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）Electro-hydraulicproportionalcontroloftwin-cylinderhydraulicelevatorsAbstractThelargesizeofthecabofanelectro-hydraulicelevatornecessitatesthearrangementoftwocylinderslocatedsymmetricallyonbothsidesofthecab.Thispaperreportsthedesignofanelectrohydraulicsystemwhichconsistsofthreeflow-controlproportionalvalves.Speedregulationofthecabandsynchronizationcontrolofthetwocylindersarealsopresented.Apseudo-derivativefeedback(PDF)controllerisappliedtoobtainavelocitypatternofthecabthatprovestobeclosetothegivenone.Thenon-synchronouserrorofthetwocylindersiskeptwithin2mmwithaconstrainedstepproportional-derivative(PD)controller.Asolenoidactuatednon-returnvalve,i.e.ahydrauliclock,isalsodevelopedtopreventcabsinkingandalloweasyinverse-fluidflow.Keywords:Hydraulicelevator；Velocitytracking；Synchronization；Hydrauliclock1.IntroductionThemodernhydraulicelevatoriscurrentlyanexcellentandlow-costsolutiontotheproblemofverticaltransportationinlowormid-risebuildings,andinthoseapplicationsrequiringverylargecapacities,slowspeedsandshorttraveldistances.Theseincludescenicelevatorsinsuperstoresorhistoricalbuildings,stageelevators,shipelevatorsandelevatorsforthedisabled,etc.Inmostcases,hydraulicelevatorscanbeadaptedtoarchitecturaldesignrequirementswithoutcompromisingenergysavingandefficiencyrequirements.Inaddition,theuseoffire-resistantfluidmakesthehydraulicelevatorasuitablechoicewhenelevatorshavetooperatenearhazardssuchasfurnacesoropenfires.Hydraulicdrivesareusedpreferablyinelevatorswherelargepayloadsneedtobecarried,suchasforcarelevatorsormarineelevators.Inheavyloadcases,anelevatorcabusuallyhasdirectlyactingorside-actinghydrauliccylinders.Thedirect-actingarrangementinvolvesadeeppit,substantialriskofcorrosionofthe大学毕业设计（外文翻译）buriedcylindersandthedifficultyofreplacingfailedcylinderparts.Thus,inmanysituationstheside-actinghydrauliccylinderispreferred,despitethefactthatitprobablyincreasesrailwearduetoinsufficientcabstiffness.Intheextremeconditions,i.e.whenlargecabsizesandunevenpayloadsareinvolved,thecabsflexibilitymayevencausetheguideshoestosticktotherails,whichisverydangerous.Therefore,insuchcases,afeasiblesolutionistoarrangetwodirectlyactingcylinderssymmetricallyoneachsideofthecab,asshowninFig.1.Itshouldbenotedthatsmoothrunningcannotbeignoredbecausepeoplemaybepartofthepayloadsthataccompanythefreight.Themajorissuewhendesigningacontrolsystemistoensurethesynchronousmotionofthetwocylinders.Theerrorduetothenon-synchronousmotionofthetwocylinderscaused,byanunevenloadunderequalpressure-control,whichisgenerallyusedforelevatorcontrolwithmultiplehydrauliccylinders,isschematicallyshowninFig.2.ItisobviousfromFig.2thatequalpressure-controlisnotsuitableforasynchronizedhydraulicelevator.Whenthepayloadislocatedontherightsideofthecab,theleftcylinder,withalighterload,willmoveupwardfasterthantherightone.Thespeeddisparitybetweenthetwocylinderswillnotceaseuntilthereactionforcesactuatedbytherailsonboththelowerleftandupperrightguideshoesattachedonthecabarebalancedbythehydraulicforcedifference.Thenon-synchronisationofthetwocylinderscanonlybereducedbyflowcontrol,i.e.byensuringthatthefluidflowsintothetwocylindersperunittimearethesame.大学毕业设计（外文翻译）Thispaperpresentsanelectro-hydraulicsystemforthecontrolofanelevatorwithtwincylindersthatarelocatedoneachsideoftheelevatorcab.Thedesignedsystemconsistsofthreeflow-controlproportionalvalves.APDFcontrollerisappliedtovelocitycontrolwhereasaconstrainedstepPDcontrollerguaranteestheminimumnon-synchronouserrorbetweenthemotionoftwocylinders.Thedesignofanewlydevelopedsolenoid-actuatednon-returnvalvei.e.ahydrauliclockisalsopresentedinthispaper.Inthisproject,experimentsareconductedwithanormalsizepassengercabinsteadofbuildinganewlarge-sizecabduetocostlimitations.Inordertoachievetheflexibleconditionofalargercab,thedistancebetweentherailsandtheircorrespondingguideshoesinthesidedirectionisextendedsothatthecabhasnoconstraintsinthisdirection.Meanwhile,intheforwardandbackwarddirection,thecabisconstrainedbytherailsjustlikeageneralpassengerelevator.Thesynchronousmotioncontrolofthetwocylindersinsuchanassemblyisanalogoustoandevenmoredifficultthanthatofalargercabwithnormalconstraints.2.Electro-hydrauliccontrolsystemdesignTherearetwodifferentfluidpowersystemsgenerallyusedinhydraulicelevators.theflow-restrictionspeed-regulationsystemandvariable-deliveryspeed-regulationsystem.Intheformersystem,thepumprunsataconstantspeedandthevalveregulatesthespeedofthecylinderinboththeupwardanddownwarddirections.In大学毕业设计（外文翻译）thelattercase,thecabisoperatedbyvaryingthespeedofthepump,whichisdrivenbyaspeed-controlledinductionmotor.Thehydraulicsystememployedinthistwin-cylinderelevatorworksaccordingtotheflow-restrictedspeedregulationprinciple,inwhichthefluidflowintoandoutofthetwocylindersiscontrolledbyappropriatevalvesettings,withtheoutputofthepumpkeptatafixedlevel.Inthissystem,therearethreeflow-controlproportionalvalves-5-7asshowninFig.3.Flow-controlproportionalvalvesactasthrottlevalvesthatrestrictthefluidflowtoasingledirection.Theycangiveasmoothsteplessvariationofflowcontrolfromnearzerouptothevalvesmaximumcapacity.Theflowratethroughvalve5remainsalmostinvariablebecauseacombinationhydrostatmaintainsaconstantlevelofpressuredifferenceacrosstheproportionalvalve,irrespectiveof