthispackageisgiveninthefollowingdiagram.Aftercreatingthispackage,verifyitwiththisdiagram:

LaunchtheAIMLserverandclientfortextchattingusingthefollowingcommand:

$roslaunchros_aimlstart_chat.launch

Whenyoulaunchthisfile,theusercaninputthetextandthereplywillbeprinted.

LaunchtheAIMLserverandclientwithtextchattingandspeechsynthesis,usingthefollowingcommand:

$roslaunchros_aimlstart_tts_chat.launch

Whenyoulaunchthisfile,itwillstartthetextchattinginterfaceandthereplytextwillbesynthesizedusingthespeechsynthesizer.

Startthepocketsphinxdemolaunchfiletostartspeechrecognition.Thefollowinglaunchfileisademothatwilldetectsomewordsandsentences.Ifwewantmoreaccuracy,wehavetotrainthemodel:

$roslaunchpocketsphinxrobocup.launch

LaunchtheAIMLserver,speechrecognition,andsynthesisclientusingthefollowingcommand:

$roslaunchros_aimlstart_speech_chat.launch

Afteryouruntheprecedinglaunchfiles,theusercaninteractwiththeAIMLserverusingspeechandtheuserwillgettheoutputasspeechaswell.

Questions1. WhatisArtificialIntelligence?2. WhatistheuseofanAIMLfile?3. WhicharethemostcommonlyusedAIMLtags?4. WhatistheuseofthePyAIMLmodule?

SummaryInthischapter,wediscussedhowtoaddArtificialIntelligencetoChefBotinordertointeractwithpeople.Thisfunctionisanadd-ontoChefBottoincreasetheinteractivityoftherobot.WeusedsimpleAItechniquessuchaspatternmatchingandsearchinginChefBot.ThepatterndatasetsarestoredinaspecialtypeoffilecalledAIML.ThePythoninterpretermoduleiscalledPyAIML.WeusedthistodecodeAIMLfiles.TheusercanstorethepatterndatainanAIMLformatandPyAIMLcaninterpretthispattern.Thismethodissimilartoastimulus-responsesystem.TheuserhastogiveastimulusintheformoftextdataandfromtheAIMLpattern,themodulefindstheappropriatereplytotheuserinput.Wesawtheentirecommunicationsystemoftherobotandhowtherobotcommunicateswithpeople.ItincludesspeechrecognitionandsynthesisalongwithAI.Wealreadydiscussedspeechinthepreviouschapter.WealsosawusefultagsusedinAIMLandthePyAIMLinstallation,howtheywork,andsomeexamples.Finally,weimplementedtheentirecodeinROSalongwiththespeechrecognitionandsynthesisunits.Inthenextchapter,wewilldiscusstheintegrationofcomponentsintherobot,whichwehavenotdiscusseduntilnow.

Chapter10.IntegrationofChefBotHardwareandInterfacingitintoROS,UsingPythonInChapter2,MechanicalDesignofaServiceRobot,wesawtheChefBotchassisdesignandnowwehavegotthemanufacturedpartsofthisrobot.Inthischapter,wewillseehowtoassemblethisrobotusingthesepartsandalsothefinalinterfacingofsensorsandotherelectronicscomponentsofthisrobottoTivaCLaunchPad.WehavealreadydiscussedinterfacingofindividualrobotcomponentsandsensorswithLaunchpad.Inthischapter,wewilltrytointerfacethenecessaryroboticcomponentsandsensorsofChefBotandprogramitinsuchawaythatitwillreceivethevaluesfromallsensorsandcontroltheinformationfromthePC.LaunchpadwillsendallsensorvaluesviaaserialporttothePCandalsoreceivecontrolinformation(suchasresetcommand,speed,andsoon)fromthePC.

AfterreceivingsensorvaluesfromthePC,aROSPythonnodewillreceivetheserialvaluesandconvertittoROSTopics.TherearePythonnodespresentinthePCthatsubscribetothesensor'sdataandproducesodometry.ThedatafromthewheelencodersandIMUvaluesarecombinedtocalculatetheodometryoftherobotanddetectobstaclesbysubscribingtotheultrasonicsensorandlaserscanalso,controllingthespeedofthewheelmotorsbyusingthePIDnode.Thisnodeconvertsthelinearvelocitycommandtodifferentialwheelvelocity.Afterrunningthesenodes,wecanrunSLAMtomaptheareaandafterrunningSLAM,wecanruntheAMCLnodesforlocalizationandautonomousnavigation.

Inthefirstsectionofthischapter,BuildingChefBothardware,wewillseehowtoassembletheChefBothardwareusingitsbodypartsandelectronicscomponents.

BuildingChefBothardwareThefirstsectionoftherobotthatneedstobeconfiguredisthebaseplate.Thebaseplateconsistsoftwomotorsanditswheels,casterwheels,andbaseplatesupports.Thefollowingimageshowsthetopandbottomviewofthebaseplate:

Baseplatewithmotors,wheels,andcasterwheels

Thebaseplatehasaradiusof15cmandmotorswithwheelsaremountedontheoppositesidesoftheplatebycuttingasectionfromthebaseplate.Arubbercasterwheelismountedontheoppositesideofthebaseplatetogivetherobotgoodbalanceandsupportfortherobot.Wecaneitherchooseballcasterwheelsorrubbercasterwheels.Thewiresofthetwomotorsaretakentothetopofthebaseplatethroughaholeinthecenterofthebaseplate.Toextendthelayersoftherobot,wewillputbaseplatesupportstoconnectthenextlayers.Now,wecanseethenextlayerwiththemiddleplateandconnectingtubes.Therearehollowtubes,whichconnectthebaseplateandthemiddleplate.Asupportisprovidedonthebaseplateforhollowtubes.Thefollowingfigureshowsthemiddleplateandconnectingtubes:

Middleplatewithconnectingtubes

Theconnectingtubeswillconnectthebaseplateandthemiddleplate.Therearefourhollowtubesthatconnectthebaseplatetothemiddleplate.Oneendofthesetubesishollow,whichcanfitinthebaseplatesupport,andtheotherendisinsertedwithahardplasticwithanoptiontoputascrewinthehole.Themiddleplatehasnosupportexceptfourholes:

Fullyassembledrobotbody

Themiddleplatemaleconnectorhelpstoconnectthemiddleplateandthetopofthebaseplatetubes.Atthetopofthemiddleplatetubes,wecanfitthetopplate,whichhasfoursupportsontheback.Wecaninsertthetopplatefemaleconnectorintothetopplatesupportandthisishowwewillgetthefullyassembledbodyoftherobot.

ThebottomlayeroftherobotcanbeusedtoputthePrintedCircuitBoard(PCB)andbattery.Inthemiddlelayer,wecanputKinectandIntelNUC.Wecanputaspeakerandamicifneeded.Wecanusethetopplatetocarryfood.ThefollowingfigureshowsthePCBprototypeofrobot;itconsistsofTivaCLaunchPad,amotordriver,levelshifters,andprovisionstoconnecttwomotors,ultrasonic,andIMU:

ChefBotPCBprototype

Theboardispoweredwitha12Vbatteryplacedonthebaseplate.ThetwomotorscanbedirectlyconnectedtotheM1andM2maleconnectors.TheNUCPCandKinectareplacedonthemiddleplate.TheLaunchpadboardandKinectshouldbeconnectedtotheNUCPCviaUSB.ThePCandKinectarepoweredusingthesame12Vbatteryitself.Wecanusealead-acidorlithium-polymerbattery.Here,weareusingalead-acidcellfortestingpurposes.Wewillmigratetolithium-polymerforbetterperformanceandbetterbackup.ThefollowingfigureshowsthecompleteassembleddiagramofChefBot:

Fullyassembledrobotbody

Afterassemblingallthepartsoftherobot,wewillstartworkingwiththerobotsoftware.ChefBot'sembeddedcodeandROSpackagesareavailableinGitHub.Wecanclonethecodeandstartworkingwiththesoftware.

ConfiguringChefBotPCandsettingChefBotROSpackagesInChefBot,weareusingIntel'sNUCPCtohandletherobotsensordataanditsprocessing.AfterprocuringtheNUCPC,wehavetoinstallUbuntu14.04.2orthelatestupdatesof14.04LTS.AftertheinstallationofUbuntu,installcompleteROSanditspackageswementionedinthepreviouschapters.WecanconfigurethisPCseparately,andafterthecompletionofallthesettings,wecanputthisintotherobot.ThefollowingaretheprocedurestoinstallChefBotpackagesontheNUCPC.

CloneChefBot'ssoftwarepackagesfromGitHubusingthefollowingcommand:

WecanclonethecodeinourlaptopandcopythechefbotfoldertoIntel'sNUCPC.ThechefbotfolderconsistsoftheROSpackagesofChefBot.IntheNUCPC,createaROScatkinworkspace,copythechefbotfolderandmoveitinsidethesrcdirectoryofthecatkinworkspace.

BuildandinstallthesourcecodeofChefBotbysimplyusingthefollowingcommandThisshouldbeexecutedinsidethecatkinworkspacewecreated:

$catkin_make

IfalldependenciesareproperlyinstalledinNUC,thentheChefBotpackageswillbuildandinstallinthissystem.AftersettingtheChefBotpackagesontheNUCPC,wecanswitchtotheembeddedcodeforChefBot.Now,wecanconnectallthesensorsinLaunchpad.AfteruploadingthecodeinLaunchpad,wecanagaindiscussROSpackagesandhowtorunit.TheclonedcodefromGitHubcontainsTivaCLaunchPadcode,whichisgoingtobeexplainedintheupcomingsection.

InterfacingChefBotsensorswithTivaCLaunchPadWehavediscussedinterfacingofindividualsensorsthatwearegoingtouseinChefBot.Inthissection,wewilldiscusshowtointegratesensorsintotheLaunchpadboard.TheEnergiacodetoprogramTivaCLaunchPadisavailableontheclonedfilesatGitHub.TheconnectiondiagramofTivaCLaunchPadwithsensorsisasfollows.Fromthisfigure,wegettoknowhowthesensorsareinterconnectedwithLaunchpad:

SensorinterfacingdiagramofChefBot

M1andM2aretwodifferentialdrivemotorsthatweareusinginthisrobot.ThemotorswearegoingtousehereisDCGearedmotorwithanencoderfromPololu.ThemotorterminalsareconnectedtotheVNH2SP30motordriverfromPololu.Oneofthemotorsisconnectedinreversepolaritybecauseindifferentialsteering,onemotorrotatesoppositetotheother.Ifwesendthesamecontrolsignaltoboththemotors,eachmotorwillrotateintheoppositedirection.Toavoidthiscondition,wewillconnectitinoppositepolarities.ThemotordriverisconnectedtoTivaCLaunchPadthrougha3.3V-5Vbidirectionallevelshifter.Oneofthelevelshifterwewillusehereisavailableat:https://www.sparkfun.com/products/12009.

ThetwochannelsofeachencoderareconnectedtoLaunchpadviaalevelshifter.Currently,weareusingoneultrasonicdistancesensorforobstacledetection.Infuture,wecouldexpandthisnumber,ifrequired.Togetagoododometryestimate,wewillputIMUsensorMPU6050throughanI2Cinterface.ThepinsaredirectlyconnectedtoLaunchpadbecauseMPU6050is3.3Vcompatible.ToresetLaunchpadfromROSnodes,weareallocatingonepinastheoutputandconnectedtoresetpinofLaunchpad.WhenaspecificcharacterissenttoLaunchpad,itwillsettheoutputpintohighandresetthedevice.Insomesituations,theerrorfromthecalculationmayaccumulateanditcanaffectthenavigationoftherobot.WeareresettingLaunchpadtoclearthiserror.Tomonitorthebatterylevel,weareallocatinganotherpintoreadthebatteryvalue.ThisfeatureisnotcurrentlyimplementedintheEnergiacode.

ThecodeyoudownloadedfromGitHubconsistsofembeddedcode.Wecanseethemainsectionofthecodehereandthereisnoneedtoexplainallthesectionsbecausewealreadydiscussedit.

EmbeddedcodeforChefBotThemainsectionsoftheLaunchpadcodeisdiscussedhere.Thefollowingaretheheaderfilesusedinthecode:

//LibrarytocommunicatewithI2Cdevices

#include"Wire.h"

//I2CcommunicationlibraryforMPU6050

#include"I2Cdev.h"

//MPU6050interfacinglibrary

#include"MPU6050_6Axis_MotionApps20.h"

//Processingincomingserialdata

#include<Messenger.h>

//Containdefinitionofmaximumlimitsofvariousdatatype

#include<limits.h>

ThemainlibrariesusedinthiscodeareforthepurposeofcommunicatingwithMPU6050andprocesstheincomingserialdatatoLaunchpad.MPU6050canprovidetheorientationinquaternionorEulervaluesbyusingtheinbuiltDigitalMotionProcessor(DMP).ThefunctionstoaccessDMPiswritteninMPU6050_6Axis_MotionApps20.h.ThislibraryhasdependenciessuchasI2Cdev.handWire.h;that'swhyweareincludingtheseheadersaswell.ThesetwolibrariesareusedforI2Ccommunication.TheMessenger.hlibraryallowsyoutohandleastreamoftextdatafromanysourceandhelpstoextractthedatafromit.Thelimits.hheadercontainsdefinitionsofmaximumlimitsofvariousdatatypes.

Afterweincludetheheaderfiles,weneedtocreateanobjecttohandleMPU6050andprocesstheincomingserialdatausingtheMessengerclass:

//CreatingMPU6050Object

MPU6050accelgyro(0x68);

//Messengerobject

MessengerMessenger_Handler=Messenger();

Afterdeclaringthemessengerobject,themainsectionistoassignpinsforthemotordriver,encoder,ultrasonicsensor,MPU6050,reset,andbatterypins.Afterassigningthepins,wecanseethesetup()

functionofthecode.Thedefinitionofthesetup()functionisgivenhere:

//Setupserial,encoders,ultrasonic,MPU6050andResetfunctions

voidsetup()

//InitSerialportwith115200baudrate

//SetupEncoders

SetupEncoders();

//SetupMotors

SetupMotors();

//SetupUltrasonic

SetupUltrasonic();

//SetupMPU6050

Setup_MPU6050();

//SetupResetpins

SetupReset();

//SetupMessengerobjecthandler

Messenger_Handler.attach(OnMssageCompleted);

Theprecedingfunctioncontainscustomroutinetoconfigureandallocatepinsforallthesensors.Thisfunctionwillinitializeserialcommunicationwith115,200baudrateandsetpinsfortheencoder,motordriver,ultrasonic,andMPU6050.TheSetupReset()functionwillassignapintoresetthedevice,asshownintheconnectiondiagram.Wehavealreadyseenthesetuproutinesofeachsensorsinthepreviouschapters,sothereisnoneedtoexplainthedefinitionofeachfunctions.TheMessengerclasshandlerisattachedtoafunctioncalledOnMssageCompleted(),whichwillbecalledwhenadataisinputtotheMessenger_Handler.

Thefollowingisthemainloop()functionofthecode.Themainpurposeofthisfunctionistoreadandprocessserialdataandsendavailablesensorvaluesaswell:

voidloop()

//ReadfromSerialport

Read_From_Serial();

//Sendtimeinformationthroughserialport

Update_Time();

//Sendencodersvaluesthroughserialport

Update_Encoders();

//Sendultrasonicvaluesthroughserialport

Update_Ultra_Sonic();

//UpdatemotorspeedvalueswithcorrespondingspeedreceivedfromPCandsend

speedvaluesthroughserialport

Update_Motors();

//SendMPU6050valuesthroughserialport

Update_MPU6050();

//Sendbatteryvaluesthroughserialport

Update_Battery();

TheRead_From_Serial()functionwillreadserialdatafromthePCandfeeddatatotheMessenger_Handlerhandlerforprocessingpurpose.TheUpdate_Time()functionwillupdatethe

timeaftereachoperationintheembeddedboard.WecantakethistimevaluetoprocessinthePCortakethePCtimeforprocessing.

WecancompilethecodeinEnergiaIDEandcanburnthecodeinLaunchpad.Afteruploadingthecode,wecandiscusstheROSnodestohandletheLaunchpadsensorvalues.

WritingaROSPythondriverforChefBotAfteruploadingtheembeddedcodetoLaunchpad,thenextstepistohandletheserialdatafromLaunchpadandconvertittoROSTopicsforfurtherprocessing.Thelaunchpad_node.pyROSPythondrivernodeinterfacesTivaCLaunchPadtoROS.Thelaunchpad_node.pyfileisonthescriptfolder,whichisinsidethechefbot_bringuppackage.Thefollowingistheexplanationoflaunchpad_node.pyinimportantcodesections:

#ROSPythonclient

importrospy

importsys

importtime

importmath

#Thispythonmodulehelpstoreceivevaluesfromserialportwhichexecuteina

thread

fromSerialDataGatewayimportSerialDataGateway

#ImportingrequiredROSdatatypesforthecode

fromstd_msgs.msgimportInt16,Int32,Int64,Float32,String,Header,UInt64

#ImportingROSdatatypeforIMU

fromsensor_msgs.msgimportImu

Thelaunchpad_node.pyfileimportstheprecedingmodules.ThemainmoduleswecanseeisSerialDataGateway.ThisisacustommodulewrittentoreceiveserialdatafromtheLaunchpadboardinathread.WealsoneedsomedatatypesofROStohandlethesensordata.Themainfunctionofthenodeisgiveninthefollowingcodesnippet:

rospy.init_node('launchpad_ros',anonymous=True)

launchpad=Launchpad_Class()

launchpad.Start()

rospy.spin()

exceptrospy.ROSInterruptException:

rospy.logwarn("Errorinmainfunction")

launchpad.Reset_Launchpad()

launchpad.Stop()

ThemainclassofthisnodeiscalledLaunchpad_Class().Thisclasscontainsallthemethodstostart,stop,andconvertserialdatatoROSTopics.Inthemainfunction,wewillcreateanobjectofLaunchpad_Class().Aftercreatingtheobject,wewillcalltheStart()method,whichwillstarttheserialcommunicationbetweenTivaCLaunchPadandPC.IfweinterruptthedrivernodebypressingCtrl+C,itwillresettheLaunchpadandstoptheserialcommunicationbetweenthePCandLaunchpad.

ThefollowingcodesnippetisfromtheconstructorfunctionofLaunchpad_Class().Inthefollowingsnippet,wewillretrievetheportandbaudrateoftheLaunchpadboardfromROSparametersandinitializetheSerialDateGatewayobjectusingtheseparameters.TheSerialDataGatewayobject

callsthe_HandleReceivedLine()functioninsidethisclasswhenanyincomingserialdataarrivesontheserialport.

Thisfunctionwillprocesseachlineofserialdataandextract,convert,andinsertittotheappropriateheadersofeachROSTopicdatatype:

#GetserialportandbaudrateofTivaCLaunchpad

port=rospy.get_param("~port","/dev/ttyACM0")

baudRate=int(rospy.get_param("~baudRate",115200))

#################################################################

rospy.loginfo("Startingwithserialport:"+port+",baudrate:"+

str(baudRate))

#InitializingSerialDataGatewayobjectwithserialport,baud

rateandcallbackfunctiontohandleincomingserialdata

self._SerialDataGateway=SerialDataGateway(port,baudRate,

self._HandleReceivedLine)

rospy.loginfo("Startedserialcommunication")

###################################################################Subscribersand

Publishers

#Publisherforleftandrightwheelencodervalues

self._Left_Encoder=rospy.Publisher('lwheel',Int64,queue_size=10)

self._Right_Encoder=rospy.Publisher('rwheel',Int64,queue_size=10)

#PublisherforBatterylevel(forupgradepurpose)

self._Battery_Level=rospy.Publisher('battery_level',Float32,queue_size=10)

#PublisherforUltrasonicdistancesensor

self._Ultrasonic_Value=rospy.Publisher('ultrasonic_distance',Float32,queue_size=

#PublisherforIMUrotationquaternionvalues

self._qx_=rospy.Publisher('qx',Float32,queue_size=10)

self._qy_=rospy.Publisher('qy',Float32,queue_size=10)

self._qz_=rospy.Publisher('qz',Float32,queue_size=10)

self._qw_=rospy.Publisher('qw',Float32,queue_size=10)

#Publisherforentireserialdata

self._SerialPublisher=rospy.Publisher('serial',String,queue_size=10)

WewillcreatetheROSpublisherobjectforsensorssuchastheencoder,IMU,andultrasonicsensoraswellasfortheentireserialdatafordebuggingpurpose.Wewillalsosubscribethespeedcommandsfortheleft-handsideandtheright-handsidewheeloftherobot.WhenaspeedcommandarrivesonTopic,itcallstherespectivecallbackstosendspeedcommandstotherobot'sLaunchpad:

self._left_motor_speed=

rospy.Subscriber('left_wheel_speed',Float32,self._Update_Left_Speed)

self._right_motor_speed=

rospy.Subscriber('right_wheel_speed',Float32,self._Update_Right_Speed)

AftersettingtheChefBotdrivernode,weneedtointerfacetherobottoaROSnavigationstackin

ordertoperformautonomousnavigation.Thebasicrequirementfordoingautonomousnavigationisthattherobotdrivernodes,receivevelocitycommandfromROSnavigationalstack.Therobotcanbecontrolledusingteleoperation.Inadditiontothesefeatures,therobotmustbeabletocomputeitspositionalorodometrydataandgeneratethetfdataforsendingintonavigationalstack.TheremustbeaPIDcontrollertocontroltherobotmotorvelocity.ThefollowingROSpackagehelpstoperformthesefunctions.Thedifferential_drivepackagecontainsnodestoperformtheprecedingoperation.Wearereusingthesenodesinourpackagetoimplementthesefunctionalities.Thefollowingisthelinkforthedifferential_drivepackageinROS:

http://wiki.ros.org/differential_drive

Thefollowingfigureshowshowthesenodescommunicatewitheachother.Wecanalsodiscusstheuseofothernodestoo:

Thepurposeofeachnodeinthechefbot_bringuppackageisasfollows:

twist_to_motors.py:ThisnodewillconverttheROSTwistcommandorlinearandangularvelocitytoindividualmotorvelocitytarget.Thetargetvelocitiesarepublishedatarateofthe~rateHertzandthepublishtimeout_tickstimesvelocityaftertheTwistmessagestops.ThefollowingaretheTopicsandparametersthatwillbepublishedandsubscribedbythisnode:

PublishingTopics:lwheel_vtarget(std_msgs/Float32):Thisisthethetargetvelocityoftheleftwheel(m/s).rwheel_vtarget(std_msgs/Float32):Thisisthetargetvelocityoftherightwheel(m/s).

SubscribingTopics:Twist(geometry_msgs/Twist):ThisisthetargetTwistcommandfortherobot.ThelinearvelocityinthexdirectionandangularvelocitythetaoftheTwistmessagesareusedinthisrobot.

ImportantROSparameters:~base_width(float,default:0.1):Thisisthedistancebetweentherobot'stwowheelsinmeters.~rate(int,default:50):Thisistherateatwhichvelocitytargetispublished(Hertz).~timeout_ticks(int,default:2):ThisisthenumberofthevelocitytargetmessagepublishedafterstoppingtheTwistmessages.

pid_velocity.py:ThisisasimplePIDcontrollertocontrolthespeedofeachmotorsbytakingfeedbackfromwheelencoders.Inadifferentialdrivesystem,weneedonePIDcontrollerforeachwheel.Itwillreadtheencoderdatafromeachwheelsandcontrolthespeedofeachwheels.

PublishingTopics:motor_cmd(Float32):ThisisthefinaloutputofthePIDcontrollerthatgoestothemotor.WecanchangetherangeofthePIDoutputusingtheout_minandout_maxROSparameter.wheel_vel(Float32):Thisisthecurrentvelocityoftherobotwheelinm/s.

SubscribingTopics:wheel(Int16):ThisTopicistheoutputofarotaryencoder.ThereareindividualTopicsforeachencoderoftherobot.wheel_vtarget(Float32):Thisisthetargetvelocityinm/s.

Importantparameters:~Kp(float,default:10):ThisparameteristheproportionalgainofthePIDcontroller.~Ki(float,default:10):ThisparameteristheintegralgainofthePIDcontroller.~Kd(float,default:0.001):ThisparameteristhederivativegainofthePIDcontroller.~out_min(float,default:255):Thisistheminimumlimitofthevelocityvaluetomotor.Thisparameterlimitsthevelocityvaluetomotorcalledwheel_velTopic.~out_max(float,default:255):Thisisthemaximumlimitofwheel_velTopic(Hertz).~rate(float,default:20):Thisistherateofpublishingwheel_velTopic.ticks_meter(float,default:20):Thisisthenumberofwheelencodertickspermeter.Thisisaglobalparameterbecauseit'susedinothernodestoo.vel_threshold(float,default:0.001):Iftherobotvelocitydropsbelowthisparameter,weconsiderthewheelasstopped.Ifthevelocityofthewheelislessthanvel_threshold,weconsideritaszero.encoder_min(int,default:32768):Thisistheminimumvalueofencoderreading.encoder_max(int,default:32768):Thisisthemaximumvalueofencoderreading.wheel_low_wrap(int,default:0.3*(encoder_max-encoder_min)+encoder_min):Thesevaluesdecidewhethertheodometryisinnegativeorpositive

direction.wheel_high_wrap(int,default:0.7*(encoder_max-encoder_min)+encoder_min):Thesevaluesdecidewhethertheodometryisinthenegativeorpositivedirection.

diff_tf.py:Thisnodecomputesthetransformationofodometryandbroadcastbetweentheodometryframeandtherobotbaseframe.

PublishingTopics:odom(nav_msgs/odometry):Thispublishestheodometry(currentposeandtwistoftherobot.tf:Thisprovidestransformationbetweentheodometryframeandtherobotbaselink.

SubscribingTopics:lwheel(std_msgs/Int16),rwheel(std_msgs/Int16):Thesearetheoutputvaluesfromtheleftandrightencoderoftherobot.

chefbot_keyboard_teleop.py:ThisnodesendstheTwistcommandusingcontrolsfromthekeyboard.

PublishingTopics:cmd_vel_mux/input/teleop(geometry_msgs/Twist):Thispublishesthetwistmessagesusingkeyboardcommands.

Afterdiscussingnodesinthechefbot_bringuppackage,wewilllookatthefunctionsoflaunchfiles.

UnderstandingChefBotROSlaunchfilesWewilldiscussthefunctionsofeachlaunchfilesofthechefbot_bringuppackage.

robot_standalone.launch:Themainfunctionofthislaunchfileistostartnodessuchaslaunchpad_node,pid_velocity,diff_tf,andtwist_to_motortogetsensorvaluesfromtherobotandtosendcommandvelocitytotherobot.keyboard_teleop.launch:Thislaunchfilewillstarttheteleoperationbyusingthekeyboard.Thislaunchstartsthechefbot_keyboard_teleop.pynodetoperformthekeyboardteleoperation.3dsensor.launch:ThisfilewilllaunchKinectOpenNIdriversandstartpublishingRGBanddepthstream.Itwillalsostartthedepthstreamtolaserscannernode,whichwillconvertpointcloudtolaserscandata.gmapping_demo.launch:ThislaunchfilewillstartSLAMgmappingnodestomaptheareasurroundingtherobot.amcl_demo.launch:UsingAMCL,therobotcanlocalizeandpredictwhereitstandsonthemap.Afterlocalizingonthemap,wecancommandtherobottomovetoapositiononthemap,thentherobotcanmoveautonomouslyfromitscurrentpositiontothegoalposition.view_robot.launch:ThislaunchfiledisplaystherobotURDFmodelinRViz.view_navigation.launch:Thislaunchfiledisplaysallthesensorsnecessaryforthenavigationoftherobot.

WorkingwithChefBotPythonnodesandlaunchfilesWealreadysetChefBotROSpackagesinIntel'sNUCPCanduploadedtheembeddedcodetotheLaunchpadboard.ThenextstepistoputtheNUCPContherobot,configureremoteconnectionfromthelaptoptotherobot,testingeachnodes,andworkingwithChefBotLaunchfilestoperformautonomousnavigation.

ThemaindeviceweshouldhavebeforeworkingwithChefBotisagoodwirelessrouter.Therobotandtheremotelaptophavetoconnectonthesamenetwork.IftherobotPCandremotelaptopareonthesamenetwork,theusercanconnectfromtheremotelaptoptotherobotPCthroughSSHusingitsIP.BeforeputtingtherobotPCintherobot,weshouldconnecttherobotPCinthewirelessnetwork,soonceit'sconnectedtothewirelessnetwork,itwillremembertheconnectiondetails.Whentherobotpowers,thePCshouldautomaticallyconnecttothewirelessnetwork.OncetherobotPCisconnectedtothewirelessnetwork,wecanputitintheactualrobot.ThefollowingfigureshowstheconnectiondiagramoftherobotandremotePC:

WirelessconnectiondiagramoftherobotandremotePC

TheprecedingfigureassumesthattheChefBotIPis192.168.1.106andtheremotePCIPis192.168.1.101.

WecanremotelyaccesstheChefBotterminalusingSSH.WecanusethefollowingcommandtologintoChefBot,whererobotistheusernameofChefBotPC:

$sshrobot@192.168.1.106

WhenyoulogintoChefBotPC,itwillaskfortherobotPCpassword.AfterenteringthepasswordoftherobotPC,wecanaccesstherobotPCterminal.AfterloggingintotherobotPC,wecanstarttestingtheROSnodesofChefBotandtestwhetherwecanreceivetheserialvaluesfromtheLaunchpadboardinsideChefBot.NotethatyoushouldloginagaintoChefBotPCthroughSSHifyouareusinganewterminal.

IftheChefbot_bringuppackageisproperlyinstalledonthePCandiftheLaunchpadboardisconnected,thenbeforerunningtheROSdrivernode,wecanruntheminiterm.pytooltocheckwhethertheserialvaluescomeproperlytothePCviaUSB.Wecanfindtheserialdevicenameusingthedmesgcommand.Wecanrunminiterm.pyusingthefollowingcommand:

$miniterm.py/dev/ttyACM0115200

Ifitshowsthepermissiondeniedmessage,setthepermissionoftheUSBdevicebywritingrulesontheudevfolderaswedidinChapter5,WorkingwithRoboticActuatorsandWheelEncodersofthisbookorwecantemporarilychangethepermissionusingthefollowingcommand.WeareassumingttyACM0isthedevicenameofLaunchpad.IfthedevicenameisdifferentinyourPC,thenyouhavetousethatnameinsteadofttyACM0:

$sudochmod777/dev/ttyACM0

Ifeverythingworksfine,wewillgetvalueslikethoseshowninfollowingscreenshot:

Theletterbisusedtoindicatethebatteryreadingoftherobot;currently,it'snotimplemented.Thevalueissettozeronow.Thelettertindicatesthetotaltimeinmicrosecondsaftertherobotstartsrunningtheembeddedcode.Thesecondvalueistimeinseconds;it'sthetimetakentocompleteoneentireoperationinLaunchpad.Wecanusethisvalueifweareperformingreal-timecalculationsoftheparametersoftherobot.Currently,wearenotusingthisvalue;wemayusethisinthefuture.Thelettereindicatesvaluesoftheleftandrightencoderrespectively.Boththevaluesarezeroherebecausetherobotisnotmoving.Theletteruindicatesthevaluesfromtheultrasonicdistancesensor.Thedistancevaluewegetisincentimeters.Thelettersindicatesthecurrentrobotwheelspeedofthe

robot.Thisvalueisforinspectionpurpose.Actually,speedisacontroloutputfromthePCitself.

ToconverttheseserialdatatoROSTopics,wehavetorunthedrivenodecalledlaunchpad_node.py.Thefollowingcodeshowshowtoexecutethisnode.

First,wehavetorunroscorebeforestartinganynodes:

$roscore

Runlaunchpad_node.pyusingthefollowingcommand:

$rosrunchefbot_bringuplaunchpad_node.py

Ifeverythingworksfine,wewillgetthefollowingoutputinthenoderunningterminal:

Afterrunninglaunchpad_node.py,wewillseethefollowingTopicsgenerated,asgiveninthefollowingscreenshot:

Wecanviewtheserialdatareceivedbydrivernodebysubscribing/serialTopic.Wecanuseitfordebugpurposes.IftheserialTopicshowsthesamedataaswesawonminiterm.py,thenwecanconfirmthatthenodesareworkingfine.Thefollowingscreenshotistheoutputof/serialTopic:

Aftersettingthechefbot_bringuppackage,wecanstartworkingwiththeautonomousnavigationofChefBot.Currently,weareaccessingonlytheChefBotPC'sterminal.Tovisualizetherobotmodel,sensordata,maps,andsoon,wehavetouseRVizintheuser'sPC.WehavetodosomeconfigurationintherobotanduserPCtoperformthisoperation.Itshouldbenotedthattheuser'sPCshouldhavethesamesoftwaresetupasintheChefBotPC.

Thefirstthingwehavetodois,settheChefBotPCasaROSmaster.WecansettheChefBotPCastheROSmasterbysettingtheROS_MASTER_URIvalue.ROS_MASTER_URIisarequiredsetting,ItinformsthenodesabouttheUniformResourceIdentifier(URI)oftheROSmaster.WhenyousetthesameROS_MASTER_URIfortheChefBotPCandtheremotePC,wecanaccesstheTopicsoftheChefBotPCintheremotePC.So,ifwerunRVizlocally,thenitwillvisualizetheTopicsgeneratedintheChefBotPC.

AssumethattheChefBotPCIPis192.168.1.106andtheremotePCIPis192.168.1.101.TosetROS_MASTER_URIineachsystem,thefollowingcommandshouldincludethe.bashrcfileinthehomefolder.Thefollowingfigureshowsthesetupneededtoinclude.bashrcineachsystem:

Addtheselinesatthebottomof.bashrconeachPCandchangetheIPaddressaccordingtoyournetwork.

Afterweperformthesesettings,wecanjuststartroscoreontheChefBotPCterminalandexecutecommandrostopiclistontheremotePC.

IfyouseeanyTopics,youaredonewiththesettings.Wecanfirstruntherobotusingthekeyboardteleoperationtochecktherobot'sfunctioningandconfirmwhetherwegetthesensorvalues.

Wecanstarttherobotdriverandothernodesusingthefollowingcommand.NotethatthisshouldexecuteintheChefBotterminalafterlogin,usingSSH:

$roslaunchchefbot_bringuprobot_standalone.launch

Afterlaunchingtherobotdriverandnodes,startthekeyboardteleoperationusingthefollowingcommand.ThisalsohastobedoneonthenewterminaloftheChefBotPC:

$roslaunchchefbot_bringupkeyboard_teleop.launch

ToactivateKinect,executethefollowingcommand.ThiscommandisalsoexecutedontheChefBotterminal:

$roslaunchchefbot_bringup3dsensor.launch

Toviewsensordata,wecanexecutethefollowingcommand.ThiswillviewtherobotmodelinRVizandshouldbeexecutedintheremotePC.Ifwesetupthechefbot_bringuppackageintheremotePC,wecanaccessthefollowingcommandandvisualizetherobotmodelandsensordatafromChefBotPC:

$roslaunchchefbot_bringupview_robot.launch

ThefollowingscreenshotistheoutputofRViz.WecanseeLaserScanandPointCloudinthescreenshots:

ChefBotLaserScandatainRViz

TheprecedingscreenshotshowsLaserScaninRViz.WeneedtotickLaserScanTopicfromtheleft-handsidesectionofRViztoenablethelaserscandata.Thelaserscandataismarkedontheviewport.IfyouwanttowatchthePointClouddatafromKinect,clickontheAddbuttonontheleft-handsideofRVizandselectPointCloud2fromthepopupwindow.

SelectTopic/camera/depth_registeredfromthelistandyouwillseethefollowingscreenshot:

ChefBotwithPointClouddata

Afterworkingwithsensors,wecanperformSLAMtomaptheroom.ThefollowingprocedurehelpstostartSLAMonthisrobot.

WorkingwithSLAMonROStobuildthemapoftheroomToperformgmapping,wehavetoexecutethefollowingcommands:

StartingtherobotdriverintheChefBotterminal:

Executethefollowingcommandtostartthegmappingprocess.NotethatitshouldbeexecutedontheChefBotterminal:

$roslaunchchefbot_bringupgmapping_demo.launch

Gmappingwillonlyworkiftheodometryvaluereceivedisproper.Iftheodometryvalueisreceived

fromtherobot,wewillreceivethefollowingmessagefortheprecedingcommand.Ifwegetthismessage,wecanconfirmthatgmappingwillworkfine:

Tostartthekeyboardteleoperation,usethefollowingcommand:

$roslaunchchefbot_bringupkeyboard_teleop.launch

Toviewthemapbeingcreated,weneedtostartRVizintheremotesystemusingthefollowingcommand:

$roslaunchchefbot_bringupview_navigation.launch

AfterviewingtherobotinRViz,youcanmovetherobotusingthekeyboardandseethemapbeingcreated.Whenitmapstheentirearea,wecansavethemapusingthefollowingcommandontheChefBotPCterminal:

$rosrunmap_servermap_saver-f~/test_map

wheretest_mapisthenameofthemapbeingstoredonthehomefolder.Thefollowingscreenshotshowsthemapofaroomcreatedbytherobot:

Mappingaroom

Afterthemapisstored,wecanworkwiththelocalizationandautonomousnavigationusingROS.

WorkingwithROSlocalizationandnavigationAfterbuildingthemap,closealltheapplicationsandreruntherobotdriverusingthefollowingcommand:

Startlocalizationandnavigationonthestoredmapusingthefollowingcommand:

$roslaunchchefbot_bringupamcl_demo.launchmap_file:=~/test_map.yaml

StartviewingtherobotusingthefollowingcommandintheremotePC:

InRViz,wemayneedtospecifytheinitialposeoftherobotusingthe2DPoseEstimatebutton.Wecanchangetherobotposeonthemapusingthisbutton.Iftherobotisabletolocatethemap,thenwecanusethe2DNavGoalbuttontocommandtherobottomovetothedesiredposition.Whenwestartlocalization,wecanseetheparticlecloudbytheAMCLalgorithmaroundtherobot:

Thefollowingisascreenshotoftherobotthatnavigatesautonomouslyfromthecurrentpositiontothegoalposition.Thegoalpositionismarkedasablackdot:

Theblacklinefromtherobottotheblackdotistherobot'splannedpathtoreachthegoalposition.Iftherobotisnotabletolocatethemap,wemightneedtofine-tunetheparameterfilesintheChefbot_bringupparamfolder.Formorefinetuningdetails,youcangothroughtheAMCLpackageonROS.Youcanvisitthefollowinglink:

http://wiki.ros.org/amcl?distro=indigo

Questions1. WhatisuseoftherobotROSdrivernode?2. WhatistheroleofthePIDcontrollerinnavigation?3. Howtoconverttheencoderdatatoodometrydata?4. WhatisroleofSLAMinrobotnavigation?5. WhatisroleofAMCLinrobotnavigation?

SummaryThischapterwasaboutassemblingthehardwareofChefBotandintegratingtheembeddedandROScodeintotherobottoperformautonomousnavigation.WesawtherobothardwarepartsthatweremanufacturedusingthedesignfromChapter5,WorkingwithRoboticActuatorsandWheelEncoders.WeassembledindividualsectionsoftherobotandconnectedtheprototypePCBthatwedesignedfortherobot.ThisconsistsoftheLaunchpadboard,motordriver,leftshifter,ultrasonic,andIMU.TheLaunchpadboardwasflashedwiththenewembeddedcode,whichcaninterfaceallsensorsintherobotandcansendorreceivedatafromthePC.Afterdiscussingtheembeddedcode,wewrotetheROSPythondrivernodetointerfacetheserialdatafromtheLaunchpadboard.AfterinterfacingtheLaunchpadboard,wecomputedtheodometrydataanddifferentialdrivecontrollingusingnodesfromthedifferential_drivepackagethatexistedintheROSrepository.WeinterfacedtherobottoROSnavigationstack.ThisenablestoperformSLAMandAMCLforautonomousnavigation.WealsodiscussedSLAM,AMCL,createdmap,andexecutedautonomousnavigationontherobot.

Chapter11.DesigningaGUIforaRobotUsingQtandPythonInthelastchapter,wediscussedtheintegrationofrobotichardwarecomponentsandsoftwarepackagesforperformingautonomousnavigation.Aftertheintegration,thenextstepistobuildaGUItocontroltherobot.WearebuildingaGUIthatcanactasatriggerfortheunderlyingROScommands.Insteadofrunningallthecommandsontheterminal,theusercanworkwiththeGUIbuttons.TheGUIwearegoingtodesignisforatypicalhotelroomwithninetables.Theusercansetatablepositioninthemapofthehotelroomandcommandtherobottogotoaparticulartabletodeliverfood.Afterdeliveringthefood,theusercancommandtherobottogotoitshomeposition.

SomeofthemostpopularGUIframeworkscurrentlyavailableareQt(http://qt.digia.com)andGTK+(http://www.gtk.org/),QtandGTK+areopensource,cross-platformuserinterfacetoolkitsanddevelopmentplatforms.ThesetwosoftwareframeworksarewidelyusedinLinuxdesktopenvironments,likeGNOMEandKDE.

Inthischapter,wewillbeusingPythonbindingoftheQtframeworktoimplementtheGUIbecausePythonbindingofQtismorestablethanotherUIPythonbindings.WecanseehowtodevelopaGUIfromscratchandprogramitusingPython.AfterdiscussingbasicPythonandQtprogramming,wewilldiscussROSinterfacesofQt,whicharealreadyavailableinROS.WewillfirstlookatwhatistheQtUIframeworkisandhowtoinstallitonourPC.

InstallingQtonUbuntu14.04.2LTSQtisacross-platformapplicationframeworkthatiswidelyusedtodevelopapplicationsoftwarewithaGUIinterfaceaswellascommandlinetools.Qtisavailableonalmostalloperatingsystems,likeWindows,MacOSX,Android,andsoon.ThemainprogramminglanguageusedfordevelopingQtapplicationsisC++buttherearebindingsavailableforlanguagessuchasPython,Ruby,Java,andsoon.Let'stakealookathowtoinstallQtSDKonUbuntu14.04.2.WewillinstallQtfromtheAdvancePackagingTool(APT)inUbuntu.TheAPTalreadycomeswiththeUbuntuinstallation.SoforinstallingQt/QtSDK,wecansimplyusethefollowingcommand,whichwillinstallQtSDKanditsrequireddependenciesfromtheUbuntupackagerepository.WecaninstallQtversion4usingthefollowingcommand:

$sudoapt-getinstallqt-sdk

ThiscommandwillinstalltheentireQtSDKanditslibrariesrequiredforourproject.ThepackagesavailableonUbunturepositoriesmaynotbethelatestversions.TogetthelatestversionofQt,wecandownloadtheonlineorofflineinstallerofQtforvariousOSplatformsfromthefollowinglink:

http://qt-project.org/downloads

AfterinstallingQtonoursystem,wecanseehowwecandevelopaGUIusingQtandinterfacewithPython.

WorkingwithPythonbindingsofQtLet'sseehowwecaninterfacePythonandQt.Ingeneral,therearetwomodulesavailableinPythonforconnectingtotheQtuserinterface.Thetwomostpopularframeworksare:

PyQtPySide

PyQtPyQtisoneofthepopularmostPythonbindingsforQtcross-platform.PyQtisdevelopedandmaintainedbyRiverbankComputingLimited.ItprovidesbindingforQtversion4andQtversion5,andcomeswithGPL(version2or3)alongwithacommerciallicense.PyQtisavailableforQtversion4and5,calledPyQt4andPyQt5,respectively.ThesetwomodulesarecompatiblewithPythonversions2and3.PyQtcontainsmorethan620classesthatcoveruserinterface,XML,networkcommunication,web,andsoon.

PyQtisavailableonWindows,Linux,andMacOSX.ItisaprerequisitetoinstallQtSDKandPythoninordertoinstallPyQt.ThebinariesforWindowsandMacOSXareavailableonthefollowinglink:

http://www.riverbankcomputing.com/software/pyqt/download

WecanseehowtoinstallPyQt4onUbuntu14.04.2usingPython2.7.

InstallingPyQtonUbuntu14.04.2LTS

IfyouwanttoinstallPyQtonUbuntu/Linux,usethefollowingcommand.ThiscommandwillinstallthePyQtlibrary,itsdependencies,andsomeQttools:

$sudoapt-getinstallpython-qt4pyqt4-dev-tools

PySidePySideisanopensourcesoftwareprojectthatprovidesPythonbindingfortheQtframework.ThePySideprojectwasinitiatedbyNokia,andoffersafullsetofQtbindingformultipleplatforms.ThetechniqueusedinPySidetowraptheQtlibraryisdifferentfromPyQt,buttheAPIofbothissimilar.PySideiscurrentlynotsupportedonQt5.PySideisavailableforWindows,Linux,andMacOSX.ThefollowinglinkwillguideyoutosetupPySideonWindowsandMacOSX:

http://qt-project.org/wiki/Category:LanguageBindings::PySide::Downloads

TheprerequisitesofPySidearethesameasPyQt.Let'sseehowwecaninstallPySideonUbuntu14.04.2LTS.

InstallingPySideonUbuntu14.04.2LTS

ThePySidepackageisavailableontheUbuntupackagerepository.ThefollowingcommandwillinstallthePySidemoduleandQttoolsonUbuntu:

$sudoapt-getinstallpython-pysidepyside-tools

Let'sworkwithbothmodulesandseethedifferencesbetweenboth.

WorkingwithPyQtandPySideAfterinstallingthePyQtandPySidepackages,wecanseehowtowriteaHelloWorldGUIusingPyQtandPySide.ThemaindifferencebetweenPyQtandPySideisonlyinsomecommands;mostofthestepsarethesame.Let'sseehowtomakeaQtGUIandconvertitintoPythoncode.

IntroducingQtDesignerQtDesigneristhetoolfordesigningandinsertingcontrolintoQtGUI.QtGUIisbasicallyanXMLfilethatcontainstheinformationofitscomponentsandcontrols.ThefirststeptoworkwithGUIisitsdesigning.TheQtDesignertoolprovidesvariousoptionstomakeexcellentGUIs.

StartQtDesignerbyenteringthecommanddesigner-qt4intheterminal.Thefollowingimageshowswhatyouwillbeabletoseeafterrunningthiscommand:

TheprecedingimageshowstheQtdesignerinterface.SelecttheWidgetoptionfromtheNewFormwindowandclickontheCreatebutton.Thiswillcreateanemptywidget;wecandragvariousGUIcontrolsfromtheleft-handsideofQt4designertotheemptywidget.QtwidgetsarethebasicbuildingblocksofQtGUI.

ThefollowingimageshowsaformwithaPushButtondraggedfromtheleft-handsidewindowofQtDesigner:

TheHelloWorldapplicationthatwearegoingtobuildhasaPushButton,whenweclickonthePushButton,aHelloWorldmessagewillbeprintedontheterminal.BeforebuildingtheHelloWorldapplication,weneedtounderstandwhatQtsignalsandslotsare,becausewehavetousethesefeaturesforbuildingtheHelloWorldapplication.

QtsignalsandslotsInQt,GUIeventsarehandledusingthesignalsandslotsfeatures.AsignalisemittedfromtheGUIwhenaneventoccurs.QtWidgetshavemanypredefinedsignals,anduserscanaddcustomsignalsforGUIevents.Aslotisafunctionthatiscalledinresponsetoaparticularsignal.Inthisexample,weareusingtheclicked()signalofPushButtonandcreatingacustomslotforthissignal.Wecanwriteourowncodeonthiscustomfunction.Let'sseehowwecancreateabutton,connectasignaltoaslot,andconverttheentireGUItoPython.

HerearethestepsinvolvedincreatingtheHelloWorldGUIapplication:

1. DragandcreateaPushButtonfromQtDesignertotheemptyForm.2. Assignaslotforthebuttonclickedevent,whichemitsasignalcalledclicked().3. SavethedesignedUIfileinthe.uiextension.4. ConvertUIfilestoPython.5. Writethedefinitionofthecustomslot.6. PrinttheHelloWorldmessageinsidethedefinedslot/function.

WehavealreadydraggedabuttonfromQtDesignertoanemptyForm.PresstheF4keytoinsertaslotonthebutton.WhenwepressF4,thePushButtonturnsred,andwecandragalinefromthebuttonandplacethegroundsymbol( )inthemainwindow.Thisisshowninthefollowingscreenshot:

Selecttheclicked()signalfromtheleft-handsideandclickontheEdit..buttontocreateanewcustomslot.WhenweclickontheEdit..button,anotherwindowwillpopuptocreateacustomfunction.Youcancreateacustomfunctionbyclickingonthe+symbol.

Wecreatedacustomslotcalledmessage(),asshowninthescreenshotbelow:

ClickontheOKbuttonandsavetheUIfileashello_world.ui,andquittheQtdesigner.AftersavingtheUIfile,let'sseehowwecanconvertaQtUIfileintoaPythonfile.

ConvertingaUIfileintoPythoncodeAfterdesigningtheUIfile,wecanconverttheUIfileintoitsequivalentPythoncode.Theconversionisdoneusingapyuiccompiler.WehavealreadyinstalledthistoolwhileinstallingPyQt/PySide.ThefollowingarethecommandstoconvertaQtUIfileintoaPythonfile.

WehavetousedifferentcommandsforPyQtandPySide.ThefollowingcommandistoconvertUIintoitsPyQtequivalentfile:

$pyuic4-xhello_world.ui-ohello_world.py

Thepyuic4isaUIcompilertoconvertaUIfileintoitsequivalentPythoncode.WeneedtomentiontheUIfilenameafterthe-xargumentandmentiontheoutputfilenameafterthe-oargument.

TherearenotmanychangesforthePySidecommand,insteadofpyuic4,PySideusespyside-uictoconvertUIfilesintoPythonfiles.Theremainingargumentsarethesame:

$pyside-uic-xhello_world.ui-ohello_world.py

TheprecedingcommandwillgenerateanequivalentPythoncodefortheUIfile.IfwerunthisPythoncode,theUIdesignedinQtDesignerwillpopup.Thegeneratedscriptwillnothavethedefinitionofthecustomfunctionmessage().Weshouldaddthiscustomfunctiontogeneratethecode.The

followingprocedurewillguideyouthroughaddingthecustomfunction;sowhenyouclickonthebutton,thecustomfunctionmessage()willbeexecuted.

AddingaslotdefinitiontoPyQtcodeThegeneratedPythoncodefromPyQtisgivenhere.Thecodegeneratedbypyuic4andpyside-uicarethesame,exceptinimportingmodulenames.Allotherpartsarethesame.TheexplanationofthecodegeneratedusingPyQtisalsoapplicabletoPySidecode.Thecodegeneratedfromtheaboveconversionisasfollows.ThecodestructureandparameterscanchangeaccordingtotheUIfilethatyouhavedesigned:

fromPyQt4importQtCore,QtGui

_fromUtf8=QtCore.QString.fromUtf8

exceptAttributeError:

_fromUtf8=lambdas:s

classUi_Form(object):

defsetupUi(self,Form):

Form.setObjectName(_fromUtf8("Form"))

Form.resize(514,355)

self.pushButton=QtGui.QPushButton(Form)

self.pushButton.setGeometry(QtCore.QRect(150,80,191,61))

self.pushButton.setObjectName(_fromUtf8("pushButton"))

self.retranslateUi(Form)

QtCore.QObject.connect(self.pushButton,

QtCore.SIGNAL(_fromUtf8("clicked()")),Form.message)

QtCore.QMetaObject.connectSlotsByName(Form)

defretranslateUi(self,Form):

Form.setWindowTitle(QtGui.QApplication.translate("Form","Form",None,

QtGui.QApplication.UnicodeUTF8))

self.pushButton.setText(QtGui.QApplication.translate("Form","Press",None,

QtGui.QApplication.UnicodeUTF8))

importsys

app=QtGui.QApplication(sys.argv)

Form=QtGui.QWidget()

ui=Ui_Form()

ui.setupUi(Form)

Form.show()

sys.exit(app.exec_())

TheprecedingcodeistheequivalentPythonscriptoftheQtUIfilethatwedesignedintheQtdesignerapplication.Hereisthestep-by-stepprocedureoftheworkingofthiscode:

1. Thecodewillstartexecutingfromif__name__=="__main__":.ThefirstthinginaPyQt

codeistocreateaQApplicationobject.AQApplicationclassmanagestheGUIapplication'scontrolflowandmainsettings.TheQApplicationclasscontainsthemaineventloop,wherealleventsfromtheWindowssystemandothersourcesareprocessedanddispatched.Italsohandlesinitializationandfinalizationofanapplication.TheQApplicationclassisinsidetheQtGuimodule.ThiscodecreatesanobjectofQApplicationcalledapp.

2. TheForm=QtGui.QWidget()linecreatesanobjectcalledFormfromtheQWidgetclassthatispresentinsidetheQtGuimodule.TheQWidgetclassisthebaseclassofalltheuserinterfaceobjectsofQt.ItcanreceivethemouseandkeyboardeventfromthemainWindowssystem.

3. Theui=Ui_Form()linecreatesanobjectcalleduifromtheUi_Form()classdefinedinthecode.TheUi_Form()objectcanaccepttheQWidgetclassthatwecreatedinthepreviouslineanditcanaddbuttons,text,buttoncontrol,andotherUIcomponentsintothisQWidgetobject.TheUi_Form()classcontainstwofunctions:setupUi()andretranslateUi().WecanpasstheQWidgetobjecttothefunctioncalledsetupUi().ThisfunctionwilladdUIcomponentsonthiswidgetobjectsuchasbuttons,assigningslotsforsignals,andsoon.TheretranslateUi()functionwilltranslatethelanguageoftheUItootherlanguagesifneeded,forexample,ifweneedtranslationfromEnglishtoSpanish,wecanmentionthecorrespondingSpanishwordinthisfunction.

4. TheForm.show()linedisplaysthefinalwindowwithbuttonsandtext.

Thenextthingistocreatetheslotfunction,whichprintstheHelloWorldmessage.TheslotdefinitioniscreatedinsidetheUi_Form()class.Thefollowingstepsinserttheslotcalledmessage()intotheUi_Form()class.

Themessage()functiondefinitionisasfollows:

defmessage(self):

print"HelloWorld"

ThisshouldbeinsertedasafunctioninsidetheUi_Form()class.Also,changethefollowinglineinthesetupUi()functioninsidetheUi_Form()class:

QtCore.QObject.connect(self.pushButton,QtCore.SIGNAL(_fromUtf8("clicked()")),

Form.message)

TheForm.messageparametershouldbereplacedwiththeself.messageparameter.TheprecedinglineconnectsthePushBbuttonsignalclicked()totheself.message()slotthatwealreadyinsertedintheUi_Form()class.

UpandrunningofHelloWorldGUIapplicationAfterreplacingtheForm.messageparameterwiththeself.messageparameter,wecanexecutethecodeandtheoutputwilllooklikethis:

WhenweclickonthePressbutton,itwillprinttheHelloworldmessage.ThisisallaboutsettingacustomGUIwithPythonandQt.

Inthenextsection,wewillseetheactualGUIthatwearedesigningfortherobot.

WorkingwithChefBot'scontrolGUIAftercompletingtheHelloWorldapplicationinPyQt,nextwecandiscussaGUIforcontrollingChefBot.ThemainuseofbuildingaGUIistocreateaneasierwaytocontroltherobot,forexample,iftherobotisdeployedinahoteltoservefood,thepersonwhocontrolsthisrobotneednothaveknowledgeaboutthecomplexcommandstostartandstopthisrobot;sobuildingaGUIforChefBotcanreducethecomplexityandmakeiteasierfortheuser.WeareplanningtobuildaGUIusingPyQt,ROSandPythoninterface.TheChefBotROSpackageisavailableonGitHubonthefollowinglink:

https://github.com/qboticslabs/Chefbot_ROS_pkg.git

Ifyouhaven'tclonedthecodeyet,youcandoitnowusingfollowingcommand:

TheGUIcodenamedrobot_gui.pyisplacedinthescriptsfolder,whichisinsidethechefbot_bringuppackage.

ThefollowingscreenshotshowstheGUIthatwehavedesignedforChefBot:

TheGUIhasthefollowingfeatures:

Itcanmonitorrobotbatterystatusandrobotstatus.Robotstatusindicatestheworkingstatusoftherobot,forexample,iftherobotencountersanerror,itwillindicatetheerroronthisGUI.Itcancommandtherobottomoveintoatablepositionfordeliveringfood.ThereisaspinboxwidgetontheGUItoinputthetableposition.Currently,weareplanningthisGUIforaninetableroom,butwemayexpanditintoanynumberaccordingtorequirement.Afterinputtingthetablenumber,wecancommandtherobottogotothattablebyclickingontheGobutton;therobot

willgetintothatposition.Ifwewanttoreturntherobottotheinitialposition,wecanclickontheHomebutton.Ifwewanttocancelthecurrentrobotmovement,clickonCanceltostoptherobot.TheworkingofthisGUIapplicationisasfollows:

WhenwehavetodeployChefBotinahotel,thefirstprocedurethatwehavetodoistocreateamapoftheroom.Aftermappingtheentireroomproperly,wehavetosavethemapontherobot'sPC.Therobotdoesthemappingonlyonce,aftermappingwecanrunthelocalizationandnavigationroutines,andcommandtherobottogetintoapositiononthemap.TheChefBotROSpackagecomeswithamapandsimulationmodelofahotel-likeenvironment.WecanrunthissimulationandlocalizationnowfortestingtheGUIandinthenextchapter,wecandiscusshowtocontrolthehardwareusingtheGUI.IfyouinstallChefBotROSpackagesonyourlocalsystem,wecansimulateahotelenvironmentandtesttheGUI.

StarttheChefBotsimulationinahotel-likearrangementusingthefollowingcommand:

$roslaunchchefbot_gazebochefbot_hotel_world.launch

AfterstartingtheChefBotsimulation,wecanrunthelocalizationandnavigationroutinesusinganalreadybuiltmap.Themapisplacedonthechefbot_bringuppackage.Wecanseeamapfolderinsidethispackage.Here,wewillusethismapforperformingthistest.Wecanloadthelocalizationandnavigationroutineusingthefollowingcommand:

$roslaunchchefbot_gazeboamcl_demo.launch

map_file:=/home/lentin/catkin_ws/src/chefbot/chefbot_bringup/map/hotel1.yaml

Thepathofthemapfilecanchangeinadifferentsystem,sousethepathinyoursysteminsteadofthispath.

Ifthepathmentionediscorrect,itwillstartrunningtheROSnavigationstack.Ifwewanttoseetherobotpositiononthemapormanuallysettheinitialpositionofrobot,wecanuseRVizusingthefollowingcommand:

InRViz,wecancommandtherobottogotoanymapcoordinatesusingthe2DNavGoalbutton.

Wecancommandtherobottogotoanymapcoordinatesusingprogrammingtoo.TheROSnavigationstackisworkingusingtheROSactionliblibrary.TheROSactionliblibraryisforperformingpreemptabletasks,itissimilartoROSServices.AnadvantageoverROSservicesisthatwecancanceltherequestifwedon'twantitatthattime.

IntheGUI,wecancommandtherobottogotoamapcoordinateusingPythonactionliblibrary.Wecangetthetablepositiononthemapusingthefollowingtechnique.

AfterstartingthesimulatorandAMCLnodes,launchthekeyboardteleoperationandmovetherobotneareachtable.Usethefollowingcommandtogetthetranslationandrotationoftherobot:

$rosruntftf_echo/map/base_link

WhenweclickontheGobutton,thatpositionisfedtothenavigationstackandtherobotplansitspathandreachesitsgoal.Wecanevencancelthetaskatanytime.SotheChefBotGUIactsasanactionlibclient,whichsendsmapcoordinatestotheactionlibserver,thatis,thenavigationstack.

WecanruntherobotGUInowtocontroltherobotusingthefollowingcommand:

$rosrunchefbot_bringuprobot_gui.py

WecanselectatablenumberandclickontheGobuttonformovingrobottoeachtable.

Assumingthatyouclonedthefilesandgottherobot_gui.pyfile,wecandiscussthemainslotsweaddedintotheUi_Form()classfortheactionlibclientandtogetvaluesofbatterylevelandrobotstatus.

WeneedtoimportthefollowingPythonmodulesforthisGUIapplication:

importrospy

importactionlib

frommove_base_msgs.msgimport*

importtime

fromPyQt4importQtCore,QtGui

TheadditionalmoduleswerequireareROSPythonclientrospy,andtheactionlibmoduletosendvaluestothenavigationstack.Themove_base_msgsmodulecontainsthemessagedefinitionofthegoalthatneedstobesenttothenavigationstack.

TherobotpositionneareachtableismentionedinaPythondictionary.Thefollowingcodeshowshardcodevaluesoftherobot'spositionneareachtable:

table_position=dict()

table_position[0]=(-0.465,0.37,0.010,0,0,0.998,0.069)

table_position[1]=(0.599,1.03,0.010,0,0,1.00,-0.020)

table_position[2]=(4.415,0.645,0.010,0,0,-0.034,0.999)

table_position[3]=(7.409,0.812,0.010,0,0,-0.119,0.993)

table_position[4]=(1.757,4.377,0.010,0,0,-0.040,0.999)

table_position[5]=(1.757,4.377,0.010,0,0,-0.040,0.999)

table_position[6]=(1.757,4.377,0.010,0,0,-0.040,0.999)

table_position[7]=(1.757,4.377,0.010,0,0,-0.040,0.999)

table_position[8]=(1.757,4.377,0.010,0,0,-0.040,0.999)

table_position[9]=(1.757,4.377,0.010,0,0,-0.040,0.999)

Wecanaccessthepositionoftherobotneareachtablebyaccessingthisdictionary.

Currently,wehaveinsertedonlyfourvaluesforademonstrationpurpose.Youcanaddmorevaluesbyfindingthepositionofothertables.

Weareassigningsomevariablestohandlethetablenumber,thepositionofrobotandtheactionlibclientinsidetheUi_Form()class.

#Handletablenumberfromspinbox

self.table_no=0

#Storescurrenttablerobotposition

self.current_table_position=0

#CreatingActionlibclient

self.client=actionlib.SimpleActionClient('move_base',MoveBaseAction)

#Creatinggoalmessagedefinition

self.goal=MoveBaseGoal()

#Startthisfunctionforupdatingbatteryandrobotstatus

self.update_values()

Thefollowingcodeshowsthesignalsandslotsassignmentinthiscodeforbuttonsandspinboxwidgets:

#Handlespinboxsignalandassigntoslotset_table_number()

QtCore.QObject.connect(self.spinBox,QtCore.SIGNAL(_fromUtf8("valueChanged(int)")),

self.set_table_number)

#HandleHomebuttonsignalandassigntoslotHome()

QtCore.QObject.connect(self.pushButton_3,QtCore.SIGNAL(_fromUtf8("clicked()")),

self.Home)

#HandleGobuttonsignalandassigntoslotGo()

QtCore.QObject.connect(self.pushButton,QtCore.SIGNAL(_fromUtf8("clicked()")),

self.Go)

#HandleCancelbuttonsignalandassigntoslotCancel()

QtCore.QObject.connect(self.pushButton_2,QtCore.SIGNAL(_fromUtf8("clicked()")),

self.Cancel)

ThefollowingslothandlesthespinboxvaluefromtheUIandassignsatablenumber.Also,itconvertsthetablenumbertothecorrespondingrobotposition:

defset_table_number(self):

self.table_no=self.spinBox.value()

self.current_table_position=table_position[self.table_no]

HereisthedefinitionoftheGoslotfortheGobutton.Thisfunctionwillinsertintotherobotpositionoftheselectedtableinagoalmessageheaderandsendittothenavigationstack:

defGo(self):

#Assigningx,y,zposeandorientationtotarget_posemessage

self.goal.target_pose.pose.position.x=float(self.current_table_position[0])

self.goal.target_pose.pose.position.y=float(self.current_table_position[1])

self.goal.target_pose.pose.position.z=float(self.current_table_position[2])

self.goal.target_pose.pose.orientation.x=

float(self.current_table_position[3])

self.goal.target_pose.pose.orientation.y=float(self.current_table_position[4])

self.goal.target_pose.pose.orientation.z=float(self.current_table_position[5])

#Frameid

self.goal.target_pose.header.frame_id='map'

#Timestamp

self.goal.target_pose.header.stamp=rospy.Time.now()

#Sendinggoaltonavigationstack

self.client.send_goal(self.goal)

ThefollowingcodeistheCancel()slotdefinition.Thiswillcancelalltherobotpathsthatitwasplanningtoperformatthattime.

defCancel(self):

self.client.cancel_all_goals()

ThefollowingcodeisthedefinitionofHome().Thiswillsetthetablepositiontozero,andcalltheGo()function.Thetableatpositionzeroisthehomepositionoftherobot:

defHome(self):

self.current_table_position=table_position[0]

self.Go()

Thefollowingdefinitionsarefortheupdate_values()andadd()functions.Theupdate_values()methodwillstartupdatingthebatterylevelandrobotstatusinathread.Theadd()functionwillretrievetheROSparametersofthebatterystatusandrobotstatus,andsetthemtotheprogressbarandlabel,respectively:

defupdate_values(self):

self.thread=WorkThread()

QtCore.QObject.connect(self.thread,QtCore.SIGNAL("update(QString)"),

self.add)

self.thread.start()

defadd(self,text):

battery_value=rospy.get_param("battery_value")

robot_status=rospy.get_param("robot_status")

self.progressBar.setProperty("value",battery_value)

self.label_4.setText(_fromUtf8(robot_status))

TheWorkThread()classusedintheprecedingfunctionisgivenhere.TheWorkThread()classisinheritedfromQThreadprovidedbyQtforthreading.Thethreadsimplyemitsthesignalupdate(Qstring)withaparticulardelay.Intheprecedingfunctionupdate_values(),theupdate(QString)signalisconnectedtotheself.add()slot;sowhenasignalupdate(QString)isemittedfromthread,itwillcalltheadd()slotandupdatethebatteryandstatusvalue:

classWorkThread(QtCore.QThread):

def__init__(self):

QtCore.QThread.__init__(self)

def__del__(self):

self.wait()

defrun(self):

whileTrue:

time.sleep(0.3)#artificialtimedelay

self.emit(QtCore.SIGNAL('update(QString)'),"")

return

WehavediscussedhowtomakeaGUIforChefBot,butthisGUIisonlyfortheuserwhocontrolsChefBot.Ifsomeonewantstodebugandinspecttherobotdata,wemayhavetogoforothertools.ROSprovidesanexcellentdebuggingtooltovisualizedatafromtherobot.

TherqttoolisoneofthemostpopularROStools,whichisbasedonaQt-basedframeworkforGUIdevelopmentforROS.Let'sdiscusstherqttool,installationprocedure,andhowwecaninspectthesensordatafromtherobot.

InstallingandworkingwithrqtinUbuntu14.04.2LTSrqtisasoftwareframeworkinROS,whichimplementsvariousGUItoolsintheformofplugins.Wecanaddpluginsasdockablewindowsinrqt.

InstallingrqtinUbuntu14.04.2canbedoneusingthefollowingcommand.Beforeinstalling,ensurethatyouhavethefullinstallationofROSIndigo.

$sudoapt-getinstallros-indigo-rqt

Afterinstallingtherqtpackages,wecanaccesstheGUIimplementationofrqtcalledrqt_gui,inwhichwecandockrqtpluginsinasinglewindow.

Let'sstartusingrqt_gui.

Runtheroscorecommandbeforerunningrqt_gui:

$roscore

Runthefollowingcommandtostartrqt_gui:

$rosrunrqt_guirqt_gui

Wewillgetthefollowingwindowifthecommandsworkfine:

Wecanloadandunloadpluginsatruntime.ToanalyzetheROSmessagelog,wecanloadtheConsolepluginfromPlugins|Logging|Console.Inthefollowingexample,weloadtheConsolepluginandrunatalkernodeinsiderospy_tutorials,whichwillsendaHelloWorldmessagetoaTopiccalled/chatter.

Runthefollowingcommandtostartthenodetalker.py:

$rosrunrospy_tutorialstalker.py

Inthefollowingscreenshot,rqt_guiisloadedwithtwopluginsnamedConsoleandTopicMonitor.TheTopicMonitorplugincanbeloadedfromPlugins|Topics|TopicMonitor.TheConsolepluginmonitorsthemessagesprintingoneachnodesandtheirseverity.Itisveryusefulfordebuggingpurposes.Inthefollowingfigure,theleftsectionofrqt_guiisloadedwiththeConsolepluginandtherightsideisloadedwithTopicMonitor.TopicMonitorwilllistthetopicsavailableandwillmonitortheirvalues.

Inthefollowingfigure,theConsolepluginmonitorsthetalker.pynode'smessagesandtheirseveritylevelwhereasTopicMonitormonitorsthevalueinsidethe/chatterTopic.

Wecanalsovisualizedatasuchasimagesandplotgraphsonrqt_gui.Forrobotnavigationanditsinspection,therearepluginsforembeddingRVizinrqt_gui.TheNavigationviewerpluginviewsthefrom/mapTopic.ThevisualizationpluginsareavailableinPlugin|Visualization.

Questions1. WhatarethepopularUItoolkitsavailableontheLinuxplatform?2. WhatarethedifferencesbetweenPyQtandPySideQtbindings?3. HowdoyouconvertaQtUIfileintoPythonscript?4. WhatareQtsignalsandslots?5. Whatisrqtandwhatareitsmainapplications?

SummaryInthischapter,wediscussedcreatingaGUIforChefBotthatcanbeusedbyanordinaryuserwhodoesn'thaveanyideaabouttheinternalworkingofarobot.WeusedPythonbindingofQtcalledPyQttocreatethisGUI.BeforewegotothemainGUIdesign,wesawaHelloWorldapplicationtogetaneasierunderstandingofPyQt.TheUIdesignwasdoneusingtheQtDesignertoolandtheUIfilewasconvertedintoitsequivalentPythonscriptusingPythonUIcompiler.AfterdesigningthemainGUIinQtDesigner,weconvertedtheUIfileintoPythonscriptandinsertedthenecessaryslotsinthegeneratedscript.TheChefBotGUIcanstarttherobot,selectatablenumber,andcommandtherobottogetintothatposition.ThepositionofeachtableisacquiredfromthegeneratedmapwehardcodedthepositionsinthisPythonscriptfortesting.Whenatableisselected,wesetagoalpositiononthemap,andwhenweclickontheGobutton,therobotwillmoveintothegoalposition.Theusercancanceltheoperationatanytimeandcommandtherobottocometothehomeposition.TheGUIcanalsoreceivethereal-timestatusoftherobotanditsbatterystatus.AfterdiscussingtherobotGUI,wesawthedebuggingGUItoolinROScalledrqt.Wesawsomepluginsusedfordebuggingthedatafromtherobot.Inthenextchapter,wewillseethecompletetestingandcalibrationoftherobot.

Chapter12.TheCalibrationandTestingofChefBotInthischapter,wewilldiscussthecalibrationandtestingofChefBotthatisnecessarybeforedeployingtherobotintheworkplace.ThetestingcanbedoneusingtheGUIthatwebuiltinthepreviouschapter.Beforethetestrun,wecancalibratethesensorsandaddresstheissuesintheChefBothardwareandsoftware.Inthetestingprocedure,wecanbuildamapofahotelkindofarrangementandnavigateonthemapusingROSonChefBot.WecanalsoseewaystoimproveaccuracyandupgradetheChefBotprototypeinfuture.

First,wewilllookatthecalibrationofsensorssuchasKinect,Quadratureencoder,andIMUtoimprovetheaccuracyoftherobot.

TheCalibrationofXboxKinectusingROSKinectcalibrationisrequiredtoimprovetheaccuracyoftheKinectdata.Inthisrobot,Kinectisusedinsteadofalaserscanner.WecangeneratedataequivalenttothatprovidedbylaserscannerbyconvertingPointClouddata,usingadepthimagetolaserscannerconverterpackageinROS.Thisconverteddatamaynotbeaspreciseasanactuallaserscanner,soineffect,theerrorfromtheconvertedlaserscannercanaffectrobotmapping,navigation,andlocalization.Toreducetheerrorstosomeextent,wecandoacalibrationpriortoourapplication.Kinectcanevenworkonfactorysettingswithoutbeingcalibrated,eachdevicehasitsowncameraparametersandthesecanchangefromdevicetodevice.Someofthecameraparametersarefocallength,formatsizeprinciplepoint,andlensdistortion.Whenweperformcameracalibration,weareabletoadjustthesevalues.

OneofthecalibrationsusedinKinectisintrinsiccalibration.Someoftheintrinsicparametersarefocallengthanddistortionmodel.Usingintrinsiccalibration,wecancorrectthesevaluesofIR(depth)andRGBcameraintrinsicparameters.

Let'sseehowtoperformKinectintrinsiccalibrationusingROSandPython.

CalibratingtheKinectRGBcameraBeforecalibratingKinectusingROS,ensurethattheOpenNIdriverpackagesandcameracalibrationpackagesofROSareinstalled.Iftheyarenotinstalled,wecaninstallthemusingthefollowingcommand:

$sudoapt-getinstallros-indigo-openni-launchros-indigo-camera-calibration

Beforethecalibration,printan8x6checkerboardof0.108meterinlength.Wewillgetastandard8x6checkerboardfilefromthefollowinglink:

http://wiki.ros.org/camera_calibration/Tutorials/MonocularCalibration

FollowtheproceduretocalibratetheRGBcamerainKinect:

1. StarttheOpenNIdriverusingthefollowingcommand.ThiswillstartKinectRGBanddepthstreamimages:

2. Afterlaunchingdrivers,runthecalibratorcodeavailableonthecamera_calibrationpackage.Thecameracalibrator.pyfileisthenodethatperformscameracalibration.WehavetospecifytheRGBrawimagetopic,cameratopic,sizeofthecheckerboardandsizeofthesquarethatweareusing.Simplyrunthecalibratornodebyusingfollowingcommand:

$rosruncamera_calibrationcameracalibrator.pyimage:=/camera/rgb/image_raw

camera:=/camera/rgb--size8x6--square0.108

3. Theabovecommandwillopenthefollowingwindow:

4. AssumingthatyouhaveaprintedcheckerboardandyouholditinyourhandandshowitontheKinectRGBcamera,youcanseepatternsgettingdetected,asinthepreceedingfigure.Ifitisdetectedproperly,thenmovethecheckerboardtotheleft,right,top,andbottomofthecamera

view,asshowninthefollowingfigure.Therearefourbarsontheright;theXandYbarindicatetheamountofdatacollectedinthexandydirectionandtheSizeandSkewbarsindicatethesamplesofimages,thatare,towards/awayfromthecameraandtiltedup/downrespectively.

5. Ateachstep,holdthecheckerboardstilluntiltheimagegetshighlightedbythedetectionpatterninthecalibrationwindow.Thenecessarycheckerboardpositionisshownasfollows:

6. WhenwemovethecheckerboardaroundtheRGBcamera,thesizeofthebarsincreaseandwhenthecalibrationprogramgetsenoughsamplesforcalibration,theCALIBRATEbuttonwillbecomeactive.

7. WeclickontheCALIBRATEbuttontostartcalibration.Thecalibrationprocesscantakeaboutaminute.Thecalibrationwindowmaybenon-responsiveforsometime,butitwillbereadyeventually.

Afterthecalibrationprocessiscomplete,wecanseethecalibrationresultsintheterminalandthecorrectedimagewillbeshowninthecalibrationwindow.

Asuccessfulcalibrationwillresultinarectifiedimageandafailedcalibrationusuallyresultsinablankorunrecognizableimage.

Aftercalibration,wecanusetheslideronthetopofthecalibrationwindowtoadjustthesizeoftherectifiedimage.Thescalevaluewillshowaszerotherectifiedimage,andsomepixelsintheoriginalimagewillbediscarded.Ascaleof1.0meanswecanseetheoriginalimageandtherectifiedimagehasblackborderswheretherearenoinputpixelsintheoriginalimage.

Ifyouaresatisfiedwiththecalibration,clickontheCOMMIT buttontosendthecalibrationparameterstothecameraforpermanentstorage.TheGUIexitsandyoushouldseewritingcalibrationdatato...intheconsole.

CalibratingtheKinectIRcameraKinectcandetectthedepthoftheenvironmentusinganIRcameraandanIRspeckleprojector,whichcanperformthesamefunctionasastereocamera.WecancalibratethedepthimagethatwegotfromKinectusingthecheckerboardthatweusedfortheRGBcameracalibration.

Thedifficultyincalibratingadepthimageisthatthespecklepatternonthedepthimagecanblocktheaccuratedetectionofthecornersofthecheckerboard.OnepossiblesolutionistocovertheIRprojectorandilluminateitwithanotherIRsourcesuchassunlight,incandescentlamp,andsoon.ThefirstfigureshowsthecheckerboardwiththespecklepatternandthesecondfigureshowsthedepthimageilluminatedbyanincandescentlampandcoveringthespeckleIRprojector.

ThePythonscriptusedfortheRGBcameracanbeusedfordepthcalibration.ThefollowingcommandisusedtocalibratetheIRcamera.Runthecalibratornodeusingthedepthimagetopic;weareusingthe8x6checkerboardwithasizeof0.108meter,asshowninthefollowingexample:

$rosruncamera_calibrationcameracalibrator.pyimage:=/camera/ir/image_raw

camera:=/camera/ir--size8x6--square0.108

TheROSdriverforKinectcannotstreambothIRandRGBimages.Itwilldecidewhichofthetwotostream,basedontheamountofsubscribers.ItisbesttonotrunanyROSnodesduringthecalibrationofthedepthimage,whichsubscribeRGBframes.

RepeatthesamemovementsoftheRGBcameracalibrationindepthcameratoo.Aftercalibration,wecanpresstheCOMMIT buttontosavethecalibrationvaluestoafile.WhenwepresstheCOMMITbutton,thevalueswillbesenttotheopenni_cameradriverpackageinaformofROSservicecall.

Whenopenni_camerareceivesthecameraparameters,itwillstorethemtoafilewiththehelpofanROSpackagecalledcamera_info_manager.Thecamera_info_managerpackagecanhandletheseparametersandstoretheminsomelocation.Thedefaultlocationofintrinsicparametersis$HOME/.ros/camera_info/NAME.yamlandthenameoffilecontainsthecameranameanddeviceserialnumber.Thisfilecanbemovedtoanypubliclocationwewant.ThenameofthefilesofRGBanddepthcalibrationwilllooklikergb_A00362903124106A.yamlanddepth_A00362903124106A.yaml.

ThecontentoftheRGBcameracalibrationfileisgivenasfollows:

image_width:640

image_height:480

camera_name:rgb_A00362903124106A

camera_matrix:

rows:3

cols:3

data:[543.275251827696,0,286.5024846235134,0,544.9622371717294,

270.5536535568697,0,0,1]

distortion_model:plumb_bob

distortion_coefficients:

rows:1

cols:5

data:[0.1236660642773772,-0.2974236496563437,0.008147821573873778,

-0.03185623828978901,0]

rectification_matrix:

rows:3

cols:3

data:[1,0,0,0,1,0,0,0,1]

projection_matrix:

rows:3

cols:4

data:[531.7443237304688,0,263.0477918357592,0,0,559.802490234375,

274.1133349321171,0,0,0,1,0]

Ifthefilesareplacedinthedefaultlocation,theOpenNIdrivercanautomaticallytakethecalibrationfilesfromthislocation.Ifwewanttosavetheminsomeotherlocation,wehavetousethelaunchfilesectiongiveninthefollowingcodeandmentionthepathofthecameracalibrationfilesasargumentsofopenni.launch:

<includefile="$(findopenni_launch)/launch/openni.launch">

<argname="rgb_camera_info_url"

value="file:///public/path/rgb_A00362903124106A.yaml"/>

<argname="depth_camera_info_url"

value="file:///public/path/depth_A00362903124106A.yaml"/>

</include>

</launch>

WheelodometrycalibrationCalibrationisrequiredinodometrytoreducenavigationalerrors.ThemainparameterneededtocalibratethisisthemeasureofDistanceperencoderticksofthewheels.Itisthedistancetraversedbytherobotwheelafterduringeachencodertick.

Thewheelbaseisthedistancebetweenthetwodifferentialdrivewheels.Distanceperencoderticksisthedistancetraversedbythewheeloneachencodercount.Wecancalibratetherobotbymonitoringencodercountsofeachwheelbydrivingforafixeddistance.Theaverageofthesecountsisdividedbythetotaldistancetraveledtogetastartingvaluefortheencoderclick,whichhappenspermillimeter.Theencodermanufacturermaymentionanencodercountinonerevolution,butinapracticalscenario,therewillbechangesinit.

Tocalibratetherobot,drivetherobotforafixeddistanceandnotedowntheencodercountsintheleftandrightmotor.Thefollowingequationcangiveanaveragecountpermillimeter:

Countspermillimeter=(leftcounts+rightcounts)/2)/totalmillimetertraveled

ErroranalysisofwheelodometryAnerrorfromthewheelodometrycanresultinaccumulationoferrorsinthepositionoftherobot.Theodometryvaluecanchangewhenthewheelslipsonthegroundormovesonanuneventerrain.Theodometryerrorgeneratedwhiletherobotrotatescancausesevereerrorsintherobot'sfinalposition.Forexample,ina10metertripofrobot,ifbothwheelsslipby1centimeter,itcancause0.1percenterrorsinthetotaldistanceandtherobotwillarrive1cmshortofitsdestination.

However,iftheslipbetweentwowheelsis1centimeter,itcancausemoreerrorsthanthefirstcasethatwediscussed.ThiscanresultinalargeerrorinbothXandYcoordinates.

Assumethattherobotwheelbaseis10centimeterandaslipof1centimeterbetweentwowheelscanresultin0.1radianerror,whichisabout5.72degrees.Givenhereistheequationtofindtheheadingerror:

headingerror=(left-right)/Wheelbase

=(0.01/0.1)

=0.1radians*(180/PI)=~5.72degrees

Wecanfindthefinalpositionoftherobotafter10meterswithaheadingerrorof0.1radian,asshownhere:

X'=10*sin(5.72)=~1meter

Y'=10*cos(5.72)=9.9meter

Fromthesecalculations,weknowthataheadingerrorof0.1radiancausesashiftof1meterinthexdirectionfromthedestinationposition.Theillustrationofthiserrorisgivenasfollows:

Fromthisanalysis,weunderstoodthatasmallerrorinθproduceslargeerrorsinXandY.Themainerroraffectstheorientationoftherobotratherthanthedistancetraveled.Therearesomemethodstoreducethiserror.Thesearementionedinthefollowingsection.

ErrorcorrectionFromtheaboveanalysis,itcanbeseenthatthemostimportanterrorintherobot'spositioncalculationistheerrorinheading,theθcalculation.Someofthemethodstoreduceθerrorsareasfollows:

Digitalcompass:Wecandeployadigitalcompassintherobottogettheheadingoftherobotandtherebyreducetherobotheadingerror.Digitalcompasscanbeusedalonebutitmayencounterproblemssuchasifthereisanylocalmagneticanomaly,itcanmakeabignoiseinthereading.Also,thecompassmustbeperfectlyinclinedtotherobot'ssurface;ifthesurfaceisuneven,therewillbeerrorsinthecompassreadings.Digitalgyroscope:Thedigitalgyroscopeprovidestherateofchangeoftheangleorangularvelocity.Ifweknowtheangularvelocity,wecanfindtheanglebyintegratingthevaluesoveraperiodoftime.Wecanfindtheangularvelocityoftherobotusinggyro;butthegyrovaluecanmakeerrorstoo.Ifarobothastocoveragreatdistance,theerrorcomputingfromgyrowillincrease,sogyrocanonlybeusediftherobotcoversashortdistance.Iftherobotcoversagreatdistance,wecanusethecombinationofagyroscopeandacompass.Gyro-correctedcompass:Inthismethod,weincorporatethegyroandcompassintoasingleunit,sothatonesensorcancorrecttheother.CombiningthesesensorvaluesusingaKalmanfiltercangivebetterheadingvaluesfortherobot.

IntheChefBotprototype,weareusingGyroalone.Infutureupgrades,wewillreplacegyrowiththe

combinationofgyroandcompass.

WeareusinganIMUcalledMPU-6050byInvensetogettheheadingoftherobot.ThefollowingsectionexplainsasimplecalibrationmethodtoreducetheoffsetofMPU6050.Herearetheprocedurestocalibratethesensor.

CalibratingtheMPU6050MPU6050calibrationcanbedoneusingtheEnergiacode,whichisusedtodisplaytherawvaluesofthesensormentionedinChapter6,WorkingwithRoboticSensors.ThisexampleisalreadyavailableinEnergiaexamples.YouwillgetthiscodebynavigatingtoFile/Examples/MPU6050/Examples/MPU6050_raw.LoadthissketchintoEnergiaandfollowtheproceduregivenhere:

1. PlacetheMPU6050breakoutboardonaflatsurface.Wecanuseaninclinometertochecktheinclinationofthesurface.

2. Modifythecurrentprogrambysettingtheoffsettozero.Wecansettheoffsetofthreeaxesvaluesofgyroscopeto0usingthefollowingfunction:

("setXGyroOffset,setYGyroOffset,setZGyroOffset"=0)

3. UploadtherawcodetoLaunchpadandtaketheEnergiaserialmonitortoconfirmwhethertheserialdataiscomingfromtheLaunchpad.Leavethebreakoutfor5to10minutestoallowthetemperaturetostabilizeandreadthegyrovaluesandnotedownthevalues.

4. SettheoffsetvaluestothereadingsnotedanduploadthecodeagaintotheLaunchpad.5. Repeatthisprocedureuntilwegetareadingof0fromeachgyroaxis.6. Afterachievingthegoal,wefinallygettheoffsetsthatcanbeusedforfuturepurposes.

ThesearethenecessaryprocedurestocalibrateMPU6050.Aftersensorcalibration,wecantesttherobothardwareusingtheGUI.

TestingoftherobotusingGUIWehavealreadydiscussedhowtobuildamapoftheenvironmentusingtherobotsimulationandrobothardware.Inthissection,wediscusshowtocommandtherobottogointoaparticularplaceofthemap.Abetterwaytofindthepositionoftherobotineachtableistomanuallydrivetherobotusingteleoperation.

AssumingthatChefBotpackagesareconfiguredinboththerobot'sPCandtheuser'sPC,thereshouldbeWi-FinetworkstowhichboththerobotanduserPCscanconnectandcommunicateusingtheIPassignedtoeachPC.ItshouldbenotedthatwehavetosetROS_MASTER_URIandROS_IP,asmentionedinChapter10,IntegrationofChefBotHardwareandInterfacingitintoROS,UsingPython.

Thefollowingprocedurecanbeusedtotesttherobotsthatareworkinginahotelenvironment:

1. RemotelogintotherobotPCfromtheuserPCusingthesshcommand.Thecommandisgivenasfollows:

$ssh<robot_pc_ip_address>

2. Iftheroomisnotmappedyet,wecanmapitusingthefollowingcommandsintherobotterminal.Starttherobotsensorsandtheodometryhandlingnodesusingthefollowingcommand:

3. Afterstartingthenodes,wecanstartthegmappingnodesusingthefollowingcommand:

$roslaunchchefbot_bringupgmapping_demo.launch

4. Afterstartinggmapping,wecanstartthekeyboardteleoperationnodestomovetherobotusingthekeyboard:

$roslaunchchefbot_bringupkeyboard_telop.launch

5. Afterlaunchingtheteleoperation,runRVizintheusersystemtoviewthemapgenerated:

6. Atypicalmapisgivenintheprecedingfigure.Itcanvaryaccordingtotheenvironment.Aftergeneratingthemap,wehavetorunthefollowingcommandtosavethegeneratedmapinthehomefolder:

$rosrunmap_servermap_saver-f~/<name_of_the_map>

7. Aftersavingthemap,wecanstarttheAMCLnodeforautonomousnavigation:

$roslaunchchefbot_bringupamcl_demo.launchmap_file:=~/<map_name.yaml>

8. TherobotonthemapafterstartingAMCLisshowninthefigure.AfterrunningAMCL,startthekeyboardteleoperationandmovetoeachtablereferringthemap.

9. Checkwhethertherobot'spositionisthesameinmapandintheactualenvironment.Ifthereisahugedifference,thenweneedtoremaptheroom.Ifthereislessdifference,wecanretrieveandviewrobot'spositionneareachtablewithrespecttothemap,usingthefollowingcommand:

$rosruntftf_echo/map/base_link

Wewillgetthetranslationandrotationvalueoftherobotineachposition,asshowninthefollowingscreenshot:

NotethecorrespondingpositionoftherobotneareachtableandfeedittotheGUIcode.TheeditingGUIcodemustbeontheuserPC.AfterinsertingthepositionoftherobotineachtableontheGUIcode,runtheGUInodeusingthefollowingcommandontheusersystem:

$rosrunchefbot_bringuprobot_gui.py

ThefollowingGUIwillpopupandwecancontroltherobotusingthisGUI.

WecancommandtherobottogointoaparticulartablebygivingthetablenumberontheGUIandpressingtheGobutton.WhenwepresstheGobutton,thecorrespondinggoalpositionissenttothenavigationstack.AftertestingtheGUI,wecandeploytherobotonthecurrentenvironment.

Wecanseetheadvantagesanddisadvantagesofthisnavigationmethod.ThenavigationmethodmainlydependsontheROSframeworkandprogrammingusingPython.

ProsandconsoftheROSnavigationThemainhighlightoftheROSnavigationisthatthecodeisopenandreusable.Also,itissimpletounderstand,evenifthehandlingtechnologyiscomplex.Peoplewithminimalcomputerknowledgecanprogramanautonomousrobot.

Theconsofthismethodare:thisisnotyetstableandisstillinthetestingstage,wecan'texpecthighaccuracyfromthismethod,andthecodemaynotbeofindustrialstandards.

Questions1. WhatisthemainuseoftheintrinsiccalibrationofKinect?2. HowwecancalibrateMPU6050values?3. Howwecancalibratethewheelodometryparameters?4. Whatarethepossibleerrorsinwheelodometry?5. Whataretheprosandconsofthisrobotdesign?

SummaryInthischapter,wehavediscussedallthepossibleerrorsandcalibrationsrequiredbeforestartingtherobot.Thecalibrationisrequiredtoreduceerrorsfromthesensors.WealsosawallthestepstodobeforeworkingwithrobotGUIthatwehavedesigned.Wealsohaveseentheprosandconsofthismethod.Theareawearehandlingisstillbeingresearchedsowecan'texpecthighaccuracyfromthecurrentprototype.

IndexA

A*searchalgorithmabout/Wheredorobotscomefrom?

A.L.I.C.Eabout/LoadingasingleAIMLfilefromthecommand-lineargument

A.L.I.C.E.AIMLfilesworkingwith/WorkingwithA.L.I.C.E.AIMLfilesreferencelink/WorkingwithA.L.I.C.E.AIMLfilesloading,intomemory/LoadingAIMLfilesintomemoryloading/LoadingAIMLfilesandsavingtheminbrainfilessaving,inbrainfile/LoadingAIMLfilesandsavingtheminbrainfilesloading,Bootstrapmethodused/LoadingAIMLandbrainfilesusingtheBootstrapmethod

AbsoluteZero,LibreCAD/Creatinga2DCADdrawingoftherobotusingLibreCADacousticmodel

about/BlockdiagramofaspeechrecognitionsystemActiveStatePython2.7bit

URL,fordownloading/InstallationoftheSpeechSDKAdaptiveMonteCarloLocalization(AMCL)

URL/CreatingtheGazebomodelfromTurtleBotpackagesAdvancePackagingTool(APT)

about/InstallingQtonUbuntu14.04.2LTSAIML

about/IntroductiontoAIMLworkingwith/WorkingwithAIMLandPython

AIMLtagsabout/IntroductiontoAIMLtags<aiml>tag/IntroductiontoAIMLtags<category>tag/IntroductiontoAIMLtags<pattern>tag/IntroductiontoAIMLtags<template>tag/IntroductiontoAIMLtags<starindex=$n$/>ta/IntroductiontoAIMLtags<srai>tag/IntroductiontoAIMLtagsreferencelink/IntroductiontoAIMLtags

aiml_client.pyfile/aiml_client.pyaiml_server.pyfile/aiml_server.pyaiml_speech_recog_client.pyfile/aiml_speech_recog_client.pyaiml_tts_client.pyfile/aiml_tts_client.pyAlicebotfreesoftwarecommunity

URL/IntroductiontoAIMLAMCLpackage

URL/WorkingwithROSlocalizationandnavigation

apt-keyabout/InstallingROSIndigoonUbuntu14.04.2

ArduinoURL/Embeddedcontrollerboard

AsusXtionPROURL/Kinect

AsusXtionPro/ListofroboticvisionsensorsandimageprocessinglibrariesAutoCAD

URL/Robotchassisdesignautonomoussystem/Moderndefinitionofarobot

Bbags/TheROSComputationGraphbaudRatevariable

about/WorkingwithDynamixelactuatorsBeagleBone

URL/CentralProcessingUnitbinaries,forWindowsandMacOSX

URL/PyQtBlender

URL/Robotchassisdesignabout/Robotchassisdesign,InstallingLibreCAD,Blender,andMeshLabinstalling/InstallingBlenderURL,fordownloading/InstallingBlenderURL,fordocumentation/InstallingBlenderURL,fortutorials/Workingwitha3DmodeloftherobotusingBlenderURL,forPythonscripting/PythonscriptinginBlender

BlenderPythonAPIsabout/IntroductiontoBlenderPythonAPIs

Block,LibreCADreferencelink/Creatinga2DCADdrawingoftherobotusingLibreCAD

blockdiagram,robotabout/Blockdiagramoftherobotmotor/Motorandencoderencoder/Motorandencodermotordriver/MotordriverEmbeddedControllerboard/Embeddedcontrollerboardultrasonicsensors/UltrasonicsensorsInertialMeasurementUnit(IMU)/InertialMeasurementUnitkinect/KinectCentralProcessingUnit/CentralProcessingUnitSpeakers/Mic/Speakers/micPowerSupply/Battery/Powersupply/battery

blockdiagram,speechrecognitionsystemabout/Blockdiagramofaspeechrecognitionsystem

featureextraction/Blockdiagramofaspeechrecognitionsystemacousticmodel/Blockdiagramofaspeechrecognitionsystemlexicon/Blockdiagramofaspeechrecognitionsystemlanguagemodel/Blockdiagramofaspeechrecognitionsystemsearchalgorithm/Blockdiagramofaspeechrecognitionsystemrecognizedwords/Blockdiagramofaspeechrecognitionsystem

Bootstrapmethodused,forloadingbrainfiles/LoadingAIMLandbrainfilesusingtheBootstrapmethodused,forloadingA.L.I.C.E.AIMLfiles/LoadingAIMLandbrainfilesusingtheBootstrapmethod

bpymoduleabout/IntroductiontoBlenderPythonAPIsContextAccess/IntroductiontoBlenderPythonAPIsDataAccess/IntroductiontoBlenderPythonAPIsOperators/IntroductiontoBlenderPythonAPIs

brainfileA.L.I.C.E.AIMLfiles,savingin/LoadingAIMLfilesandsavingtheminbrainfilesloading,Bootstrapmethodused/LoadingAIMLandbrainfilesusingtheBootstrapmethod

breakoutboardURL,forpurchasing/InertialMeasurementUnit

BulletURL/IntroducingGazebo

CCADtools

SolidWorks/RobotchassisdesignAutoCAD/RobotchassisdesignMaya/RobotchassisdesignGoogleSketchUp/RobotchassisdesignInventor/RobotchassisdesignBlender/RobotchassisdesignLibreCAD/Robotchassisdesign

calibrationURL/CalibratingtheKinectRGBcamera

Carmine/ListofroboticvisionsensorsandimageprocessinglibrariesURL,forpurchasing/Listofroboticvisionsensorsandimageprocessinglibraries

casterwheelsreferencelink/Casterwheeldesign

catkindefining/IntroducingcatkinURL/Introducingcatkin

CentralProcessingUnit/CentralProcessingUnitCentreofSpeechTechnologyResearch(CSTR)

about/FestivalChefBot

ROSPythondriver,writingfor/WritingaROSPythondriverforChefBotChefBotdescriptionROSpackage

creating/CreatingaChefBotdescriptionROSpackagechefbot_base_gazebo.urdf.xacro/chefbot_base_gazebo.urdf.xacrokinect.urdf.xacro/kinect.urdf.xacrochefbot_base.urdf.xacro/chefbot_base.urdf.xacro

ChefBothardwarespecifications/SpecificationsoftheChefBothardwareworking/WorkingoftheChefBothardwarebuilding/BuildingChefBothardware

ChefBotPCconfiguring/ConfiguringChefBotPCandsettingChefBotROSpackages

ChefBotPythonnodesworkingwith/WorkingwithChefBotPythonnodesandlaunchfiles

ChefBotROSlaunchfilesdefining/UnderstandingChefBotROSlaunchfiles

ChefBotROSpackageURL/WorkingwithChefBot'scontrolGUI

ChefBotROSpackagessetting/ConfiguringChefBotPCandsettingChefBotROSpackages

ChefBotsensorsinterfacing,toTivaCLaunchPad/InterfacingChefBotsensorswithTivaCLaunchPad

ChefBotsimulation,inhotelenvironmentabout/SimulatingChefBotandTurtleBotinahotelenvironment

CloudSimframeworkURL/IntroducingGazebo

CMakeList.txtandpackage.xmlfile/Whatisarobotmodel,URDF,xacro,androbotstatepublisher?cmudict

about/CMUSphinx/PocketSphinxCMUSphinx

about/CMUSphinx/PocketSphinxURL/CMUSphinx/PocketSphinx

codeinterfacing/Interfacingcode

code,ofTivaCLaunchPadinterfacing/InterfacingcodeofTivaCLaunchPad

command-lineargumentsingleAIMLfile,loadingfrom/LoadingasingleAIMLfilefromthecommand-lineargument

CommandBox,LibreCADreferencelink/Creatinga2DCADdrawingoftherobotusingLibreCAD

communicationsystem,ChefBotblockdiagram/BlockdiagramofthecommunicationsysteminChefBot

components,robot

about/Whatcanwefindinarobot?physicalbody/Thephysicalbodysensors/Sensorseffectors/Effectorscontrollers/Controllers

controlGUI,ChefBotworkingwith/WorkingwithChefBot'scontrolGUIfeatures/WorkingwithChefBot'scontrolGUI

countsperrevolution(CPR)about/Processingencoderdata

CUDA,forGPUaccelerationURL/WhatisOpenCV?

cv_bridgeused,fordisplayingKineticimages/DisplayingKinectimagesusingPython,ROS,andcv_bridge

D2DCADdrawing,ofrobot

creating,LibreCADused/Creatinga2DCADdrawingoftherobotusingLibreCADbaseplatedesign/Thebaseplatedesignbaseplatepoledesign/BaseplatepoledesignWheel,Motor,andMotorClampDesign/Wheel,motor,andmotorclampdesignCasterWheelDesign/CasterwheeldesignMiddlePlateDesign/MiddleplatedesignTopPlateDesign/Topplatedesign

3Dmodelofrobot,withBlenderabout/Workingwitha3DmodeloftherobotusingBlenderPythonscripting/PythonscriptinginBlender

DARTURL/IntroducingGazebo

DCgearedmotorinterfacing,toTivaCLaunchPad/InterfacingDCgearedmotorwithTivaCLaunchPad

deadreckoningabout/InertialNavigation

degreesoffreedom(DOF)about/Introductiontothedifferentialsteeringsystemandrobotkinematics

differentialdrivemechanismdifferentialwheeledrobot/DifferentialwheeledrobotEnergiaIDE,installing/InstallingtheEnergiaIDEcode,interfacing/Interfacingcode

differentialdriverobotabout/Robotdrivemechanism

differentialwheeledrobot/Differentialwheeledrobotdifferential_drivepackage

URL/WritingaROSPythondriverforChefBot

DigitalMotionProcessor(DMP)about/EmbeddedcodeforChefBot

DirectCurrent(DC)/BlockdiagramoftherobotDistanceperencoderticksofthewheels

about/WheelodometrycalibrationDynamixel

about/WorkingwithDynamixelactuatorsDynamixelactuators

workingwith/WorkingwithDynamixelactuatorsDynamixelservos

URL/WorkingwithDynamixelactuators

EEchopin

about/InterfacingHC-SR04toTivaCLaunchPadeffectors,robot

locomotion/Effectorsmanipulation/Effectors

embeddedcode,forChefBotabout/EmbeddedcodeforChefBot

EmbeddedControllerboardabout/Embeddedcontrollerboard

encoderabout/Motorandencoderselecting,forrobot/Selectingmotors,encoders,andwheelsfortherobot

encoderdataprocessing/Processingencoderdata

EnergiaURL/Embeddedcontrollerboard,Differentialwheeledrobotabout/Differentialwheeledrobotdownloading/InstallingtheEnergiaIDE

EnergiaIDEinstalling/InstallingtheEnergiaIDE

eSpeakabout/eSpeakURL/eSpeaksetting,inUbuntu14.04.2/SettingupeSpeakandFestivalinUbuntu14.04.2

ExtensibleMark-upLanguage(XML)about/IntroductiontoAIML

Ffeatureextraction

about/Blockdiagramofaspeechrecognitionsystemfeatures,Gazebo

dynamicsimulation/IntroducingGazeboadvanced3DGraphics/IntroducingGazebosensorssupport/IntroducingGazeboplugins/IntroducingGazeboTCP/IPTransport/IntroducingGazeboCloudSimulation/IntroducingGazebocommand-linetools/IntroducingGazebo

Festivalabout/FestivalURL/Festivalsetting,inUbuntu14.04.2/SettingupeSpeakandFestivalinUbuntu14.04.2

fileslaunching/WorkingwithChefBotPythonnodesandlaunchfiles

forwardkinematicsequation/Explainingoftheforwardkinematicsequation

GGazebo

about/UnderstandingroboticsimulationURL/Understandingroboticsimulationdefining/IntroducingGazebofeatures/IntroducingGazeboinstalling/InstallingGazebotesting,withROSinterface/TestingGazebowiththeROSinterface

Gazebomodelcreating,fromTurtleBotpackages/CreatingtheGazebomodelfromTurtleBotpackages

GazebosimulatorURL/InstallingGazebo

General-PurposeInput/Output(GPIO)/Embeddedcontrollerboardgmappingpackage

URL/WorkingwithSLAMusingROSandKinectGoogleSketchUp

URL/Robotchassisdesigngraycodes

URL/ProcessingencoderdataGTK+

about/InstallingTurtleBotRobotpackagesonROSIndigoGUI

used,fortestingrobot/TestingoftherobotusingGUI

HH-bridge

about/MotordriverHC-SR04

about/Selectingtheultrasonicsensor

interfacing,toTivaCLaunchPad/InterfacingHC-SR04toTivaCLaunchPadworking/WorkingofHC-SR04

HelloWorldGUIapplicationcreating/Qtsignalsandslotsrunning/UpandrunningofHelloWorldGUIapplication

Hello_world_publisher.py/Hello_world_publisher.pyHello_world_subscriber.py/Hello_world_subscriber.pyhierarchical(deliberative)control/Hierarchical(deliberative)controlHMM(HiddenMarkovModels)/Blockdiagramofaspeechrecognitionsystemhybridcontrol/Hybridcontrol

Iimage

displaying,withPython-OpenCVinterface/ReadinganddisplayinganimageusingthePython-OpenCVinterfacecapturing,fromwebcamera/Capturingfromwebcamera

imageprocessinglibrariesabout/Listofroboticvisionsensorsandimageprocessinglibraries

IMUworkingwith/WorkingwithInertialMeasurementUnitinertialnavigationsystem/InertialNavigationMPU6050,interfacingwithTivaCLaunchPad/InterfacingMPU6050withTivaCLaunchPadcodeofEnergia,interfacing/InterfacingcodeofEnergia,InterfacingMPU6050toLaunchpadwiththeDMPsupportusingEnergia

in-builtencoderabout/InterfacingquadratureencoderwithTivaCLaunchpad

InertialMeasurementUnit(IMU)about/chefbot_base_gazebo.urdf.xacro,InertialMeasurementUnitURL/chefbot_base_gazebo.urdf.xacro

inertialnavigationsystem/InertialNavigationInertialNavigationSystem(INS)/InertialNavigationinputpins,motordriver/InputpinsInstantaneousCenterofCurvature(ICC)

about/ExplainingoftheforwardkinematicsequationIntelDN2820FYKH/CentralProcessingUnitInterruptServiceRoutine(ISR)/QuadratureencoderinterfacingcodeInventor

URL/RobotchassisdesignInverseKinematics/InversekinematicsIRproximitysensor

workingwith/WorkingwiththeIRproximitysensorItseez

URL/WhatisOpenCV?

JJulius

about/JuliusURL/Juliusspeechrecognitionaccuracy,improvingin/ImprovingspeechrecognitionaccuracyinPocketSphinxandJulius

Juliusspeechrecognizerinstalling/InstallationofJuliusspeechrecognizerandPythonmodule

KKalmanfilter

URL/InertialNavigationkinect

about/KinectURL,forpurchasing/Kinect

Kinectabout/Listofroboticvisionsensorsandimageprocessinglibrariesprogramming,withPython/ProgrammingKinectwithPythonusingROS,OpenCV,andOpenNI

Kinectimagesdisplaying,Pythonused/DisplayingKinectimagesusingPython,ROS,andcv_bridgedisplaying,ROSused/DisplayingKinectimagesusingPython,ROS,andcv_bridgedisplaying,cv_bridgeused/DisplayingKinectimagesusingPython,ROS,andcv_bridge

KinectIRcameracalibrating/CalibratingtheKinectIRcamera

KinectRGBcameracalibrating/CalibratingtheKinectRGBcamera

kinematicsequationsURL/Inversekinematics

Kobukiabout/InstallingTurtleBotRobotpackagesonROSIndigo

LL-bracket,motor

referencelink/Selectingmotors,encoders,andwheelsfortherobotlanguagemodel

about/Blockdiagramofaspeechrecognitionsystemlaserscandata

PointCloud,convertingto/ConversionofPointCloudtolaserscandatalaunchfolder

launchfiles/CreatingtheGazebomodelfromTurtleBotpackagesLaunchpad

functionalities/Embeddedcontrollerboard

laws,roboticsfirstlaw/Wheredorobotscomefrom?secondlaw/Wheredorobotscomefrom?thirdlaw/Wheredorobotscomefrom?zerothlaw/Wheredorobotscomefrom?

LayerList,LibreCADreferencelink/Creatinga2DCADdrawingoftherobotusingLibreCAD

levelconvertorURL/InterfacingDCgearedmotorwithTivaCLaunchPad

levelshifterabout/WorkingoftheChefBothardwareURL/InterfacingChefBotsensorswithTivaCLaunchPad

lexiconabout/Blockdiagramofaspeechrecognitionsystem

LibreCADURL/Robotchassisdesignabout/Robotchassisdesign,InstallingLibreCAD,Blender,andMeshLabreferences,forinstalling/InstallingLibreCAD,Blender,andMeshLabURL,fordocumentation/InstallingLibreCAD,Blender,andMeshLabinstalling/InstallingLibreCAD

LibreCADtoolsreferencelink/Creatinga2DCADdrawingoftherobotusingLibreCADCommandBox/Creatinga2DCADdrawingoftherobotusingLibreCADLayerList/Creatinga2DCADdrawingoftherobotusingLibreCADBlock/Creatinga2DCADdrawingoftherobotusingLibreCADAbsoluteZero/Creatinga2DCADdrawingoftherobotusingLibreCAD

linesperrevolution(LPR)about/Processingencoderdata

LM(LanguageModel)/WorkingwithPocketSphinxPythonbindinginUbuntu14.04.2loop()function/Quadratureencoderinterfacingcode

MMacOSX

URL/InstallingtheEnergiaIDEmathematicalmodeling,ofrobot

about/Mathematicalmodelingoftherobotsteeringsystem/Introductiontothedifferentialsteeringsystemandrobotkinematicsrobotkinematics/Introductiontothedifferentialsteeringsystemandrobotkinematicsforwardkinematicsequation/ExplainingoftheforwardkinematicsequationInverseKinematics/Inversekinematics

MayaURL/Robotchassisdesign

memoryA.L.I.C.E.AIMLfiles,loadinginto/LoadingAIMLfilesintomemory

MeshLab

about/Robotchassisdesign,InstallingLibreCAD,Blender,andMeshLabinstalling/InstallingMeshLabURL,forsourcecode/InstallingMeshLabURL/chefbot_base.urdf.xacro

methods,forreducingerrorsdigitalcompass/Errorcorrectiondigitalgyroscope/Errorcorrectiongyro-correctedcompass/Errorcorrection

motorabout/Motorandencoderselecting,forrobot/Selectingmotors,encoders,andwheelsfortherobot

motordriverabout/Motordriverselecting/Selectingamotordriver/controllerreferencelink/Selectingamotordriver/controllerinputpins/Inputpinsoutputpins/Outputpinspowersupplypins/Powersupplypins

motorrotationfeedbackreferencelink/Motorandencoder

motors,RobotDriveMechanismselecting/SelectionofmotorsandwheelsRPMofmotors,calculating/CalculationofRPMofmotorsMotorTorque,calculating/Calculationofmotortorque

mountinghubreferencelink/Selectingmotors,encoders,andwheelsfortherobot

MPU6050about/InertialNavigationinterfacing,withTivaCLaunchPad/InterfacingMPU6050withTivaCLaunchPadcalibrating/CalibratingtheMPU6050

MPU6050librarysetting,inEnergia/SettinguptheMPU6050libraryinEnergia

NNaturalinteraction(NI)/WhatisOpenNINextUnitofComputing(NUC)/CentralProcessingUnitnServosvariable

about/WorkingwithDynamixelactuatorsNUC

URL,forpurchasing/CentralProcessingUnitNumPy

about/ReadinganddisplayinganimageusingthePython-OpenCVinterfaceURL/ReadinganddisplayinganimageusingthePython-OpenCVinterface

NXPURL/Listofroboticvisionsensorsandimageprocessinglibraries

Oodometryvalues

about/ExplainingoftheforwardkinematicsequationOGREframework

URL/IntroducingGazeboOpenCV

about/WhatisOpenCV?applications/WhatisOpenCV?installing/InstallationofOpenCVfromsourcecodeinUbuntu14.04.2URL/InstallationofOpenCVfromsourcecodeinUbuntu14.04.2

OpenCV,inMacOSXURL/WhatisOpenCV?

OpenCV,inWindowsURL/WhatisOpenCV?

OpenCV-PythontutorialsURL/Capturingfromwebcamera

OpenCVsupportROSpackage,creatingwith/CreatingROSpackagewithOpenCVsupport

OpenDynamicsEngine(ODE)URL/IntroducingGazebo

OpenNIabout/WhatisOpenNIinstalling,inUbuntu14.04.2/InstallingOpenNIinUbuntu14.04.2

OpenNIdriverlaunching/HowtolaunchOpenNIdriver

OpenSlamURL/WorkingwithSLAMusingROSandKinect

OpenSourceComputerVision(OpenCV)about/Understandingroboticsimulation

outputpins,motordriver/Outputpins

about/WhatisPCL?URL,fordownloading/WhatisPCL?

PCM(PulseCodeModulation)/BlockdiagramofaspeechrecognitionsystemPersonalComputer(PC)

about/Robotchassisdesignphysicalworld/Moderndefinitionofarobotpinout,TexasInstrumentLaunchpadseries

referencelink/Embeddedcontrollerboardpins,motordrivers

about/InterfacingDCgearedmotorwithTivaCLaunchPadpitch

about/IntroductiontothedifferentialsteeringsystemandrobotkinematicsPixy/CMUcam5

URL/ListofroboticvisionsensorsandimageprocessinglibrariesPocketSphinx

about/CMUSphinx/PocketSphinxsetting,inUbuntu14.04.2/SettingupPocketSphinxanditsPythonbindinginUbuntu14.04.2speechrecognitionaccuracy,improvingin/ImprovingspeechrecognitionaccuracyinPocketSphinxandJulius

pocketsphinxpackageinstalling,inROSIndigo/InstallationofthepocketsphinxpackageinROSIndigo

PocketSphinxPythonbinding,Ubuntu14.04.2about/WorkingwithPocketSphinxPythonbindinginUbuntu14.04.2

pocketsphinxROSpackagereferencelink/WorkingwithSpeechrecognitioninROSIndigoandPython

PointCloudworkingwith/WorkingwithPointCloudsusingKinect,ROS,OpenNI,andPCLgeneration/OpeningdeviceandPointCloudgenerationconverting,tolaserscandata/ConversionofPointCloudtolaserscandata

PololuURL/Selectingmotors,encoders,andwheelsfortherobot

PololuH-Bridgeusing/InterfacingDCgearedmotorwithTivaCLaunchPad

portNamevariableabout/WorkingwithDynamixelactuators

PowerSupply/Battery/Powersupply/batterypowersupplypins,motordriver/PowersupplypinsPrintedCircuitBoard(PCB)

about/BuildingChefBothardwarepulsesperrevolution(PPR)

about/ProcessingencoderdataPyAIML

about/IntroductiontoPyAIMLinstalling,inUbuntu14.04.2/InstallingPyAIMLonUbuntu14.04.2installing,fromsourcecode/InstallingPyAIMLfromsourcecode

PyAIML,integratingintoROSabout/IntegratingPyAIMLintoROSaiml_server.pyfile/aiml_server.pyaiml_client.pyfile/aiml_client.pyaiml_tts_client.pyfile/aiml_tts_client.pyaiml_speech_recog_client.pyfile/aiml_speech_recog_client.pystart_chat.launchfile/start_chat.launchstart_tts_chat.launchfile/start_tts_chat.launchstart_speech_chat.launchfile/start_speech_chat.launch

pydynamixel

about/WorkingwithDynamixelactuatorsURL/WorkingwithDynamixelactuators

pyjuliusURL,fordownloading/InstallationofJuliusspeechrecognizerandPythonmodule

PyQtabout/PyQtURL/PyQtinstalling,inUbuntu14.04.1LTS/InstallingPyQtonUbuntu14.04.2LTSworkingwith/WorkingwithPyQtandPySide

PyQtcodeslotdefinition,addingto/AddingaslotdefinitiontoPyQtcode

PySerialmoduleabout/InterfacingTivaCLaunchPadwithPythonURL/InterfacingTivaCLaunchPadwithPython

PySideabout/PySideURL/PySideinstalling,onUbuntu14.04.2LTS/InstallingPySideonUbuntu14.04.2LTSworkingwith/WorkingwithPyQtandPySide

PythonTivaCLaunchPad,interfacingwith/InterfacingTivaCLaunchPadwithPythonKinetic,programmingwith/ProgrammingKinectwithPythonusingROS,OpenCV,andOpenNIused,fordisplayingKineticimages/DisplayingKinectimagesusingPython,ROS,andcv_bridgeworkingwith/WorkingwithAIMLandPython

Python-Juliusclientcode,speechrecognition/Python-JuliusclientcodePython-OpenCVinterface

image,readingwith/ReadinganddisplayinganimageusingthePython-OpenCVinterfaceimage,displayingwith/ReadinganddisplayinganimageusingthePython-OpenCVinterface

PythonAPIs,Blenderabout/IntroductiontoBlenderPythonAPIs

Pythonbindingsetting,inUbuntu14.04.2/SettingupPocketSphinxanditsPythonbindinginUbuntu14.04.2

Pythonbindings,ofQtworkingwith/WorkingwithPythonbindingsofQtPyQt/PyQtPySide/PySide

PythoncodeUIfile,convertinginto/ConvertingaUIfileintoPythoncode

Pythonmoduleinstalling/InstallationofJuliusspeechrecognizerandPythonmodule

Pythonscript,robotmodel/Pythonscriptoftherobotmodel

Pythonwrapper,forWindowsSpeechSDKURL,fordownloading/InstallationoftheSpeechSDK

pyuic4about/ConvertingaUIfileintoPythoncode

installing,onUbuntu14.04.2LTS/InstallingQtonUbuntu14.04.2LTSabout/InstallingQtonUbuntu14.04.2LTSURL/InstallingQtonUbuntu14.04.2LTSsignals/Qtsignalsandslotsslots/Qtsignalsandslots

QtDesignerdefining/IntroducingQtDesigner

quadratureencoderinterfacing,withTivaCLaunchPad/InterfacingquadratureencoderwithTivaCLaunchpad

quadratureencoderinterfacingcodeabout/Quadratureencoderinterfacingcode

RRaspberryPi

URL/CentralProcessingUnitreactivecontrol/Reactivecontrolreal-timespeechrecognition,GStreamer/Real-timespeechrecognitionusingPocketSphinx,GStreamer,andPythoninUbuntu14.04.2real-timespeechrecognition,PocketSphinx/Real-timespeechrecognitionusingPocketSphinx,GStreamer,andPythoninUbuntu14.04.2real-timespeechrecognition,Python/Real-timespeechrecognitionusingPocketSphinx,GStreamer,andPythoninUbuntu14.04.2recognitiongrammar,Julius

referencelink/ImprovingspeechrecognitionaccuracyinPocketSphinxandJuliusrecognizedwords

about/BlockdiagramofaspeechrecognitionsystemRoboLogix

about/Understandingroboticsimulationrobot

about/Whatisarobot?,Wheredorobotscomefrom?,Whatcanwefindinarobot?history/Historyofthetermrobot,Wheredorobotscomefrom?defining/Moderndefinitionofarobotbuilding/Howdowebuildarobot?reactivecontrol/Reactivecontrolhierarchical(deliberative)control/Hierarchical(deliberative)controlhybridcontrol/Hybridcontroltesting,GUIused/TestingoftherobotusingGUI

Robotchassisdesignabout/Robotchassisdesign

RobotDriveMechanismabout/Robotdrivemechanismmotors,selecting/Selectionofmotorsandwheelswheels,selecting/Selectionofmotorsandwheelsdesignsummary/Thedesignsummary

robotdynamicsabout/Introductiontothedifferentialsteeringsystemandrobotkinematics

roboticsabout/Wheredorobotscomefrom?

roboticsimulationabout/Understandingroboticsimulationadvantages/Understandingroboticsimulationdisadvantages/Understandingroboticsimulationmathematicalmodeling,ofrobot/MathematicalmodelingoftherobotROS/IntroductiontoROSandGazeboGazebo/IntroductiontoROSandGazeboROSIndigo,installingonUbuntu14.04.1/InstallingROSIndigoonUbuntu14.04.2ChefBotsimulation,inhotelenvironment/SimulatingChefBotandTurtleBotinahotelenvironment

roboticsimulatorapplicationsGazebo/UnderstandingroboticsimulationV-REP/Understandingroboticsimulationwebots/UnderstandingroboticsimulationRoboLogix/Understandingroboticsimulation

roboticvisionsensorsabout/Listofroboticvisionsensorsandimageprocessinglibraries

robotkinematics/Introductiontothedifferentialsteeringsystemandrobotkinematicsrobotmodel/Whatisarobotmodel,URDF,xacro,androbotstatepublisher?RobotShop

URL/CalculationofRPMofmotorsrobotstatepublisher/Whatisarobotmodel,URDF,xacro,androbotstatepublisher?robot_state_publisher

about/Whatisarobotmodel,URDF,xacro,androbotstatepublisher?roll

about/IntroductiontothedifferentialsteeringsystemandrobotkinematicsRoomba

about/RobotchassisdesignROS

about/IntroductiontoROSandGazebodefining/IntroductiontoROSandGazeboURL/IntroductiontoROSandGazebofeatures/IntroductiontoROSandGazebofilesystem/ROSConcepts

ComputationGraph/ROSConceptscommunity/ROSConceptsused,fordisplayingKineticimages/DisplayingKinectimagesusingPython,ROS,andcv_bridgeused,forcalibratingXboxKinect/TheCalibrationofXboxKinectusingROS

ROS-PCLpackageURL,fordownloading/WhatisPCL?

ros-usersmailinglistabout/TheROScommunitylevel

ROScommunitylevelabout/TheROScommunitylevelDistributions/TheROScommunitylevelRepositories/TheROScommunitylevelROSWiki/TheROScommunitylevelMailingLists/TheROScommunitylevel

ROSComputationGraphabout/TheROSComputationGraphnodes/TheROSComputationGraphROSMaster/TheROSComputationGraphParameterserver/TheROSComputationGraphmessages/TheROSComputationGraphtopics/TheROSComputationGraphservices/TheROSComputationGraphbags/TheROSComputationGraph

rosdepabout/InstallingROSIndigoonUbuntu14.04.2

ROSfilesystemabout/TheROSfilesystempackages/TheROSfilesystemPackageManifests/TheROSfilesystemmessage(msg)types/TheROSfilesystemservice(srv)types/TheROSfilesystem

ROSIndigoinstalling,onUbuntu14.04.1/InstallingROSIndigoonUbuntu14.04.2catkin,defining/IntroducingcatkinROSpackage,creating/CreatinganROSpackageHello_world_publisher.py/Hello_world_publisher.pyHello_world_subscriber.py/Hello_world_subscriber.pyGazebo,defining/IntroducingGazeboGazebo,installing/InstallingGazeboGazebo,testingwithROSinterface/TestingGazebowiththeROSinterfaceTurtleBotRobotpackages,installing/InstallingTurtleBotRobotpackagesonROSIndigoTurtleBotRobotpackages,installinginUbuntu/InstallingTurtleBotROSpackagesusingtheaptpackagemanagerinUbuntuTurtleBot,simulating/SimulatingTurtleBotusingGazeboandROS

Gazebomodel,creatingfromTurtleBotpackages/CreatingtheGazebomodelfromTurtleBotpackagesrobotmodel/Whatisarobotmodel,URDF,xacro,androbotstatepublisher?URDF/Whatisarobotmodel,URDF,xacro,androbotstatepublisher?xacro/Whatisarobotmodel,URDF,xacro,androbotstatepublisher?robotstatepublisher/Whatisarobotmodel,URDF,xacro,androbotstatepublisher?ChefBotdescriptionROSpackage,creating/CreatingaChefBotdescriptionROSpackagepocketsphinxpackage,installingin/InstallationofthepocketsphinxpackageinROSIndigo

ROSinterface,ofOpenCVabout/TheROSinterfaceofOpenCV

ROSlocalizationworkingwith/WorkingwithROSlocalizationandnavigation

ROSnavigationworkingwith/WorkingwithROSlocalizationandnavigationpros/ProsandconsoftheROSnavigationcons/ProsandconsoftheROSnavigation

ROSpackagecreating/CreatinganROSpackagecreating,withOpenCVsupport/CreatingROSpackagewithOpenCVsupport

ROSpackagesURL/InstallingROSIndigoonUbuntu14.04.2,CreatingtheGazebomodelfromTurtleBotpackages

ROSPythondriverwriting,forChefBot/WritingaROSPythondriverforChefBot

Rossum'sUniversalRobots(R.U.R)/Historyofthetermrobotrqt

about/InstallingandworkingwithrqtinUbuntu14.04.2LTSinstalling,inUbuntu14.04.2LTS/InstallingandworkingwithrqtinUbuntu14.04.2LTSdefining,inUbuntu14.04.2LTS/InstallingandworkingwithrqtinUbuntu14.04.2LTS

rvizabout/SimulatingChefBotandTurtleBotinahotelenvironmentURL/SimulatingChefBotandTurtleBotinahotelenvironment

SSAPI(SpeechApplicationProgrammingInterface)

about/WorkingwithspeechrecognitionandsynthesisinWindowsusingPythonsearchalgorithm

about/BlockdiagramofaspeechrecognitionsystemSerialClockLine(SCL)

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about/InterfacingTivaCLaunchPadwithPythonServiceRobot

requisites/TheRequirementsofaservicerobotsetuptools,Python

URL,fordownloading/InstallationofJuliusspeechrecognizerandPythonmoduleShakey

about/Wheredorobotscomefrom?SharpGP2D12sensor

URL/WorkingwiththeIRproximitysensorsignals

about/QtsignalsandslotsSimbody

URL/IntroducingGazeboSimultaneousLocalizationAndMapping(SLAM)/CreatingtheGazebomodelfromTurtleBotpackagessingleAIMLfile

loading,fromcommand-lineargument/LoadingasingleAIMLfilefromthecommand-lineargument

SLAMworkingwith/WorkingwithSLAMusingROSandKinect

SLAM,onROSworkingwith/WorkingwithSLAMonROStobuildthemapoftheroom

slotabout/Qtsignalsandslots

slotdefinitionadding,toPyQtcode/AddingaslotdefinitiontoPyQtcode

SolidWorksURL/Robotchassisdesign

sourcecodePyAIML,installingin/InstallingPyAIMLfromsourcecode

spamfilters/ModerndefinitionofarobotSpeakers/Mic/Speakers/micspecifications,ChefBothardware/SpecificationsoftheChefBothardwarespeechrecognition

about/Understandingspeechrecognitiondecoding,fromwavefile/WorkingwithPocketSphinxPythonbindinginUbuntu14.04.2

speechrecognition,inUbuntu14.04.2about/WorkingwithspeechrecognitionandsynthesisinUbuntu14.04.2usingPythonoutput/Output

speechrecognition,Julius/SpeechrecognitionusingJuliusandPythoninUbuntu14.04.2speechrecognition,Python/SpeechrecognitionusingJuliusandPythoninUbuntu14.04.2

about/WorkingwithSpeechrecognitioninROSIndigoandPythonspeechrecognition,ROSIndigo

about/WorkingwithSpeechrecognitioninROSIndigoandPythonspeechrecognitionaccuracy

improving,inPocketSphinx/ImprovingspeechrecognitionaccuracyinPocketSphinxandJulius

improving,inJulius/ImprovingspeechrecognitionaccuracyinPocketSphinxandJuliusspeechrecognitionlibraries

about/SpeechrecognitionlibrariesCMUSphinx/CMUSphinx/PocketSphinxPocketSphinx/CMUSphinx/PocketSphinxJulius/Julius

speechrecognitionsystemblockdiagram/Blockdiagramofaspeechrecognitionsystem

SpeechSDKinstalling/InstallationoftheSpeechSDKURL,fordownloading/InstallationoftheSpeechSDK

speechsynthesisabout/Speechsynthesis

speechsynthesis,inUbuntu14.04.2about/WorkingwithspeechrecognitionandsynthesisinUbuntu14.04.2usingPythonoutput/Output

speechsynthesis,Python/WorkingwithspeechsynthesisinROSIndigoandPythonspeechsynthesis,ROSIndigo/WorkingwithspeechsynthesisinROSIndigoandPythonspeechsynthesislibraries

about/SpeechsynthesislibrarieseSpeak/eSpeakFestival/Festival

speechsynthesisstagestextanalysis/Speechsynthesisphoneticanalysis/Speechsynthesisprosodicanalysis/Speechsynthesisspeechsynthesis/Speechsynthesis

StanfordResearchInstitute(SRI)about/Wheredorobotscomefrom?

start_chat.launchfile/start_chat.launchstart_speech_chat.launchfile/start_speech_chat.launchstart_tts_chat.launchfile/start_tts_chat.launchstatetransitions

about/Processingencoderdatasteeringsystem/IntroductiontothedifferentialsteeringsystemandrobotkinematicsSTereoLithography(STL)/IntroductiontoBlenderPythonAPIssynaptic

about/InstallingTurtleBotRobotpackagesonROSIndigosysmodule

about/InterfacingTivaCLaunchPadwithPythonSystemOnChip(SOC)/Listofroboticvisionsensorsandimageprocessinglibraries

Ttexttospeech(TTS)/Speakers/mictf

URL/Whatisarobotmodel,URDF,xacro,androbotstatepublisher?TivaCLaunchPad

URL/Embeddedcontrollerboardabout/EmbeddedcontrollerboardDCgearedmotor,interfacingto/InterfacingDCgearedmotorwithTivaCLaunchPadquadratureencoder,interfacingwith/InterfacingquadratureencoderwithTivaCLaunchpadHC-SR04,interfacingto/InterfacingHC-SR04toTivaCLaunchPadinterfacing,withPython/InterfacingTivaCLaunchPadwithPythonMPU6050,interfacingwith/InterfacingMPU6050withTivaCLaunchPadChefBotsensors,interfacingto/InterfacingChefBotsensorswithTivaCLaunchPad

topics/TheROSComputationGraphTrigpin

about/InterfacingHC-SR04toTivaCLaunchPadtruthtable

about/InterfacingDCgearedmotorwithTivaCLaunchPadTurtleBot

URL/Robotchassisdesignsimulating,Gazeboused/SimulatingTurtleBotusingGazeboandROSsimulating,ROSused/SimulatingTurtleBotusingGazeboandROS

TurtleBotpackagesGazebomodel,creatingfrom/CreatingtheGazebomodelfromTurtleBotpackages

TurtleBotrobotchassisdesignabout/Robotchassisdesign

TurtleBotRobotpackagesinstalling,onROSIndigo/InstallingTurtleBotRobotpackagesonROSIndigoURL/InstallingTurtleBotRobotpackagesonROSIndigo

TurtlebotROSpackagesinstalling,aptpackagemanagerused/InstallingTurtleBotROSpackagesusingtheaptpackagemanagerinUbuntu

UUbuntu14.04.2

OpenNI,installingin/InstallingOpenNIinUbuntu14.04.2PocketSphinx,settingin/SettingupPocketSphinxanditsPythonbindinginUbuntu14.04.2Pythonbinding,settingin/SettingupPocketSphinxanditsPythonbindinginUbuntu14.04.2eSpeak,settingin/SettingupeSpeakandFestivalinUbuntu14.04.2Festival,settingin/SettingupeSpeakandFestivalinUbuntu14.04.2PyAIML,installingin/InstallingPyAIMLonUbuntu14.04.2

Ubuntu14.04.2LTSQt,installingon/InstallingQtonUbuntu14.04.2LTS

UIfileconverting,intoPythoncode/ConvertingaUIfileintoPythoncode

ultrasonicdistancesensorsworkingwith/WorkingwithultrasonicdistancesensorsHC-SR04,interfacingtoTivaCLaunchPad/InterfacingHC-SR04toTivaCLaunchPad

ultrasonicsensorselecting/Selectingtheultrasonicsensor

ultrasonicsensorsabout/Ultrasonicsensors

UniformResourceIdentifier(URI)about/WorkingwithChefBotPythonnodesandlaunchfiles

UniversalAsynchronousReceiver/Transmitter(UART)/EmbeddedcontrollerboardUnmannedAerialVehicles(UAVs)/WorkingwithInertialMeasurementUnitUpdate_Time()function

about/EmbeddedcodeforChefBotURDF/Whatisarobotmodel,URDF,xacro,androbotstatepublisher?

URL/Whatisarobotmodel,URDF,xacro,androbotstatepublisher?,chefbot_base_gazebo.urdf.xacrofunctionality/CreatingaChefBotdescriptionROSpackagechefbot_base.urdf.xacro/CreatingaChefBotdescriptionROSpackagechefbot_base_gazebo.urdf.xacro/CreatingaChefBotdescriptionROSpackagechefbot_gazebo.urdf.xacro/CreatingaChefBotdescriptionROSpackagechefbot_library.urdf.xacro/CreatingaChefBotdescriptionROSpackagechefbot_properties.urdf.xacro/CreatingaChefBotdescriptionROSpackagecommon_properties.urdf.xacro/CreatingaChefBotdescriptionROSpackagekinect.urdf.xacro/CreatingaChefBotdescriptionROSpackagechefbot_circles_kinect_urdf.xacro/CreatingaChefBotdescriptionROSpackage

VV-REP

about/UnderstandingroboticsimulationURL/Understandingroboticsimulation

VirtualBoxURL/InstallingROSIndigoonUbuntu14.04.2

VNH2SP30motorabout/InterfacingChefBotsensorswithTivaCLaunchPad

Wwavefile

speechrecognition,decodingfrom/WorkingwithPocketSphinxPythonbindinginUbuntu14.04.2

webcameraimage,capturingfrom/Capturingfromwebcamera

webotsabout/Understandingroboticsimulation

wheelbase

about/Wheelodometrycalibrationwheelencoders

about/Explainingoftheforwardkinematicsequationwheelodometrycalibration

defining/Wheelodometrycalibrationerroranalysis,ofwheelodometry/Erroranalysisofwheelodometryerrorcorrection/Errorcorrection

wheelsselecting,forrobot/Selectingmotors,encoders,andwheelsfortherobot

wheels,RobotDriveMechanismselecting/Selectionofmotorsandwheels

WindowsURL/InstallingtheEnergiaIDE

WindowsSpeechSDKabout/WindowsSpeechSDK

WiringURL/Differentialwheeledrobot

worldfiles/Whatisarobotmodel,URDF,xacro,androbotstatepublisher?

Xxacro/Whatisarobotmodel,URDF,xacro,androbotstatepublisher?

URL/Whatisarobotmodel,URDF,xacro,androbotstatepublisher?XboxKinect

calibrating,ROSused/TheCalibrationofXboxKinectusingROS

about/Introductiontothedifferentialsteeringsystemandrobotkinematics

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