并联液压混合动力装载机的系统配置和能源控制策略的研究

ResearchonthesystemconfigurationandenergycontrolstrategyforparallelhydraulichybridloaderSunHui,,JingJunqingJiangsuXuzhouConstructionMachineryResearchInstitute,Jiangsu,ChinaAccepted30October2009.Availableonline22November2009.–moderatebrakingoperatingmodeswhileensureshybridsystemworkinginhigherefficiencyregion.Accordingtothehigherpowerdensitycharacteristicofhydraulichybridsystem,theregenerativebrakingstrategyandenergyreusestrategyaredesignedtocoordinateallthepowertraincomponentsinanoptimalmannerwhilesatisfyingperformanceconstraintsofloader.Energycontrollerusinglogicthresholdapproachisbuiltuptocontrolthedynamictransitionsamongthevariousoperationmodes.Simulationandexperimentalresultsshowtheparallelhydraulichybridloader(PHHL)effectivelyrecoveredandreusedthebrakingenergy,improvedtheworkingperformanceofloaderandeffectivelyreducedthefuelconsumption.KeywordsLoader;Hydraulichybridsystem;Brakingenergyregeneration;Energymanagement;Hydraulicpump/motor1.IntroductionWiththerisingconcerninaglobalscaleenvironmentalissue,energysavinginautomobilesisaveryimportantsubject[1]and[2].Off-roadvehicleshavebeenpaidmuchattentioninthefieldofenergysavingandenvironmentprotection,forthereasonoftheirlargeapplicationquantities,highfuelconsumptionandbademissions[3].Loaderhasthecharacteristicsoffrequentstarts/stopsandlargervehicleweightwhichgeneratedsignificantamountsofbrakingenergy.Usually,thispartofenergyiswastedbythefrictionalbrakingsystemwhichcausedtheenergylossandheatgenerationinthesystem.Therefore,thebrakingenergyrecoveryandreuseisapromisingwaytoimprovefueleconomyandworkingperformanceofoff-roadvehicles[4]and[5].Thereisawealthofliteraturefocusedonhybridelectricengineeringvehicles,butthepublicationsdevotedtohydraulicpropulsionoptionsarerelativelyscarce[6]and[7].Aparallelhydraulichybridloaderisonethatcontainstwosourcesofpower,withonesourcebeinganinternalcombustionengine.Theotherpowersourceishydraulicpump/motorandaccumulators.OnefeatureofPHHListheabilitytorecoverenergynormallylostduringbrakingandstoretheenergyinahydraulicaccumulator.Thestoredenergyisusedtoprovidethetotalcommandpowerduringloaderlaunchingorprovideauxiliarytractionpowerduringshovelingoperationmode,whichavoidstheengineworkingintheregionsoflowefficiencyandsignificantemissions.Inthispaper,anenergysavingschemewithparallelhydraulichybridsystemisproposedtocapturethebrakingenergynormallylosttofrictionbrakes.Hydraulichybridsystemisdesignedandsizedtocapturebrakingenergyfromnormal-moderatebrakingoperatingmodeswhileensureshybridsystemworkinginhigherefficiencyregion.Accordingtotheadvantageofhighpowerdensityforhydraulicaccumulatorandtheoperationcharacteristicsofloader(stop-and-godutycycles),theregenerativebrakingstrategyandenergyreusestrategyaredesignedtocoordinateallthepowertraincomponentsinanoptimalmannerwhilesatisfyingperformanceconstraints.Energycontrolstrategyisbuiltuparoundtheconceptofmulti-levelhierarchiccontrolsystem.PHHLsimulationmodelandthecontrolsystemsimulationmodelbasedontheproposedenergycontrolstrategyaredevelopedinMatlab/Simulinkenvironment.ExperimentalresultsandsimulationresultsdemonstratethatPHHLwithproposedcontrolstrategyeffectivelyimprovesthefueleconomyandworkingperformance.2.ConfigurationofthePHHL2.1.OperatingprincipleofPHHLFig.1presentstheconfigurationofproposedPHHL,whichconsistsprimarilyofanengine,hydraulictorqueconverter,boomtanks,dumptanks,ahighpressureaccumulator,ahydraulicreservoir,avariabledisplacementhydraulicpump,andavariabledisplacementhydraulicpump/motorunit,clutch,transmission,torquecoupleranddifferential.Thehydraulicpump/motoriscoupledtothepropellershaftviaatorquecoupler.Engineisthepowersourceoftheloader,onepartoftheenginepowerisusedtodrivetheloaderthroughhydraulictorqueconverterandtransmission,theremainderpartofenginepowerisusedtorealizetheshiftingandloadingfunctionsbymeansofhydrauliccylinders.Hydraulicregenerativesystem,whichconsistsofahydraulicpump/motor,hydraulicaccumulator,hydraulicreservoirandhydraulicreliefvalve,etal.drivestheloadertogetherwiththeengine.Duringdeceleration,thehydraulicpump/motordeceleratestheloaderwhileoperatingasapumptocapturetheenergynormallylosttofrictionbrakesinaconventionalloader.Also,whenthevehiclebrakeisapplied,thehydraulicpump/motorusesthebrakingenergytochargethehydraulicfluidfromalowpressurehydraulicaccumulatorintoahigh-pressureaccumulator,increasingthepressureofthenitrogengasinthehighpressureaccumulator.Thehighpressurehydraulicfluidisusedbythehydraulicpump/motorunittogeneratetorqueduringthenextacceleration[8]and[9].Hydraulicpump/motorisdesignedandsizedtocapturebrakingenergyfromnormal,moderatebrakingeventsandissupplementedbyfrictionbrakesforaggressivebraking.Whiles