汽车转向系统英文文献

S¯adhan¯aVol.33,Part5,October2008,pp.581–590.©PrintedinIndiaDSP-basedelectricpowerassistedsteeringusingBLDCmotorRMURUGAN,SNANDAKUMARandMSMOHIYADEENBharatElectronicsLimited,Nandambakkam,Chennai600089e-mail:[e-mail];[e-mail];[e-mail]gnandimplementationofelectricallyassistedpowersteering(EAS)usingBLDCmotorforavehicle.Thecontrolarchi-tectureconsistsoftwolayersofcontrol,namelythevehiclespeedassociatedcontrolandthetorqueassistcontrol.Inthehigherlevelofcontrolarchitecture,thevehiclespeedcontrollerworksasanassistancelevelcontrollerforthesteeringeffort.Inthelowerlevel,thetorquecontrollergivestheeffortlevelcontrol.ThishasbeenrealizedbytorquesensorandvehiclesensorinterfacedintheDSP.Forimplement-inginthesystem,aDSP-basedBLDCmotorcontrollerwiththree-phaseinvertermoduleisspeciallydesignedusingHall-effectsensorfeedbackandasingledc-linkcurrentsensor.ThisworkisimplementedinaLightCommercialVehiclehavingarecirculatingballtypegear.Thisisforthefirsttime(EAS)beingimplementedforthistypeofvehicleanywhereintheworld.Generally,EAShavingclutchtodisconnectthemotorinhighspeedorabnormalconditionsfromthegearbox.Inthisimplementationthemotorisdirectlycoupledtogearboxwithoutclutchandallabnormalitiesarehandledbytheprocessor.Thisisimplementedwithoutmodify-ingthevehiclesupplysystemlikechangingtheexistingalternatororratingofthebatteryandusingtheexistingsensors.Thedesignissuchawaythatthefeelofthedriverassistancecanbevariedeasilyatanytime.TheperformanceofthecontrolsystemisexperimentallyverifiedanditistestedinoneoftheLightCommercialVehicle(LCV).Keywords.BLDCmotor;EAS;steering.1.IntroductionPowersteeringisasystemforreducingthesteeringeffortonvehiclesbyusingexternalsourcetoassistinturningthewheels.Mostnewgenerationvehiclesnowhavepowersteering,owingtothetrendstowardgreatervehiclemassandwidertires,allincreasethesteeringeffortneeded.Modernvehicleswouldbedifficulttomaneuveratlowspeeds(e.g.whenparking)withoutassistance.Mostpowersteeringsystemsworkbyusingabelt-drivenpumptoprovidehydraulicpressuretothesystem.Thishydraulicpressureisgeneratedbyapumpwhichisdrivenbythevehicle’sengine.Whilethepowersteeringisnotused,i.e.drivinginastraightline,twinhydrauliclinesprovideequalpressuretobothsidesofthesteeringwheelgear.581582RMurugan,SNandakumarandMSMohiyadeenWhentorqueisappliedtothesteeringwheel,thehydrauliclinesprovideunequalpressuresandhenceassistinturningthewheelsintheintendeddirection.ElectricPowerSteeringsystemsuseelectriccomponentswithnohydraulicsystemsatall.Sensorsdetectthemotionandtorqueofthesteeringcolumnandacomputermoduleappliesassistivepowerviaanelectricmotorcoupleddirectlytoeitherthesteeringgearorsteeringcolumn.Thisallowsvaryingamountsofassistancetobeapplieddependingondrivingconditions.Intheeventofcomponentfailure,amechanicallinkagesuchasarackandpinionservesasaback-upinamannersimilartothatofhydraulicsystems.Electricsystemshaveanadvantageinfuelefficiencybecausethereisnohydraulicpumpconstantlyrunning.Theirotherbigadvantageistheeliminationofabelt-drivenengineaccessory,andseveralhigh-pressurehydraulichosesbetweenthehydraulicpump,mountedontheengine,andthesteeringgear,mountedonthechassis.Thisgreatlysimplifiesmanufacturing.Thedemandofelectricallyassistedpowersteering(EAS)hasrapidlyincreasedinpastfewyearsbecauseofenergysavingscomparedtoHydraulicPowerSteering(HPS).Alternatingcurrent(ac)motorsaredesignedtobehighlyefficientandeasilycontrolledwithmodernpowercircuitry.Becauseofthedevelopmentsinswitchingtechniques,itisquitefeasibletouseacmotorswithabatterysupplyassource.ThetraditionalwormgeardrivendcmotorsystemisconstrainedbythelimitationsofthedcmotorbrushesandsizeofthemotorforthesametorqueofBLDC.InthiscaseBLDCmotorhasbeenusedasanactuatorintheapplicationforelectricpowersteering.TheBLDCmotorprovideshightorqueandeasycontrol(Chan&Fang2002;Chuetal2001;Desai&Emadi2005;Jun-UkChuetal2004;KevinBrownetal1990;NamhunKimetal2007).Thebasicmechanicalpropertiesofthevehicleareessentiallyinvariantamongalloftheavailablebrands.TheelectricallyassistedpowersteeringsystemconsistsofBLDCmotormountedtotheframeofthesteeringcolumnandcoupledtothewheelsthroughawormspeedreducer.Electricallyassistedpowersteeringisshowninfigure1.Anelectricallyassistedpowersteeringiscomposedofseveralpartssuchastorquesensor,enginespeedsensor,vehiclespeedsensor,steeringcolumn,torsionbarandelectroniccontrolunit.Figure1.Electricallyassistedpowersteering.DSP-basedelectricpowerassistedsteeringusingBLDCmotor583Torquesensoroutputgivesthetorquedifferencetobedevelopedbythemotortoreducetheeffortrequiredbythedriverwhileheissteering.EnginespeedsignalisrequiredtostarttheassistanceonlywhentheengineisONinordertosavethebatterylife.Vehiclespeedsignalisrequiredtocontroltheassistancedevelopedbythemotor(forthesameleveloftorquesignal)atvariousvehiclespeed,asassistancerequirementcomesdownasspeedofthevehicleincreases.Thecontrolarchitectureconsistsoftwolayersofcontrol,namelytheassistancelevelcontrolandthetorquecontrol.Inthehigherlevelofcontrolarchitecture,vehiclespeedsignalworksasa