外文翻译--以知识为基础的方法在机械产品设计任务中的实施.doc -- 5 元

AknowledgebasedapproachforthetaskimplementationinmechanicalproductdesignAbstractAlthoughadvanceshavebeenmadetointegratetheCADsystemwithdesignknowledge,therearestillsomebarrierstoapplytheknowledgebaseddesignapproachtowidepractice.Ataskimplementationmethodisproposedforthemechanicalproductdesignprocess.Thedesigntaskimplementationmodelisconstructedbasedonitsorganizedmodeandmodularity.Declarativeknowledgeprimitivesmakeupofthekernelcompositionofdesigntask.Itmakesthedesigntaskmorecontrollableandautomatable.Solutionoftheknowledgeprimitivesisdirectlyusedtodrivethemechanicalproduct.TheproposedmodulehasbeendevelopedforIntesolid2.0system,amechanicalCADsystem,andithasbeenevaluatedwithadesignexampleofatwostagegearbox.1IntroductionIncreasingcompetitionofthemarketforcesenterprisestoseekwaystobeleadinginproductdesignandmanufacturing.Designinearlystagesofdevelopmentisadvocatedforapplicationtoengineeringdesigntoshortenandautomatethedevelopmentprocess.ComputeraideddesignsystemsarenowbeingappliedtoupstreamdesignactivitiesIntegrationofhighendmechanicalcomputeraideddesignMCADsystemswithdesignactivitiesanddesignknowledgewouldallowmanufacturerstoautomatetheirengineeringandmanufacturingprocessescapturingthedesignrules,experienceandexpertiseandleveragingitduringnewproductdevelopment.Thedevelopmentofaproductshouldtakeintoaccounttheissuesofengineeringperformance,manufacturability,andcost.ApuregeometricMCADsystemonlysupportslowleveldesignautomation.ItmakeslittleuseofdesignknowledgeotherthanthedesignersdexteritywiththeMCADtool,andcannotmeettheexpectationofcustomersforrapiddesign,rapidmanufacturing,andhighreliability.KnowledgebasedengineeringKBEprovidesawayofformalizingandautomatingproductdevelopment.Designknowledgeisutilizedtoexpeditethecycletimefromproductdesigntomanufacturing,atthetimeitassurestheartifactsmeetstandardsacrossdesignandmanufacturingdisciplines.Anumberofapproachestoknowledgeengineeringfordesigntaskhavebeenreportedduringthelasttwodecades.TheseworkshavebeenconcentratedondesigntaskanalysisanddisjointfromMCADsystem.However,designactivitiesandknowledgeshouldbedeeplyintegratedintothesystemprocessesandeffectivelyutilizethefriendlyinterfaceoftheexistingCADsystem.Thoughtaskanalysisisalsoemployed,thefocusofthispaperisontheknowledgerepresentationschemefortaskimplementationintheMCADsystemandanefficientreasoningandcomputationmethodologyforengineeringknowledge.2RelatedresearchThissectiondescribesrelatedresearchthathavebeendevotedtointegrationoftheMCADsystemwithknowledgefortheenhancementofproductivityandreusabilityofKBEmethodologies.Intheseresearchanddevelopments,multilayeredmodelingapproachesandtheobjectorientedmethodarecommonlyusedtoconstructknowledge,designprocess,andproductstructure.Leeetal.6havesuggestedanintegratedinferencearchitectureofanintelligentCADsystemformachinetoolsdesign.Inthisapproach,themachinetoolsdesignproblemisfirstdecomposedintodesignmodules,anddesignmodulesaredecomposedfurtherbyactives.Fourtypesofknowledgeinactivities,i.e.,equations,ifthenrules,multicriteriadescisionmakingrules,tableandgraphdata,havebeenprocessedbyahybridengine.However,thedesignproblemissimplydecomposedandtherelationshipsbetweendifferentdesignactivitiesanddifferentmodulesareignored.Valaseketal.7presentedthearchitectureoftheCOLINsystemwhichisdevelopedformotorvehicledesignThedesignproblemisrepresentedbyanetworkofbasicdesigntasksBDTs.DifferentBDTsareachievedbyaspecialsoftwaretool,suchasAutoCAD,Matlab,Excel,Simulink,Lispetc.ABDTisincludedinthetasknetworkaccordingtowhetheritsknowledgerequirementsaresatisfied.TheknowledgemodelisemployedfortheproposerevisecontrolandselectionofBDTs,butimplementationofaspecificdesigntaskisnotwellsupportedintheknowledgebasedapproach.Wongetal.1proposedfourtypesofknowledgecells,i.e.,functioncell,selectioncell,graphicscell,andlogiccellinthedevelopedcomputeraidedlogicaldesignsystem.Differentobjectsencapsulatetheproductform,designinformation,process,mail,andsoon.Gortietal.11alsopresentedaknowledgerepresentationmodelintheirSHAREDsystemandfiveobjectstodefinedesignprocess,namelygoal,plan,specification,decision,andcontext.TheresearchpresentedinthispaperprovidesamorenaturalwaytointegrateknowledgeanddesigntaskintotheMCADsystem.Aproblemsolvingmethodforknowledgeprimitivesindesigntaskisalsodiscussedinthefollowingsections.3RepresentationfordesigntaskmodelNormally,thebeginningofthedevelopmentofaproductmodelisananalysisofrelevantproductsandrelateddesigntasksanddesigners.Normally,thebeginningofthedevelopmentofaproductmodelisananalysisofrelevantproductsandrelateddesigntasksanddesigners.Moreover,theknowledgedrivenmethodologyisgivenwiththeassociationbetweendesignobjectsandknowledgeprimitives.Inthecognitiveviewpoint,ageneraldesignprocessisconsideredtobecomposedofseveraldesigntaskswiththeparticipationofcomputerandhumandesignersasillustratedinFig.1.Tofacilitatethedesignprocess,designtasksshouldbeasautomatedaspossible.Inthispaperitisassumedthatdesignobjectsandrelevanttaskcanbeprimarilyidentified.Fig.1.AutomationofdesignprocessTable1.Thedescriptionofdesignobjectinknowledgeprimitive3.1DesigntaskInthetaskanalysismethod,thetaskmodelhasbeenviewedasstructuredanalysistechniqueoroneofimplementationmodelwhichisabouthowto.Here,thetraditionaltaskanalysismethodisalsoused,buttomakethedesigntaskmoreautonomousanddynamic,differentknowledgeprimitivesandsomenecessaryprocessingmechanismandarebuiltintoit.WepresentanexelicitdescriptionschemaforthedesigntaskTid,name,input,output,sub一task,knowledgeprimitive,goal,action.Iduniqueidentifierforthedesigntask..Namenameofthetask.Input/outputrequirementsandidentifieddataflowsuchasthedescriptionofdesignobjectanddesigntaskforce,torque,velocity,mass,length,volume,etc..Subtasktopdownanalysisofproblemsolvingresultsinhierarchicaldecompositionofthewholetaskintosubtasks..Knowledgeprimitivethedomainknowledgeandtheknowledgeaboutstrategiccontrol,forexampletheknowledgeconductthenextdesigntaskaccordingtothepreviousone..Goalgoalsaredefinedaboutwhatshouldbedonewithinthetask.Theyareusuallysubjecttocertainconstraints,andcanberepresentedbyknowledgeprimitive.Everydesigntaskhasatleastoneknowledgeprimitiveasitsgoalrequiredtobeachieved..Actionthedesigntaskactaccordinglyinresponsetoitsresolution.Actioniscategorizedintotwotypesdefaultactionanduserdefinedaction.DefaultactiondrivethedesignobjectintheMCADsystem,anduseractionneedshumaninvolvement,forinstance,modificationofvalidationcondition.Table1illustratesthebendingstressvalidationofthedesigntaskforgeardesign.InBendstress_Feedback,afeedbackknowledgeprimitive,ofTable1,isusedtocontrolthedesigntaskbacktothepreviousonespecifiedinit.Someofthevariablesareaddedbyaniterativevaluebeforethecurrentdesigntaskischanged.Thisschemaofdesigntaskextendsthetraditionaltaskanalysismethodologyinthreeways1.Knowledgeprimitivesareusedasconstraintsforproblemsolvingofdesigntask,whichmakesthedesigntaskexecutable.Differenttypesofknowledgeprimitivesworkforthegoalsofadesigntask,thischaracteristichasasignificantimplicationonthenotionoftaskimplementation.2.Knowledgeprimitivecanalsobeusedasaguideoftaskimplementationoranadvisorforhumaninvolvement.Therearenotonlythedesignobjects,thereareseveralsuccessfuldesigntasksandknowledgeprimitivesinrepositorycanbereusedorconsultedforanewproductdevelopment.Therefore,theefficiencyofcoordinationbetweendesigntasksorcooperationbetweendesigntaskandhumanuserscouldbegreatlyimproved.3.TheactionmechanismprovidesthecapabilityfordrivingtheMCADsystemafterthesolutionofthedesigntask.3.2KnowledgeprimitiveMostofcurrentknowledgebaseddesignsystemsprovideinteractivemeanstointegrateknowledgewithspecifichighlevellanguage.However,anylanguagespecializesincomputationbutnotrepresentingknowledgeandreasoning.Furthermore,learningaspeciallanguage,codingandmaintenanceisalsoalaboriousprocess.Thedesignershouldconcentratehiseffortonthemainfunctionoftheartifactwithleastprogramming.Likeanyfeaturesandgeometryprimitive,knowledgeprimitivecanbeaddedpiecebypieceinMCADsystem.Everypieceofknowledgeisdescribedinafamiliarwayfordesigner,