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外文翻译---多畴模拟挖掘机的机械学和液压学.doc

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外文翻译---多畴模拟挖掘机的机械学和液压学.doc

附录AMultiDomainSimulationMechanicsandHydraulicsofanExcavatorHirokazuAraya,MasayukiKagoShimaMechanicalEngineeringResearchLaboratoryKobesteel,Ltd,NishiKvKobeHyogo6512271,JapanAbstractItisdemonstratedhowtomodelandsimulateanexcavatorwithModelicaandDymolabyusingModelicalibrariesformultibodyandforhydraulicsystems.Thehydraulicsystemiscontrolledbyaloadsensingcontroller.Usually,modelscontaining3dimensionalmechanicalandhydrauliccomponentsaredifficulttosimulate.AthandoftheexcavatoritisshownthatModelicaiswellsuitedforsuchkindsofsystemsimulations.1.IntroductionThedesignofanewproductrequiresanumberofdecisionsintheinitialphasethatseverelyaffectthesuccessofthefinishedmachine.Today,digitalsimulationisthereforeusedinearlystagestolookatdifferentconcepts.Theviewofthispaperisthatanewexcavatoristobedesignedandseveralcandidatesofhydrauliccontrolsystemshavetobeevaluated.Systemsthatconsistof3dimensionalmechanicalandofhydrauliccomponents–likeexcavators–aredifficulttosimulate.Usually,twodifferentsimulationenvironmentshavetobecoupled.Thisisofteninconvenient,leadstounnecessarynumericalproblemsandhasfragileinterfaces.InthisarticleitisdemonstratedathandofthemodelofanexcavatorthatModelicaiswellsuitedforthesetypesofsystems.The3dimensionalcomponentsoftheexcavatoraremodeledwiththenew,freeModelicaMultiBodylibrary.Thisallowsespeciallytouseananalyticsolutionofthekinematicloopatthebucketandtotakethemassesofthehydrauliccylinders,i.e.,theforceelements,directlyintoaccount.Thehydraulicpartismodeledinadetailedway,utilizingpump,valvesandcylindersfromHyLib,ahydraulicslibraryforModelica.Forthecontrolpartagenericloadsensingcontrolsystemisused,modeledbyasetofsimpleequations.Thisapproachgivestherequiredresultsandkeepsthetimeneededforanalyzingtheproblemonareasonablelevel.2.ModelingChoicesThereareseveralapproacheswhensimulatingasystem.Dependingonthetaskitmaybenecessarytobuildaveryprecisemodel,containingeverydetailofthesystemandneedingalotofinformation,e.g.,modelparameters.Thiskindofmodelsisexpensivetobuildupbutontheotherhandveryusefulifparametersofawelldefinedsystemhavetobemodified.AtypicalexampleistheoptimizationofparametersofacounterbalancevalveinanexcavatorKraft1996.Theotherkindofmodelisneededforafirststudyofasystem.Inthiscasesomepropertiesofthepump,cylindersandloadsarespecified.Requiredisinformationabouttheperformanceofthatsystem,e.g.,thespeedofthepistonsorthenecessaryinputpoweratthepumpshaft,tomakeadecisionwhetherthisdesigncanbeusedinprincipleforthetaskathand.Thismodelhasthereforetobecheap,i.e.,itmustbepossibletobuilditinashorttimewithoutdetailedknowledgeofparticularcomponents.Theauthorsintendedtobuildupamodelofthesecondtype,runitandhavefirstresultswithaminimumamountoftimespent.ToachievethisgoalthemodelinglanguageModelicaModelica2002,theModelicasimulationenvironmentDymolaDymola2003,thenewModelicalibraryfor3dimensionalmechanicalsystemsMultiBodyOtteretal.2003andtheModelicalibraryofhydrauliccomponentsHyLibBeater2000wasused.Themodelconsistsofthe3dimensionalmechanicalconstructionoftheexcavator,adetaileddescriptionofthepowerhydraulicsandagenericloadsensingcontroller.ThismodelwillbeavailableasademointhenextversionofHyLib.3.ConstructionofExcavatorsInaschematicdrawingofatypicalexcavatorunderconsiderationisshown.Itconsistsofachaintrackandthehydraulicpropeldrivewhichisusedtomanoeuvrethemachinebutusuallynotduringaworkcycle.Ontopofthatisacarriagewheretheoperatorissitting.Itcanrotatearoundaverticalaxiswithrespecttothechaintrack.ItalsoholdstheDieselengine,thehydraulicpumpsandcontrolsystem.Furthermore,thereisaboom,anarmandattheendabucketwhichisattachedviaaplanarkinematiclooptothearm.Boom,armandbucketcanberotatedbytheappropriatecylinders.Figureshowsthattherequiredpressuresinthecylindersdependontheposition.Forthestretchedsituationthepressureintheboomcylinderis60higherthanintheretractedposition.Notonlythepositionbutalsothemovementshavetobetakenintoaccount.Figure3showsasituationwherethearmhangsdown.Ifthecarriagedoesnotrotatethereisapullingforcerequiredinthecylinder.Whenrotating–excavatorscantypicallyrotatewithupto12revolutionsperminute–theforceinthearmcylinderchangesitssignandnowapushingforceisneeded.Thischangeisverysignificantbecausenowtheactivechamberofthecylinderswitchesandthatmustbetakenintoaccountbythecontrolsystem.Bothfiguresdemonstratethatasimulationmodelmusttakeintoaccountthecouplingsbetweenthefourdegreesoffreedomthisexcavatorhas.Asimplermodelthatusesaconstantloadforeachcylinderandtheswiveldriveleadstoerroneousresults4.LoadSensingSystemExcavatorshavetypicallyoneDieselengine,twohydraulicmotorsandthreecylinders.Thereexistdifferenthydrauliccircuitstoprovidetheconsumerswiththerequiredhydraulicenergy.AtypicaldesignisaLoadSensingcircuitthatisenergyefficientanduserfriendly.Theideaistohaveaflowratecontrolsystemforthepumpsuchthatitdeliversexactlytheneededflowrate.Asasensorthepressuredropacrossanorificeisused.Thereferencevalueistheresistanceoftheorifice.Aschematicdrawingisshowninfigure4,agoodintroductiontothattopicisgiveninanon.1992.Thepumpcontrolvalvemaintainsapressureatthepumpportthatistypically15barhigherthanthepressureintheLSlineLoadSensingline.Ifthedirectionalvalveisclosedthepumphasthereforeastandbypressureof15bar.Ifitisopenthepumpdeliversaflowratethatleadstoapressuredropof15baracrossthatdirectionalvalve.NoteThedirectionalvalveisnotusedtothrottlethepumpflowbutasaflowmeterpressuredropthatisfedbackandasareferenceresistance.Thecircuitisenergyefficientbecausethepumpdeliversonlytheneededflowrate,thethrottlinglossesaresmallcomparedtoothercircuits.Ifmorethanonecylinderisusedthecircuitbecomesmorecomplicated,seefigure5.E.g.iftheboomrequiresapressureof100barandthebucketapressureof300barthepumppressuremustbeabove300barwhichwouldcauseanunwantedmovementoftheboomcylinder.Thereforecompensatorsareusedthatthrottletheoilflowandthusachieveapressuredropof15baracrosstheparticulardirectionalvalve.Thesecompensatorscanbeinstalledupstreamordownstreamofthedirectionalvalves.Anadditionalvalvereducesthenominalpressuredifferentialifthemaximumpumpflowrateorthemaximumpressureisreachedseee.g.Nikolaus1994.5.ModelofMechanicalPartInFigure6,aModelicaschematicofthemechanicalpartisshown.Thechaintrackisnotmodeled,i.e.,itisassumedthatthechaintrackdoesnotmove.Componentsrev1,...,rev4arethe4revolutejointstomovethepartsrelativetoeachother.Theiconswiththelongblacklinearevirtualrodsthatareusedtomarkspecificpointsonapart,especiallythemountingpointsofthehydrauliccylinders.Thelightbluespheresb2,b3,b4,b5arebodiesthathavemassandaninertiatensorandareusedtomodelthecorrespondingpropertiesoftheexcavatorparts.Thethreecomponentscyl1f,cyl2f,andcyl3farelineforcecomponentsthatdescribeaforceinteractionalongalinebetweentwoattachmentpoints.Thesmallgreensquaresatthesecomponentsrepresent1dimensionaltranslationalconnectorsfromtheModelica.Mechanics.Translationallibrary.Theyareusedtodefinethe1dimensionalforcelawactingbetweenthetwoattachmentpoints.Here,thehydrauliccylindersdescribedinthenextsectionaredirectlyattached.Thesmalltwospheresintheiconsofthecyl1f,cyl2f,cyl3fcomponentsindicatethatoptionallytwopointmassesaretaken

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