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外文翻译--电液比例控制的双缸液压升降机.doc

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外文翻译--电液比例控制的双缸液压升降机.doc

大学毕业设计(外文翻译)ElectrohydraulicproportionalcontroloftwincylinderhydraulicelevatorsAbstractThelargesizeofthecabofanelectrohydraulicelevatornecessitatesthearrangementoftwocylinderslocatedsymmetricallyonbothsidesofthecab.Thispaperreportsthedesignofanelectrohydraulicsystemwhichconsistsofthreeflowcontrolproportionalvalves.Speedregulationofthecabandsynchronizationcontrolofthetwocylindersarealsopresented.ApseudoderivativefeedbackPDFcontrollerisappliedtoobtainavelocitypatternofthecabthatprovestobeclosetothegivenone.Thenonsynchronouserrorofthetwocylindersiskeptwithin±2mmwithaconstrainedstepproportionalderivativePDcontroller.Asolenoidactuatednonreturnvalve,i.e.ahydrauliclock,isalsodevelopedtopreventcabsinkingandalloweasyinversefluidflow.KeywordsHydraulicelevatorVelocitytrackingSynchronizationHydrauliclock1.IntroductionThemodernhydraulicelevatoriscurrentlyanexcellentandlowcostsolutiontotheproblemofverticaltransportationinlowormidrisebuildings,andinthoseapplicationsrequiringverylargecapacities,slowspeedsandshorttraveldistances.Theseincludescenicelevatorsinsuperstoresorhistoricalbuildings,stageelevators,shipelevatorsandelevatorsforthedisabled,etc.Inmostcases,hydraulicelevatorscanbeadaptedtoarchitecturaldesignrequirementswithoutcompromisingenergysavingandefficiencyrequirements.Inaddition,theuseoffireresistantfluidmakesthehydraulicelevatorasuitablechoicewhenelevatorshavetooperatenearhazardssuchasfurnacesoropenfires.Hydraulicdrivesareusedpreferablyinelevatorswherelargepayloadsneedtobecarried,suchasforcarelevatorsormarineelevators.Inheavyloadcases,anelevatorcabusuallyhasdirectlyactingorsideactinghydrauliccylinders.Thedirectactingarrangementinvolvesadeeppit,substantialriskofcorrosionofthe大学毕业设计(外文翻译)buriedcylindersandthedifficultyofreplacingfailedcylinderparts.Thus,inmanysituationsthesideactinghydrauliccylinderispreferred,despitethefactthatitprobablyincreasesrailwearduetoinsufficientcabstiffness.Intheextremeconditions,i.e.whenlargecabsizesandunevenpayloadsareinvolved,thecabsflexibilitymayevencausetheguideshoestosticktotherails,whichisverydangerous.Therefore,insuchcases,afeasiblesolutionistoarrangetwodirectlyactingcylinderssymmetricallyoneachsideofthecab,asshowninFig.1.Itshouldbenotedthatsmoothrunningcannotbeignoredbecausepeoplemaybepartofthepayloadsthataccompanythefreight.Themajorissuewhendesigningacontrolsystemistoensurethesynchronousmotionofthetwocylinders.Theerrorduetothenonsynchronousmotionofthetwocylinderscaused,byanunevenloadunderequalpressurecontrol,whichisgenerallyusedforelevatorcontrolwithmultiplehydrauliccylinders,isschematicallyshowninFig.2.ItisobviousfromFig.2thatequalpressurecontrolisnotsuitableforasynchronizedhydraulicelevator.Whenthepayloadislocatedontherightsideofthecab,theleftcylinder,withalighterload,willmoveupwardfasterthantherightone.Thespeeddisparitybetweenthetwocylinderswillnotceaseuntilthereactionforcesactuatedbytherailsonboththelowerleftandupperrightguideshoesattachedonthecabarebalancedbythehydraulicforcedifference.Thenonsynchronisationofthetwocylinderscanonlybereducedbyflowcontrol,i.e.byensuringthatthefluidflowsintothetwocylindersperunittimearethesame.大学毕业设计(外文翻译)Thispaperpresentsanelectrohydraulicsystemforthecontrolofanelevatorwithtwincylindersthatarelocatedoneachsideoftheelevatorcab.Thedesignedsystemconsistsofthreeflowcontrolproportionalvalves.APDFcontrollerisappliedtovelocitycontrolwhereasaconstrainedstepPDcontrollerguaranteestheminimumnonsynchronouserrorbetweenthemotionoftwocylinders.Thedesignofanewlydevelopedsolenoidactuatednonreturnvalvei.e.ahydrauliclockisalsopresentedinthispaper.Inthisproject,experimentsareconductedwithanormalsizepassengercabinsteadofbuildinganewlargesizecabduetocostlimitations.Inordertoachievetheflexibleconditionofalargercab,thedistancebetweentherailsandtheircorrespondingguideshoesinthesidedirectionisextendedsothatthecabhasnoconstraintsinthisdirection.Meanwhile,intheforwardandbackwarddirection,thecabisconstrainedbytherailsjustlikeageneralpassengerelevator.Thesynchronousmotioncontrolofthetwocylindersinsuchanassemblyisanalogoustoandevenmoredifficultthanthatofalargercabwithnormalconstraints.2.ElectrohydrauliccontrolsystemdesignTherearetwodifferentfluidpowersystemsgenerallyusedinhydraulicelevators.theflowrestrictionspeedregulationsystemandvariabledeliveryspeedregulationsystem.Intheformersystem,thepumprunsataconstantspeedandthevalveregulatesthespeedofthecylinderinboththeupwardanddownwarddirections.In大学毕业设计(外文翻译)thelattercase,thecabisoperatedbyvaryingthespeedofthepump,whichisdrivenbyaspeedcontrolledinductionmotor.Thehydraulicsystememployedinthistwincylinderelevatorworksaccordingtotheflowrestrictedspeedregulationprinciple,inwhichthefluidflowintoandoutofthetwocylindersiscontrolledbyappropriatevalvesettings,withtheoutputofthepumpkeptatafixedlevel.Inthissystem,therearethreeflowcontrolproportionalvalves57asshowninFig.3.Flowcontrolproportionalvalvesactasthrottlevalvesthatrestrictthefluidflowtoasingledirection.Theycangiveasmoothsteplessvariationofflowcontrolfromnearzerouptothevalvesmaximumcapacity.Theflowratethroughvalve5remainsalmostinvariablebecauseacombinationhydrostatmaintainsaconstantlevelofpressuredifferenceacrosstheproportionalvalve,irrespectiveofsystemorloadpressurechanges.Inthecaseofthrottlevalves,6and7inFig.3,theirfluidflowswillchangewithsystemorloadpressurechanges.Valve5,herecalledvelocityvalve,controlsthevelocityoftheelevator.Theupwardmotionofthecabisdrivenbyfixeddisplacementpistonpump1.Whenmotor2startstowork,

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