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外文翻译--控制移动液压起重机.doc

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外文翻译--控制移动液压起重机.doc

翻译部分英文原文CONTROLOFMOBILEHYDRAULICCRANESMarcE.MÜNZERAalborgUniversityInstituteofEnergyTechnology,Pontoppidanstræde101DK9220Aalborg,DenmarkThegoalofthethesisdescribedinthispaperistoimprovethecontrolofmobilehydrauliccranes.Thethesisissplitintofivepartsarequirementsanalysis,ananalysisofthecurrentsystemsandtheirproblems,ananalysisofdifferentpossibilitiesforsystemtopologies,developmentofanewcontrolsystemforthenearfuturebasedonelectrohydraulicseparatemeterin/separatemeteroutvalves,andfinallyananalysisofmoreadvancedandcomplexsolutionswhichcanbeappliedinthemoredistantfuture.Theworkofthethesiswillbedoneincooperationwithindustrysothethesiswillhavemoreofanindustrialfocusthanapurelytheoreticalfocus.KeywordsMobileHydraulicCranes,ControlStrategies,SeparateMeterin/SeparateMeterout.1INTRODUCTIONThegoalofthethesisdescribedinthispaperistoimprovethecontrolofmobilehydrauliccranes.Amobilehydrauliccranecanbethoughtofasalargeflexiblemechanicalstructurewhichismovedbysomesortofcontrolsystem.Thecontrolsystemtakesitsinputfromahumanoperatorandtranslatesthiscommandintothemotionofactuatorswhichmovethemechanicalstructure.Thedefinitionofthiscontrolsystemispurposelyleftvagueinordernottoimposeanyconstraintsonitsdesign.Thecontrolsystemconsistsofactuatorswhichmovethemechanicalstructure,ameansofcontrollingtheactuators,ameansofsupplyingpowertotheactuators,andawayofacceptinginputsfromtheoperator.Itisthiscontrolsystemwhichisthetargetofthisthesis.Thegoalistoanalyzetherequirementsmadeonthecontrolsystemandpresentguidelinesforthedesignofnewcontrolsystems.Thethesiswillbesplitintofiveparts1.Analysisoftherequirementsofthecontrolsystem,fromtheperspectiveoftheoperator,themechanicalsystem,efficiency,stability,andsafetyrequirements.2.Analysisofcurrentcontrolsystemsandwhattheirproblemsare.3.Analysisofthedifferentoptionsforthecontrolsystemdifferenttypesofactuators,differenttypesofcontrolstrategies,anddifferentwaysoforganizingcomponents.4.Presentationofanewtypeofcontrolsystem,whichiscommerciallyimplementable.Asystemthatwillmeettheneedsofindustryinthenearfuture.5.Analysisofmoreoptimizedsystems,withhigherperformance,betterefficiency,moreflexiblecontrol,etc.Thiswillbelesscommerciallyapplicablebutwillbeastartingpointformoreresearch.2SECTIONSOFTHETHESIS2.1RequirementsAnalysisoftheControlSystemBeforestartingdetailedworkondevelopingnewcontrolsystems,itisimportanttoanalyzewhattheexactdemandsareonthecontrolsystem.Thecontrolsystemisinfluencedbymanyfactors.Forexamplethemechanicalstructureitiscontrolling,thehumanoperator,efficiency,stability,andindustryregulations.Industryregulationsarethefirstrequirementsthathavetobeaddressed.Thingslikehoseruptureprotectionandrunawayloadprotectionmakealotofdemandsonthecontrolsystem.Afterregulations,stabilityisthenextmostimportantrequirementwithoutstabilitythecontrolsystemcantbeused.Oncestabilityhasbeenassured,theperformancerequirementsofthecontrolsystemhavetobeset.Theyaredeterminedbythemechanicalstructureofthecraneandthehumanoperator.Themechanicalstructureofamobilehydrauliccraneisaverylargeflexiblestructurewhichhasverylownaturalfrequencies.Topreventoscillationsitisnecessarytokeepthespeedofthecontrolsystembelowthisnaturalfrequencyortodevelopacontrolsystemwhichcanincreasethisfrequency.Thehumanoperatoralsoimposeslimitsonthecontrolsystem.Ifthecontrolsystemistooslowortoofastthenitisimpossibleforahumanoperatortogiveitproperinputs.Andfinally,oncetheregulationshavebeenmet,stabilityisassured,andtheperformanceisattherightlevel,thepowerefficiencyofthecontrolsystemhastobeoptimized.2.2AnalysisofCurrentControlSystemsBeforedesigninganewcontrolsystemitisgoodtoanalyzethecurrentcontrolsystemstofindoutwhattheirproblemsare.Currentcontrolsystemsaremainlyhydraulicandcansufferfromthreemainproblems1.Instability2.Highcost3.Inefficiency2.2.1InstabilityInstabilityisaseriousproblemasitcancauseinjurytohumanoperatorsordamagetoequipment.Whenasystembecomesunstableitusuallystartstooscillateviolently.Toavoidinstabilityincurrentsystems,thedesignerseithersacrificecertainfunctionswhicharedesirable,oraddcomplexityandcost.Forexample,inthecraneshowninFigure1,itwouldbedesirabletohavecontroloverthespeed.Butduetothesafetysystemthatcranesarerequiredtohave,standardspeedcontrolisnotstable.Toaddspeedcontrolrequiresamorecomplexandmoreexpensivemechanicalsystem.Theparametersofahydraulicsystem,suchastemperatureorloadforce,alsoaffectstability.Asystemthatisstablewithonesetofparametersmightbeunstablewithanotherset.Toensurestabilityovertheentireoperatingrangeofthesystem,performancemustsometimesbesacrificedatoneendoftheparameterrange.2.2.2HighcostCurrentsystemsarepurelyhydraulicmechanical,soiftheuserwantsacertainfunction,theuserbuysacertainhydraulicmechanicalcomponent.Becausemostusershavedifferentrequirements,therearemanydifferentvariationsofthesamebasiccomponent.Thismeansthatmanyspecializedcomponentsmustbemanufacturedratherthanonestandardproduct.Thisdrivesupthecostofcomponents.2.2.3InefficiencyOneformofinefficiencyincurrentsystemsisduetothelinkbetweentheflowsofthetwoportsofthecylinder.Thisisbecausemostvalvesuseasinglespooltocontroltheflowinbothports.Becauseofthislink,itisimpossibletosetthepressurelevelsinthetwosidesofthecylinderindependently.Therefore,theoutletsidewilldevelopabackpressurewhichactsinoppositiontothedirectionoftravel,whichincreasesthepressurerequiredontheinletsidetomaintainmotion.Sincetheforcegeneratedbytheactuatorisproportionaltothepressuredifferencebetweenthetwosides,theactualpressuresinthecylinderdontaffecttheactionofthecylinder.Forexample,theactionofthecylinderfor0psi/600psiwouldbethesameas1000psi/1600psi.However,inthesecondcase,thepowersupplywouldhavetosupplymuchmorepower.Thisextrapoweriswasted.2.3DifferentOptionsforControlSystemsCurrentcontrolsystemsusehydraulicactuatorswithdirectional/proportionalvalvestocontrolthemovement.Howevertherearemanydifferentoptionsforcontrollingacylinder.Optionsrangefromnewhighperformanceelectrohydraulicvalves,toseparatemeterin/separatemeteroutSMISMOvalves,tohydraulicbussystems,tointelligentactuatorswithbuiltinpowersupplies,topumpbasedcontrolstrategies.Thesesystemsallhaveadvantagesanddisadvantageswhichneedtobeanalyzedifthemostoptimumsolutionistobechosen.2.4NearFutureSolutionItisexpectedthatevenifitisproventhatacompletelynewsystemtopologyistheoptimumconfiguration,thecranemanufacturersandcomponentmanufacturerswillnotacceptthenewtechnologyovernight.Thiswillmostlikelytaketime,soaninterimsolutionwillbedeveloped.ThissolutionwillbemadeupofmicrocomputercontrolledSeparateMeterIn/SeparateMeterOutSMISMOvalvesElfving,Palmberg1997Jansson,Palmberg,1990Mattila,Virvalo1997.SMISMOvalveswillmakeitpossibletoimplementnewcontrolstrategieswhicharemoreefficientandstable.Themicrocomputerwillmakeitpossibletointroduceflexibilitytovalves.Variantscanbeprogrammedinsoftware.Thiseliminatestheneedtomanufacturehundredsofdifferentvariants.Thecranemanufacturerwillbeabletochoosetheexactfunctionshewantsinhisvalve,whilethecomponentmanufacturerwillhavetomanufactureonlyonevalve.Thiswilllowerthecost,eventhoughtheperformancewillhaveincreased.2.5AnalysisofHigherPerformanceSolutionsThisanalysiswilldependontheresultsoftheanalysisofdifferenttopologies.Ifitisshownthatpumpbasedcontrolistobethewayofthefutureforexample,thenanalysiswillbeperformedinthisarea.Anotherareawhichwillalsobeexplored,istoolpositioncontrol.3LABORATORYFACILITIESAsthefocusofthisthesisisondevelopingcontrolstrategiesthatcanbeimplementedoncommercialmachinery,muchemphasiswillbeplacedonexperimentalresults.Experimentalresultswillbeobtainedfromtwosystems.Thefirst,asimpleonedegreeoffreedomcrane,wasdesignedasanexperimentalplatform.ThesecondisarealcranewhichwasdonatedtotheUniversitybyHøjbjergMaskinfabrikHMFaDanishcranemanufacturer.RefertoFigure1.Figure1ExperimentalSystemsinLaboratory.LeftOneDOFcranemodel.RightRealMobileHydraulicCraneAstherearecurrentlynocommerciallyavailableseparatemeterin/separatemeteroutvalves,twoseparatevalveswillbeusedinstead.AsamplecircuitofonecylinderisshowninFigure2.Thecontrolalgorithmswhichcontrolthevalves,willbeprogrammedonaDigitalSignalProcessorDSP/Pentiumdualprocessorsystem.TheDSPwillrunthecontrolcodeandthePentiumwilldodiagnosticsandprovideagraphicaluserinterface.

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