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外文翻译--组合机床设计的模块化建模方法.doc外文翻译--组合机床设计的模块化建模方法.doc -- 5 元

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附录外文文献AMODULARMODELINGAPPROACHFORTHEDESIGNOFRECONFIGURABLEMACHINETOOLSTulgaErsalGraduateStudentResearchAssistantDepartmentofMechanicalEngineeringUniversityofMichigan,AnnArbortersalumich.eduJeffreyL.SteinProfessorDepartmentofMechanicalEngineeringUniversityofMichigan,AnnArborsteinumich.eduLoucasS.LoucaLecturerDepartmentofMechanicalandManufacturingEngineeringUniversityofCypruslsloucaucy.ac.cyABSTRACTAnewgenerationofmachinetoolscalledReconfigurableMachineToolsRMTsisemergingasameansforindustrytobemorecompetitiveinamarketthatexperiencesfrequentchangesindemand.Newmethodologiesandtoolsarenecessaryfortheefficientdesignofthesemachinetools.ItisthepurposeofthispapertopresentamodularapproachforRMTservoaxismodeling,whichispartofalargerefforttodevelopanintegratedRMTdesignandcontrolenvironment.Thecomponentsofthemachinetoolaremodeledinamodularway,suchthatthemodelofanygivenconfigurationcanbeobtainedbyassemblingthecorrespondingcomponentmodelstogetherbasedonthetopologyofthemachine.Thecomponentmodelsarebuiltusingthebondgraphlanguagethatenablesthestraightforwarddevelopmentoftherequiredmodularlibrary.Thesemachinetoolmodelscanbeusedfortheevaluation,designandcontroloftheRMTservoaxes.Theapproachisdemonstratedthroughexamples,andthebenefitsanddrawbacksofthisapproacharediscussed.TheresultsshowthattheproposedapproachisapromisingsteptowardsanautomatedandintegratedRMTdesignenvironment,andthechallengesinordertocompletethisgoalarediscussed.INTRODUCTIONTheevergrowingcompetitionforcesmanufacturerstorespondmorequicklytochangesindemand.Asaresult,manufacturershavetodealwithshortproductlifecycles,shortrampuptimesandfrequentchangesinproductmixandvolumes,withoutcompromisingproductqualityandcost.Beingtheheartofamanufacturingsystem,improvedmachinetoolsholdthekeyinmeetingtheabovementionedrequirements.Theshortcomingsofconventionalmachinetools,whichcanbeclassifiedasdedicatedandflexible,arebeingfeltmoretodaythaninthepastWiththeirdesignfocusbeingasinglepart,dedicatedmachineslacktheflexibilityandscalabilitythattheflexiblemachinesoffer.Ontheotherhand,flexiblemachinescannotachievetherobustness,thecosteffectivenessandthethroughputlevelsofdedicatedmachines1.AnewgenerationofmachinetoolsisbeingdevelopedintheEngineeringResearchCenterforReconfigurableManufacturingSystemsattheUniversityofMichigan,AnnArbor,aspartofanefforttoovercometheinsufficienciesofcurrentmanufacturingsystems.ThesemachinetoolsarecalledReconfigurableMachineToolsRMTs2,andtheycombinetheadvantagesoftheirdedicatedandflexiblecounterparts.Theyaredesignedaroundapartfamilyandtheirstructure,intermsofbothhardwareandsoftware,canbechangedquicklyandcosteffectivelytoachievetheexactfunctionalityandcapacitydesired3.Containingseveralconfigurationstoprovidetheneededflexibilityandscalability,RMTsintrinsicallyleadtomorecomplexmachinetooldesignproblems.MethodologiesandtoolsthatwouldhelpfacilitatethedesignofRMTscouldhighlybenefitandencouragetheemploymentofreconfigurablemanufacturingsystems46.OneimportantaspectoftheRMTdesignproblemisdevelopingdynamicmodelsforthedesign,evaluationandcontrolofservoaxes.WhatmakestheproblemofmodelingRMTsuniqueisthateventhoughthereisasinglemachinetool,thereexistseveralconfigurations,whichseparatemodelshavetobedevelopedfor.Developingdynamicmodelsforallpossibleconfigurationscouldbeacumbersomeandtimeconsumingtaskifadhocmethodsareutilized.Moreover,withoutasystematicmethodologymodelingwouldrequirealotofexpertiseandwouldbepronetoerrors,whichwoulddegradetheefficiencyofusingmodelsinthedesign.InthispaperwepresentamethodologythatcouldhelpmaketheRMTmodelingtasklesstimedemanding,lesserrorproneandlesschallenging.ThekeyideaofthismethodologyistotakeadvantageofthemodularstructureoftheRMTsandadoptmodularmodelingconceptsintotheRMTmodelingmethodology.First,thephysicalcomponentsofanRMTaremodeledinamodularwayusingthebondgraphmodelingtool7.Thebondgraphmodelisencapsulatedinaschematicrepresentationwithdefinedconnectionports.Then,theschematiccomponentmodelsareassembledbyfollowingthetopologyofagivenconfigurationtoobtainthemodeloftheconfiguration.Theconfigurationmodelcanbeeasilyintegratedwiththemodulesofnonenergeticcomponentssuchasinterpolatorsandcontrollers,whichcanbeconvenientlyrepresentedwithblockdiagramshoweverthisisbeyondthescopeofthispaper.BACKGROUNDTheRMTconceptwasintroducedbyKorenandKota2,andsincetheirintroduction,thedesignofRMTshasbeenanactiveresearcharea.MethodologiesandtoolsfordesigningRMTs4aswellasevaluatingstructuralstiffnesses5andtooltiperrors6ofdesignalternativeshavebeendeveloped.However,theproblemofdevelopingasystemlevelmodelingmethodologyforRTMshasnotbeenaddressedyet.Traditionally,machinetoolmodelsdepictthemachinetoolasagroupofservomotorandfeeddriveassembliesthataremodeledasfirstorsecondordersystems8,9.ChenandTlusty,however,showedthatthestructuraldynamicsofthefeeddrivecouldaffectthesystemperformanceoncehighspeedmachinetoolsareconsidered10.Manyresearchersidentifiedthenecessitytousehigherordermodelsforhighspeedmachinetoolstocopewithstructuraldynamicsinordertobeabletodesignthecontrolsystemsuccessfully1113.Thesepublicationsclearlyindicatethatmodelingamachinetoolisnotatrivialtaskandcaremustbetakenwhendecidingonthecomplexityofthemodel,buttheydonotprovideasystematicwayofmodelingand,therefore,remainapplicationspecificapproaches.Therehavebeenresearcheffortstohelpthedesignandcontrolofmachinetoolfeeddrivesbyautomaticallyprovidingsimulationmodels.WilsonandSteindevelopedasoftwareprogramcalledModelBuildingAssistanttoautomaticallysynthesizeaminimumordermodelofthemachinetooldrivesystemforagivenfrequencyrangeofinterestFROI14.Thecomplexityofthemodel,whichincludesaflywheel,atorsionalshaft,aballscrew,aballnut,aDCmotor,atorsionalcoupling,abeltdriveandagearpairascomponents,isautomaticallyincreaseduntiltheeigenvaluesofthesystemfallbeyondthespecifiedFROI.Thisworkwasaproofofconceptforamodeldeductionalgorithmandcannotbeappliedtoanyrealmachinetoolsystem.However,suchalgorithmcanbeusedtodeterminetheappropriatemodelcomplexityafterthedevelopmentofthesystemmodel.Gautieretal.havedevelopedasoftwarepackagecalledSICOMATSimulationandControlanalysisofMachineToolswhichhelpswiththemodeling,simulation,modalanalysisandcontrollertuningofoneortwodecoupledortwocoupledmachinetoolaxes15.Theirmodelsdescribethedynamicsofthemechanicalsystembyanumberofmassesandsprings.Thisworkmakesthemodelingofamachinetoolprocessmoresystematic,andisthereforeavaluabletooltothemodelingengineerhowever,itlacksthegenerality,modularityandflexibilitythattheRMTdesignmethodologydemands.TheRMTmodelingmethodologyFigure1showstheenvisionedRMTmodelingenvironment.ItisdesiredtoautomatethetaskofRMTmodeling,wherethemodelofagivenRMTconfigurationisautomaticallyassembledfromalibraryofmodularcomponentmodels.Thisway,allthecandidatedesigns,whicharegeneratedeithermanuallyorautomatically4,canbemodeledquicklyandthemodelscanbeusedtoevaluatethecandidatesintermsoftheirservoaxisdynamicperformanceandhelpwiththeirdesign.AsFigure1alsoimplies,themodularcomponentmodellibraryisakeypartfortheautomatedRMTmodelingenvironment.Therefore,thefirststepoftheproposedmethodologyistodevelopmodularmodelsforthecomponentsthatareusedtogeneratetheRMTconfigurations.Thispaperputstheemphasisonmechanicalpartsanddiscussestheirmodelinginamodularway,becausetheenergyinteractionbetweenthemechanicalcomponentsmakestheirmodularmodelingmoreintriguing.Modularmodelingofcomponentsthatonlyexchangesignals,e.g.interpolatorsandcontrollers,presentsarelativelysimplerproblemandarenotdiscussedhere.Topromotemodularityandtobeabletodealwiththeenergyinteractionsbetweenthecomponentsandtheirenvironmentrathereasily,bondgraphsareutilizedasthemodelinglanguage.Bondgraphsprovideapowerbasedgraphicalrepresentationofaphysicalsystem.Moreover,bondgraphsdescribedifferentenergydomainsinaunifiedway,whichisarelevantadvantageforRMTmodeling,sincetheirservoaxesmayincludecomponentsfromdifferentenergydomains,suchasmechanical,electricalorhydraulic.Bondgraphsareonlyonelevelinthehierarchyofmodelrepresentationsusedinthiswork.Underneaththebondgraphlevelthemathematicalequationsrepresentthephysicalphenomenacapturedbythebondgraphandthismathematicalrepresentationisthelowestlevelinthehierarchy.Inthehighestlevelbondgraphsareencapsulatedinaschematicrepresentation,whichnotonlyallowsforacompactrepresentation,butalsoshowstheconnectionportswherethemodelcaninteractwithitsenvironment.Figure2illustratesthishierarchyofmodelrepresentations.Inthispaperallthemodelsareshownintheschematiclevel,becausethegoalofthispaperisnottodiscusstheirderivation,butrathertoshowwhatcanbedoneoncethosemodelsareobtained.Adetaileddescriptionofthemodelsusedinthispapercanbefoundin16.Inordertobeabletocopewithanyspatialmotionthatthemechanicalcomponentsmaygothroughindifferentconfigurations,modelsthatcapturethethreedimensionaldynamicsareused.Moreover,theinitialassumptionismadethatinthemechanicaldomainallcomponentscanbeadequatelyrepresentedasrigidbodies.Figure3showstheschematicrepresentationofagenericrigidbodywithNconnectionports,whichisoneofthemainmodelmodulesinthelibrary.Theportscorrespondtopointsofinterestontherigidbody,wherethephysicalinteractionswiththeenvironmentoccur.Bondslineswithhalfarrowsareusedtoindicatethataportisapowerport,i.e.thebodycanexchangeenergywithitsenvironmentthroughthoseports,whereasactivebondslineswithfullarrowsindicatesignalports,i.e.onlyinformationistransferredthroughtheseports.Themodellibraryalsocontainsthreedimensionaljointmodelsthatcanbeusedtodescribetherelativemotionsbetweenthecomponentmodels.Thesejointmodelsarealsodevelopedinamodularwaywithports,wheretheycanbeconnectedtoothermodelmodules.Thelibraryofferstwowaystoexpresstheconstraints1stiffspringsanddamperscanbeusedtoimplementmorerealisticconstraintsortoapproximateidealconstraints2Lagrangemultiplierscanbeintroducedtoexpresstheconstraintsideally.Foradiscussionofjointmodelsthereaderisalsoreferredto16.Oncethemodellibraryispopulatedwithsomebasicmodularrigidbodyandjointmodels,themodelingprocedurecanbecarriedoutasfollowsTheRMTcomponentsarebrokendownintosubcomponentsandeachsubcomponentisassociatedwithamodelinthelibrary.Ifnoneofthemodelmodulesinthelibrarycandescribethesubcomponentadequately,anewmodelhastobedevelopedforthatsubcomponentandaddedtothelibrary.Then,themodelsareassembledbyfollowingthetopologyofthecomponentsandusingthenecessaryjointmodels.Onceacomponentmodelisobtained,itcanbestoredinthelibraryforreuse.Finally,thecomponentmodelsareassembledbyfollowingthetopologyofagivenconfigurationtoobtainthemodelofthatconfiguration.TheprocessisillustratedinFigure4asaflowchartanddemonstratedinthefollowingsectionthroughexamples.EXAMPLES
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