外文文献原稿和译文.docx

外文文献原稿和译文.docx

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外文文献原稿和译文

外文文献原稿和译文

原稿

MechanicalandRegenerativeBrakingIntegrationforaHybridElectricVehicle

Abstract

Hybridelectricvehicletechnologyhasbecomeapreferredmethodfortheautomotiveindustrytoreduceenvironmentalimpactandfuelconsumptionoftheirvehicles.Hybridelectricvehiclesaccomplishthesereductionsthroughtheuseofmultiplepropulsionsystems,namelyanelectricmotorandinternalcombustionengine,whichallowtheeliminationofidling,operationoftheinternalcombustionengineinamoreefficientmannerandtheuseofregenerativebraking.However,theaddedcostofthehybridelectricsystemhashinderedthesalesofthesevehicles.

Amorecosteffectivedesignofanelectro-hydraulicbrakingsystemispresented.Thesystemelectro-mechanicallycontrolledtheboostforcecreatedbythebrakeboosterindependentlyofthedriverbrakingforceandwithadequatetimeresponse.Thesystemallowedfortheblendingofthemechanicalandregenerativebrakingtorquesinamannertransparenttothedriverandallowedforregenerativebrakingtobeconductedefficiently.

Asystematicdesignprocesswasfollowed,withemphasisplacedondemonstratingconceptualdesignfeasibilityandpreliminarydesignfunctionalityusingvirtualandphysicalprototyping.Thevirtualandphysicalprototypeswerethenusedincombinationasapowerfultooltovalidateanddevelopthesystem.Theroleofprototypinginthedesignprocessispresentedanddiscussed.

Throughtheexperiencesgainedbytheauthorduringthedesignprocess,itisrecommendedthatstudentscreatephysicalprototypestoenhancetheireducationalexperience.Theseexperiencesareevidentthroughoutthethesispresented.

1.1ModernHybridElectricVehicles

Withrisinggaspricesandtheoverwhelmingconcernfortheenvironment,consumersandthegovernmenthaveforcedtheautomotiveindustrytostartproducingmorefuelefficientvehicleswithlessenvironmentalimpact.Onepromisingmethodthatiscurrentlybeingimplementedisthehybridelectricvehicle.

Hybridvehiclesaredefinedasvehiclesthathavetwoormorepowersources[25].Therearealargenumberofpossiblevariations,butthemostcommonlayoutofhybridvehiclestodaycombinesthepowerofaninternalcombustionengine（ICE）withthepowerofanelectricmotorandenergystoragesystem（ESS）.Thesevehiclesareoftenreferredtoashybridelectricvehicles（HEV’s）[25].Thesetwopowersourcesareusedinconjunctiontooptimizetheefficiencyandperformanceofthevehicle,whichinturnwillincreasefueleconomyandreducevehicleemissions,allwhiledeliveringtheperformancetheconsumerrequires.In1997,theToyotaPriusbecamethefirsthybridvehicleintroducedintomassproductioninJapan.Ittookanotherthreeyearsforthefirstmassproducedhybridvehicle,theHondaInsight,tobeintroducedintotheNorthAmericanmarket.ThereleaseoftheHondaInsightwascloselyfollowedbythereleaseoftheToyotaPriusinNorthAmericaacoupleofmonthslater[35].

Hybridelectricvehicleshavethedistinctadvantageofregenerativebraking.Theelectricmotor,normallyusedforpropulsion,canbeusedasageneratortoconvertkineticenergyofthevehiclebackintoelectricalenergyduringbraking,ratherthanwastingenergyasheat.ThiselectricalenergycanthenbestoredinanESS（e.g.batteriesorultracapacitors）andlaterreleasedtopropelthevehicleusingtheelectricmotor.

Thisprocessbecomesevenmoreimportantwhenconsideringtheenergydensityofbatteriescomparedtogasolineordieselfuel.Energydensityisdefinedastheamountofenergystoredinasystemperunitvolumeormass[44].Toillustratethispoint,4kilograms（4.5litres）ofgasolinewilltypicallygiveamotorvehiclearangeof50kilometres.Tostorethesameamountofusefulelectricenergyitrequiresaleadacidbatterywithamassofabout270kilograms[25].Thisdemonstratestheneedforefficientregenerativebrakingtostoreelectricalenergyduringdriving,whichinturnwillkeepthemassoftheenergystoragesystemdownandimprovetheperformanceandefficiencyoftheHEV.

1.2ResearchScope-RegenerativeBrakingSystems

Thescopeoftheresearchpresentedistocreatealowcostregenerativebrakingsystemtobeusedonfutureeconomicalhybridvehiclestostudytheinteractionbetweenregenerativeandmechanicalbrakingofthesystem.Thissystemshouldbeabletocontrolthecombinationofbothregenerativeandmechanicalbrakingtorquedependingondriverdemandandshouldbeabletodososmoothlyandsafely.Controllingtheregenerativebrakingtorquecanbedoneusingcontrolalgorithmsandvectorcontrolforinductionmotors.However,controllingthemechanicalbrakingtorqueindependentlyofthedriverpedalforce,whilemaintainingpropersafetyback-ups,provedtobemoreofachallenge.Toovercomethisproblem,asystemwasdevelopedthatwouldattenuatethepressureinthebrakeboosterinordertocontroltheamountofmechanicaltorquedevelopedbythebrakingsystem．

2.1HybridElectricVehicleOverview

Hybridvehicleshaveemergedasoneoftheshorttermsolutionsforreducingvehicle　emissionsandimprovingfueleconomy.Overthepast10yearsalmostallofthemajor　automotive　companieshavedevelopedandreleasedforsaletheirownhybridelectric　vehiclestothepublic.Thepopularityofhybridelectricvehicleshasgrownconsiderablysincetheturnof　thecentury.Withenormouspressuretobecomemoreenvironmentallyfriendlyandwith　unpredictablegasprices,thesalesofhybridelectricvehicleshaveincreaseddramatically　inrecentyears.

2.1.1HybridConfigurations

Forthepast100yearstheobjectiveofthehybridhasbeentoextendtherangeofelectric　vehiclesandtoovercometheproblemoflongrechargingtimes[35].Therearethree　predominanthybridelectricvehicleconfigurationscurrentlyonthemarkettoday.Theseconfigurationsareknownasserieshybrids,parallelhybridsandseries/parallelhybrids.

Eachconfigurationhasitsadvantagesanddisadvantageswhichwillbediscussedinthefollowingsections.

SeriesHybrids

Inserieshybridsthemechanicaloutputfromtheinternalcombustionengineisusedto　driveageneratorwhichproduceselectricalpowerthatcanbestoredinthebatteriesor　usedtopoweranelectricmotoranddrivethewheels.Thereisnodirectmechanical　connectionbetweentheengineandthedrivenwheels.Serieshybridstendtobeusedin　highpowersystemssuchaslargetrucksorlocomotivesbutcanalsobeusedforlowerpowerpassengervehicles[18].Themechanicallygeneratedelectricalpoweriscombinedwiththepowerfromthebatteryinanelectroniccontroller.Thiscontrollerthencomparesthedriverdemandwiththevehiclespeedandavailabletorquefromtheelectricmotortodeterminetheamountofpowerrequiredfromeachsourcetodrivethevehicle.Duringbraking,thecontrolleralsoswitchesthepowerelectronicstoregenerativemode,anddirectsthepowerbeingregeneratedtothebatteries[55].

Therearemanyadvantagesmadepossiblebythearrangementdescribedabove.ItispossibletoruntheICEconstantlyatitsmostefficientoperatingpointandshareitselectricaloutputbetweenchargingthebatteryanddrivingtheelectricmotor.Byoperatingtheengineatitsmostefficientoperatingpoint,emissionscanbegreatlyreducedandthemostelectricalpowercanbegeneratedpervolumeoffuel.Thisconfigurationisalsoeasiertoimplementintoavehiclebecauseitislesscomplexwhichmakesthismethodmorecosteffective.

ParallelHybrids

InparallelhybridconfigurationsthemechanicalenergyoutputfromtheICEistransmittedtoagearbox.InthisgearboxtheenergyfromtheICEcanbemechanicallycombinedwithaseconddrivefromanelectricmotor.Thecombinedmechanicaloutputisthenusedtodrivethewheels[35].Inthisconfigurationthereisadirectconnectionbetweentheengineandthedrivenwheels.Asinserieshybridsthecontrollercomparesthedriverdemandwiththevehiclespeedandoutputtorqueanddeterminestheamountofpowertobeusedfromeachsourcetomeetthedemand,whileobtainingthebestpossibleefficiency.Aparallelhybridalsocontrolsregenerativebrakingsimilarlytoaserieshybrid.Parallelhybridsareusuallyusedinlowerpowerelectricvehiclesinwhichbothdrivescanbeoperatedinparalleltoprovidehigherperformance[18].

Thereareanumberofadvantagesofaparallelhybridoveraserieshybrid.Themostimportantadvantageisthatsinceonlyoneconversionbetweenelectricalandmechanicalpowerismade,efficiencywillbemuchbetterthantheserieshybridinwhichtwoconversionsarerequired.Sincetheparallelhybridhastheabilitytocombineboththeengineandelectricmotorpowerssimultaneously,smallerelectricmotorscanbeusedwithoutsacrificingperformance,whilegettingthefuelconsumptionandemissionreductionbenefits.Lastly,parallelhybridsonlyneedtooperatetheenginewhenthevehicleismovinganddonotneedasecondgeneratortochargethebatteries.

Series/ParallelHybrids

Combinedhybridshavethefeaturesofbothseriesandparallelconfigurations.Theyuseapowersplitdevicetodrivethewheelsusingdualsourcesofpower（e.g.electricmotoronly,ICEonlyoracombinationofboth）.Whiletheaddedbenefitsofbothserieshybridsandparallelhybridsareachievedforthisconfiguration,controlalgorithmsbecomeverycomplexbecauseofthelargenumberofdrivingpossibilitiesavailable.

2.1.2DegreeofHybridization

SincemostHEV’sontheroadtodayareeitherparallelorseries/parallel,itisusefultodefineavariablecalledthe‘degreeofhybridization’toquantifytheelectricalpowerpotentialofthesevehicles.

Thedegreeofhybridizatio