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外文翻译--基于实例推理的夹具设计.doc

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外文翻译--基于实例推理的夹具设计.doc

英文原文ApplicationanddevelopmentOfcasebasedreasoninginfixturedesignAbstractBasedonthecasebaseddesigningCBDmethodology,thefixturesimilarityisintworespectsthefunctionandthestructureinformation.Then,thecomputeraidedfixturedesignsystemiscreatedoncasebasedreasoningCBR,inwhichtheattributesofthemainfeaturesofworkpieceandstructureoffixtureascaseindexcodearedesignedfortheretrieveofthesimilarcases,andthestructureandhierarchicalrelationofcaselibraryaresetupforstore.Meanwhile,thealgorithmbasedontheknowledgeguidedintheretrieveofthesimilarcases,thestrategyofcaseadaptationandcasestorageinwhichthecaseidentifcationnumberisusedtodistinguishfromsimilarcasesarepresented.Theapplicationofthesysteminsomeprojectsimprovesthedesignefficiencyandgetsagoodresult.KeywordscasebasedreasoningfixturedesigncomputeraideddesignCADFixturesaredevicesthatserveasthepurposeofholdingtheworkpiecesecurelyandaccurately,andmaintainingaconsistentrelationshipwithrespecttothetoolswhilemachining.Becausethefixturestructuredependsonthefeatureoftheproductandthestatusoftheprocessplanningintheenterprise,itsdesignisthebottleneckduringmanufacturing,whichrestrainstoimprovetheefficiencyandleadtime.Andfixturedesignisacomplicatedprocess,basedonexperiencethatneedscomprehensivequalitativeknowledgeaboutanumberofdesignissuesincludingworkpiececonfiguration,manufacturingprocessesinvolved,andmachiningenvironment.ThisisalsoaverytimeconsumingworkwhenusingtraditionalCADtoolssuchasUnigraphics,CATIAorPro/E,whicharegoodatperformingdetaileddesigntasks,butprovidefewbenefitsfortakingadvantageofthepreviousdesignexperienceandresources,whicharepreciselythekeyfactorsinimprovingtheefficiency.ThemethodologyofcasebasedreasoningCBRadaptsthesolutionofapreviouslysolvedcasetobuildasolutionforanewproblemwiththefollowingfourstepsretrieve,reuse,revise,andretain1.Thisisamoreusefulmethodthantheuseofanexpertsystemtosimulatehumanthoughtbecauseproposingasimilarcaseandapplyingafewmodificationsseemstobeselfexplanatoryandmoreintuitivetohumans.Sovariouscasebaseddesignsupporttoolshavebeendevelopedfornumerousareas24,suchasininjectionmoldinganddesign,architecturaldesign,diecastingdiedesign,processplanning,andalsoinfixturedesign.Sunusedsixdigitalstocomposetheindexcodethatincludedworkpieceshape,machineportion,bushing,the1stlocatingdevice,the2ndlocatingdeviceandclampingdevice5.Butthesystemcannotbeusedforotherfixturetypesexceptfordrillfixtures,andcannotsolvetheproblemofstorageofthesameindexcodethatneedstoberetained,whichisveryimportantinCBR6.1ConstructionofaCaseIndexandCaseLibrary1.1CaseindexThecaseindexshouldbecomposedofallfeaturesoftheworkpiece,whicharedistinguishedfromdifferentfixtures.Usingallofthemwouldmaketheoperationinconvenient.Becausetheformsofthepartsarediverse,andthetechnologyrequirementsofmanufactureintheenterprisealsodevelopcontinuously,lotsoffeaturesusedasthecaseindexwillmakethesearchrateslow,andthemainfeatureunimportant,forthereasonthattherelativeweightwhichisallottedtoeveryfeaturemustdiminish.Andontheotherhand,itishardtoincludeallthefeaturesinthecaseindex.Therefore,consideringthepracticalityandthedemandofrapiddesign,thecaseindexincludesboththemajorfeatureoftheworkpieceandthestructureoffixture.Thecaseindexcodeismadeupof16digits13digitsforcasefeaturesand3digitsforcaseidentificationnumber.Thefirst13digitsrepresent13features.Eachdigitiscorrespondingtoanattributeofthefeature,whichmaybeoneof,,1,2,,A,B,,Z,,etc.Inwhich,meansanyone,uncertain,0nothing.Thesystemrulesfixturetype,workpieceshape,locatingmodelcannotbeor.Whenthesystemisdesigned,theattributeinformationofthethreeitemsdoesnothavetheseoptions,whichmeansthecertainattributemustbeselected.Thelastthreedigitsarethecaseidentificationnumber,whichmeansthe13digitsofthecasefeaturearethesame,andthenumberofthesethreedigitsisusedfordistinguishingthem.Thesystemalsorules000isaprototypecase,whichisusedforretrieval,andothercasesare001,002,,whichareusedforreferencecasestobesearchedbydesigners.Ifoccasionallyoneofthemneedstobechangedastheprototypecase,firstitmustberequiredtoapplytochangetheoneto000,andtheformerischangedtoreferentialcaseautomatically.TheconstructionofthecaseindexcodeisshowninFig.1.1.2CaselibraryThecaselibraryconsistsoflotsofpredefinedcases.Caserepresentationisoneofthemostimportantissuesincasebasedreasoning.Socompoundingwiththeindexcode,.1.3HierarchicalformofCaseThestructuresimilarityofthefixtureisrepresentedasthewholefixturesimilarity,componentssimilarityandcomponentsimilarity.Sothewholefixturecaselibrary,componentscaselibrary,componentcaselibraryoffixtureareformedcorrespondingly.Usuallydesigninformationofthewholefixtureiscomposedofworkpieceinformationandworkpieceprocedureinformation,whichrepresentthefixturesatisfyingthespecificallydesigningfunctiondemand.Thewholefixturecaseismadeupoffunctioncomponents,whicharedescribedbythefunctioncomponentsnamesandnumbers.Thecomponentscaserepresentsthemembers.functioncomponentandotherstructurecomponents,maindrivenparameter,thenumber,andtheirconstrainrelations.Thecomponentcasethelowestlayerofthefixtureisthestructureoffunctioncomponentandothercomponents.Inthemodernfixturedesigntherearelotsofparametricstandardpartsandcommonnonstandardparts.Sothecomponentcaselibraryshouldrecordthespecificationparameterandthewayinwhichitkeepsthem.2StrategyofCaseRetrievalInthecasebaseddesignoffixtures,themostimportantthingistheretrievalofthesimilarity,whichcanhelptoobtainthemostsimilarcase,andtocutdownthetimeofadaptation.Accordingtotherequirementoffixturedesign,thestrategyofcaseretrievalcombinesthewayofthenearestneighborandknowledgeguided.Thatis,firstsearchondepth,thenonbreadththeknowledgeguidedstrategymeanstosearchontheknowledgerulefromroottotheobject,whichisfirstlysearchedbythefixturetype,thenbytheshapeoftheworkpiece,thirdlybythelocatingmethod.Forexample,ifthecaseindexcodeincludesthemillingfixtureoffixturetype,thesearchisjustforallmillingfixtures,thenforboxofworkpieceshape,thethirdfor1plane2pineoflocatingmethod.Ifthereisnomatchofit,thenthesearchstopsondepth,andreturnstotheupperlayer,andretrievesalltherelativecasesonbreadth.Retrievalalgorithms1Accordingtothecaseindexinformationoffixturecaselibrary,searchtherelevantcaselibrary2Matchthecaseindexcodewiththecodeofeachcaseofthecaselibrary,andcalculatethevalueofthesimilaritymeasure3Sorttheorderofsimilaritymeasure,thebiggestvalue,whichisthemostanalogicalcase.Similaritybetweentwocasesisbasedonthesimilaritybetweenthetwocases.features.Thecalculationofsimilaritymeasuredependsonthetypeofthefeature.Thevalueofsimilaritycanbecalculatedfornumericalvalues,forexample,compareWorkpiecewiththeweightof50kgand20kg.Thevaluecanalsobecalculatedbetweennonnumericalvalues,forexample,nowthefirst13digitsindexcodeisallnonnumericalvalues.ThesimilaritymeasureofafixtureiscalculatedasfollowswhereSisthesimilaritymeasureofcurrentfixture,nisthenumberoftheindexfeature,istheweightofeachfeature,isthesimilaritymeasureoftheattributeofthei2thfeaturewiththeattributeofrelativefeatureofthejthcaseinthecaselibrary.Atthesametime,,thevaluecountsasfollows.Whereisthevalueoftheindexattributeoftheithfeature,andisthevalueofattributeoftherelativeithfeatureofthejthcaseincaselibrary.Sotherearetwomethodstoselecttheanalogicalfixture.Oneistosetthevalue.Ifthevaluesofsimilaritymeasureofcurrentcaseswerelessthanagivenvalue,thosecaseswouldnotbeselectedasanalogicalcases.Whenthecaselibraryisinitiallysetup,andthereareonlyafewcases,thevaluecanbesetsmaller.Iftherearelotsofanalogicalcases,thevalueshouldgetlarger.Theotherisjusttosetthenumberoftheanalogicalcasessuchas10,whichisthelargestvalueofsimilaritymeasurefromthesortedorder.3CaseadaptationandCaseStorage3.1CaseadaptationThemodificationoftheanalogicalcaseinthefixturedesignincludesthefollowingthreecases1Thesubstitutionofcomponentsandthecomponent2Adjustingthedimensionofcomponentsandthecomponentwhiletheformremains3Theredesignofthemodel.Ifthecomponentsandcomponentofthefixturearecommonobjects,theycanbeedited,substitutedanddeletedwithtools,whichhavebeendesigned.3.2CasestorageBeforesavinganewfixturecaseinthecaselibrary,thedesignermustconsiderwhetherthesavingisvaluable.Ifthecasedoesnotincreasetheknowledgeofthesystem,itisnotnecessarytostoreitinthecaselibrary.Ifitisvaluable,thenthedesignermustanalyzeitbeforesavingittoseewhetherthecaseisstoredasaprototypecaseorasreferencecase.Aprototypecaseisarepresentationthatcandescribethemainfeaturesofacasefamily.Acasefamilyconsistsofthosecaseswhoseindexcodeshavethesamefirst13digitsanddifferentlastthreedigitsinthecaselibrary.Thelastthreedigitsofaprototypecasearealways000.Areferencecasebelongstothesamefamilyastheprototypecaseandisdistinguishedbythedifferentlastthreedigits.Fromtheconceptthathasbeenexplained,thefollowingstrategiesareadopted1Ifanewcasematchesanyexistingcasefamily,ithasthesamefirst13digitsasanexistingprototypecase,sothecaseisnotsavedbecauseitisrepresentedwellbytheprototypecase.Orisjustsavedasareferencecasethelast3digitsarenot000,andnotthesamewithothersinthecaselibrary.2Ifanewcasematchesanyexistingcasefamilyandisthoughttobebetteratrepresentingthiscasefamilythanthepreviousprototypecase,thentheprototypecaseissubstitutedbythisnewcase,andthepreviousprototypecaseissavedasareferencecase.3Ifanewcasedoesnotmatchanyexistingcasefamily,anewcasefamilywillbegeneratedautomaticallyandthecaseisstoredastheprototypecaseinthecaselibrary.4ProcessofCBRinFixtureDesignAccordingtothecharacteristicsoffixturedesign,thebasicinformationofthefixturedesignsuchasthenameoffixture,part,productandthedesigner,etc.mustbeinputfirst.Thenthefixturefileissetupautomatically,inwhichallcomponentsofthefixtureareputtogether.Thenthemodeloftheworkpieceisinputordesigned.Thedetailedinformationabouttheworkpieceisinput,thecaseindexcodeissetup,andthentheCBRbeginstosearchtheanalogicalcases,relyingonthesimilaritymeasure,andthemostanalogicalcaseisselectedout.Ifneeded,thecaseisadaptedtosatisfythecurrentdesign,andrestoredintothecaselibrary.TheflowchartoftheprocessisshowninFig.3.

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