外文翻译--控制移动液压起重机.doc

翻译部分英文原文CONTROLOFMOBILEHYDRAULICCRANESMarcE.MNZERAalborgUniversityInstituteofEnergyTechnology,Pontoppidanstrde101DK-9220Aalborg,DenmarkThegoalofthethesisdescribedinthispaperistoimprovethecontrolofmobilehydrauliccranes.Thethesisissplitintofiveparts:arequirementsanalysis,ananalysisofthecurrentsystemsandtheirproblems,ananalysisofdifferentpossibilitiesforsystemtopologies,developmentofanewcontrolsystemforthenearfuturebasedonelectro-hydraulicseparatemeterin/separatemeteroutvalves,andfinallyananalysisofmoreadvancedandcomplexsolutionswhichcanbeappliedinthemoredistantfuture.Theworkofthethesiswillbedoneincoop-erationwithindustrysothethesiswillhavemoreofanindustrialfocusthanapurelytheoreticalfocus.Keywords:MobileHydraulicCranes,ControlStrategies,SeparateMeter-in/SeparateMeter-out.1INTRODUCTIONThegoalofthethesisdescribedinthispaperistoimprovethecontrolofmobilehydrauliccranes.Amobilehydrauliccranecanbethoughtofasalargeflexiblemechanicalstructurewhichismovedbysomesortofcontrolsystem.Thecontrolsystemtakesitsinputfromahumanoperatorandtranslatesthiscommandintothemotionofactuatorswhichmovethemechanicalstructure.Thedefinitionofthiscontrolsystemispurposelyleftvagueinordernottoimposeanycon-straintsonitsdesign.Thecontrolsystemconsistsofactuatorswhichmovethemechanicalstructure,ameansofcontrollingtheactuators,ameansofsupplyingpowertotheactuators,andawayofacceptinginputsfromtheoperator.Itisthiscontrolsystemwhichisthetargetofthisthesis.Thegoalistoanalyzetherequirementsmadeonthecontrolsystemandpresentguidelinesforthedesignofnewcontrolsystems.Thethesiswillbesplitintofiveparts:1.Analysisoftherequirementsofthecontrolsystem,fromtheperspectiveoftheopera-tor,themechanicalsystem,efficiency,stability,andsafetyrequirements.2.Analysisofcurrentcontrolsystemsandwhattheirproblemsare.3.Analysisofthedifferentoptionsforthecontrolsystem:differenttypesofactuators,differenttypesofcontrolstrategies,anddifferentwaysoforganizingcomponents.4.Presentationofanewtypeofcontrolsystem,whichiscommerciallyimplementable.Asystemthatwillmeettheneedsofindustryinthenearfuture.5.Analysisofmoreoptimizedsystems,withhigherperformance,betterefficiency,moreflexiblecontrol,etc.Thiswillbelesscommerciallyapplicablebutwillbeastartingpointformoreresearch.2SECTIONSOFTHETHESIS2.1RequirementsAnalysisoftheControlSystemBeforestartingdetailedworkondevelopingnewcontrolsystems,itisimportanttoanalyzewhattheexactdemandsareonthecontrolsystem.Thecontrolsystemisinfluencedbymanyfactors.Forexample:themechanicalstructureitiscontrolling,thehumanoperator,effi-ciency,stability,andindustryregulations.Industryregulationsarethefirstrequirementsthathavetobeaddressed.Thingslikehoseruptureprotectionandrunawayloadprotectionmakealotofdemandsonthecontrolsystem.Afterregulations,stabilityisthenextmostimportantrequirement；withoutstabilitythecon-trolsystemcantbeused.Oncestabilityhasbeenassured,theperformancerequirementsofthecontrolsystemhavetobeset.Theyaredeterminedbythemechanicalstructureofthecraneandthehumanoperator.Themechanicalstructureofamobilehydrauliccraneisaverylargeflexiblestructurewhichhasverylownaturalfrequencies.Topreventoscillationsitisnecessarytokeepthespeedofthecontrolsystembelowthisnaturalfrequencyortodevelopacontrolsystemwhichcanincreasethisfrequency.Thehumanoperatoralsoimposeslimitsonthecontrolsystem.Ifthecontrolsystemistooslowortoofastthenitisimpossibleforahumanoperatortogiveitproperinputs.Andfinally,oncetheregulationshavebeenmet,sta-bilityisassured,andtheperformanceisattherightlevel,thepowerefficiencyofthecontrolsystemhastobeoptimized.2.2AnalysisofCurrentControlSystemsBeforedesigninganewcontrolsystemitisgoodtoanalyzethecurrentcontrolsystemstofindoutwhattheirproblemsare.Currentcontrolsystemsaremainlyhydraulicandcansufferfromthreemainproblems:1.Instability2.Highcost3.Inefficiency2.2.1InstabilityInstabilityisaseriousproblemasitcancauseinjurytohumanoperatorsordamagetoequip-ment.Whenasystembecomesunstableitusuallystartstooscillateviolently.Toavoidinsta-bilityincurrentsystems,thedesignerseithersacrificecertainfunctionswhicharedesirable,oraddcomplexityandcost.Forexample,inthecraneshowninFigure1,itwouldbedesir-abletohavecontroloverthespeed.Butduetothesafetysystemthatcranesarerequiredtohave,standardspeedcontrolisnotstable.Toaddspeedcontrolrequiresamorecomplexandmoreexpensivemechanicalsystem.Theparametersofahydraulicsystem,suchastemperatureorloadforce,alsoaffectstability.Asystemthatisstablewithonesetofparametersmightbeunstablewithanotherset.Toensurestabilityovertheentireoperatingrangeofthesystem,performancemustsometimesbesacrificedatoneendoftheparameterrange.2.2.2HighcostCurrentsystemsarepurelyhydraulic-mechanical,soiftheuserwantsacertainfunction,theuserbuysacertainhydraulic-mechanicalcomponent.Becausemostusershavedifferentrequirements,therearemanydifferentvariationsofthesamebasiccomponent.Thismeansthatmanyspecializedcomponentsmustbemanufacturedratherthanonestandardproduct.Thisdrivesupthecostofcomponents.2.2.3InefficiencyOneformofinefficiencyincurrentsystemsisduetothelinkbetweentheflowsofthetwoportsofthecylinder.Thisisbecausemostvalvesuseasinglespooltocontroltheflowinbothports.Becauseofthislink,itisimpossibletosetthepressurelevelsinthetwosidesofthecylinderindependently.Therefore,theoutletsidewilldevelopabackpressurewhichactsinoppositiontothedirectionoftravel,whichincreasesthepressurerequiredontheinletsidetomaintainmotion.Sincetheforcegeneratedbytheactuatorisproportionaltothepressuredif-ferencebetweenthetwosides,theactualpressuresinthecylinderdontaffecttheactionofthecylinder.Forexample,theactionofthecylinderfor0psi/600psiwouldbethesameas1000psi/1600psi.However,inthesecondcase,thepowersupplywouldhavetosupplymuchmorepower.Thisextrapoweriswasted.2.3DifferentOptionsforControlSystemsCurrentcontrolsystemsusehydraulicactuatorswithdirectional/proportionalvalvestocontrolthemovement.Howevertherearemanydifferentoptionsforcontrollingacylinder.Optionsrangefromnewhighperformanceelectro-hydraulicvalves,toseparatemeterin/separatemeterout(SMISMO)valves,tohydraulicbussystems,tointelligentactuatorswithbuiltinpowersupplies,topumpbasedcontrolstrategies.Thesesystemsallhaveadvantagesanddis-advantageswhichneedtobeanalyzedifthemostoptimumsolutionistobechosen.2.4NearFutureSolutionItisexpectedthatevenifitisproventhatacompletelynewsystemtopologyistheoptimumconfiguration,thecranemanufacturersandcomponentmanufacturerswillnotacceptthenewtechnologyovernight.Thiswillmostlikelytaketime,soaninterimsolutionwillbedevel-oped.ThissolutionwillbemadeupofmicrocomputercontrolledSeparateMeterIn/SeparateMeterOut(SMISMO)valves(Elfving,Palmberg1997；Jansson,Palmberg,1990；Mattila,Virvalo1997).SMISMOvalveswillmakeitpossibletoimplementnewcontrolstrategieswhicharemoreefficientandstable.Themicrocomputerwillmakeitpossibletointroduceflexibilitytovalves.Variantscanbeprogrammedinsoftware.Thiseliminatestheneedtomanufacturehundredsofdifferentvariants.Thecranemanufacturerwillbeabletochoosetheexactfunctionshewantsinhisvalve,whilethecomponentmanufacturerwillhavetomanu-factureonlyonevalve.Thiswilllowerthecost,eventhoughtheperformancewillhaveincreased.2.5AnalysisofHigherPerformanceSolutionsThisanalysiswilldependontheresultsoftheanalysisofdifferenttopologies.Ifitisshownthatpumpbasedcontrolistobethewayofthefutureforexample,thenanalysiswillbeper-formedinthisarea.Anotherareawhichwillalsobeexplored,istoolpositioncontrol.3LABORATORYFACILITIESAsthefocusofthisthesisisond