车辆工程专业毕业论文外文翻译1doc.docx
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车辆工程专业毕业论文外文翻译1doc.docx
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车辆工程专业毕业论文外文翻译1doc
Driveforcecontrolofaparallel-serieshybridsystem
Abstract
Sinceeachcomponentofahybridsystemhasitsownlimitofperformance,thevehiclepowerdependsontheweakestcomponent.Soitisnecessarytodesignthebalanceofthecomponents.Thevehiclemustbecontrolledtooperatewithintheperformancerangeofallthecomponents.Wedesignedthespecificationsofeachcomponentbackwardfromtherequireddriveforce.Inthispaperwedescribeacontrolmethodforthemotortorquetoavoiddamagetothebattery,whenthebatteryisatalowstateofcharge.SocietyofAutomotiveEngineersofJapan,Inc.andElsevierScienceB.V.Allrightsreserved.
1.Introduction
Inrecentyears,vehicleswithinternalcombustionengineshaveincreasinglyplayedanimportantroleasameansoftransportation,andarecontributingmuchtothedevelopmentofsociety.However,vehicleemissionscontributetoairpollutionandpossiblyevenglobalwarming,whichrequireeffectivecountermeasures.Variousdevelopmentsarebeingmadetoreducetheseemissions,butnofurtherlargeimprovementscanbeexpectedfrommerelyimprovingthecurrentenginesandtransmissions.Thus,greatexpectationsarebeingplacedonthedevelopmentofelectric,hybridandnaturalgas-drivenvehicles.Judgingfromcurrentlyapplicabletechnologies,andthecurrentlyinstalledinfrastructureofgasolinestations,inspectionandservicefacilities,thehybridvehicle,drivenbythecombinationofgasolineengineandelectricmotor,isconsideredtobeoneofthemostrealisticsolutions.
Generallyspeaking,hybridsystemsareclassifiedasseriesorparallelsystems.AtToyota,wehavedevelopedtheToyotaHybridSystem(hereinafterreferredtoastheTHS)bycombiningtheadvantagesofbothsystems.InthissensetheTHScouldbeclassifiedasaparallel-seriestypeofsystem.SincetheTHSconstantlyoptimizesengineoperation,emissionsarecleanerandbetterfueleconomycanbeachieved.Duringbraking,Kineticenergyisrecoveredbythemotor,therebyreducingfuelconsumptionandsubsequentCO2emissions.
EmissionsandfueleconomyaregreatlyimprovedbyusingtheTHSforthepowertrainsystem.However,theTHSincorporatesengine,motor,batteryandothercomponents,eachofwhichhasitsownparticularcapability.Inotherwords,thedrivingforcemustbegeneratedwithinthelimitsofeachrespectivecomponent.Inparticular,sincethebatteryoutputvariesgreatlydependingonitslevelofcharge,thedrivingforcehastobecontrolledwiththisinmind.
ThisreportclarifiestheperformancerequiredoftherespectiveTHScomponentsbasedonthedrivingforcenecessaryforavehicle.Themethodofcontrollingthedrivingforce,bothwhenthebatteryhashighandlowcharge,isalsodescribed.
2.Toyotahybridsystem(THS)[1,2]
AsFig.1shows,theTHSismadeupofahybridtransmission,engineandbattery.
2.1.Hybridtransmission
Thetransmissionconsistsofmotor,generator,powersplitdeviceandreductiongear.Thepowersplitdeviceisaplanetarygear.Sungear,ringgearandplanetarycarrieraredirectlyconnectedtogenerator,motorandengine,respectively.Theringgearisalsoconnectedtothereductiongear.Thus,enginepowerissplitintothegeneratorandthedrivingwheels.Withthistypeofmechanism,therevolutionsofeachoftherespectiveaxesarerelatedasfollows.Here,thegearratiobetweenthesungearandthe
Fig.1.SchematicofToyotahybridsystem(THS).
ringgearisρ:
whereNeistheenginespeed,NgthegeneratorspeedandNmthemotorspeed.
Torquetransferredtothemotorandthegeneratoraxesfromtheengineisobtainedasfollows:
whereTeistheenginetorque.
Thedriveshaftisconnectedtotheringgearviaareductiongear.Consequently,motorspeedandvehiclespeedareproportional.Ifthereductiongearratioisη,theaxletorqueisobtainedasfollows:
whereTmisthemotortorque.
Asshownabove,theaxletorqueisproportionaltothetotaltorqueoftheengineandthemotoronthemotoraxis.Accordingly,wewillrefertomotoraxistorqueinsteadofaxletorque.
2.2.Engine
Agasolineenginehavingadisplacementof1.5lspeciallydesignedfortheTHSisadopted[3].Thisenginehashighexpansionratiocycle,variablevalvetimingsystemandothermechanismsinordertoimproveengineefficiencyandrealizecleaneremissions.Inparticular,alargereductioninfrictionisachievedbysettingthemaximumspeedat4000rpm(=Nemax).
2.3.Battery
Assealednickelmetalhydridebatteryisadopted.Theadvantagesofthistypeofbatteryarehighpowerdensityandlonglife.thisbatteryachievesmorethanthreetimesthepowerdensityofthosedevelopedforconventionalelectricvehicles[4].
3.Requireddrivingforceandperformance
TheTHSoffersexcellentfueleconomyandemissionsreduction.Butitmusthavetheabilitytooutputenoughdrivingforceforavehicle.Thissectiondiscussestherunningperformancerequiredofthevehicleandtheessentialitemsrequiredoftherespectivecomponents.
Roadconditionssuchasslopes,speedlimitsandtherequiredspeedtopassothervehiclesdeterminethepowerperformancerequiredbythevehicle.Table1indicatesthepowerperformanceneededinJapan.
3.1.Planetarygearratioρ
Theplanetarygearratio(ρ)hasalmostnoeffectonfueleconomyand/oremissions.Thisisbecausetherequiredenginepower(i.e.enginecondition)dependsonvehiclespeed,drivingforceandbatterycondition,andnotontheplanetarygearratio.Conversely,itislargelylimitedbythedegreeofinstallabilityinthevehicleandmanufacturingaspects,leavinglittleroomfordesign.InthecurrentlydevelopedTHS,ρ=0.385.
3.2.Maximumenginepower
Sincethebatterycannotbeusedforcruisingduetoitslimitedpowerstoragecapacity,mostdrivingisreliantonenginepoweronly.Fig.2showsthepowerrequiredbyavehicleequippedwiththeTHS,basedonitsdrivingresistance.Accordingly,thepowerthatisrequiredforcruisingonalevelroadat140km/horclimbinga5%slopeat105km/hwillbe32kW.Ifthetransmissionlossistakenintoaccount,theenginerequires40kW(=Pemax)ofpower.TheTHSusesanenginewithmaximumpowerof43kWinordertogetgoodvehicleperformancewhilemaintaininggoodfueleconomy.
3.3.Maximumgeneratortorque
AsdescribedinSection2,themaximumenginespeedis4000rpm(=Nemax).Toattainmaximumtorqueatthisspeed,maximumenginetorqueisobtainedasfollows:
FromEq.(3),themaximumtorqueonthegeneratoraxiswillbeasfollows:
Thisisthetorqueatwhichthegeneratorcanoperatewithoutbeingdriventooverspeed.Actually,highertorqueisrequiredbecauseofacceleration/decelerationofgeneratorspeedanddispersionofengineand/orgeneratortorque.Byadding40%torquemargintothegenerator,thenecessarytorqueiscalculatedasfollows:
3.4.Maximummotortorque
FromFig.3,itcanbeseenthatthemotoraxisneedstohaveatorqueof304Nmtoacquirethe30%slopeclimbingperformance.Thistorquemerelybalancesthevehicleontheslope.Toobtainenoughstartingandacceleratingperformance,itisnecessarytohaveadditionaltorqueofabout70Nm,orabout370Nmintotal.
FromEq.
(2),thetransmittedtorquefromtheengineisobtainedasfollows:
Consequently,amotortorqueof300Nm(=Tmmax)isnecessary.
3.5.Maximumbatterypower
AsFig.2shows,drivingpowerof49kWisneededforclimbingona5%slopeat130km/h.Thus,thenecessarybatterypowerisobtainedbysubtractingtheengine-generatedpowerfromthis.Asalreadydiscussed,ifanenginehavingtheminimumrequiredpowerisinstalled,itcanonlyprovide32kWofpower,sotherequiredbatterypowerwillbe17kW.Ifthepossiblelossthatoccurswhenthebatterysuppliespowertothemotoristakenintoaccount,batterypowerof20kWwillbeneeded.Thus,itisnecessarytodeterminethebatterycapacitybytargetingthisoutputonanactualslope.Table2liststherequiredbatteryspecifications.
Table3summarizesthespecificationsactuallyadoptedbytheTHSandtherequirementsdeterminedbytheabovediscussion.Therequireditemsrepresentanexamplewhenminimumenginepowerisselected.Inotherwords,iftheengineischanged,eachoftheitemshavetobechangedaccordingly.
4.Drivingforcecontrol
TheTHSrequirescontrolsnotnecessaryforconventionalorelectricvehiclesinordertocontroltheengine,motorandgeneratorcooperatively.Fig.4outlinesthecontrolsystem.
Fig.4.ControldiagramoftheTHS.
Inputsofcontrolsystemareacceleratorposition,vehiclespeed(motorspeed),generatorspeedandavailablebatterypower.Outputsaretheengine-requiredpower,generatortorqueandmotortorque.
First,drivetorquedemandedbythedriver(convertedtothemotoraxis)iscalculatedfromtheacceleratorpositionandthevehiclespeed.Thenecessarydrivepoweriscalculatedfromthistorqueandthemotorspeed.Requiredpowerforthesystemisthetotaloftherequireddrivepower,therequiredpowertochargethebatteryandthepowerlossinthesystem.Ifthistotalrequiredpowerexceedstheprescribedvalue,itbecomesrequiredenginepower.Ifitisbelowtheprescribedvalue,thevehiclerunsonthebatterywithoutusingtheenginepower.Next,themostefficientenginespeedforgeneratingenginepoweriscalculated;thisistheenginetargetspeed.ThetargetspeedforthegeneratoriscalculatedusingEq.
(1)withenginetargetspeedandmotorspeed.ThegeneratortorqueisdeterminedbyPIDcontrol.EnginetorquecanbecalculatedinreversebyusingEq.(3)andthetorquetransferredfromtheenginetothemotoraxiscanbecalculatedfrom
(2).Themotortorqueisobtainedby
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