smart personal environment regulator - ecal · ce 186 – design of cyber physical systems final...

CE186–DesignofCyberPhysicalSystems FinalReport

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SmartPersonalEnvironmentRegulator Teammembers:JeongWhanBae,AndaiWang,NelsonXiong,LydiaYiu

I. Abstract

This project investigates the effects of personal environmental conditions on the

productivity level andwell-being of room occupants, and introduces the Smart Personal

EnvironmentRegulator(SPER)asasolutionforthepurposeofimprovingtheseconditions.

Theproblemconcerningourpersonalenvironment is thatproductivityandcomfortmay

bereducediftheroomtemperature,humidityandcarbondioxidelevelsareeithertoohigh

ortoolow.Additionally,smalleroccupantspaces,suchasadeskorclassroom,maynotbe

accuratelymonitoredbythegeneralheating,ventilation,andairventilation(HVAC)system

thatexistsinabuilding.Thus,weaimtomonitorandadjusttheenvironmentalconditions

ofanoccupantspaceforoptimalproductivityandcomfort.

Thecyber-physicalsystemconsistsofthreesensingnodesthatwillmonitortemperature,

humidity,andcarbondioxidelevels,acyberlayerthatprocessesthedatacollectedbythe

sensors,andafan-heatercombothatwilladjusttheenvironmentalconditionsaccordingto

theprocesseddataifnecessary.Withsuchfunctionality,thesystemcanbeimplementedin

placessuchasclassrooms,officesorhomeswhereproductivityandcomfortmatter.

II. Introduction

MotivationandBackground

Ourteamnoticedthatenvironmentalconditionsintheclassroomcanoftenbetoohot,too

cold, or too stuffy, which can be distracting for studying orworking purposes. This can

affecttheoccupantbycausingadecreaseinconcentrationandtheurgetofallasleepwhen

working,andcanultimatelyleadtoa lossinproductivity.Wewanttopreventunsuitable

environmental conditions in working spaces, such as on a college campus where

productivityandefficiencyishighlyvalued.


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The current system of thermal comfort regulation in buildings can be energy inefficient

because usually there is only one thermostat to control the temperature in a very large

area.Thisisinefficientbecausenotallroomsneedtobeatthesameconditions.Bytackling

the thermal comfort problem in a smaller working space, working productivity will

increase,butenergyconsumptionwillalsolikelydecrease.

RelevantLiterature

Research has found that carbon dioxide levels inworking spaces are oftenmuch higher

thanoutdoor levels.According to a study in2012, outside carbondioxide levels average

around400ppm,but indoor levels canoftenbeup to1000ppmandeven3000ppm in

offices and classrooms respectively. The study further showed that the carbon dioxide

levelsweredirectlyrelatedtotheperformanceoftheoccupantswithintheroom.

In addition to carbon dioxide, temperature and humidity also play a big part in human

comfort, and thus their performance to work. According to the Canadian Centre of

OccupationalHealthandSafetywebsite,thecomfortabletemperaturerangeforaworking

environmentisbetween21to23degreesCelsius,andshouldbeadjustedhigherwhenthe

outdoorstemperatureiswarmertominimizethediscrepancybetweenindoorandoutdoor

temperatures. There are also recommended temperature settings for varying humidity

levels.

TheASHRAE-55standardisawidelyusedindoorthermalcomfortstandardthatspecifies

conditions for acceptable thermal environments and is intended for use in design,

operation, and commissioning of buildings and other occupied spaces. It determines

acceptablecomfort“envelopes”basedonseveralfactors,suchastheairtemperature,mean

radiant temperature,humidity,metabolic rate, clothing level,andevenairspeed.For the

purposes of this project, we will be using a simplified model based on the ASHRAE-55

standardbyvaryingonly2ofthe6parametersandholdingtherestasconstants,asshown

inTable1.


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Parameter Value

Airtemperature Varying

Humidity Varying

Meanradianttemperature 25.0oC

Metabolicrate 1.1met

Clothinglevel Summerindoorclothing

Airspeed 0.1m/s

Table1:Varyingparametersandconstantparameters.

Focusofthisstudy

The focusof this project seeks to improve theproductivity and comfort inmoreof such

workingspacesbytargetingthreeparameters:temperature,humidity,andcarbondioxide.

Wehopethatthisprojectwillfurtherincreaseawarenessofthesignificanceofindoorair

qualityandcomfort,andthatfuturerenovationandconstructionprojectswillplacemore

emphasisonimprovingtheseconditionsforoccupants.

III. TechnicalDescription

Method

Theoverall cyber-physical structureofSPER is shown in the flowchartbelow(Figure1),

depictingtheimplementationofthevariouslayersofacyber-physicalsystem.Theprocess

beginswithdatacollectionby the threesensorspoweredbyanArduinomicrocontroller.

This information collected are passed by the Arduino via serial port, and collected by a

Pythonscriptthatuploadsthemtothewebserver,storingthemasstreamsinadatabase.

AnotherPythonscriptwillthencollectthesedatafromtheserver,andchecksifthelatest


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parameters collected are within the comfort envelope. If the latest conditions are

determined to be outside the comfortable range of values, a Python scriptwill send the

appropriatesignaltoasecondArduinothatcontrolsthepowerrelayofthefan-heater.

Figure1:StructureofSPERcyber-physicalsystem

Tobuildoursystem,weusedthefollowinghardwarecomponents:

● ArduinoUno

● Temperatureandhumiditysensornode(miniArduinoincluded)

● Carbondioxidesensor

● Fan-heatercombo

● X-Beemeshnetwork


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Weusedthefollowingsoftwareprogramstocompleteourcyberlayer:

Arduinosensorcode

We used the Arduinomicrocontroller to control the temperature, humidity, and carbon

dioxidesensors.WeusedanexistingcodeforreadingtheHIH6130temperature/humidity

sensor, and we created a simple code function using analogRead to read the K-30 CO2

sensor.

ListenandSend.py

Thisprogramreadstheserialoutput fromtheArduinoandsendsthis informationtothe

webserveranddatabase.Italsoactsasamessagerelayintheotherdirectionbysending

thesignalcreatedbyProcessData.pytotheactuator.

ProcessData.py

This program receives data from the database and runs it through an algorithm to

determine if the current environmental conditions fallwithin the comfort envelope. Our

criteriaareanapproximationestablishedbytheASHRAE55-2013standardthatassesses

the temperature and humidity. Since there are no explicit standards for carbon dioxide

levels,wesettheupperlimitofcarbondioxideconcentrationtobe600ppm;ifthislimitis

exceeded,weconsidertheroomconditionstobeunsuitableaswell.

Astatusvariableisinitializedinthisprogramthatservesasasignalforactuation:

● Status=0→Goodconditions,noneedforfanorheater

● Status=1→Turnonfan

● Status=2→Turnonheater

In cases where room conditions are quickly oscillating around the edge of the comfort

envelope,wepreventaback-and-forthoscillationbetweenstatussignalsbycheckingtosee

thatthelast5pointsofthestatusareconsistentbeforemakingachangetothesignal.This

ensuresthattheactuatoronlyrespondstostableandclear-cutconditions.


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SendData.ino

SendData reads the signal produced by the cyber layer and carries out the proper

actuation. There is a 10 second delay implemented in between readings to prevent a

frequentturningonandoffofthefan-heatercombo.

dashboard.js

ThisJavaScriptfilemainlydefinesthefunctionsthatcanbeactivatedinthewebsite.Firstly,

ithas functionssuchas loadContentand loadPlot to loadhtmlstructure.Secondly, ithas

functionssuchloadDataandloadStreamplotthatcanaccessthewebserver,fetchthedata

anddisplaythedataintheformofgraphs.Temperature,humidity,andcarbondioxideare

the three variables displayed as separate graphs, and a comfort envelope based on the

ASHRAEstandardisalsobeingloadedinthewebsite.Thecomfortenvelopevisualizationis

drawnusingtheD3library.

nanodashboard.html

Nanodashboard file gives the layout to our website, and adds static elements to the

webpage. The dashboard is based on bootstrap Dashboard example. Bootstrap JS

framework,highchartslibraryandcustomJSareallincludedinthehtmlfile.Thewebpage

hasanavigation sidebarandamain content container.Thenavigation sidebarenablesa

usertolearndifferentsectionsofproject:briefintroduction,plottingorourteamprofiles.

DataAnalysis

TheASHRAE55-2013standard isused to createa “comfortenvelope” forevaluating the

environmental conditions in the personal workspace. Referencing the CBE Thermal

Comfort Tool, the graphwas approximated for our own data analysis, assuming amean

radianttemperatureof25oC(sincethisparametercannotbemeasuredusingouravailable

equipment).Thisgraphplotstherelationshipbetweentemperatureandhumiditysoboth


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parametersdetermine ifweare in thecomfortzone.When the temperature iseither too

lowortoohighforagivenhumidity,theheaterandthefanwillturnon,respectively.

However,sincethereisnoexistingstandardforcarbondioxideconcentrationindoors,we

used a recommendedmaximum indoor limit of 600ppm.Beyond this concentration,we

willoperate the fan to simulateventilationpurposes.Whenscalingup thisprototype,an

actualventilationsystemmaybeusedinstead.

The following screenshots (Figures 2-4) show what is displayed on our webpage. We

display and track the levels of temperature, humidity on the plots juxtaposed by the

comfort envelope. The red dot represents our current state in the room and in this

example,wearewithinthecomfortenvelopesonoactuationisneeded.However,ifthedot

wererightoftheenvelope,orifCO2concentrationisabove600ppm,thenthefanwillturn

on.Ifthedotwereleftoftheenvelope,theheaterwillturnon.

Figure2:Livestreamoftemperaturedata


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Figure3:Livestreamofhumiditydata

Figure4:Livestreamofcarbondioxidedata

WebVisualizationThe web page serves as the visualization tool for users to monitor the status of room

environmentanditsassociatedcomfortlevel,aswellasdisplayspastcollecteddata.Figure


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5showstheoveralllayoutofthewebpage.Alongthemenubar,thereareoptionstolookat

theprojectdetailsandbackground,orinformationonourstudentteam.Acrossthetopof

thepage,thereisanoptiontoselectwhichplotyouwanttoview.

Figure5:Screenshotofawebpagethatvisualizesdatacollected

Inthecasethatthecurrentconditionsareoutsidethecomfortenvelopelikeinfigure6,we

canseethatthereddotisrightoftheenvelope.Thereisalsoanalertabovetheplotsthat

tellstheuserthatthefan-heatercomboshouldbeinfanmode.

Figure6:Useralertwhenenvironmentconditionsareoutofcomfortenvelope


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FinalProduct

Our final product is shown in the figures below. The environmental sensors and the

Arduinocontrollerareplacedintoacustomizedcase(Figure7),whichhasholestoallow

air to pass through. The data collected by the SPER module is processed and used to

actuatethefan-heater(Figure8)viatogglingofapowerrelay.

Figure7:Customizedcasecontainingsensorsandcontroller

Figure8:Fan-heateractuatorwithcontroller


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IV. Discussion

The SPER project addresses the problem of indoor environmental quality and its

correlationtoworkingproductivityandenergyefficiency.Thiswasdoneusingagroupof

sensorsmeasuring temperature, humidity, and carbondioxide levels andprocessing this

datatofindiftheenvironmentalconditionscomplywiththesuggestedstandards.

Inthisproject,wetestedSPERinsmallworkingspacessuchasadeskoraroom,butithas

the opportunity to be scaled up and implemented in larger working spaces. This will

requiremultiple sensingnodes,actuatingdevices,andabiggerX-Beemeshnetwork,but

will provide increasedmonitoring capability and potential energy savings. Furthermore,

thefan-heatercomboinourprototypeservesasarepresentationofactuatingdevices,and

can also be scaled up to include more advanced devices, such as air-conditioning or a

ventilationsystem.Bycustomizingthesettingsforthedevices,ausercansaveenergyby

onlycontrollingtheactuatorwhenoccupantsareintheindoorspace,insteadoflettingthe

actuatorsrunconstantly.

Onemajorlimitationtoalarge-scaleimplementationofSPERisthehighcostofindividual

carbon dioxide sensors. As such, it is recommended that carbon dioxide sensing should

onlybeperformedinareashighlysusceptibletocongregationsofpeopleinconfinedspaces

forprolongedperiodsoftimes,suchasinclassrooms,lecturehalls,undergroundlabsand

conferencerooms.Forallotherareas,occupantcomfortcanbemaximizedthroughtheuse

ofhumidityandtemperaturesensorsalone.

V. Summary

The final product of the Smart Personal Environment Regulator (SPER) achieves

temperature, humidity and carbon dioxide sensing and generates a signal to fan-heater

combotoaltertheenvironmentalconditionsiftheyareuncomfortable.UsingtheASHRAE

55-2013 standard as a reference, we developed an algorithm to determine if current


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workingspaceconditionsareoutside the “comfortzone,”andweuse this information to

powerthefanorheater.

Our cyber-physical system is the first prototype and it encompassesmany of the initial

features of a indoor air quality monitoring system. With further research and

improvements,westronglybelievethatthisproductcanbecomeusefulinoccupantspaces

toincreaseproductivityandcomfort,buttolowerenergyconsumptionaswell.

References

Canadian Center for Occupational Health and Safety (2015). Thermal Comfort for Office

Work.Retrievedfrom: http://www.ccohs.ca/oshanswers/phys_agents/thermal_comfort.html

The Huffington Post (2012). Carbon Dioxide Levels In Meeting Rooms, Classrooms Could

AffectDecision-Making:Study.Retrievedfrom:

http://www.huffingtonpost.com/2012/10/25/carbon-dioxide-decision-making-meeting-

rooms-classrooms_n_2006289.html

ASHRAE(2015).ASHRAE55Standard.Retrievedfrom:

https://www.ashrae.org/resources--publications/bookstore/standard-55

HoytTyler,SchiavonStefano,PiccioliAlberto,MoonDustin,andSteinfeldKyle(2013).CBE

ThermalComfortTool.CenterfortheBuiltEnvironment,UniversityofCaliforniaBerkeley,

Retrievedfrom:

http://cbe.berkeley.edu/comforttool/

RoonakDaghigh,NorMariahAdam,BarkawiSahari,BashariaA.A.Yousef.ThermalComfort

StudyandVentilationEvaluationofanOffice.

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