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

Aknowledge-basedapproachforthetaskimplementationinmechanicalproductdesignAbstractAlthoughadvanceshavebeenmadetointegratetheCADsystemwithdesignknowledge,therearestillsomebarrierstoapplytheknowledge-baseddesignapproachtowidepractice.Ataskimplementationmethodisproposedforthemechanicalproductdesignprocess.Thedesigntaskimplementationmodelisconstructedbasedonitsorganized-modeandmodularity.Declarativeknowledgeprimitivesmakeupofthekernelcompositionofdesigntask.Itmakesthedesigntaskmorecontrollableandautomatable.Solutionoftheknowledgeprimitivesisdirectlyusedtodrivethemechanicalproduct.TheproposedmodulehasbeendevelopedforIntesolid2.0system,amechanicalCADsystem,andithasbeenevaluatedwithadesignexampleofatwo-stagegearbox.1IntroductionIncreasingcompetitionofthemarketforcesenterprisestoseekwaystobeleadinginproductdesignandmanufacturing.Designinearlystagesofdevelopmentisadvocatedforapplicationtoengineeringdesigntoshortenandautomatethedevelopmentprocess.Computer-aideddesignsystemsarenowbeingappliedto"up-stream"designactivitiesIntegrationofhigh-endmechanicalcomputer-aideddesign(MCAD)systemswithdesignactivitiesanddesignknowledgewouldallowmanufacturerstoautomatetheirengineeringandmanufacturingprocessescapturingthedesignrules,experienceandexpertiseandleveragingitduringnewproductdevelopment.Thedevelopmentofaproductshouldtakeintoaccounttheissuesofengineeringperformance,manufacturability,andcost.ApuregeometricMCADsystemonlysupportslowleveldesignautomation.ItmakeslittleuseofdesignknowledgeotherthanthedesignersdexteritywiththeMCADtool,andcannotmeettheexpectationofcustomersforrapiddesign,rapidmanufacturing,andhighreliability.Knowledge-basedengineering(KBE)providesawayofformalizingandautomatingproductdevelopment.Designknowledgeisutilizedtoexpeditethecycletimefromproductdesigntomanufacturing,atthetimeitassurestheartifactsmeetstandardsacrossdesignandmanufacturingdisciplines.Anumberofapproachestoknowledgeengineeringfordesigntaskhavebeenreportedduringthelasttwodecades.TheseworkshavebeenconcentratedondesigntaskanalysisanddisjointfromMCADsystem.However,designactivitiesandknowledgeshouldbedeeplyintegratedintothesystemprocessesandeffectivelyutilizethefriendlyinterfaceoftheexistingCADsystem.Thoughtaskanalysisisalsoemployed,thefocusofthispaperisontheknowledgerepresentationschemefortaskimplementationintheMCADsystemandanefficientreasoningandcomputationmethodologyforengineeringknowledge.2RelatedresearchThissectiondescribesrelatedresearchthathavebeendevotedtointegrationoftheMCADsystemwithknowledgefortheenhancementofproductivityandreusabilityofKBEmethodologies.Intheseresearchanddevelopments,multilayeredmodelingapproachesandtheobjectorientedmethodarecommonlyusedtoconstructknowledge,designprocess,andproductstructure.Leeetal.6havesuggestedanintegratedinferencearchitectureofanintelligentCADsystemformachinetoolsdesign.Inthisapproach,themachinetoolsdesignproblemisfirstdecomposedintodesignmodules,anddesignmodulesaredecomposedfurtherbyactives.Fourtypesofknowledgeinactivities,i.e.,equations,if-thenrules,multi-criteriadescision-makingrules,tableandgraphdata,havebeenprocessedbyahybridengine.However,thedesignproblemissimplydecomposedandtherelationshipsbetweendifferentdesignactivitiesanddifferentmodulesareignored.Valaseketal.7presentedthearchitectureoftheCOLINsystemwhichisdevelopedformotorvehicledesignThedesignproblemisrepresentedbyanetworkofbasicdesigntasks(BDTs).DifferentBDTsareachievedbyaspecialsoftwaretool,suchasAutoCAD,Matlab,Excel,Simulink,Lispetc.ABDTisincludedinthetasknetworkaccordingtowhetheritsknowledgerequirementsaresatisfied.Theknowledgemodelisemployedforthepropose-revisecontrolandselectionofBDTs,butimplementationofaspecificdesigntaskisnotwellsupportedintheknowledge-basedapproach.Wongetal.1proposedfourtypesofknowledgecells,i.e.,functioncell,selectioncell,graphicscell,andlogiccellinthedevelopedcomputer-aidedlogicaldesignsystem.Differentobjectsencapsulatetheproductform,designinformation,process,mail,andsoon.Gortietal.11alsopresentedaknowledgerepresentationmodelintheirSHAREDsystemandfiveobjectstodefinedesignprocess,namelygoal,plan,specification,decision,andcontext.TheresearchpresentedinthispaperprovidesamorenaturalwaytointegrateknowledgeanddesigntaskintotheMCADsystem.Aproblem-solvingmethodforknowledgeprimitivesindesigntaskisalsodiscussedinthefollowingsections.3RepresentationfordesigntaskmodelNormally,thebeginningofthedevelopmentofaproductmodelisananalysisofrelevantproductsandrelateddesigntasksanddesigners.Normally,thebeginningofthedevelopmentofaproductmodelisananalysisofrelevantproductsandrelateddesigntasksanddesigners.Moreover,theknowledgedrivenmethodologyisgivenwiththeassociationbetweendesignobjectsandknowledgeprimitives.Inthecognitiveviewpoint,ageneraldesignprocessisconsideredtobecomposedofseveraldesigntaskswiththeparticipationofcomputerandhumandesignersasillustratedinFig.1.Tofacilitatethedesignprocess,designtasksshouldbeasautomatedaspossible.Inthispaperitisassumedthatdesignobjectsandrelevanttaskcanbeprimarilyidentified.Fig.1.AutomationofdesignprocessTable1.Thedescriptionofdesignobjectinknowledgeprimitive3.1DesigntaskInthetaskanalysismethod,thetaskmodelhasbeenviewedasstructuredanalysistechniqueoroneofimplementationmodelwhichisabouthow-to.Here,thetraditionaltaskanalysismethodisalsoused,buttomakethedesigntaskmoreautonomousanddynamic,differentknowledgeprimitivesandsomenecessaryprocessingmechanismandarebuiltintoit.Wepresentanexelicitdescriptionschemaforthedesigntask:T=(id,name,input,output,sub一task,knowledgeprimitive,goal,action).Id:uniqueidentifierforthedesigntask.Name:nameofthetask.Input/output:requirementsandidentifieddataflowsuchasthedescriptionofdesignobjectanddesigntask(force,torque,velocity,mass,length,volume,etc.).Sub-task:top-downanalysisofproblemsolvingresultsinhierarchicaldecompositionofthewholetaskintosub-tasks.Knowledgeprimitive:thedomainknowledgeandtheknowledgeaboutstrategiccontrol,forexampletheknowledgeconductthenextdesigntaskaccordingtothepreviousone.Goal:goalsaredefinedaboutwhatshouldbedonewithinthetask.Theyareusuallysubjecttocertainconstraints,andcanberepresentedbyknowledgeprimitive.Everydesigntaskhasatleastoneknowledgeprimitiveasitsgoalrequiredtobeachieved.Action:thedesigntaskactaccordinglyinresponsetoitsresolution.Actioniscategorizedintotwotypes:defaultactionanduser-definedaction.DefaultactiondrivethedesignobjectintheMCADsystem,anduseractionneedshumaninvolvement,forinstance,modificationofvalidationcondition.Table1illustratesthebendingstressvalidationofthedesigntaskforgeardesign.InBendstress_Feedback,afeedbackknowledgeprimitive,ofTable1,isusedtocontrolthedesigntaskbacktothepreviousonespecifiedinit.Someofthevariablesareaddedbyaniterativevaluebeforethecurrentdesigntaskischanged.Thisschemaofdesigntaskextendsthetraditionaltaskanalysismethodologyinthreeways:1.Knowledgeprimitivesareusedasconstraintsforproblem-solvingofdesigntask,whichmakesthedesigntaskexecutable.Differenttypesofknowledgeprimitivesworkforthegoalsofadesigntask,thischaracteristichasasignificantimplicationonthenotionoftaskimplementation.2.Knowledgeprimitivecanalsobeusedasaguideoftaskimplementationoranadvisorforhumaninvolvement.Therearenotonlythedesignobjects,thereareseveralsuccessfuldesigntasksandknowledgeprimitivesinrepositorycanbereusedorconsultedforanewproductdevelopment.Therefore,theefficiencyofcoordinationbetweendesigntasksorcooperationbetweendesigntaskandhumanuserscouldbegreatlyimproved.3.TheactionmechanismprovidesthecapabilityfordrivingtheMCADsystemafterthesolutionofthedesigntask.3.2KnowledgeprimitiveMostofcurrentknowledge-baseddesignsystemsprovideinteractivemeanstointegrateknowledgewithspecifichigh-levellanguage.However,anylanguagespecializesincomputationbutnotrepresentingknowledgeandreasoning.Furthermore,learningaspeciallanguage,codingandmaintenanceisalsoalaboriousprocess.Thedesignershouldconcentratehiseffortonthemainfunctionoftheartifactwithleastprogramming.Likeanyfeaturesandgeometryprimitive,knowledgeprimitivecanbeaddedpiecebypieceinMCADsystem.Everypieceofknowledgeisdescribedinafamiliarwayfordesigner,