Real-time knock analysis for automatic engine mapp

SAETECHNICALPAPERSERIES3rdMobilityTechnologyConference&ExhibitSãoPaulo,BrasilNovember7-9,1994TheEngineeringSocietyForAdvancingMobilityLandSeaAirandSpace®INTERNATIONALAffilatedWith400CommonwealthDrive,Warrendale,PA15096-0001U.S.A.Tel:[phone]Fax:(412)776-57609494942399ERealTimeKnockAnalysisforAutomaticEngineMappingandCalibrationK.GschweitlE.GotthardA.KampitschAVLLISTGMBHTheappearanceoftheISSNcodeatthebottomofthispageindicatesSAE'sconsentthatcopiesofthepapermaybemadeforpersonalorinternaluseofspecificclients.Thisconsentisgivenonthecondition,however,thatthecopierpaya$5.00perarticlecopyfeethroughtheCopyrightClearanceCenter,Inc.OperationsCenter,222RosewoodDrive.,MA01923forcopyingbeyondthatpermittedbySections107or108oftheU.S.CopyrightLaw.Thisconsentdoesnotextendtootherkindsofcopyingsuchascopyingforgeneraldistribution,foradvertisingorpromotionalpurposes,forcreatingnewcollectiveworks,orforresale.SAEroutinelystocksprintedpapersforaperiodofthreeyearsfollowingdateofpublication.DirectyourorderstoSAECustomerSalesandSatisfactionDepartment.QuantityreprintratescanbeobtainedfromtheCustomerSalesandSatisfactionDepartment.TorequestpermissiontoreprintatechnicalpaperorpermissiontousecopyrightedSAEpublicationsinotherworks,contacttheSAEPublicationsGroup.GLOBALMOBILITYDATABASEAllSAEpapers,standards,andselectedbooksareabstractedandindexedintheGlobalMobilityDatabase.Nopartofthispublicationmaybyreproducedinanyform,inanelectronicretrievalsystemorotherwise,withoutthepriorwrittenpermissionofthepublisher.ISSN0148-7191Copyright1994SocietyofAutomotiveEngineers,Inc.Positionsandopinionsadvancedinthispaperarethoseoftheauthor(s)andnotnecessarilythoseofSAE.Theauthorissolelyresponsibleforthecontentofthepaper.AprocessisavailablebywhichdiscussionswillbeprintedwiththepaperifitispublishedinSAEtransactions.Forpermissiontopublishthispaperinfullorinpart,contacttheSAEPublicationsGroup.PersonswishingtosubmitpaperstobeconsideredforpresentationorpublicationthroughSAEshouldsendthemanuscriptora300wordabstractofaproposedmanuscriptto:Secretary,EngineeringActivityBoard,SAE.PrintedinUSA90-1203C/PG1RealTimeKnockAnalysisforAutomaticEngineMappingandCalibrationK.GschweitlE.GotthardA.KampitschAVLLISTGMBHAbstractRisingdemandsonnewenginedevelopmentrequireanincreasinguseofcomplexenginecontrolsystems.Thecalibrationofsuchcomplexsystemsisatimeandcostconsumingtask.Today’senginetestbedtechniqueoffersfullautomaticcalibrationandoptimizationprograms.Withsuchprogramsenginemappingandcalibrationcanbecarriedoutatreasonabletimeevenwhenarisingnumberofparametersisnecessary.Oneimportantparameterinthisfieldisengineknock.Inthispaperanewapproachforrealtimeknockanalysisisdescribed.Thisnewapproachallowsahighaccurateknockdetectioninthewholeengineoperationrangewithoutanyadjustmentduringanautomatictestrun.Suchatestrunwithanapplicationofanautomaticenginemapcalibrationispresented.ThegoalforthisoptimizationtaskwasatwodimensionalcalibrationofsparkadvanceandEGRtominimizetheNOx+HCemissionundertherestrictionofadefinedfuelconsumption.IntroductionAnaimforignitionmappingisprincipallytoachieveasparkadvanceasclosetoknockaspossible.Inslightlyknockingoperationhighengineefficiencycanbeexpected.Theaveragedcylinderpressurecurvesshowninfigure1representregularcombustionatsameenginespeedandwiththesamefuelenergy.EarliersparktimingresultsinthehigherpressuretraceandhigherIMEP.Figure1:Cylinderpressureofregularcombustionwithoutknock.2Butearliersparktimingleadsfinallytoknockingcombustion.Thisdiffersalotfromaregularcombustion(seefigure2).Regularcombustionisinitiatedbythesparkenergyandspreadsthroughoutthecombustionchamberasfastastheflamefrontcanheatuptheunburntgastothenecessarytemperature.Incaseofaknockingcombustionalltheunburntgasisalreadynearitsselfignitiontemperature.Whereselfignitiontemperatureisreached,asecondflamefrontisborn.Thissecondflamefrontwithmultiplespeedcauseshighfrequentpulsations(shockwaves)ofthecombustiongas.Cavitationcanoccuranddestroymainlythepiston,pistonringandcylinderheadsealing.Onlyasmallpercentageofknockingcombustioncanbeallowedtopreventdamagetotheengine.SensorsforKnockAnalysisInthefollowingabriefsummaryofmeasurementphenomenausedforknockdetectionisshowninfigure3:•temperaturemeasurementincombustionchamber•pressuremeasurementinthecoolant•measurementoftheforcebetweensparkplugandcylinderhead•measurementofthevariationofioniccurrent•thelightemissionduringcombustion•cylinderpressuremeasurement•measurementofenginenoiseOutofthelistofpossiblemeasurementphenomenaforknockdetectionwehaveselectedcylinderpressureandstructure-bornenoise.Forthegoaltoofferareliablesystemforenginedevelopmentpurposesmostengineersjudgethesetwosignalstobethebestsuitableones.Ifindicatingworkiscarriedoutontheengine(within-cylinderpressuretransducers)thecylinderpressuresignalscouldbeusedforknockdetection.Ifnopressuretransducersaremountedspecificknocksensorshavetobeused.Bymeansoffittingaccelerometerstothecylinderblocklowestinfluenceontheengineisachieved.AsseriesknocksensorsarenotavailableatthephaseofengineFigure2:Cylinderpressureofknock