無(wú)錫太湖學(xué)院DesigningandModelingaTorqueandSpeedControlTransmission(TSCT)1BackgroundThePartnershipforaNewGenerationofVehicles(PNGV)wasformedbetweentheFederalGovernment,FordMotorCompany,GeneralMotorsCorporation,andChryslerCorporation.ThegoalofthispartnershipwastoallowthemajorU.S.automotivemanufacturestocollaboratewitheachotherandproducehighfuelefficiency,lowemissionsvehiclesforsaletothegeneralpublic.Theperformanceobjectiveforthesemanufacturerswastocreatemid-sizedpassengercarscapableofattainingan80mpg(gasoline)compositefueleconomyratingontheEnvironmentalProtectionAgency(EPA)cityandhighwaycycles.HybridvehicletechnologyhasshowngreatpromiseinattainingthegoalssetforthbythePNGV.Hybridelectricvehicles(HEV)employtechnologythathelpsbridgethegapbetweenthefuturehopeofanelectricvehicle(EV)andtodayscurrentvehicles.Withinthepastyearhybridelectricvehicleshavegainedanimportantplaceinthevehiclemarket.AmericanHondaMotorCompany,Inc.iscurrentlyreleasingtheirfirstgenerationHEV,theInsight.TheInsightisacompact,twopassengey,parallelHEVwhichachievesmorethan65mpg(composite)ontheEPAtestcycles:thehighestofanyproductionvehicleevertested.ToyotaMotorCorporationhasalsoreleasedahybridvehicleforsaletothegeneralpublic.TheToyotaPriusiscurrentlyforsaleinJapanandwillcometheUnitedStatesinthebeginningoftheyear2000.ThePriusisafourpassengercombinationhybridemployinganagasolineengine,highpowerelectricmotor,andanelectromechanicalcontinuouslyvariabletransmission(CVT)comprisedofaplanetarygeartrainandahighpoweralternator/motor.ItisthroughtechnologyincorporatedinvehiclessuchasthePriusthatautomotivetransmissiondesignandoperationwillmakesignificantnewadvances.1.1CurrentAutomotiveTransmissionTechnologiesWiththeadventoftheautomobilealsocamethecreationoftheautomotivetransmission.Earlyvehiclesweresimplewithmanualcontrolsforallfunctionsincludingthetransmission.Asadvanceshavebeenmadeinvehiclesoverthepastseveraldecades,transmissiontechnologyhasalsoadvanced.Theautomatictransmissionhasnearlyreplacedthemanualtransmissioninallbuteconomyandperformancecars.Thistrendcanbeattributedtoeaseofuse,higherpowerenginesbecomingavailable,andcongestioninurbanareas.Anothernewtransmissiontechnologybeginningtoseeapplicationparticularlyinforeignmarketsisthecontinuouslyvariabletransmissionthatofferscontinuousoperationwithoutshiftingbetweenahighandlowgearratio.Thesethreetypesoftransmissionsareallsimilarinfunctionthoughtheirobjectivesareaccomplishedindifferentways.Thecapabilitiesofthesetransmissionsarelimitedtodecouplingtheenginespeedfromthespeedofwheelsandtherebyprovidingoneofseveralforwardorreversegearratios.Eachtransmissionisalsoasingleinput(engine)andsingleoutput(drivedevice).Therearetypicallynoprovisionsforattachingmultiplepowersourcesorforextractingpowerfrommorethanonepoint.Theexceptiontothisisheavy-dutytransmissionsequippedwithprovisionsforapowertakeofffordrivingauxiliarymechanicalequipment.Singleinput,singleoutputoperationlimitsdrivetrainflexibilityfor無(wú)錫太湖學(xué)院newersystemsemployingmultiplepowersourcessuchasthoseusedinthenextgenerationofhybridvehicles.1.1.1ManualTransmissionOperationManualtransmissionsaretheleastcomplexandoldestdesignofpowertransmissionavailable.Insimplestform,amanualtransmissionisalinearcombinationofaclutchandadirectlygearedconnection.Moresophisticatedexamplesrelyonthisdesignbutaddtheabilitytoselectothergearratiostoallowdifferentoutputspeedsforthesameinputspeed.Ofthesetypesoftransmissions,therearetwovariations:synchronizedandunsynchronized.Synchronizedmanualtransmissionsaretypicallyusedforlightdutyapplications.Coupledtoeachgearisasynchronizerthatallowstheoperatortodisengagetheclutchandselectwhatevergearnecessary.Theselectionofadifferentgearengagesthesynchronizer,whichthenmatchesengineinputspeedandtransmissionoutputspeedbeforethegearsareengaged.Unsynchronizedmanualtransmissionsaremorerobustbynature.Theoperatormustdouble-clutchbetweenshiftstomatchengineandtransmissionspeedmanually.However,thisallowsatransmissionofagivensizetohandlegreaterloadasspacepreviouslyoccupiedbythesynchronizerscannowbededicatedtotheuseofwidergears.Applicationsofthesetypesofmanualtransmissionsareforover-the-roadtrucksanduptolargerequipmentwithtotalvehicleweightsover100tons.11.1.2AutomaticTransmissionOperationAutomatictransmissionsareacomplexassemblyofmanycomponentsthatallowforseamlesspowertransmission.Thosecurrentlyavailableinproductionvehiclesusetorqueconverters,clutches,andplanetarygearsetsfortheselectionofdifferentoutputratios.Theengineisconnectedtothetorqueconverterthatactsverymuchlikeaclutchundersomeconditionswhilemorelikeadirectconnectioninothers.Thetorqueconverterisahydrauliccouplingthatwillslipunderlightload(idle),butengageprogressivelyunderhigherload.Whilethetorqueconvertertransmitspowertothetransmissionthereisaspeedreductionacrosstheunitduringlowspeedoperation.Thisreductionistypicallybetween2.5:1to3.5:1.Oncehighervehiclespeedsareattained,thetorqueconverterinputandoutputmaybelockedtogethertoachieveadirectdrivethoughtheunit.Theoutputofthetorqueconverteristypicallyconnectedtoahydraulicpumpthatprovidesthenecessarypressuretoengagedifferentclutcheswithinthetransmissionandtheplanetarydrive.Differentgearratiosarecreatedthroughtheuseoftwoormoreplanetarygearsets.Thesegearsetsarecombinedwithclutchesondifferentelements.Byclutchinganddeclutchingdifferentelements,multiplegearratiosarepossible.Basicautomatictransmissionsareequippedwithasinglecontrolinputthatisthrottleposition.Thecombinationofthiswiththehydraulicpressurecreatedwithinthetransmissionallowsformechanicalopenloopcontrolofallgearselections.Newervariationsoftheautomatictransmissionareequippedwithelectronicfeedbackcontrols.Shiftlogicisdependentonmanymorevariablessuchasenginespeed,temperature,currentdrivingtrend,throttleposition,vehicleaccelerations,etc.Thisallowsthetransmissioncontrollertomonitorvehicleoperationandusingarule-basedcontrolstrategydecide,whichgearisbestsuitedtothecurrentdrivingconditions.Newersystemsarealsointegratedwiththeenginecontrollersuchthatavehiclecontrolcomputerhasauthorityoverengineandtransmissionoperationsimultaneously.Thisallowsforsuchfeaturesasincreasingenginespeedduringhigh-speeddownshiftstomatchengineandtransmissionspeedforsmoothershiftingandretardingfuelingandignitiontimingduringhighpowerupshiftstoreducejerk.Previously,無(wú)錫太湖學(xué)院transmissioncontrolwasmuchsimplerbecauseoverrunningclutcheswereemployedinhighergearsthatonlyallowedforcoastingtoconservefuel.11.1.3ContinuouslyVariableTransmissionOperationContinuouslyvariabletransmissionsareoneoftheemergingtransmissiontechnologiesofthelasttwentyyears.Thistypeoftransmissionallowspowertransmissionoveragivenrangeofoperationwithinfinitelyvariablegearratiosbetweenahighandlowextreme.Thesetransmissionsareconstructedusingtwovariablediameterpulleyswithabeltconnectingthetwo.Asonepulleyincreasesinsize,theotherdecreases.Thisisaccomplishedbylocatingononeshaftastationarysheaveandamovablesheave.Forautomotiveapplications,ahydraulicactuatorcontrolsmovementofthesheave.However,centrifugalsystemsalongwithhighpowerelectronicsolenoidsmaybeused.AsecondshaftintheCVTcontainstheotherstationarysheaveandmovablesheavealsocontrolledhydraulically.Aflexiblemetalbeltisfittedaroundthesetwopulleysandthemovablesheavesarelocatedonoppositesidesofthebelt.Therearetwovariationsofthistypeoftransmission:pushbeltandpullbeltPullbeltCVTwerethefirsttypetobemanufacturedduetosimplicity.Aclutchisattachedbetweenthefirstpulleyandtheenginewhiletheoutputofthesecondpulleywasconnectedtoadifferentialandthusthewheels.Ahydraulicpumpisusedtocontrolthediameterofthetwodifferentpulleys.Aspowerisappliedthefirstpulleycreatesatorquethatistransmittedthroughthebelt(undertension)tothesecondpulley.Controlofthetransmissionratioisusuallyadirectrelationshipdependentuponthrottleposition.PushbeltCVT,similarindesigntotheVan,aremuchthesameaspullbeltCVT,exceptthatpoweristransmittedthroughthebeltwhileundercompression.Thisprovidesahigheroverallefficiencyduetothebeltbeingpushedoutofthesecondpulleyandloweringfrictionallosses.Currentworkwiththesetransmissionsisbeingfocusedoncreatinglargerunitscapableofhandlingmoretorque.EfficiencyoftheCVTisdirectlyrelatedtohowmuchtensionisinthebeltbetweenthetwopulleys.CVTtorquehandlingcapacityincreasesastensioninthebeltincreases.However,thisincreasedtensionlowerspowertransmissionefficiency.Thebeltmustslideacrossthefacesofeachpulleyasitentersandexitsuponeachhalfrotation.Thisslidingofthebeltcreatesfrictionallosseswithinthesystem.Inaddition,theremaybesignificantparasiticlossesassociatedwithraisingthehydraulicpressurerequiredtomoveormaintainthepositionofthesheavesineachpulley.21.1.4AutomaticallyShiftedManualTransmissionOperationAutomaticallyshiftedmanualtransmissionsareafairlyrecentinnovation.Thebenefitofthemanualtransmissionisthat(duetothedirectmechanicalconnectionthroughfixedgears)efficiencyisveryhigh.Thedrawbackisthattheremustbesomeinteractionwiththeuserintheselectionandchangingofgears.Automaticallyshiftedmanualswerecreatedtoaddressthisissue.Thesetypesoftransmissionsaretraditionallysynchronizedmanualtransmissionswiththeadditionofautomationofthegearselectionandcontroloftheclutch.Alogiccontrollerisalsoemployedtodecidewhenandhowtoshift.Automaticshiftingisusuallyaccomplishedthroughtheuseofelectro-hydraulics.Ahigh-pressureelectricpumpsuppliespressuretohydraulicsolenoidsthatareusedtoshiftthetransmission.Ahydraulicramisalsousedtoengageanddisengagetheclutch.Currentversionsofthesetransmissionsalsoemployunsynchronizedgears.Thisallows無(wú)錫太湖學(xué)院foroverallsmallerpackagingtoaccomplishthesametask.Inputspeedoftheengineismonitoredalongwithlayshaftspeed.Whenagearchangeisinitiated,thecontrolleropenstheclutch,shiftstothedesiredgearwhilematchingengineandlayshaftspeed,andthenclosestheclutchagain.Thisshiftingoperationcanallbeachievedinlessthanonethirdofasecond.Automaticallyshiftedmanualtransmissionsshiftgearsfasterthanhumanlypossible.31.1.5ManuallyShiftedAutomaticTransmissionOperationManuallyshiftedautomatictransmissionsareavariationoncontrolofthetransmission.Theuserisallowedtoselecteitherautomaticormanualshiftingmodes.Duringautomaticmode,thetransmissionfunctionsidenticallytoanautomatictransmission.Whileinmanualshiftmodehowever,thetransmissioncontrollerallowstheuserfullauthorityovergearchangesaslongasthegearchangewillnotoverspeedtheengine.Thismodeofoperationtraditionallyofferstheusertighter,morepositiveshiftfeel.Theonlyrequirementofanautomatictransmissionformanualshiftingisthatshiftsmustbeaccomplishedrapidlyenoughtoallowtheuserafeelingoffluidity.Theactofshiftingmustprovidetheimmediatedesiredresponse.31.1.6PlanetaryGearDriveTransmissionOperationPlanetarygearsetsareuniqueinthatthecombinationofgearscreatesatwodegree-of-freedomsystem.Thegearsetsarecomprisedofaringgear,asungearinthecenter,andplanetarygearsthatcontactboththeringandthesungears.Motionoftheplanetarygearsiscontrolledbythecarrieronwhicheachoftheplanetarygearsrotate.Thecarriermaintainsthepositionoftheplanetsinrelationtoeachotherbutallowsrotationofallplanetsfreely.Inputs(oroutputs)tothegeartrainaretheringgear,sungear,andplanetarycarrier.Byprescribingthemotionofanytwooftheseparameters,thethirdisfixedinrelationtotheothertwo.Byemployingoneplanetarygeartrain,afixedratiobetweeninputand