Compatiability Analysis and Case Studies of Axiomatic Design and TRIZ.docx

Compatiability Analysis and Case Studies of Axiomatic Design and TRIZ.docx

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CompatiabilityAnalysisandCaseStudiesofAxiomaticDesignandTRIZ

CompatiabilityAnalysisandCaseStudiesofAxiomaticDesignandTRIZ

Thisispart2ofa2-partarticle.Part1appearedinAugust,2000.AComparisonofTRIZandAxiomaticDesign.

KaiYangandHongweiZhang

kyang@mie.eng.wayne.edu

DepartmentofIndustrialandManufacturingEngineering

WayneStateUniversity

Detroit,MI48202,USA

ABSTRACT

ThisisoursecondresearchpaperincomparisonsofTRIZandAxiomaticDesign.Inthispaper,designproblemsolvingapproachesofAxiomaticDesignandTRIZareanalyzedandcomparedindetail,andseveralcasestudiesarediscussedtosupportourpointofviewaboutthesetwomethodologies.

INTRODUCTION

ThefirstresearchpaperincomparisonsofTRIZandAxiomaticDesign,thesetwomethodologiesarereviewedandbrieflycompared.TheconclusionisthatsomedesignrulesinADandproblem-solvingtoolsinTRIZarerelatedandsharethesameideasinessence.TheobjectivesofthispaperistocompareandcontrastTRIZandAxiomaticDesignproblemsolvingmethodsindetail,andtodiscussthepossibilityofintegrationofthem.Thelong-termgoalofthisworkistodevelopagenericframeworkandtoolstohelpdesignersmakeandunderstandcorrectdesigndecisions.

Thebodyofthispaperisdividedintofiveparts.ThefirstpartdiscussesthedomainmappingtheoryinADandcontradictiontransformationideainTRIZ.ThesecondandthirdpartsanalyzetwoaxiomsandtheirpossiblecorrespondingtechniquesinTRIZ.Thefourthpartpresentscomplementarityofthesetwomethodologiesusingacasestudy,andthelastpartdiscussestheadvantagesandlimitationsofTRIZandAxiomaticdesign.

DOMAINMAPPINGINADANDCONTRADICTIONTRANSFORMATIONINTRIZ

ADstatesthatdesignisthecreationofsynthesizedsolutionsintheformofproducts,processes,orsystemsthatsatisfyperceivedneedsthroughthemappingbetweentheFRsinfunctionaldomainandtheDPsinphysicaldomain,throughtheproperselectionofDPsthatsatisfyFRs.Toconductdesign,onemustdeterminethedesignobjectivebydefiningitintermsoffunctionalrequirements.Thentosatisfythesefunctionalrequirements,aphysicalembodimentcharacterizedintermsofdesignparametersmustbecreated.ThedesignprocessinvolvesrelatingtheseFRsofthefunctionaldomaintotheDPsofthephysicaldomain.

TRIZ,ontheotherhand,statesthatsomedesignproblemmaybemodeledasatechnicalcontradiction,whichisthefunctionalconflictorcoupling.Aproblemrequirescreativitywhenattemptstoimprovesomefunctionalattributesleadtodeteriorationofotherfunctionalattributes.Adesignproblemassociatedwithapairoffunctionalcontradictioncanberesolvedeitherbyfindingatrade-offbetweenthecontradictions,orbyovercomingit.TRIZdoesnotaccepttrade-offs,anditstressesthatanidealdesignsolutionistoovercometheconflict.

Extensivestudiesininventionproblemsolvingdemonstratethatafunctionalcontradictionisderivedfromaphysicalone.Inordertoovercomeafunctionalconflict,onehastoidentifyaphysicalelementofthesystemthatcontrolsthecompetingattributes,andthiselementmustbemodifiedinsuchawaythatitwouldmeettheoppositerequirementstoitsstate.TransformingafunctionalcontradictioninsystemlevelintoaphysicalcontradictionincomponentlevelisalwaysrequiredinTRIZ.Figure1illustratesthisidea.

ThefollowingAmpoulesSealingcasestudydemonstratesthatTRIZandADtheoryofferthecompatibleideasinproblemsolving.

AmpoulesSealingCaseStudy

Inamanufacturingprocessaburnerisusedtosealampoulescontainingdrugs.Theproblemisthattheflamemayoverheatthedruginampoulesanddegradethedrugs.Whatshouldwedointhissituation?

LetususeADtheoryandTRIZtoanalyzethemanufacturingprocessandthencomparetheirsimilarityanddifferences.FromADstandpoint,thefunctionalrequirementsinthefunctionaldomainofthismanufacturingprocessmaybeexpressedastwoindependentrequirementsthatsatisfytheAxiom1.

FR1=sealampoules

FR2=protectdrugsfromdeteriorationduringtheprocess

Theoriginaldesignselectsonlyonedesignparameterinitsphysicaldomain,whichis:

DP1=heatbyaburner.

TherearetwoFRsbutonlyoneDPinthedesignsolution.ThenumberofDPsislessthanthenumberofFRs.BasedontheTheorem1,thedesigniseitheracoupleddesignresult,ortheFRscannotbesatisfied.ItisclearlythatthisisacoupleddesignbecauseDP1affectsbothFR1andFR2.Thedesignequationis:

InordertosatisfytwoFRsindependently,theprocessdesignshouldbedecoupled.Theorem2states:

whenadesigniscoupledduetothegreaternumberofFRsthanDPs（i.e,m>n）,itmaybedecoupledbyadditionofnewDPssoastomakethenumberofFRsandDPsequaltoeachother.Ifasubsetofthedesignmatrixcontainingn�nelements,onecanconstituteatriangulardesignmatrixtodecouplethepreviousdesign.

So,thecoupleddesignrepresentedbyaboveequationcanbemodifiedintoadecoupleddesignbyaddingaDPandchangingthedesignmatrixintoatriangularoneasfollows:

IftheburnerrepresentsDP1,whatisDP2?

ItisobviousthatDP2shouldcounteracttheeffectoftheheatproducedbytheburner.Inpractice,waterisanidealcomponenttooffsettheheat.So,theonepossibledesignsolutionisgiveninfigure2.

FromTRIZstandpoint,thisdesignproblemsituationcanbeeasilymodeledasthetechnicalcontradiction（functionalconflict）inthesystemlevel:

wewanttoheatampouletop（attribute揂�）tosealampoulesbutitcausesdegradationtomedicine（attribute揃�）.

TRIZcontradictionanalysisstatesthatattheheartofatechnicalcontradictionishiddenaphysicalone.Inordertoovercomethetechnicalcontradiction,aphysicalcomponentshouldbemodifiedinsuchawaythatitwouldmeettheoppositerequirements.Inthisampoulesealingcase,theheatimproves揂�（seal）,butdegrades揃�（medicineintheampoule）.So,theampoulesshouldbehottoimproveseal,anditshouldbecoldtonotdamagethemedicine.Clearlytheampouleisthephysicalcomponentthatcontrolsthetechnicalcontradiction.

TRIZKnowledgeBasetoolsprovideseveralseparationprinciplestoovercomephysicalcontradictions.Threemostfrequentlyusedprinciplesareseparationofoppositepropertiesinspace,separationofoppositepropertiesintimeandseparationofoppositepropertiesbetweenwholesystemanditscomponents.

Carefulexaminationofthreeseparationprinciples,itisnotdifficultytorecognizethatseparationinspaceshouldbeusedinthissituation.Inordertomakethetopofanampoulehotandotherpartcold,itisproposedtosurroundtheampouleswithawaterjacket.Thewatertakesexcessheatawayfromampoulestopreventoverheatingthedrag（seefigure2）.

INDEPENDENCEAXIOMINADANDSEPARATIONPRINCIPLESINTRIZ

IndependenceAxiominADimpliesthatthedesignmatrixbeofaspecialform.TheconsequencesofapplyingAxiom1tothedesignmatrixareasfollows:

Itisdesirabletohaveasquarematrix,i.e.,n=m

Thematrixshouldbeeitherdiagonalortriangular.

Inrealdesignsituation,weneedtosearchforDPsthatyieldadiagonalortriangulardesignmatrix.Thedegreeofindependencecanbetreatedasthedefinitionoftolerance.

Thereareahierarchyinboththefunctionaldomainandthephysicaldomain,andazigzaggingprocessbetweentwodomainsindesignprocess.Thedomainprocessismoststraightforwardwhenthesolutionconsistsofuncoupleddesignateachlevel.Whenthedesignisuncoupled,wecandealwiththeindividualFRsofahierarchicallevelwithoutconsideringotherFRsofthesamelevelandproceedinghierarchicallevels.Whenthedesigniscoupled,wemustconsidertheeffectofadecisiononotherFRsandDPs.Figure3showsthedesignmatricesandstructuremodels.Therefore,thedesignershouldtrytofindsolutionsbyattemptingtouncoupleordecoupleddesignineverylevelofdesignhierarchy.

Theproblemishowtodecoupleacoupleddesign.Itisobvioustomodifydesignmatrixtobeeitherdiagonalortriangular.Inpractice,manycoupleddesignsundergochangesandbecomeadecoupleddesignthroughatrialanderrorprocessthatisinoppositiontoTRIZmethodology.

InTRIZmethodology,acoupleddesignisdefinedastheexistenceofacontradiction.Removalofdependencyofcouplingmeanstoovercomeatechnicalorphysicalcontradictionbyapplyinginventiveprinciplesorseparationprinciples.Thus,theseprinciplescanserve,withADcorollariesandtheorems,astheguidelinesofde-couplingacoupleddesign.

ThedesignprocessofthePaperHandlingMechanism[11]illustrateshowseparationprinciplesinTRIZaidtosatisfyAxiom1inAD.

PaperHandlingMechanismCaseStudy

Thefunctionofthepaperhandlingmechanismusedinanautomatictellermachineis搃solateonebillfrompiledbills�,whichisthefirstFRofthesystem.Severalphysicalstructurescanbeusedtorealizethisfunctionalrequirement,suchasfriction,vacuumandleafingetc.Frictionmethodisselectedanditsmechanismisshowedinfigure4.

However,thisDPdoesnotalwaysworkcorrectlybecausethefrictionischangeableundersomecircumstances.Ifthefrictionforceworkingonthetopeofbillbecomestoolargebysomeaccident,twoormorebillswillbesentforwards,andifitbecomestoosmallthetopbillmaynotbeisolated.So,wehavetodecomposethefirstlevelfunctionalrequirementintotwofunctionalrequirements:

揼iveaforwardforcetothefirstbill�and揼iveabackwardforcetothesecondbill�.Tosatisfythesetworequirements,thenewDPofthisdesignisapairofrollersrotatinginthesa