车辆工程专业毕业论文外文翻译1doc.docx

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