外文资料--Product modularization for life cycle engineering.pdf
RoboticsandComputerIntegratedManufacturing15(1999)387401ProductmodularizationforlifecycleengineeringP.Gu!,*,S.Sosale"!DepartmentofMechanicalandManufacturingEngineering,TheUniversityofCalgary,2500UniversityDrive,Calgary,Alberta,CanadaT2N1N4"ImperialRubber,Ltd.,Edmonton,CanadaReceived24January1999;receivedinrevisedform15July1999;accepted10August1999AbstractModularproductsconsistofdetachablemodules,whichcanbemanufactured,assembled,andservicedseparately.Someofthemodulesmaybereusable,recyclableorre-manufacturableuponproductretirement.Thus,modulardesigncanprovidebene"tstomanyaspectsofproductlifecycle.Thispaperpresentsanintegratedmodulardesignmethodologyforlifecycleengineering.Themethodologyconsistsofthreephases:problemde"nition,interactionanalysisandmoduleformation.Themethodologyidenti"esthefactorsrelatedtothedesignobjectives,relatesthesefactorstodesigncomponentsthroughinteractionanalysis,andclusterscomponentsintomodules.Twocasestudiesalongwithdetailedanalysisareprovidedtoillustratethemethodologyandthealgorithms.(1999ElsevierScienceLtd.Allrightsreserved.1.IntroductionModulardesignaimstodevelopproductarchitectureconsistingofphysicallydetachableunits(modules).Therearemanyadvantagesformodularproducts.Forexample,bycarefullymodularizingaproduct,thede-signsfortheearliermodelscanbeusedinanewmodelwithoutanychanges.Modulardesigncanalsohelpincreatingarangeofproductswithminorvariances.Additionalandauxiliarymodulescouldbeaddedtoaproducttocreatenewmodels.Modulardesignalsoallowssomecomponentstobeusedacrossproductvariantsandproductlinesduetostandardizationofthefunctionsandinterfaces.Recentstudyindicatedthatafterproductsareretired,someofthemodulesmightbereusable,orremanufacturable.Infact,modulardesigncancreatebene"tsformanyaspectsofaproductlifecyclesuchasdesign,assembly,servicesandrecycling1,2.Thus,thereisaneedfordevelopingasystematicap-proachformodulardesignrelatingtoproductlifecycleengineering.Researchinlifecycleengineeringandcon-currentengineeringhassuggestedthatthemostimpor-tantdecisionsbemadeatthedesignstages38.*Correspondingauthor.E-mailaddress:guenme.ucalgary.ca(P.Gu)Therefore,productdesign,modellingandintegrationhavereceivedsigni"cantattentions9,10.Theobjectiveofthisresearchistodevelopanewmodulardesignmethodologytoaddressproductlifecycleconcernsatthedesignstage.Toachievethede"nedlifecycleengineeringobjectivesthroughmodulardesign,therelationshipsbetweentheobjectivesandthemodulesshouldbeestablished.Asproductfunctionsarerealizedbyphysicalstructures,therelationshipsbetweenfunctionsandphysicalsolutionsshouldalsobedetermined.Essentially,modulardesigndecomposesaproductorgroupscomponentsintosepar-atemodules.Specialcaremustbetakentoensurethatseparationormergerofcomponentsdoesnota!ecttheintendedfunctionsoftheproduct.Thisrequiresthecon-siderationoffunctionalandphysicalinteractionsamongcomponents.Functionalinteractionsareusuallyexpressedintheformoftheexchangeofmaterial,energyand/orsignal.Theycanbeextractedfromthefunctionalstructureoftheproduct.Whenmodulesthatexchangethefunctionoperandsareseparated,specialprovisionsareneededforinterfacing;otherwisetheexpectedfunctionsmaybea!ected.Physicalinteractionsrefertospatialandgeometricalrelationships.Theyincludeattachment(physicalcontacts,"xationsandstops,joints,fasteners,couplings,weldsandthelike),positioning(relativedistanceoranglebetween0736-5845/99/$-seefrontmatter(1999ElsevierScienceLtd.Allrightsreserved.PII:S0736-5845(99)00049-6components,alignmentincludingcoaxial,collinear,par-allel,perpendicularand#ushalignments),motion(cam-controlledobjects,trajectoryofjointsandend-e!ectors,etc.)andcontainment(e.g.componentscontainedwithinthesamehousing).Thesephysicalandstructuralcon-straintsmustbeconsideredwhencomponentsaregroupedintomodules.Forproductassembly,productarchitectureshouldbedesignedtoensuree$cientassemblyprocessandquality.Di!erentmodularizationofaproductwilldirectlya!ectassemblyprocedures,assemblye$ciencyandcosts,espe-ciallylargestructureassembly11.Modularizationwillallowmodulesproduced,assembledandtestedinconve-nientlocationswithequipment,toolsandexpertise.Forproductreuseandrecycling,di!erentcomponentsofaproductmayhavedi!erentlifeduration.Whenaproductretires,theremaybesomeusablecomponents,andsomecomponentsmayberecoveredbyre-manufac-turing.Modulardesigncangroupthesecomponentsintoeasilydetachablemodulessuchthattheycanbeeasilyreusedorremanufactured.Forrecycling,materialcompatibilityshouldbecon-sideredasdi!erentmaterialswhichmayrequiredi!erentrecyclingordisposalmethods.Amodularproductcanfacilitatetheseparationandsortingofdi!erentmaterialsforproperrecyclingordisposalprocesses.Asaconcept,modulardesignhasbeenexploredbymanyresearchers1113.Variousdesignmethodshavebeenproposed.Themethodsofusingfunctionalstruc-turesformodularizationcomposedmodulesbygroupingthefunction-relatedelementstogether1315.EppingerandPimmler16usedphysicalrelationsformoduledesign.Erixon17proposedtousequalityfunctiondeployment(QFD)tomodularizeaproduct.Hillstrom12applieddesignaxiomstoevaluatetheinterfacesamongmodules.Mistreeetal.18demonstratedwithanexamplethatthereisarelationshipbetweentheinde-pendenceamongmodulesandreducinginteractionsbetweenthem.KusiakandHuang19proposedanapproachformodularizingaproductbyconsideringthecostsandperformanceofaproduct.Tomodularizeaproduct,clusteringalgorithmsareoftenused.EppingerandPimmler16usedaheuristicswappingalgorithmtoclustercomponentsintomodules.Newcombetal.20usedtheclusteringalgorithmde-velopedbyKusiakandChow21toidentifymodulesinaproduct.Kusiakandco-workershavedevelopedsev-eralclusteringalgorithms,whichcanbeusedforcom-ponentclustering2224.Thispaperisorganizedasfollows:Thefollowingsectionintroducesthelifecycleengineeringobjectivesofmodulardesign.Theproposedmethodologyisthenprovided.Todemonstratethemethodologyandtheal-gorithms,twocasestudiesaregiveninthefollowingsection.The"nalsectionisthediscussionsandthecon-clusions.2.ProductlifecycleobjectivesofmodulardesignAproductlifecycleembracesanumberofissuesincludingdesign,manufacturing,assembly,testing,shipping,distribution,operation(use),services,reuse,re-manufacturing,recyclinganddisposal.Ideally,amodulardesigncanachievealltheselifecycleobjec-tivessimultaneously.Inreality,di!erentobjectivesmayrequiredi!erentmodulestobeformed.Consequently,con#ictsmayoccur.Acompromiseisoftenrequiredformakingdesigndecisions.Thefollowingisalistofthemodulardesignobjectivesrelatingtoproductlifecyclebene"ts.1.Dividingdesigntaskforparalleldevelopment.Designofcomplexproductsmayrequiredesignteamsconsistingofexpertsfromdi!erentdisciplines.Sequentialdevelop-mentofsuchproductsmaytakealongtime.Bybreakingdowntheoveralldesignanddevelopmenttaskintosimplersub-tasksandproperlyde"ningtheinterfacesbetweenthesub-tasks,designteamscancarryoutthesub-tasksinparalleltoreduceproductdesignanddevel-opmenttime.2.Productionandassemblyimprovement.Modulesareessentiallyindependententitiesforaproductwithde-"nedinterfaceswithothermodulesandcomponents.Modulescanbemanufacturedseparatelyindi!erentlocationstofacilitateproductionprocessesandexpertise,andtooptimizeequipmentutilization.Productarchitecturea!ectsassemblye$ciencyoftheproduct.Di!erentscenariosofmodularitymayresultindi!erentassemblyprocedureswithdi!erentassemblytimesandcosts.Incomparisonwithintegralarchitec-turesofproducts,especiallyforlarge,complexproducts,modulararchitectureallowsseparatemodulestobeas-sembledinthemostconvenientlocationsandthenputtogethertoreducethetotalassemblytimeandcosts.3.Standardization.Variousmodelsofproducts(e.g.afamilyofproducts)mayhavesomeidenticalfunctionsintheirfunctionalstructures.Thesefunctionscanberealizedbysimilarorevenidenticalphysicalstructures(modules).Thesecommonmodulescanbestandardizedandproducedinlargerbatchsizestoimproveproduc-tione$ciencyandqualityandreducecosts.Italsoen-hancesthestandardizationofacompany.4.Services.Productsusuallyrequirebothpreventivemaintenanceandrecoveryrepairs.Di!erentcomponentsofaproducthavedi!erentmaintenancefrequenciesandrepairrequirements.Bygroupingcomponentsintoeasilydisassemblemodules,faultanalysisandmaintenanceoftheproductsaremoreeasilyfacilitated.Whenafailureoccurs,thefaultymodulecanbetemporarilyreplaced,thefaultypartswithinthemodulearerepaired,andthenthemoduleisreturnedtoservice.Themainconsider-ationsrequiredforserviceabilityarefrequencyoffailure,servicerequirements,meantimeofrepairs,frequencyofpreventiveservices,accessibilityofcomponents,costof388P.Gu,S.Sosale/RoboticsandComputerIntegratedManufacturing15(1999)387401replacements,andrepaircomplexityintermsofthespecialskillsortoolsrequired.5.Upgrading.Everyproducthasalifecycleandevent-uallyretires.Manyreasonscontributetotheretirementofaproductsuchascustomerdemandfornewmodelsandwearoftheproduct.Todayshighlycompetitivemarketandhighconsumerexpectationsdemandmanu-facturerstointroducenewmodelsinashortperiodoftime.Also,therapidlychangingtechnologyquicklymakesproductsobsolete,althoughtheyareusable(e.g.computers).Thetimeande!ortrequiredtointroduceanewproductmodelareusuallysubstantial.Onewaytofacilitaterapidintroductionofnewmodelsisthroughreuseoftheexistingdesignandproductionprocessesoftheoldmodelswithaslittlechangesaspossibleinordertoreducethetimeande!ortfornewmodeldevelopment.6.Reconxguration.Whenfunctionsoftwoproductsaresosimilar,onecanbeconvertedtotheotherbysmallmodi"cations.Oftentheusersdonotneedorcannota!ord(cost,space,etc.)aspecialproductforaparticularfunction.Thecon"gurableproductscanaccommodatetheneeds.Bychangingthearrangementofafewmodulesoraddingoneormoremodules,therequiredfunctionsmayberealizedbytheexistingproduct.Anexampleofthistypeofmodularityisrecon"gurablemachinetools.Byaddinganauxiliaryattachment,averticalmillingmachinecanbeusedforhorizontalmillingoperations.7.Recycling,reuseanddisposal.Di!erentcomponentsofaproductmayhavedi!erentlifeduration.Whenaproductretires,theremaybesomeusablecomponents.Modulardesigncangroupthesecomponentsintoeasilydetachablemodulessuchthattheycanbeeasilyreused.Forrecycling,materialcompatibilityshouldbeconsideredasdi!erentmaterialsmayrequiredi!erentrecyclingordisposalmethods.Amodularproductcanfacilitatetheseparationandsortingofdi!erentmaterialsforproperrecyclingordisposalprocesses.8.Productvarietyandcustomization.Customersusu-allyhaveindividualtastesandpreferences.Itisdi$culttodesignandmanufactureasinglemodelofproductsthatcansatisfyallcustomers.Oftenaproductentersthemarketinvariousmodelswithslightlydi!erentfeaturesandoptionstosatisfycustomerdemands,whilethemainfunctionremainsthesame(e.g.camcorders).Thistypeofmodelvarietyisusuallyo!eredbymanufacturers(e.g.choiceofsedanorstationwagonforcars).Manufacturerscanalsocreatemodelsforindividualcustomers(e.g.custom-madebicyclesandcomputers).Amodularprod-uctcanprovidecustomerswithchoiceofmodelsthroughre-arrangingafewoptionalmodules.Theaboveisalistofproductlifecycleobjectivesandbene"tsthatmodularproductscanprovide.Mostlikely,itisnotpossiblethatallofthebene"tscanbeachievedsimultaneously.Productdesignersanddevelopersshouldidentifythemostimportantcharacteristicsoftheproductsandusethefollowingmethodologytoachievethem.3.TheproposedmethodologyAnewmodulardesignmethodologyisdevelopedthatconsidersvariouslifecycleengineeringobjectivessuchasassembly,maintenance,reuseandrecycling.Itisidealifamodularcon"gurationcanachieveallobjectives.How-ever,itisexpectedthatcon#ictsarise.Itisthedesignersresponsibilitytomaketrade-o!decisions.Modularde-signcanbeapproachedintwoways:(1)formmodulesbasedoneachobjectiveseparatelyandthenmaketrade-o!decisionsbetweendi!erentmodularcon"gurations,or(2)modularizeaproductbasedonaweightedaverageobjective.Theproposedmethodologycanbeusedforthebothways.Themethodologyconsistsofthreemainphases:problemde"nition,interactionanalysisandmoduleformation.3.1.Phase1:problemdexnitionTheproblemde"nitionincludesidentifyingthetypeandcharacteristicsofthedesignproblem,decomposingtheoverallproblemintosub-problems,anddeterminingtheobjectivesofmodularization,oneormoreoftheobjectivesasdiscussedintheprecedingsection.3.1.1.IdentixcationoftypeandcharacteristicsofthedesignproblemManydecisionsmadeduringdesignprocessdependonthetypeofdesigntasks.Thedesigntaskscanbedi!erentintermsofthedegreeoforiginalityofthedesign,thevarietyoftheproducts(asingleproductversusafamilyofproductswithsimilarfunctions),lifespanofdi!erentmodulesoftheproduct(e.g.existenceoflong-lastingandshort-lifemoduleswithintheproduct),andthescaleofthedesignproject(budget,productionrate).Fortheoriginaldesign,designknowledgeisintheformoffunctionsandthusthedecompositiondeterminesthefunctionalstructureoftheproduct.Foradaptivedesign(re-design)wherethephysicalsolutionisalreadyknown,thedecompositionistheidenti"cationofphys-icalcomponentsorsub-systemswithintheproduct(physicalstructure).Thedecompositionofaproductde-signintofunctionalandphysicalstructuresisaprerequi-siteformodularizingaproduct.3.1.2.IdentixcationofmodulardesignobjectivesAsmentionedintheprevioussection,aproductismodularizedforvariousobjectives.Forexample,foralargeandcomplexproductassemblythatconsistsofthousandsofpartsandhasashortdeliverytime,modularizationforassemblyisimportant.P.Gu,S.Sosale/RoboticsandComputerIntegratedManufacturing15(1999)387401389Fig.1.Thehierarchyofobjectivesandrelevantfactors.Table1StandardrelationshipfortwocomponentsNo.TypeofrelationshipInteractionvalueRelationship(forparticularobjective)1Verystrong10Firmconnectionandhighrelationship(functionallyinseparable)2Strong8Mediumconnectionbuthighrelationship3Mediumstrong6Firmconnectionandmediumrelationship4Medium5Mediumconnectionandmediumrelationship5Mediumweak4Looselyconnectedandmediumrelationship6Weak2Notadjacentrelationshipwithitsadjacentcomponent7No0NorelationatallSub-assemblies(modules)canbepreparedinparallelandthenassembledintothe"nalproduct.Inanothersituation,whenafamilyofsimilarproductsistobemade,modulardesignforstandardizationcanhelpcreatecommonmodulestoreducecomponentvarietyandcostsofproductdesignandmanufacturing.Also,modulardesignobjectivesmaybepursuedindividuallyorintegratedassingleobjectiveusingtheweightedaver-ageapproach.3.2.Phase2:interactionanalysisAllmodulardesignapproachesattempttoclustercomponentsintomodulessuchthatinteractionsarelo-calizedwithineachmoduleandinteractionsbetweenmodulesareminimized.3.2.1.IdentixcationofrelevantfactorsEachobjectiveofmodulardesigndemandsasetoffactorstobeconsidered.Checklistshavebeendevelopedtohelpdesignersidentifyrelevantinteractionfactorsforeachoftheobjectives.Forexample,thelifeexpectancyofcomponentsisamainfactorforreuse.Eachinteractionfactorcanbedecomposedintosub-factors.Forexample,thephysicalfactorincludessub-factorsofcontact,alignmentandcontainment.Toevaluatetheinteractionsfortheobjective,valuesforeachinteractionareassigned.Thisformsahierarchyofobjec-tives,factorsandsub-factorsforinteractionanalysis(Fig.1).Atthelowestlevelfortheobjectives-factors-sub-factorsahierarchy,thevaluesofinteractionsamongallcomponentsmustbedetermined.Thesevaluesaretabulatedinanarraycalledtheinteractionmatrix.Aninteractionvalueisanelementoftheinteractionmatrixandindicatesthedegreeofimportancethattwocompo-nents(therowandcolumncomponents)tobeinthesamemodule.Thesevaluesarethenscaledtorangebetween0and10(seeTable1).3.2.2.CalculationofweightedaverageAllinteractionvaluesatthelowestlevelcanbeusedcollectivelytocalculatetheweightedsumofinteractionsforanobjective.Inthehierarchyofinteractionsgener-atedintheabovesteps,alltheweightsthatrepresenttherelativeimportanceofthefactorsandtheobjectivesarenormalizedsuchthatthesummationofallbranchesfromeachnodeisequalto1.Forexample,ifthefunctionisa!ectedbyinteractionsintermsofenergyandmaterialexchangeonly,therelativeimportanceof,say,0.3and0.7areassignedtothesetwoaspects.Afteralllinksareevaluated,thecombinedmutualinteractionsbetweenthepartsarecalculatedby(i,j)"K+k/1=fkfk(i,j)#L+l/1=rlrl(i,j),(1)where(i,j)istheweightedaverageinteractionforthetwocomponentsiandj,fk(i,j)thekthfunctionalinter-actionofcomponentsiandj,rl(i,j)thelthobjectiveinteractionofcomponentsiandj,=fkthekthfunctionalfactorweightand=rlthelthobjectivefactorweight.Theresultofthisphaseisa"nalinteractingmatrixwhichrepresentsalltherelevantinformationformoduleclustering.3.3.Phase3:moduleformationSeveralalgorithmshavebeenimplementedtoclustercomponentsintomodulessuchthattheinteractionsbe-tweencomponentswithinmodulesaremaximized.Thesimulatedannealingalgorithmispresentedinthispaperto"ndtheoptimumornear-optimumsolution.Thecomponentsinthematrixareassumedtobeseparable.Iftwocomponentsarenotseparableatall,theyarecon-sideredasasinglecomponent.390P.Gu,S.Sosale/RoboticsandComputerIntegratedManufacturing15(1999)387401