Idle speed control of a direct injection spark ignition

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*Correspondenceto:J.W.Grizzle,ControlSystemsLaboratory,ElectricalEngineeringandComputerScienceDepart-ment,UniversityofMichigan,AnnArbor,MI48109-2122,U.S.A.RE-mail:grizzle@umich.edu

Contract/grantsponsor:NSF;contract/grantnumber:IIS-9988695Contract/grantsponsor:FordMotorCompany

Copyright󰀁2001JohnWiley&Sons,Ltd.

INTERNATIONALJOURNALOFROBUSTANDNONLINEARCONTROLInt.J.RobustNonlinearControl2001;11:1043}1071(DOI:10.1002/rnc.644)

Idlespeedcontrolofadirectinjectionsparkignitionstrati"edchargeengine

J.W.Grizzle󰀁󰀂*󰀂R,JuliaBuckland󰀃andJingSun󰀃󰀁ControlSystemsLaboratory,ElectricalEngineeringandComputerScienceDepartment,UniversityofMichigan,AnnArbor,MI48109-2122,U.S.A.󰀃PowertrainControlSystemsDepartment,FordResearchLaboratory,2101VillageRoad,POBox2053,Dearborn,MI48121-2053,U.S.A.

SUMMARYIdlespeedcontrolisinvestigatedforadirectinjection,sparkignition,strati"edcharge(DISC)engineequippedwithanelectronicthrottle.Suchenginescanbeoperatedinmultiplecombustionmodes.Whenoperatinginstrati"edchargecombustionmode,theyareverydi!erentfromconventionalstoichiometricengines,creatingnewopportunitiesforimprovedspeedcontrol.Withcurrentafter-treatmenttechnology,simultaneoushighfueleconomyandemissionsconversione$ciencycannotbeachievedbyoperatingtheengineinasteady-statemanner:itmustbecycledbetweenrunningultra-lean(forfueleconomy)andrich(toservicetheafter-treatmentsystem).Anidlespeedcontrolsystemisdesignedtomeettheconsiderablefeedbackcontroldemandsrequiredbythesenewengines.Copyright󰀁2001JohnWiley&Sons,Ltd.

KEYWORDS:hybridmodel;decentralizedcontrol;gainscheduling;switchingcontrol

1.INTRODUCTIONInrecentyears,manyresearchanddevelopmentactivitieshavefocusedonachievingfueleconomyimprovementsinsparkignitionenginesthroughreducedpumpinglosses[1}5].Onesuchtechnologyisthedirectinjectionstrati"edcharge(DISC)gasolineengine[6].ItsrecentintroductionintotheJapaneseandEuropeanmarketsmayextendtoNorthAmericainresponsetoincreasedenvironmentalpressuresandhighercustomerexpectationsforfueleconomyandperformance.Inthistypeofengine,fuelisinjecteddirectlyintothecombustionchamberduringtheintakestroketoformahomogeneousmixture,orduringthecompressionstroketoformaveryheterogeneousmixturereferredtoasastrati"edcharge,orboth.Withstrati"edcharge,theSTheshapeofthepistonisdesignedtoenhanceairmotion(swirlortumble).Theairmotion,incombinationwithproperfuelinjectiontiming,permitsthecreationofaconcentrated,ignitablemixturearoundthesparkplug[6].AAsnotedearlier,chargecompositiondependsdirectlyonfuelinjectiontiming.

enginecanoperateatoverallair}fuelratiosupto40:1orhigher,Stherebyreducingpumpinglossesandincreasingthermale$ciency.Withitssophisticatedcombustionchamberandfuelingsystem,andincombinationwithanadvancedexhaustafter-treatmentsystem,aDISCenginehasthepotentialofimprovingfueleconomyandCO󰀃emissionsatanacceptablecost.TheimplementationofDISCtechnologies,however,reliescriticallyonthedevelopmentofthecontrolsystemtodelivertheexpectedbene"ts.ForaDISCengine,thetaskofmaintainingoptimalfueleconomyoperatingconditionswhilesatisfyingemissionanddriveabilityconstraintsoverawiderangeofenginespeedandloadconditionsissigni"cantlymorecomplicatedthanthatforconventionalport-fuelinjected(PFI)engines.ThefollowingspecialfeaturesassociatedwithDISCenginesimposemajorchallengesforcontrolsystemdevelopment:

ECurrentDISCenginescanoperateinmultiplecombustionmodes,characterizedbychargecomposition,orequivalently,timeofinjection:Ahomogeneous(earlyinjection),strati"ed(lateinjection),andevenmultipleinjection.Becauseofsigni"cantdi!erencesintorqueandemissioncharacteristics,adistinctcontrolstrategyisrequiredtooptimizetheengineoperationineachmode.Acontrolsystemhastodeterminedynamicallynotonlyinwhichmodetheengineshouldberunningaccordingtoengineandafter-treatmentdeviceoperatingconditionsanddriver'sinput,butalsoe!ectivelymanagesmoothtransitionsfromonemodetoanother.EADISCenginehasmorecontrolinputsthanaconventionalPFIengine.Besidesthestandardactuatorssuchasthrottle,fuel,spark,andexhaustgasrecirculation(EGR),additionalinputs,suchasfuelinjectiontimingandfuelsystempressure,havesigni"cante!ectsonDISCengineperformance,unlikePFIengines,wherethee!ectsarerelativelyminor.Flowcontroldevices,suchasaswirlcontrolvalve(SCV),arealsonecessaryforpropermixingandchargeformation.Furthermore,otheradvancedactuators,suchasvariablecamtiming(VCT),continuouslyvariabletransmission(CVT)andboostingdevicessuchasavariablegeometryturbocharger(VGT)havebeenconsideredforDISCapplicationstorealizethefullbene"tsofleanoperation.Whilethesenewactuatorswillenhancetheoverallsystem'scapabilitytodelivergoodfueleconomyandemissions,theyhavegreatlyincreasedsystemcomplexitytherebynecessitatingasystemengineeringapproachtoe!ectivelymanagethismulti-objective,multi-variableproblem.