翻译—基于事例推理的夹具设计研究与应用.pdf

1ApplicationanddevelopmentOfOOOcasebasedreasoninginfixturedesignAbstract:Basedonthecasebaseddesigning(CBD)methodology,thefixturesimilarityisintworespects:thefunctionandthestructureinformation.Then,thecomputeraidedfixturedesignsystemiscreatedoncasebasedreasoning(CBR),inwhichtheattributesofthemainfeaturesofworkpieceandstructureoffixtureascaseindexcodearedesignedfortheretrieveofthesimilarcases,andthestructureandhierarchicalrelationofcaselibraryaresetupforstore.Meanwhile,thealgorithmbasedontheknowledgeguidedintheretrieveofthesimilarcases,thestrategyofcaseadaptationandcasestorageinwhichthecaseidentifcationnumberisusedtodistinguishfromsimilarcasesarepresented.Theapplicationofthesysteminsomeprojectsimprovesthedesignefficiencyandgetsagoodresult.Keywords:KKKcasebasedreasoning;fixturedesign;computeraideddesign(CAD)Fixturesaredevicesthatserveasthepurposeofholdingtheworkpiecesecurelyandaccurately,andmaintainingaconsistentrelationshipwithrespecttothetoolswhilemachining.Becausethefixturestructuredependsonthefeatureoftheproductandthestatusoftheprocessplanningintheenterprise,itsdesignisthebottleneckduringmanufacturing,whichrestrainstoimprovetheefficiencyandleadtime.Andfixture2designisacomplicatedprocess,basedonexperiencethatneedscomprehensivequalitativeknowledgeaboutanumberofdesignissuesincludingworkpiececonfiguration,manufacturingprocessesinvolved,andmachiningenvironment.ThisisalsoaverytimeconsumingworkwhenusingtraditionalCADtools(suchasUnigraphics,CATIAorPro/E),whicharegoodatperformingdetaileddesigntasks,butprovidefewbenefitsfortakingadvantageofthepreviousdesignexperienceandresources,whicharepreciselythekeyfactorsinimprovingtheefficiency.Themethodologyofcasebasedreasoning(CBR)adaptsthesolutionofapreviouslysolvedcasetobuildasolutionforanewproblemwiththefollowingfoursteps:retrieve,reuse,revise,andretain1.Thisisamoreusefulmethodthantheuseofanexpertsystemtosimulatehumanthoughtbecauseproposingasimilarcaseandapplyingafewmodificationsseemstobeselfexplanatoryandmoreintuitivetohumans.Sovariouscasebaseddesignsupporttoolshavebeendevelopedfornumerousareas2-4,suchasininjectionmoldinganddesign,architecturaldesign,diecastingdiedesign,processplanning,andalsoinfixturedesign.Sunusedsixdigitalstocomposetheindexcodethatincludedworkpieceshape,machineportion,bushing,the1stlocatingdevice,the2ndlocatingdeviceandclampingdevice5.Butthesystemcannotbeusedforotherfixturetypesexceptfordrillfixtures,andcannotsolvetheproblemofstorageofthesameindexcodethatneedstoberetained,whichisveryimportantinCBR6.1ConstructionofaCaseIndexand3CaseLibrary1.1CaseindexThecaseindexshouldbecomposedofallfeaturesoftheworkpiece,whicharedistinguishedfromdifferentfixtures.Usingallofthemwouldmaketheoperationinconvenient.Becausetheformsofthepartsarediverse,andthetechnologyrequirementsofmanufactureintheenterprisealsodevelopcontinuously,lotsoffeaturesusedasthecaseindexwillmakethesearchrateslow,andthemainfeatureunimportant,forthereasonthattherelativeweightwhichisallottedtoeveryfeaturemustdiminish.Andontheotherhand,itishardtoincludeallthefeaturesinthecaseindex.Therefore,consideringthepracticalityandthedemandofrapiddesign,thecaseindexincludesboththemajorfeatureoftheworkpieceandthestructureoffixture.Thecaseindexcodeismadeupof16digits:13digitsforcasefeaturesand3digitsforcaseidentificationnumber.Thefirst13digitsrepresent13features.Eachdigitiscorrespondingtoanattributeofthefeature,whichmaybeoneof“*”,“？”,“1”,“2”,“A”,“B”,“Z”,etc.Inwhich,“*”meansanyone,“?”uncertain,“0”nothing.Thesystemrules:fixturetype,workpieceshape,locatingmodelcannotbe“*”or“?”.Whenthesystemisdesigned,theattributeinformationofthethreeitemsdoesnothavetheseoptions,whichmeansthecertainattributemustbeselected.Thelastthreedigitsarethecaseidentificationnumber,whichmeansthe13digitsofthecasefeaturearethe4same,andthenumberofthesethreedigitsisusedfordistinguishingthem.Thesystemalsorules:“000”isaprototypecase,whichisusedforretrieval,andothercasesare“001”,“002”,whichareusedforreferencecasestobesearchedbydesigners.Ifoccasionallyoneofthemneedstobechangedastheprototypecase,firstitmustberequiredtoapplytochangetheoneto“000”,andtheformerischangedtoreferentialcaseautomatically.TheconstructionofthecaseindexcodeisshowninFig.1.1.2CaselibraryThecaselibraryconsistsoflotsofpredefinedcases.Caserepresentationisoneofthemostimportantissuesincasebasedreasoning.Socompoundingwiththeindexcode,.1.3HierarchicalformofCaseThestructuresimilarityofthefixtureisrepresentedasthewholefixturesimilarity,componentssimilarityandcomponentsimilarity.Sothewholefixturecaselibrary,componentscaselibrary,componentcaselibraryoffixtureareformedcorrespondingly.Usuallydesigninformationofthewholefixtureiscomposedofworkpieceinformationandworkpieceprocedureinformation,whichrepresentthefixturesatisfyingthespecificallydesigningfunctiondemand.Thewholefixturecaseismadeupoffunctioncomponents,whicharedescribedbythefunctioncomponentsnamesandnumbers.Thecomponentscaserepresentsthemembers.(functioncomponentand5otherstructurecomponents，maindrivenparameter,thenumber,andtheirconstrainrelations.)Thecomponentcase(thelowestlayerofthefixture)isthestructureoffunctioncomponentandothercomponents.Inthemodernfixturedesigntherearelotsofparametricstandardpartsandcommonnonstandardparts.Sothecomponentcaselibraryshouldrecordthespecificationparameterandthewayinwhichitkeepsthem.2StrategyofCaseRetrievalInthecasebaseddesignoffixtures,themostimportantthingistheretrievalofthesimilarity,whichcanhelptoobtainthemostsimilarcase,andtocutdownthetimeofadaptation.Accordingtotherequirementoffixturedesign,thestrategyofcaseretrievalcombinesthewayofthenearestneighborandknowledgeguided.Thatis,firstsearchondepth,thenonbreadth;theknowledgeguidedstrategymeanstosearchontheknowledgerulefromroottotheobject,whichisfirstlysearchedbythefixturetype,thenbytheshapeoftheworkpiece,thirdlybythelocatingmethod.Forexample,ifthecaseindexcodeincludesthemillingfixtureoffixturetype,thesearchisjustforallmillingfixtures,thenforboxofworkpieceshape,thethirdfor1plane+2pineoflocatingmethod.Ifthereisnomatchofit,thenthesearchstopsondepth,andreturnstotheupperlayer,andretrievesalltherelativecasesonbreadth.Retrievalalgorithms:1)Accordingtothecaseindexinformationoffixturecaselibrary,searchtherelevantcaselibrary;2)Matchthecaseindexcodewiththecodeofeachcaseofthecaselibrary,6andcalculatethevalueofthesimilaritymeasure;3)Sorttheorderofsimilaritymeasure,thebiggestvalue,whichisthemostanalogicalcase.Similaritybetweentwocasesisbasedonthesimilaritybetweenthetwocases.features.Thecalculationofsimilaritymeasuredependsonthetypeofthefeature.Thevalueofsimilaritycanbecalculatedfornumericalvalues,forexample,compareWorkpiecewiththeweightof50kgand20kg.Thevaluecanalsobecalculatedbetweennonnumericalvalues,forexample,nowthefirst13digitsindexcodeisallnonnumericalvalues.Thesimilaritymeasureofafixtureiscalculatedasfollows:whereSisthesimilaritymeasureofcurrentfixture,nisthenumberoftheindexfeature,istheweightofeachfeature,isthesimilaritymeasureoftheattributeofthei2thfeaturewiththeattributeofrelativefeatureofthej-thcaseinthecaselibrary.Atthesametime,thevaluecountsasfollows:.Whereisthevalueoftheindexattributeofthei-thfeature,andis7thevalueofattributeoftherelativei-thfeatureofthej-thcaseincaselibrary.Sotherearetwomethodstoselecttheanalogicalfixture.Oneistosetthevalue.Ifthevaluesofsimilaritymeasureofcurrentcaseswerelessthanagivenvalue,thosecaseswouldnotbeselectedasanalogicalcases.Whenthecaselibraryisinitiallysetup,andthereareonlyafewcases,thevaluecanbesetsmaller.Iftherearelotsofanalogicalcases,thevalueshouldgetlarger.Theotherisjusttosetthenumberoftheanalogicalcases(suchas10),whichisthelargestvalueofsimilaritymeasurefromthesortedorder.3CaseadaptationandCaseStorage3.1CaseadaptationThemodificationoftheanalogicalcaseinthefixturedesignincludesthefollowingthreecases:1)Thesubstitutionofcomponentsandthecomponent;2)Adjustingthedimensionofcomponentsandthecomponentwhiletheformremains;3)Theredesignofthemodel.Ifthecomponentsandcomponentofthefixturearecommonobjects,theycanbeedited,substitutedanddeletedwithtools,whichhavebeendesigned.3.2CasestorageBeforesavinganewfixturecaseinthecaselibrary,thedesignermustconsiderwhetherthesavingisvaluable.Ifthecasedoesnotincreasetheknowledgeofthesystem,itisnotnecessarytostoreitinthecaselibrary.Ifitisvaluable,thenthedesignermustanalyzeitbeforesavingittoseewhetherthecaseisstoredasaprototypecaseorasreferencecase.A8prototypecaseisarepresentationthatcandescribethemainfeaturesofacasefamily.Acasefamilyconsistsofthosecaseswhoseindexcodeshavethesamefirst13digitsanddifferentlastthreedigitsinthecaselibrary.Thelastthreedigitsofaprototypecasearealways“000”.Areferencecasebelongstothesamefamilyastheprototypecaseandisdistinguishedbythedifferentlastthreedigits.Fromtheconceptthathasbeenexplained,thefollowingstrategiesareadopted:1)Ifanewcasematchesanyexistingcasefamily,ithasthesamefirst13digitsasanexistingprototypecase,sothecaseisnotsavedbecauseitisrepresentedwellbytheprototypecase.Orisjustsavedasareferencecase(thelast3digitsarenot“000”,andnotthesamewithothers)inthecaselibrary.2)Ifanewcasematchesanyexistingcasefamilyandisthoughttobebetteratrepresentingthiscasefamilythanthepreviousprototypecase,thentheprototypecaseissubstitutedbythisnewcase,andthepreviousprototypecaseissavedasareferencecase.3)Ifanewcasedoesnotmatchanyexistingcasefamily,anewcasefamilywillbegeneratedautomaticallyandthecaseisstoredastheprototypecaseinthecaselibrary.4ProcessofCBRinFixtureDesignAccordingtothecharacteristicsoffixturedesign,thebasicinformationofthefixturedesignsuchasthenameoffixture,part,productandthedesigner,etc.mustbeinputfirst.Thenthefixturefileissetupautomatically,inwhichall9componentsofthefixtureareputtogether.Thenthemodeloftheworkpieceisinputordesigned.Thedetailedinformationabouttheworkpieceisinput,thecaseindexcodeissetup,andthentheCBRbeginstosearchtheanalogicalcases,relyingonthesimilaritymeasure,andthemostanalogicalcaseisselectedout.Ifneeded,thecaseisadaptedtosatisfythecurrentdesign,andrestoredintothecaselibrary.TheflowchartoftheprocessisshowninFig.3.5IllustratingforFixtureDesignbyCBRThisisaworkpiece(seeFig.4).Itsmaterialis45#steel.Itsnameisseat.Itsshapeisblock,andtheproductbatchsizeismiddle,etc.Afixtureisturningfixturethatservestoturnthehole,whichneedstobedesigned.Thevalueoffeature,attribute,caseindexcodeandweightoftheworkpieceisshowninTab.2.10Throughsearching,andcalculatingthesimilarity,thecaseindexcodeofthemostsimilarcaseis19325513321402000,andthedetailedinformationisshowninTab.3.Thesimilarityiscalculatedasfollows:Sothevalueofsimilaritymeasureofthefixturewhichneedstobedesignedwiththemostanalogicalcaseincaselibraryis0.806,andthestr