a can to flexray migration framework

Waterford Institute of Technology

Ireland InstitiidTeicneolaochtaPhortLirge

ire

A CAN to FlexRay Migration

Framework Richard Murphy B.Sc. (Hons)

M.Sc. Thesis

(Supervisor)Frank Walsh B.A., B.A.I., M.Sc.

SubmittedtoWaterfordInstituteofTechnologyAwardsCouncil,September2009

Acknowledgments

i

Acknowledgments

Iwouldliketothanksincerelythefollowingpeople,forwithouttheirinputthisthesis

wouldnothavebeenpossible.

IwouldliketothankmysupervisorFrankWalshforhisideasandinputespeciallywhen

thingswerenotgoingtoplanhewasalwayswillingtogiveuphistimetodiscussany

issues.Iwouldalsoliketothankthegroupleader,BrendanJackmanforhisassistance

and inputanytime itwasaskedofhim.AbigthankyoumustgotoGareth,Roband

WeiDawhohelpedmeanytime Iaskedevenwhiletheywerebusyconductingtheir

ownresearch.

Iwould like to thankSumitomoYstrad.The financialbackingofSumitomohasmade

this thesis possible. I would like to especially thank Paul, Jim and Eamonn whose

hospitalityandassistancewassecondtononeduringmyvisitsthere.

FinallyIwouldliketothankmyparentsMiloandKittywhobackedmebothfinancially

andwithencouragement.WithoutthemIwouldnotbewhereIamnow.

Declaration

ii

Declaration

IRichardMurphy,declarethatthisthesisissubmittedbymeinpartialfulfilmentofthe

requirement for thedegreeM.Sc., isentirelymyownworkexceptwhereotherwise

accredited.Ithasnotatanyothertimewholeorinpartbeensubmittedforanyother

educationalaward.

Signature:

RichardMurphy

9thofOctober2009

Abstract

iii

Abstract

Oneofthefirstelectronicscomponentsusedinanautomobilewasthefuse.Additional

features were developed such as engine management systems. These additional

featuresincreasedtheamountofwiringinawiringharness.Thiscontributedtowards

thenecessitytodevelopthebusstructureinthe1980s.Thedefactobusstructurein

the automotive industry became CAN (Controller Area Network). By using a bus

structure this resulted in less hard wiring being required in the production of an

automobilewhich further lead to a reduction in production cost. CAN is an event

triggered protocol which denotes it is nondeterministic and it has a theoretical

bandwidthlimitof1Mbit\s.Thepracticallimitisnearer500kbit\s.Duringthe80sand

90s, automotive electronics development increased; this was primarily driven by

increaseddevelopmentofsafetyfeaturessuchasABS(AntilockBrakingSystem).The

increaseinthenumberoffeaturesandnodescausedincreasedtrafficonthebus.The

CANprotocolwillbeunabletomeettherequirementsfortheextraapplications.

This resulted in the development of FlexRay in 2000 by a consortium originally

consisting of amongst others BMW, Daimler Chrysler, Freescale and Philips. This

protocol can implement both timetriggered and eventtriggered messages,

determinism, fault tolerance, redundancy and can operate at 10Mbit\s. Newly

developedtechnologieshavehighinitialcoststhereforebeinginitiallymoreexpensive

thanestablished technologies.This could result in itbeing financiallyunworkable to

replace a complete automotive buswith FlexRay. FlexRay can possibly be used for

mission critical applications such as powertrain applications, while other protocols

suchasCANandLIN(LocalInterconnectNetwork)maypossiblybeusedforlesscritical

applications.

The aim of this research is to design and develop a framework that allows the

implementationofaCANapplicationontheFlexRayprotocol,withoutdegradingthe

applicationsperformance.

TableofContents

iv

Table of Contents

Acknowledgments.......................................................................................................i

Declaration.................................................................................................................ii

Abstract.....................................................................................................................iii

TableofContents......................................................................................................iv

TableofFigures..........................................................................................................x

TableofTables.........................................................................................................xv

TableofEquations..................................................................................................xvii

SectionIThesisOverview.........................................................................................1

1 ThesisOverview:.................................................................................................2

1.1 ProblemSpecification.....................................................................................2

1.2 SpecifiedSolution...........................................................................................3

1.3 ResearchQuestions........................................................................................4

1.4 DocumentLayout...........................................................................................5

SectionIILiteratureReview......................................................................................7

2 AutomotiveNetworksReview:...........................................................................8

2.1 Introduction....................................................................................................8

2.2 ComputerNetworks.......................................................................................8

2.3 NetworkFunction...........................................................................................9

2.4 NetworkTopologies......................................................................................10

2.5 LAN(LocalAreaNetwork)&WAN(WideAreaNetwork).............................13

2.6 CommunicationProtocol..............................................................................14

2.7 AutomotiveNetworksHistory......................................................................15

2.8 AutomotiveNetworksDescription................................................................16

TableofContents

v

2.9 ECU...............................................................................................................20

2.10 AutomotiveNetworkProtocols....................................................................22

2.11 Conclusion....................................................................................................25

2.12 References....................................................................................................27

3 CAN(ControllerAreaNetwork):........................................................................28

3.1 Introduction..................................................................................................28

3.2 CANPhysicalStructure.................................................................................29

3.3 CANFrameFormat.......................................................................................30

3.4 BusArbitration..............................................................................................34

3.5 CANErrorHandling.......................................................................................35

3.6 CANProtocolFeatures..................................................................................39

3.7 TTCAN(TimeTriggeredControllerAreaNetwork)Introduction...................40

3.8 Conclusion....................................................................................................43

3.9 References....................................................................................................44

4 FlexRay:............................................................................................................45

4.1 Introduction..................................................................................................45

4.2 FlexRayFeatures...........................................................................................46

4.3 FlexRayCycleStructure.................................................................................48

4.4 FlexRayNodeStructure................................................................................50

4.5 FlexRayFrameStructure...............................................................................52

4.6 FlexRayTimingHierarchy..............................................................................56

4.7 CommunicationCycle...................................................................................58

4.8 Conclusion....................................................................................................62

4.9 References....................................................................................................63

5 AutomotiveEmbeddedSystemsDesign:...........................................................64

5.1 AutomotiveEmbeddedSystemDesign.........................................................64

TableofContents

vi

5.2 DistributedArchitecturesIntroduction.......................................................64

5.3 RealTimeOperatingSystem(RTOS).............................................................66

5.4 OSEK/VDX.....................................................................................................67

5.5 ProcessModels.............................................................................................70

5.6 TaskSchedulingPolicies................................................................................70

5.7 TaskGraphs..................................................................................................74

5.8 CriticalPathAnalysis(CPA)...........................................................................74

5.9 TaskGraphAnalysis......................................................................................77

5.10 DesignProcess..............................................................................................87

5.11 Conclusion....................................................................................................90

5.12 References....................................................................................................91

6 AutomotiveNetworkMigration:.......................................................................93

6.1 AutomotiveNetworkMigration....................................................................93

6.2 Introduction..................................................................................................93

6.3 ProtocolMigrationRequirements................................................................93

6.4 SidebySideMigration(UsingaGateway)....................................................95

6.5 FullMigration..............................................................................................100

6.6 Conclusion..................................................................................................112

6.7 References..................................................................................................114

7 LiteratureReviewConclusion..........................................................................116

7.1 Conclusion..................................................................................................116

7.2 References..................................................................................................119

SectionIIIFrameworkDevelopment.....................................................................120

8 MigrationFrameworkRequirements:.............................................................121

8.1 Introduction................................................................................................121

8.2 MigrationRequirements.............................................................................121

TableofContents

vii

8.3 ApplicationDefinition.................................................................................122

8.4 CANParameterAbstraction........................................................................123

8.5 Migration....................................................................................................124

8.6 FlexRayFrameImplementation..................................................................124

8.7 FlexRayApplicationConfiguration..............................................................125

8.8 Conclusion..................................................................................................126

9 CANtoFlexRayMigrationMethodology:........................................................127

9.1 Introduction................................................................................................127

9.2 FrameworkDevelopment...........................................................................127

9.3 SystemImplementation..............................................................................129

9.4 Verification.................................................................................................130

9.5 ImplementationofAnalysisFindings..........................................................130

9.6 ApplyingFrameworktoaRealWorldApplication......................................131

9.7 GenericCANtoFlexRayDevelopment........................................................131

9.8 StaticSegmentDevelopment.....................................................................132

9.9 DynamicSegmentDevelopment.................................................................140

9.10 Conclusion..................................................................................................143

9.11 References..................................................................................................147

10 DevelopmentToolsandApplications:.............................................................148

10.1 Introduction................................................................................................148

10.2 Hardware....................................................................................................148

10.3 Software.....................................................................................................154

10.4 Conclusion..................................................................................................169

10.5 References..................................................................................................170

SectionIVTesting&Results.................................................................................171

11 SystemModel.................................................................................................172

TableofContents

viii

11.1 Introduction................................................................................................172

11.2 TractionControl&AdaptiveCruiseControlSummary................................172

11.3 ApplicationModels.....................................................................................173

11.4 Hardware....................................................................................................178

11.5 Software.....................................................................................................181

11.6 ExtractionMethod......................................................................................182

11.7 VerificationofParameterConsistency........................................................182

11.8 ValidationCheck.........................................................................................183

11.9 Conclusion..................................................................................................183

11.10 References................................................................................................184

12 FrameworkImplementationProcedure:.........................................................185

12.1 Introduction................................................................................................185

12.2 Abstract(TC)Implementation(TestCase1)...............................................185

12.3 DynamicSegmentVerification....................................................................197

12.4 FinalAbstractCaseParameters..................................................................201

12.5 ExperimentalImplementation(ACC)(TestCase2).....................................202

12.6 DynamicSegmentAnalysis.........................................................................209

12.7 FinalExperimentalCaseParameters...........................................................211

12.8 VerificationofTimeTriggeredProperties(TestCase3).............................213

12.9 FinalPracticalCaseParameters..................................................................219

12.10 Conclusion................................................................................................220

12.11 References................................................................................................222

13 TestResults&Verification:.............................................................................223

13.1 Introduction................................................................................................223

13.2 TestCase2:ACCConfiguration...................................................................224

13.3 CANResults.................................................................................................225

TableofContents

ix

13.4 FlexRayResults...........................................................................................245

13.5 DiscussionofResults...................................................................................272

13.6 TestCase3:VerificationofTimeTriggeredProperties...............................277

13.7 Conclusion..................................................................................................282

SectionVConclusion............................................................................................283

14 Conclusion:.....................................................................................................284

14.1 ResearchSummary.....................................................................................284

14.2 SummaryofTestingandResults.................................................................285

14.3 ResearchQuestions....................................................................................287

14.4 AreasforFutureResearch..........................................................................288

SectionVIAppendices...........................................................................................290

AppendixA..................................................................................................................I

14.5 PublishedMaterial...........................................................................................I

AppendixB.................................................................................................................II

14.6 Bibliography....................................................................................................II

AppendixC................................................................................................................V

14.7 Calculations.....................................................................................................V

TableofFigures

x

Table of Figures

FIGURE21:ASIMPLENETWORKEXAMPLE................................................................................................9

FIGURE22:BUSTOPOLOGY......................................................................................................................10

FIGURE23:STARTOPOLOGY....................................................................................................................11

FIGURE24:RINGTOPOLOGY....................................................................................................................12

FIGURE25:MESHTOPOLOGY...................................................................................................................12

FIGURE26:TCP/IPMODEL........................................................................................................................14

FIGURE28:COSTVSDATARATEOFDIFFERENTAUTOMOTIVEPROTOCOLS..........................................17

FIGURE29:BASICNETWORKCONFIGURATION........................................................................................18

FIGURE210:POINTTOPOINTNETWORK................................................................................................19

FIGURE211:ABASICNODECOMPRISINGOFASENSORANDECU..........................................................20

FIGURE212:MICROPROCESSORBLOCKDIAGRAM..................................................................................21

FIGURE213:TIMETRIGGEREDSLOTSONANETWORK............................................................................24

FIGURE31:CANSRELATIONTOTHEOSIMODEL.....................................................................................29

FIGURE32:TERMINATINGRESISTORS(TOSTOPREFLECTION)................................................................30

FIGURE33:CANSTANDARDFRAMEFORMAT..........................................................................................31

FIGURE34:CANEXTENDEDFORMAT.......................................................................................................31

FIGURE35:REMOTEFRAME.....................................................................................................................32

FIGURE36:ERRORFRAMEFORMAT.........................................................................................................33

FIGURE37:OVERLOADFRAMEFORMAT..................................................................................................33

FIGURE38:ARBITRATIONPROCESS..........................................................................................................35

FIGURE39:TTCANMATRIXCYCLE............................................................................................................41

FIGURE310:TTCANSAMPLEWINDOWTIME...........................................................................................42

FIGURE41:POSSIBLEFLEXRAYIMPLEMENTATION..................................................................................46

FIGURE42:STARANDBUSTOPOLOGYCOMBINATION............................................................................48

FIGURE:43:FLEXRAYCYCLESTRUCTURE..................................................................................................49

FIGURE44:NODEARCHITECTURE(CONSORTIUM,2005)........................................................................50

FIGURE45:NODECOMPONENTS.............................................................................................................51

FIGURE46:ROLETHECHIHASINTHEPEINTERACTINGWITHTHEHOSTPROCESSOR(CONSORTIUM,

2005).................................................................................................................................................52

FIGURE47:FRAMEFORMAT(CONSORTIUM,2005).................................................................................53

FIGURE48:PAYLOADSEGMENTCONTAININGTHENETWORKMANAGEMENT(NM)VECTOR&MESSAGE

ID.......................................................................................................................................................54

FIGURE49:FLEXRAYTIMINGHIERARCHY(CONSORTIUM,2005).............................................................57

TableofFigures

xi

FIGURE410:POSSIBLEFLEXRAYFRAMECYCLECONFIGURATION............................................................58

FIGURE51:BASICDISTRIBUTEDARCHITECTURE......................................................................................65

FIGURE52:GENERALNODEPROPERTIES.................................................................................................65

FIGURE53:OSEKMODELVSOSI7LAYERMODEL...................................................................................69

FIGURE54:BASICTASKGRAPH.................................................................................................................70

FIGURE55:SIMPLEACTIVITYCONFIGURATION........................................................................................75

FIGURE56:SAMPLEPROCESSMODEL......................................................................................................76

FIGURE:57:ALTERNATIVEACTIVITYTASKCONFIGURATIONS..................................................................76

FIGURE:58:SAMPLECOMPLEXCPAMODEL............................................................................................77

FIGURE:59:TASKCONTENTS....................................................................................................................77

FIGURE:510:TWOTASKS,T1&T2,CONNECTEDBYAMESSAGEM1......................................................78

FIGURE511:TASKT1SRELEASEANDDEADLINEPARAMETERS................................................................78

FIGURE512:TASKGRAPHEXAMPLE(HURLEY,1994)...............................................................................79

FIGURE513:GANTTCHARTFORTASKSINFIGURE512(HURLEY,1994).................................................79

FIGURE514:FOURPHASESOFATASKSEXECUTION................................................................................83

FIGURE61:PROTOCOLCOMMONFUNCTIONALITY.................................................................................94

FIGURE62:CONVERTERBETWEENTWODIFFERENTPROTOCOLS...........................................................94

FIGURE63:EXAMPLEGATEWAYUSAGE...................................................................................................95

FIGURE64:AUTOSARGATEWAYSTRUCTURE..........................................................................................97

FIGURE65:FLOWCHARTCONVERTINGFLEXRAYTOCAN(SUKHYUNSEOL,2006)................................99

FIGURE66:ALGORITHMFORGENERATINGANINDIVIDUAL(SHANDING,2005)..................................103

FIGURE67:NETWORKTOPOLOGYSYNTHESISALGORITHM(ALOUL,2005)...........................................106

FIGURE68:DESIGNHEURISTIC(TRAIANPOP,2002)..............................................................................107

FIGURE69:TTANDDYNSCHEDULABILITYALGORITHMS(TRAIANPOP,2006)......................................107

FIGURE610:OPTIMISEDBUSCONFIGURATIONALGORITHM(TRAIANPOP,2007)...............................108

FIGURE611:GLOBALSCHEDULINGALGORITHM(TRAIANPOP,2006)...................................................110

FIGURE81:FRAMEWORKDEVELOPMENTSTAGES.................................................................................122

FIGURE91:STFRAMEDATAGRAPHPROFILE.........................................................................................137

FIGURE92:ILLUSTRATIONOFPERIODICITYANDDISTANCECONSTRAINT.............................................139

FIGURE93:STSCHEDULINGALGORITHM...............................................................................................145

FIGURE94:DYNSCHEDULINGALGORITHM............................................................................................146

FIGURE95:FLEXRAYEXTRACTIONPARAMETERS...................................................................................146

FIGURE101:FUJITSUSK91F467DFLEXRAYSTARTERKIT......................................................................150

FIGURE102:FLEXRAYPHYSICALLAYERDRIVERMODULE......................................................................151

FIGURE103:VN3600FLEXRAYINTERFACE.............................................................................................152

FIGURE104:CANCARDXL........................................................................................................................153

FIGURE105:FLEXRAYPASSIVESTAR......................................................................................................153

FIGURE106:SOFTUNEWORKBENCHV6.................................................................................................154

TableofFigures

xii

FIGURE107:FMEFRFLASHPROGRAMMER...........................................................................................155

FIGURE108:DECOMSYS::DESIGNERPRO...............................................................................................156

FIGURE109:FLEXRAYNODEANDCLUSTERCONFIGURATION...............................................................157

FIGURE1010:CONSTRAINTVIOLATION..................................................................................................157

FIGURE1011:SAMPLEFRAMESCHEDULE..............................................................................................159

FIGURE1012:ECUCONFIGURATIONSCREEN.........................................................................................160

FIGURE1013:COMMSTACKFLEXRAYCONTROLLERSTATEMACHINE(EGGENBAUER,2006)...............161

FIGURE1014:FLEXRAYSAMPLEFLOWDIAGRAM..................................................................................167

FIGURE1015:FLEXRAYFRAMEPANEL....................................................................................................168

FIGURE1016:CAPLBROWSERPANEL.....................................................................................................168

FIGURE111:ABSTRACTIMPLEMENTATIONSTAGES..............................................................................173

FIGURE112:TRACTIONCONTROLTASKGRAPHMODEL........................................................................174

FIGURE113:ACCTASKGRAPHREPRESENTATION..................................................................................176

FIGURE114:ACCBLOCKDIAGRAMREPRESENTATION...........................................................................177

FIGURE115:TESTCASETHREETASKGRAPHCONFIGURATION............................................................178

FIGURE116:CANPHYSICALTESTCONFIGURATION...............................................................................180

FIGURE117:FLEXRAYPHYSICALTESTCONFIGURATION........................................................................181

FIGURE121:FIRSTFRAMEWORKDEVELOPMENTSTAGE.......................................................................186

FIGURE122:MIGRATIONSTEPTWO.....................................................................................................186

FIGURE123:FRAMEWORKDEVELOPMENTSTAGETHREE.....................................................................187

FIGURE124:PATHP4ONTHETRACTIONCONTROLMODEL.................................................................190

FIGURE125:FLOWCHARTDEVELOPMENTSTAGEFOUR........................................................................192

FIGURE126:STAGEFIVEDEVELOPMENT..............................................................................................193

FIGURE127:PAYLOADGRAPHPROFILE..................................................................................................195

FIGURE128:CONFIGUREDABSTRACTPARAMETERS.............................................................................201

FIGURE129:PAYLOADGRAPHPROFILE..................................................................................................207

FIGURE1210:CONFIGUREDABSTRACTPARAMETERS...........................................................................212

FIGURE1211:FRAMEWORKDEVELOPMENTSTAGESIX.........................................................................212

FIGURE1212:PATHTHROUGHTASKGRAPH..........................................................................................214

FIGURE1213:PAYLOADGRAPHPROFILE................................................................................................217

FIGURE1214:CONFIGUREDABSTRACTPARAMETERS...........................................................................220

FIGURE131:STANDARDTASKNODALASSIGNMENT.............................................................................224

FIGURE132:MINIMALTASKNODALASSIGNMENT................................................................................225

FIGURE133:STAGESEVENOFTHEFRAMEWORKDEVELOPMENT........................................................225

FIGURE134:NORMALBUSLOAD............................................................................................................227

FIGURE135:MESSAGETRANSMISSIONTIMESATNORMALLOAD........................................................228

FIGURE136:APPLICATIONCYCLETIMESATNORMALLOAD..................................................................229

FIGURE137:NUMBEROFFRAMESPERCYCLEATNORMALLOAD.........................................................230

TableofFigures

xiii

FIGURE138:60%BUSLOAD....................................................................................................................231

FIGURE139:MESSAGETRANSMISSIONTIMESAT60%LOAD................................................................232

FIGURE1310:APPLICATIONCYCLETIMESAT60%LOAD.......................................................................232

FIGURE1311:NUMBEROFFRAMESPERCYCLEAT60%LOAD...............................................................233

FIGURE1312:MAXIMUMBUSLOAD.......................................................................................................234

FIGURE1313:MESSAGETRANSMISSIONTIMESATMAXIMUMLOAD...................................................235

FIGURE1314:APPLICATIONCYCLETIMESATMAXIMUMLOAD............................................................236

FIGURE1315:NUMBEROFFRAMESPERCYCLEATMAXIMUMLOAD...................................................237

FIGURE1316:MESSAGETRANSMISSIONTIMESATNORMALLOAD......................................................238

FIGURE1317:APPLICATIONCYCLETIMESATNORMALLOAD................................................................239

FIGURE1318:NUMBEROFFRAMESPERCYCLEATNORMALLOAD.......................................................239

FIGURE1319:MESSAGETRANSMISSIONTIMESAT60%LOAD..............................................................240

FIGURE1320:APPLICATIONCYCLETIMESAT60%LOAD.......................................................................241

FIGURE1321:NUMBEROFFRAMESPERCYCLEAT60%LOAD...............................................................242

FIGURE1322:MESSAGETRANSMISSIONTIMESATMAXIMUMLOAD...................................................243

FIGURE1323:APPLICATIONCYCLETIMESATMAXIMUMLOAD............................................................244

FIGURE1324:NUMBEROFFRAMESPERCYCLEATMAXIMUMLOAD...................................................245

FIGURE1325:NOREDUNDANCYNORMALBUSLOADCHA....................................................................247

FIGURE1326:NOREDUNDANCYNORMALBUSLOADCHB....................................................................248

FIGURE1327:MESSAGETRANSMISSIONTIMESNORMALLOAD...........................................................249

FIGURE1328:APPLICATIONCYCLETIMESNORMALLOAD.....................................................................250

FIGURE1329:NUMBEROFSTFRAMESPERCYCLE(NOREDUNDANCY)................................................251

FIGURE1330:NUMBEROFDYNFRAMESPERCYCLENORMALLOAD....................................................251

FIGURE1331:MESSAGETRANSMISSIONTIMESHIGHDATARATE........................................................253

FIGURE1332:APPLICATIONCYCLETIMESHIGHDATARATE..................................................................254

FIGURE1333:NUMBEROFDYNFRAMESPERCYCLEHIGHDATARATE.................................................254



FIGURE1336:NUMBEROFDYNFRAMESPERCYCLEATNORMALLOAD...............................................257






FIGURE1342:NUMBEROFDYNFRAMESPERCYCLEATNORMALLOAD...............................................263



FIGURE1345:NUMBEROFSTFRAMESPERCYCLEHIGHDATARATE....................................................266

TableofFigures

xiv


FIGURE1347:MESSAGETRANSMISSIONTIMESATNORMALLOADS....................................................268

FIGURE1348:APPLICATIONCYCLETIMESATNORMALLOADS..............................................................268

FIGURE1349:NUMBEROFDYNFRAMESPERCYCLEATNORMALLOADS.............................................269




FIGURE1353:MESSAGETRANSMITTIMES(MINIMALCONFIGURATION).............................................275

FIGURE1354:MESSAGETRANSMITTIMES(NORMALCONFIGURATION)..............................................275

FIGURE1355:CANCONFIGURATIONTESTTHREE..................................................................................279

FIGURE1356:GRAPHOFCANAPPLICATIONEXECUTIONTIMES............................................................280

FIGURE1357:FLEXRAYCONFIGURATIONTESTTHREE...........................................................................281

TableofTables

xv

Table of Tables

TABLE31:CANERRORSTATES..................................................................................................................38

TABLE61:EXAMPLECANNETWORK.......................................................................................................111

TABLE101:OFFSTATE............................................................................................................................162

TABLE102:STARTUPSTATE...................................................................................................................163

TABLE103:ONSTATE.............................................................................................................................164

TABLE104:ONLINESTATE......................................................................................................................164

TABLE105:CONFIGURATIONSTATE.......................................................................................................165

TABLE106:RESETSTATE.........................................................................................................................165

TABLE107:WAKEUPSTATE....................................................................................................................165

TABLE108:ANALYSISFUNCTIONBLOCKOVERVIEW..............................................................................166

TABLE111:TRACTIONCONTROLTASKFUNCTIONS...............................................................................174

TABLE112:ADAPTIVECRUISECONTROLTASKFUNCTIONS...................................................................175

TABLE121:PARAMETERCM&JMIDENTIFICATION.................................................................................188

TABLE122:WMFIVEITERATIONSOFTHEQUEUINGDELAY...................................................................189

TABLE123:WORSTCASERESPONSETIME.............................................................................................189

TABLE124:OBTAININGSLACK................................................................................................................190

TABLE125:TASKGRAPHPARAMETERS..................................................................................................191

TABLE126:FINALTASKGRAPHPARAMETERS........................................................................................191

TABLE127:MESSAGEDEADLINES...........................................................................................................192

TABLE128:PAYLOADCALCULATIONS.....................................................................................................194

TABLE129:INITIALDYNAMICDATA.......................................................................................................197

TABLE1210:DYNAMICCOMMUNICATIONTIME...................................................................................198

TABLE1211:MPARAMETERS................................................................................................................199

TABLE1212:WM(T)PARAMETER............................................................................................................200

TABLE1213:DYNAMICRESPONSETIMES...............................................................................................200

TABLE1214:CANINITIALPARAMETERS.................................................................................................203

TABLE1215:OBTAININGSLACKPARAMETER.........................................................................................203

TABLE1216:TASKGRAPHPARAMETERS................................................................................................204

TABLE1217:FINALTASKGRAPHPARAMETERS......................................................................................204

TABLE1218:MESSAGEDEADLINES.........................................................................................................205

TABLE1219:PAYLOADCALCULATIONS...................................................................................................206

TABLE1220:APERIODICCANDATA........................................................................................................210

TABLE1221:MPARAMETERS................................................................................................................210

TABLE1222:WM(T)PARAMETER............................................................................................................211

TableofTables

xvi

TABLE1223:DYNAMICRESPONSETIMES...............................................................................................211

TABLE1224:CANINITIALPARAMETERSTESTCASETHREE....................................................................213

TABLE1225:OBTAININGSLACKPARAMETER.........................................................................................214

TABLE1226:TASKGRAPHPARAMETERS................................................................................................215

TABLE1227:FINALTASKGRAPHPARAMETERS......................................................................................215

TABLE1228:MESSAGEDEADLINES.........................................................................................................216

TABLE1229:PAYLOADCALCULATIONS...................................................................................................216

TABLE131:NORMALBUSLOAD..............................................................................................................227

TABLE132:MESSAGEDEADLINES...........................................................................................................228

TABLE133:60%BUSLOAD......................................................................................................................230

TABLE134:MAXIMUMBUSLOAD...........................................................................................................234

TABLE135:MESSAGEDELAYS.................................................................................................................235

TABLE136:NORMALBUSLOAD..............................................................................................................237

TABLE137:60%BUSLOAD......................................................................................................................240

TABLE138:MAXIMUMBUSLOAD...........................................................................................................242

TABLE139:MESSAGEDELAYS.................................................................................................................244

TABLE1310:STANDARDBUSLOAD.........................................................................................................247

TABLE1311:REVISEDFLEXRAYMESSAGEDEADLINES...........................................................................248

TABLE1312:HIGHDATARATEBUSLOAD...............................................................................................252

TABLE1313:NORMALBUSLOAD............................................................................................................255






TABLE1319:NUMBEROFCANFRAMESPERSECOND............................................................................273

TABLE1320:NUMBEROFFLEXRAYFRAMESPERSECOND.....................................................................273

TABLE1321:ACCCANAPPLICATIONCYCLESTANDARDDEVIATION......................................................276

TABLE1322:ACCFLEXRAYAPPLICATIONCYCLESTANDARDDEVIATION...............................................277

TABLE1323:APPLICATIONIDS................................................................................................................278

TABLE1324:APPLICATIONEXECUTIONTIMES.......................................................................................279

TableofEquations

xvii

Table of Equations

EQUATION51:UTILISATIONBOUND........................................................................................................72

EQUATION52:WCET................................................................................................................................80

EQUATION53:MESSAGEDELAY...............................................................................................................80

EQUATION54:RECURRENCERESPONSETIME.........................................................................................81

EQUATION55:RESPONSETIME................................................................................................................83

EQUATION56:RESPONSETIME(INCLUDINGJITTER)...............................................................................83

EQUATION57:COMMUNICATIONTIME...................................................................................................83

EQUATION58:BLOCKINGDELAY..............................................................................................................84

EQUATION59:QUEUINGDELAY...............................................................................................................84

EQUATION510:REOCCURRENCEQUEUINGDELAY..................................................................................84

EQUATION511:CONVERGENCE...............................................................................................................84

EQUATION512:RESPONSETIME..............................................................................................................84

EQUATION513:RECURRENCERESPONSE................................................................................................85

EQUATION514:UPDATEDRESPONSETIME.............................................................................................85

EQUATION515:WORSECASEDELAY........................................................................................................85

EQUATION516:UPDATEDWCRT..............................................................................................................85

EQUATION517:UPDATEDDELAY.............................................................................................................86

EQUATION518:TRANSMISSIONTIME......................................................................................................86

EQUATION519:SIMPLIFIEDTRANSMISSIONTIME...................................................................................86

EQUATION61:USEDMESSAGESIZEOFNODEI.....................................................................................103

EQUATION62:MAXIMUMMESSAGESIZEOFNODEI............................................................................103

EQUATION63:DATAELEMENTOPTIMUMPERIOD................................................................................104

EQUATION64:OVERALLFITNESS...........................................................................................................104

EQUATION65:SLOTDURATION.............................................................................................................105

EQUATION66:SLOTREUSE....................................................................................................................106

EQUATION67:MNEWTRANSMISSIONSLOTPORTIONWITHINPERIOD(MNEW).......................................106

EQUATION68:DYNWORSECASERESPONSETIME................................................................................109

EQUATION69:WORSECASEDELAYM..................................................................................................110

EQUATION610:COMMUNICATIONTIME...............................................................................................110

EQUATION91:CANMESSAGESET..........................................................................................................132

EQUATION92:MESSAGECOMPONENTS................................................................................................132

EQUATION93:TASKGRAPHEXECUTIONTIME.......................................................................................132

EQUATION94:INTERMEDIATETASKSCHEDULING................................................................................133

EQUATION95:TOTALAVAILABLESLACK................................................................................................133

TableofEquations

xviii

EQUATION96:SLACKPERTASK..............................................................................................................133

EQUATION97:PARAMETERVALIDATIONCHECK...................................................................................134

EQUATION98:TRANSMISSIONDEADLINE..............................................................................................134

EQUATION99:TRANSMISSIONDELAY....................................................................................................134

EQUATION910:FLEXRAYFRAMESIZE....................................................................................................135

EQUATION911:FRAMESPERAPPLICATIONCYCLE(STDATA)...............................................................135

EQUATION912:TOTALREQUIREDBYTES...............................................................................................136

EQUATION913:SLOTDURATION...........................................................................................................138

EQUATION914:DISCRETISEDSLOTDELAY.............................................................................................138

EQUATION915:PERIODICITYANDDISTANCECONSTRAINTVALIDATION..............................................140

EQUATION916:TOTALDYNCOMMUNICATIONTIME...........................................................................141

EQUATION917:MINIMUMNUMBEROFREQUIREDDYNSLOTS...........................................................141

EQUATION918:SLOTQUANTITYVERIFICATION....................................................................................141

EQUATION919:DYNAMICWORSTCASERESPONSETIME.....................................................................142

EQUATION920:COMMUNICATIONTIME...............................................................................................142

EQUATION921:MDELAY......................................................................................................................142

EQUATION922:NUMBEROFUNUSEDMINISLOTS................................................................................143

EQUATION923:WM(T)DELAY.................................................................................................................143

EQUATION121:TASKRESPONSETIME...................................................................................................187

EQUATION122:MESSAGETRANSMISSION/COMMUNICATIONTIME...................................................187

EQUATION123:REVISEDTOTALFLEXRAYDATA....................................................................................194

EQUATION124:RESPONSETIMEANALYSISEQUATION.........................................................................198

EQUATION125:TOTALDYNCOMMUNICATIONTIME...........................................................................198

EQUATION126:MDELAY......................................................................................................................199

EQUATION127:WMDELAY.....................................................................................................................199

EQUATION128:RESPONSETIMEANALYSISEQUATION.........................................................................209

EQUATION129:MDELAY......................................................................................................................210

EQUATION1210:WMDELAY...................................................................................................................210

SectionIThesis

Overview

ThesisOverview

2

1 Thesis Overview:

1.1 ProblemSpecification

The aimof this research is todevelop a framework tomigrate an application from

CAN,aneventdrivennetworkprotocol,usedprincipallyinautomotiveapplicationsto

FlexRay,a timetriggeredprotocol.Within theautomotive industry thepredominant

networkhasbeenCAN(ControllerAreaNetwork)andthisisdiscussedingreaterdetail

in Chapter 3. In the past eight to ten years it has been realised by automobile

manufacturers that the CAN protocol will not be sufficient for future application

requirements (Thomas Noltey, 2005). This is the main reason behind FlexRays

development. The FlexRay protocol is not intended necessarily to replace CAN.

Throughbeingabletooperateasingleprotocolforanapplicationthiscanreducethe

complexityassociatedwithoperatingmultipleprotocolsviagateway/s.Consideration

ofvariousaspectsofeachprotocolaretobetakeintoaccountsuchascost,knowledge

of all protocols and the time required to implement these protocols are some

examplesofsomeofthepossibleissuesencountered.

Asconsumersexpecthigher luxury levels inautomobiles, this increases the loadson

thecurrentnetworkprotocols(Schedl,2007).This,combinedwiththeeverincreasing

amountofsafetyapplicationsbeingdeveloped,hasresultedinpredictionsbyDrAnton

SchedlattheVectorFlexRaySymposium2007amongstothers, thatcurrentnetwork

protocolswillnotbeabletocopewiththisdemandinthenearfuture(Schedl,2007).

In 2000 the FlexRay consortiumwas founded by automobilemanufacturers BMW,

Daimler Chrysler and semiconductor manufacturers Motorola semiconductors

products sector (now Freescale semiconductors) and Philips semiconductors.Other

leading companies in the automotive industry soon joined. It is anticipated that

ThesisOverview

3

FlexRaywill replaceCAN (as thedefactoautomobilenetwork) forcriticalandsafety

applications.

WhileFlexRayisanticipatedasthesolutiontosafetycriticalhighspeedapplications,it

is also anticipated that CAN technology will continue to be used in less critical

applications. Amigration from the CAN network to the FlexRay networkwould be

requiredwhereCANhasreachedmaximumcapacityornewfeaturesareaddedtoan

application that requires someof the featuresprovided foron theFlexRaynetwork.

This research aims to provide a framework that will allow applications that have

previously operated on the CAN network, to successfully operate on the FlexRay

network.

1.2 SpecifiedSolution

One solution is to develop a framework tomigrate from the CAN network to the

FlexRaynetwork.Toachieveasuccessfulmigrationaminimumrequirementisthatthe

minimumtimingparametersintheCANnetworkareatleastachievedorexceededin

the FlexRay network. This requires a detailed understanding of both network

technologies,butspecificallytheFlexRaynetworkasitismorecomplex.

ThesisOverview

4

1.3 ResearchQuestions

Question1:

Whatarethebenefitsofusingthemigrationframeworkversustheuseofagateway?

Question2:

Whatmigration techniques used in other or similar protocols are applicable in this

research?

Question3:

Whatparametersarerequiredinrelationtotheapplicationandnetworkprotocol,for

migrationtobeundertaken?

ThesisOverview

5

1.4 DocumentLayout

Thethesisisarrangedasfollows;

SectionI:ThesisOverviewThis section, Thesis Overview presents the problem specification and the

researchquestions.

SectionII:LiteratureReviewThe Literature Review section discusses the background of automotive

networks before presenting the CAN and FlexRay protocols in depth. An

embedded systemoverview isdiscussedbefore the section concludeswitha

reviewofmigrationprocedurescarriedoutbyotherauthors.

SectionIII:FrameworkDevelopmentThis section, Framework Development, presents the requirements and

methodologyforundertakingthismigrationprocedure.

SectionIV:Testing&ResultsSection IV, Testing & Results, presents the system model and the actual

migrationframework.Thesectionproceedswiththeabstractandexperimental

implementationsof thegenericmodeland theACC (AdaptiveCruiseControl)

referencemodelandtheVerificationofTimeTriggeredproperties.Thesection

concludeswithapresentationoffindingsandadiscussionofresults.

SectionV:ConclusionSectionV contains the conclusion, and anypotential futurework thatwould

improvethisresearch.

SectionVI:AppendicesSectionVIconcludesthethesiswiththeappendices.

ThesisOverview

6

1.4.1 References

THOMASNOLTEY,H.H.,LUCIALOBELLO(2005)AutomotiveCommunicationsPast,CurrentandFuture

SchedlDA,2007,GoalsandArchitectureforFlexRayatBMW,1stVectorFlexRaySymposium,Stuttgart,Germany.

SectionIILiterature

Review

AutomotiveNetworksReview

8

2 Automotive Networks Review:

2.1 Introduction

This chapter contains a general assessment of what a computer network is, and

reviewscommonnetworktopologies.TheTCP/IPandOSIreferencemodel layersare

presenteddue to their use in the transportationofdatapackets. This leadsonto a

historyofautomotivenetworksdiscussingvariousclassesofautomotiveprotocols.The

ElectronicControlUnit(ECU)ispresentedduetoitscoreuseinthedevelopmentand

implementationofnetworks intheautomotive industry.Finallyautomotiveprotocols

arediscussedateventtriggeredand timetriggered levelandadirect comparison is

madebetweenthenaturesofbothprotocols.

2.2 ComputerNetworks

A network is a series of points or nodes interconnected by communication paths

(Harbeck,2006)

TheInternetisthemostcommondatanetworkthatpeoplecomeintocontactwithon

adailybasis.TheInternetevolvedfromasmallacademicresearchprojectinvolvinga

few dozen sites to become a vast worldwide system of interconnected networks

providing various functions and services. The first computer networks were

timesharing networks that usedmainframes and attached terminals (Teare, 1999).

Timesharingistheconceptofmultipleusersgettingaccesstotheprocessorduringthe

processorsidletime.

By networking remote locations to these powerful computers (timesharing) the

required tasks could be completedmore economically. Currently an entire industry

providesnetworkingtechnologiesandservices.


9

2.3 NetworkFunction

AnetworkconsistsoftwoormoredevicesinterconnectedasillustratedinFigure21.

One of the earliest network typeswas built to allow several computers to share a

singleprinter.

A networks function is the transportation of data (e.g. data from a computer to a

printer).Networkingcanbecomplexbecausetherearesomanydifferenttechnologies

availablethatcanbeusedtoconnecttwoormorenetworkstogether(Comer,2001).

Asdatanetworksweredevelopingduring the 1970s and the 1980s the automotive

industry was also starting to realise the advantages of implementing networks in

automobiles. Originally, automobiles had relatively small quantities of electric and

electroniccomponents,usuallyintheformofclosedloopcircuits.Forexample,oneof

theearliestapplicationswas the controlandoperationof lights.Additional features

suchaswindscreenwipersandenginemanagementsystemsincreasedthecomplexity

andvolumeofwiring in thewiringharness.This led to thedevelopmentof thebus

structureinthe1980s.Thedefactobusstructureintheautomotiveindustrybecame

theControllerAreaNetwork(CAN).Thestructuresofconventionaldatanetworksand

automotivenetworkshavesomesimilarities. In the followingsection the featuresof

both network types are discussed at network level in relation to the following;

topology,architectureandprotocols.

Figure 2-1: A Simple Network Example


10

2.4 NetworkTopologies

ThetermTopologyreferstothelayoutoftheinterconnectingdevicesonanetwork.

Thereare two typesof topologies; thephysical topologywhichdescribes thecable,

node,andconnectorarrangements,andthere isthe logicaltopologywhichdescribes

thearrangementofdevicesonanetwork (Steinke,2000).The followingdescription

dealswithphysicaltopologies.

ThemainphysicaltopologiesareBus,StarandRing.Thenamesaregiveninrelationto

the general shape of each network. The type of topology used depends on the

configurationrequirementsofthesystem.

2.4.1 BusTopology

TheBusTopology(showninFigure22)canconsistofacommonmedium,suchasco

axialcable (10base2 (thinnet)or10base5 (thicknet))orun/shielded twistedpair

(Institute,2002).

All the other nodes on the network can be directly connected off this. Because all

nodes share a commonbus they can also share communication.Thebeginning and

endofthebusareterminatedtopreventsignalreflectingbackdownthecable.Ifthe

centralbus fails (e.g. thecable iscut)nodesateithersideof thebreakcancease to

functioncorrectly,iftheyarerequiredtocommunicatewitheachother.UsingtheCAN

protocol information travelsalong thecentralbusandwhichevernode requests the

Figure 2-2: Bus topology


11

informationmatchesthemessageIDandthenitcanextracttheinformationfromthe

bus. Ifthemessage IDdoesnotmatchthenode IDthenodedoesnotgainaccessto

thatmessage.Ifasinglenodeisremovedfromthenetworkitdoesnotaffecttherest

ofthesystem.

2.4.2 StarTopology

The Star Topology is basedon theprinciple of a centralisedhost throughwhich all

other nodes communicate (Figure 23). If one node wants to communicate with

anothernode it is required tosend thedata through thecentralprocessorand then

distribute it to the desired node. If the central processor node fails, subsequently

communicationishalted.

2.4.3 RingTopology

The Ring Topology or RingNetwork consists of each node being connected totwo

othernodestoformaringasillustratedinFigure24.Ifonenodesendsdatatoanode

that isnotdirectly connected, thedatahas togo throughall theothernodes in its

path.Thedatacantraveltwopaths(leftorright)togettoitsdestinationnode.

Figure 2-3: Star Topology


12

2.4.4 MeshTopology

InafullyconnectedMeshTopology(asillustratedinFigure25)everynodeisdirectly

connected toallothernodeson thenetwork.Thismakes itpossible forallnodes to

senddataat thesame time.Thisalsoallows for redundancy tobe incorporated into

any systemusingamesh topology configuration.Amessage can takeanalternative

routeifonerouteiscorruptedorblocked.Duetotheamountofwiringrequiredthisis

consideredacostlyapproach.

Figure 2-4: Ring Topology

Figure 2-5: Mesh Topology


13

2.4.5 HybridTopology

ThesethreetopologytypescanbecombinedtomakeHybridTopologiessuchasaTree

Topology where there is a central bus and there is a ring and/or star topologies

branchingoff.

2.5 LAN(LocalAreaNetwork)&WAN(WideAreaNetwork)

Networkscangenerallybecategorised inoneoftwofundamentalgroups;LAN(Local

AreaNetwork)andWAN(WideAreaNetwork).Theseincorporatesomefeaturesfrom

theOSI(OpenSystemsInterconnect)modelwhichisdiscussedindetailinsection2.9.

2.5.1 LAN

LANs connect as few as two devices together or asmany as a few thousand. The

interconnectionbetweenthedevicescanbeviacableorwirelessmeans.LANsusually

connectdevicesthatareinrelativecloseproximitytoeachothersuchasaworkstation

andaprinterinthesamebuilding.InaLAN,aservercancontaindataapplicationsand

servicesthatotherdevicesareallowedaccess.Ethernetisatechnologythatiswidely

associatedwith LANs. Ethernet LAN primarily dealswith the physical and datalink

layers (Teare, 1999). TheMAC layer on a LAN uses amethod called Carrier Senses

Multiple Access/Collision Detection (CSMA/CD) for dealing with contention on the

network. A device using CSMA/CD, listens on the networkwhen it has data to be

transmittedand,ifnootherdeviceisusingthenetworkittransmits.Aftertransmission

it listenstosee ifacollisionhasoccurred. Ifacollisionhasoccurredeachmessage is

retransmittedafterarandom lengthoftime. Ifanumberofotherdevicesareusing

the network, performance degrades due to the increased number of collisions.

Introducing switches on a network subdivides the network into smaller collision

domainsresultinginlesscontentionandimprovedperformance.


14

2.5.2 WAN

WANsareusedtoconnectmultipleLANsoveralargerarea.AWANusesdedicatedor

switched connections to link computers in geographically remote locations that are

toowidely dispersed to be directly linked to the LAN (Parnell, 1997). They can be

connected via public telecommunications system or private communications. The

Internetisanexampleofapubliccommunicationssystem.

2.6 CommunicationProtocol

Acommunicationprotocolisasetofrulesorstandardsthatenablescommunications

ordata transferbetween twoendpoints (SearchNetworking.com,2007).Aprotocol

enables communication between a host and a remote host as long as the

communication takes place on the same level. If the rules are not kept then

communicationcannotoccur.TheTCP/IP referencemodel is illustrated in figure26

butisnotpresentedindetailasitisnotcoveredinthescopeofthisresearch.

Figure 2-6: TCP/IP Model


15

2.7 AutomotiveNetworksHistory

Asdatanetworksbeganevolving,theautomotiveindustrywasbeginningtoaddmore

electronic components and features to automobiles, such as air conditioning and

electricwindows.Whiledatanetworksweredevelopedto improvequalityofservice

and increase data transfer rates, the automotive industries initialmotivationwould

havebeenfundamentallyfinancial.Thishaschangedinrecentyearsasthenumberof

safety critical applications increases and consumers demand more comfort

applicationssuchasclimatecontrol.Theintroductionofanetworkedbusstructurein

automobileshasleadtoareductioninthesizeofwiringharnesses.Reducingthesize

ofawiringharnessalsoyieldedareductionintheweightoftheautomobileandinturn

thiswouldimprovefuelefficiency.

While initially introducing networks in cars reducedweight, this also lead to other

safety/nonsafety applications being developed, this increased weight and power

consumption.Theavailabilityofintegratedcircuitsinthe1960sandthe1970sallowed

furtherdevelopmentofautomotiveelectronicsandthedevelopmentoftheelectronic

controlunit(ECU).TheuseoftheECUallowedenginemanagementparameterstobe

varieddependingonexternalconditions likeengine loadandairtemperature.Atthe

time, the main factor pushing automotive electronics development was exhaust

emissions regulations.Mechanicalmethods alone could not provide themeans to

meet these new requirements while maintaining performance and efficiency

(Fischerkeller, 2007). It was then realised that the microcomputer adapted for

automotive use could address the requirements for emission controls while

maintainingperformanceforthedrivingenthusiast.Themicrocomputercouldhandle

data from the spark timingwith variations in the load speed, inputs from sensors

providing data on crankshaft position, coolant temperature etc (Jurgen, 1999).

Increaseddevelopmentof integratedcircuitsallowedcarmanufacturers toeliminate

passivecomponents.Thenwiththedevelopmentofmicroprocessor,electronicengine


16

controls, antilock braking systems and trip computer revolutionised automobile

electronics(Buchholz,2006).

Originally, as automobile manufactures started to develop more electronic based

applications for cars, there was no link between the electronics industry and the

automotive industry. The automotive industry wanted the technology to be as

economical aspossible,butwithin theelectronics industry allnew technologies are

initiallyexpensive (due to research anddevelopment costs) and thenbecomemore

cost effective due to improvements in productionmethods, product life cycles and

widespreadadaption.

It is no coincidence that during the 1980s the seminal breakthrough in automotive

network development was facilitated by the production of more powerful ICs

(IntegratedCircuits).TheCANprotocolwasalsodevelopedduringthisperiodandby

theearly1990shadbecomethedefactostandard intheautomotive industry.There

havebeenothervariantsof thisprotocolsuchasTTCAN,CANOpen,DeviceNet,CAN

Kingdom and J1939. Proprietary variants such as J1850 PWM, J1850 VPM and ISO

91412weredevelopedindividuallybymanufacturersbutthesearenotincludedinthe

scopeofthisresearch.Therearealsothreeotherprimaryautomotiveprotocols.Local

InterconnectNetwork (LIN)wasdevelopedasa lowcost, lower speedalternative to

CAN for use primarily in noncritical body control unit (BCU) functions. TheMedia

Oriented System Transport (MOST) protocol was developed with high bandwidth

infotainmentsystemsspecificallyinmind.TheFlexRayprotocolwasdevelopedforuse

insafetycriticalapplications.

2.8 AutomotiveNetworksDescription

Automotive networks can be classified by their protocols. There are four main

protocolsCAN,LIN,FlexRayandMOST.Eachprotocolisselectedforitsabilitytomeet

thesystemrequirementswhilekeepingthe implementationandbuildcostsas lowas

possible.TherelativecostperdatarateisillustratedinFigure28.


17

Ageneralruleofthumbisthatthefastestnetworkstendtobethemostexpensiveas

is illustratedbyFigure28. LINoperatesat speedswithamaximumdata rateof20

Kbit/sandistypicallyusedinapplicationsthatrequirethedrivertoinitiateoperation.

In critical applications that occur rapidly or do not require the driver to initiate

operationthefasternetworkssuchasCANandFlexRaywithspeedsofupto10Mbit/s

(1Mbit/sforCAN)areusedeventhoughtheyaremoreexpensiveto implementthan

LIN. In 1994 the SocietyofAutomotive Engineers (SAE) defined the classificationof

fourclassesofnetworks;ClassA,ClassB,ClassCandD.

ClassA:Datarates10kbits/orlower ClassB:Dataratesfrom10to125kbits/s ClassC:Dataratesfrom125kbits/sto1Mbit/s ClassD:Dataratesover1Mbit/s

ClassA isused inthebodyelectronicsofthecarandanexampleisLINasmentioned

above.ClassB isused to share informationbetweenECUs to reduce thenumberof

sensors required.A low speedCANnetworkwould fall into this category.A classC

network would be utilised by a realtime highspeed communications system i.e.

Figure 2-7: Cost Vs Data Rate of Different Automotive Protocols


18

powertrain or chassis applications using high speed CAN. And finally the class D

network isusedbyMOSTandFlexRay inapplications that requirepredictabilityand

faulttolerance(NICOLASNAVET,2005).

While the protocol parameters change from protocol to protocol a basic network

structurecanbesummarised inFigure29.CAN (ControllerAreaNetwork) is thede

factonetwork standard in theautomotive industry.CANoperatesonapeertopeer

basisi.e.nomasterorslave,amessageistransmittedandthenodethatrequiresthe

datagainsaccesstothedataandprocessesit.

InFigure210we seean illustrationofanetworkconfigurationwhereeachnode is

directly connected to every other node on the network (pointtopoint). Figure 25

(meshtopology)isalsoanexampleofthisasispreviouslyexplained.Forasimplefour

nodesystem there isnotmuchsystemcomplexity,butmodernhigh tomediumend

automobiles have over 70 interconnected ECUs therefore dramatically increasing

system complexity (A. Albert1, 2005). Networking eliminates redundant wiring

becauseasensoronlyhastobewiredtothenearestcontrollerandthecontrollerwill

transmittheinformationoverthenetwork(JaredBusen,2006).

Figure 2-8: Basic Network Configuration


19

Networking improvesmany aspectswithin the automotive industry such as design

flexibility,diagnosticsandreducedwiring/weigh/cost (PhilipKoopman,1998).Design

flexibilityisimprovedbecausedesignersjusthavetodesignasfarasthecontrollerand

thenetworktakestheinformationtotherequiredcontrollerinadifferentpartofthe

automobile.Havingonecentralaccesspointonthenetworkandconnectingthis into

thediagnosticstoolenableserrormessagesonthebustobereadandanalysed.This

enables problems to be located quicker than having to test each functional area

individually.

Networkingallowstheprovisionforscalabilitywithinasystem.Thisallowsasystemto

growasmoreapplicationsareadded.Asystemcanonlygrow if in the initialdesign

stageprovisionismadeforpossibleexpansionorincreaseddatathroughputatalater

stage.

2.8.1 GenericNodeComposition

Examining the componentsof a typical automotivenetworknode reveals a general

outlinesimilartothatinFigure211.HereasensorprovidesinputdatatoanElectronic

ControlUnit (ECU).Thesensorsdata isprocessed in theECUand transmittedacross

Figure 2-9: Point-to-Point Network


20

thenetworksothatanyrequiredactionswillbetakenifnecessary.Foroutputdatawe

couldhaveanactuatorinplaceofthesensor.

BeforetheintroductionofECUsintoenginemanagementsystemstheamountoffuel

inacylinder,quantityofairmixedinandtheignitiontimeofthesparkplugswereall

parameterssetbythedesigneratdesigntime.ByintroducingECUsthisenabledthese

parameters to bemapped depending on varying engine load values, quality of air

mixture etc. By having optimum operating conditions the car can achieve its best

performance as efficiently as possible.With greater emphasis on reducing carbon

emissions, it iswith the aidof an ECU that these regulations canbemet. The ECU

receives data from the sensor and uses data tables and calculations to make

adjustmentstotheactuatingdevices(Jurgen,1999).TheECUcanalsohelptoperform

systemdiagnosiswheneveranerroroccurs.

2.9 ECU

Theelectroniccontrolunit(ECU)inanautomobilehasthreemainfunctions;

Performdecisionmakingcapabilities(e.g.adjustintakevalues) Performarithmeticcalculations Storedata Readinputsfromsensors PerformActuationsbasedondecisions

Figure 2-10: A Basic Node Comprising of a Sensor and ECU


21

TheECU isbasedaround themicroprocessorbecause itcanperform the threebasic

requirementsasmentionedabove.Modernautomobilesneedprocessingcapabilities

ofcomputersandcomputersarebasedaroundmicroprocessors.Themicroprocessor

acts as a CPU (Central Processing Unit) for a computer. Early microprocessors

processeduptoeightbitsatatimebutnowadaysmicroprocessorsareavailablein16

bitand32bitformat,whichenableshigherprocessingspeeds.

TheCPUworksinasequentialmannerandaclock,usuallyacrystalclock,controlsthe

timing.Thisenables frequenciesofseveralmegahertzgivinghigherprocessorspeeds

and greater accuracy for clock samples.When an instruction is received and needs

temporarystorageintheCPUitisstoredinthememoryregisters.Withintheregisters

eachwordreceivedisstoredinmemory.

Figure212illustratesamicroprocessorwithassociatedregisters.Italsoillustratesthe

program counter that keeps track of where any instructions are stored and what

instructions theCPU requires running.TheALU (ArithmeticLogicUnit)performs the

arithmeticcalculationsinbinary.AnydatathatisbeingprocessedbytheALUisstored

intheaccumulatoruntilthecalculationisfinished.Thecontrolunitdirectsmovement

ofdata in thecomputer.Whatenablesamicroprocessor tocarryout instructions in

Figure 2-11: Microprocessor Block Diagram


22

thedesiredmanneraretheinstructionsitreceives,theseinstructionswouldusuallybe

conveyedviasoftwarethroughaprogram.

A basic computer can consist of the following elements; a microprocessor, extra

memory,inputsandoutputs.Dataisstoredataspecificaddressismemoryand,when

theprocessorrequiresdata,fetchesitfromthataddress.

When storing data inmemory the type ofmemory used is influenced by the tasks

function.Sourcecodedoesnotchangeandthereforewouldbestored inROM(Read

OnlyMemory). If the same taskwas performed repeatedlywithout change in the

processthenROMtypeofmemorycanbeselected,anexampleofthiswouldbeona

fuel management system that uses fixed data. If the data is only required for a

temporaryperiodthenRAM(RandomAccessMemory)canbeused.Oncethepoweris

disconnectedfromthistypeofmemorythedataislost.Anexampleofthiswouldbea

tripcomputer inaautomobile (alsocalledruntimedata) (Hillier,1996).Nonvolatile

RAM (NVRAM) isalsoused in instanceswhere storeddata isnot tobeerased.The

primaryareawhereNVRAMisusedisindatarecordingsuchasintheodometer.

Abusinterconnectsthecomponentsofthemicroprocessor;thesebusesarenamedin

relationtothedatatheycarrysuchastheaddressbus,databusandcontrolbus.For

an automotive based computer the inputs and outputswould typically be sensors,

transducersandactuators.

Current practice in the automotive industry is that the physical network bus

interconnecting between nodes is a cable. Connectors attach the cable to the

hardware.Theprotocolisacontributingfactorwhencablespecificationsareset.

2.10 AutomotiveNetworkProtocols

Asdiscussedintheprevioussectiononereasonforintroducingnetworksintomodern

automobiles was due to the increased levels of new features and applications in

automobiles. Design engineers decide what protocol is run on the network. Some


23

considerationsthathavetobetaken intoaccountwhendecidingwhatprotocolshall

beusedare;

Istheapplicationcritical? Whatspeedsarerequiredfortheapplication? Whatcostsareassociatedwitheachprotocol? Isthetechnologyreadilyavailabletodeveloptheapplicationwiththechosen

protocol?

Theanswertothesequestionswilloftendecidetheprotocolchosen,whetheritisan

eventtriggered(ET)ortimetriggered(TT)system.

2.10.1 EventTriggeredProtocols

Inaneventtriggered(ET)system,trafficgetsputontothenetworkafteraneventhas

occurredsuchasthedriverpressingthebrakes.Thisisasynchronoustransferbecause

there isnopredetermined timeatwhich theseeventswilloccur.Becauseanyevent

canoccuratanytimeinanyorder,thenetworkhastohaveadevelopedsystemthat

willavoidcollisions if twomessageson twoseparatenodes trytogainaccessto the

networkat the same time.This isachievedby taggingeachmessagewithapriority

level.Themessagewiththehighestprioritywillbegrantedaccesstothebusonceitis

free.Thisisanefficientuseofbandwidthduetothefactthatonlymessagesthatneed

tobetransmittedwillbelookingforaccesstothenetwork(NICOLASNAVET,2005).An

eventtriggeredcommunicationcontrollerdoesnotneedadispatchingtablebecause

thetransmissionofamessageistriggeredbyasendcommandfromthehost(Kopetz,

2000).


24

2.10.2 TimeTriggeredProtocols

Withthetimetriggered(TT)protocol,transmissionoccursatpredefinedpointsintime

(AndreiHagiescu,2007).Activitiescanonlyoccurwiththeprogressionoftimeandthe

activity ispredefined.This requires thenetwork tohaveapredefinedschedule that

assignsactivities/tasksasectionofthetime(timeslot)toperformtherequiredaction.

Eachtask ismadeupofmessages. Ifamessage isnottransmitted in itsdefinedtime

slotitwaitsuntilitsnexttimeslot.

InFigure213,amessageisassignedslottwo(S2)inwhichtotransmit.Ifthemessage

doesnotobtainaccesstothebus inslot(S2) itsnextassignedslotwhere itwillgeta

chancetogainaccesstothebusisinslotseven(S7).

A timetriggered communication controller contains a dispatching table in its local

memory that determineswhat point in time a particularmessage is transmitted or

whenthatmessageisexpectedtobereceived(Kopetz,2000).Ifanewnodeisadded

tothenetworkallothernodesneedtobeupdatedduetoachangeintheschedule(if

the new nodewas an unplanned addition). This can result in inefficient bandwidth

usageassomemessagesmightnotneedtotransmitthewholetime,butwillneedto

beallocatedslotsbythesystemdesigner(AndreiHagiescu,2007).

2.10.3 ComparisonofEventTriggeredandTimeTriggeredNetworks

ETsystemshaveanadvantageoverTTsystemswhen itcomes toaddingnewnodes

onto thenetwork.WithET systems thenewnode canbeaddedonwhere as inTT

systems the new node has to be scheduled into the system at design time. This

Figure 2-12: Time Triggered Slots on a Network


25

involvesthesystemdesignerreorganisingthesystemscheduletoaccommodatethe

new IDsonthenewnode.Asstatedpreviouslybandwidthefficiency isgreateronET

systemsbecauseamessagecanbetransmittedifbandwidthisavailablewhereasona

TTsystemamessagecanonly transmitwhen ithasbeenscheduledtodosoeven if

therearenomessagesscheduledintheslotsbeforeit.TTsystemscanbefaulttested

to ahigherdegreebecause thedesignerhas the scheduleprior to execution. InET

systems run time testing is critical for catchingpotential faultsdue to theaperiodic

natureoftheprotocol.AlsoinTTnetworks,sincetheapplicationdoesnotcontrolthe

timings there isacommon timebase forallnodeswhichallows thecommunication

controllertosynchronisetothemessageschedule(Hartwich,2007).

After considering these features the properties of each protocol can be examined.

OnlyCANandFlexRayarediscussedasLINandMOSTwerenotencounteredduring

thisresearch.

2.11 Conclusion

In this chapter the conceptof computernetworkswas introduced startingwith the

generalprincipleandmovingontoautomotivesystems.Differingnetwork topologies

andarchitectureswerediscussedbeforeanexampleoftheTCP/IPreferencemodelis

presented,whoseprotocolisusedextensivelyintheInternet.Thesevenlayersofthe

OSIreferencemodelareexplainedasthisreferencemodel isusedtocompare layers

ofotherprotocols.Abriefhistoryaboutthereasonsforusingofnetworkswithinthe

automotive industry is presented along with an overview of a nodes hardware

composition.Finally thechapterconcludeswithadiscussiononTTandETprotocols

andacomparisonofstrengthsandweaknessofthetwo.

This chapterpresents thenecessarybackground tounderstanding thepurposesand

requirementsofnetworkswithintheautomotiveindustry.Bypresentingdatanetwork

models suchas theOSImodel thisallows comparisons tobemadewhendiscussing

automotive protocols in later chapters such as the comparisonmade in Chapter 3

betweenCANand theOSImodel.Bypresentinganoverviewof thevariousnetwork


26

types (TT and ET) the limitations and advantages of each architecture type are

revealed.


27

2.12 References

A.Albert1BP,F.Voetz1,2005,SimulationEnvironmentforInvestigatingtheImpactsofTimeTriggeredCommunicationonaDis

a can to flexray migration framework

Documents

development of flexray

thi automotive industry

powertrain applications

eventtriggered messages

eventtriggered protocol

production cost

thesis supervisorfrank

fault tolerance