Design_Axioms

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1、Lecture2:ThePrinciplesofDesign&DesignAxiomsBackground•Theconventionaldesignprocessreliesonintuitionandruleofthumbmethods.•Axiomaticapproach(basedondesignaxioms)establishascientificfoundationforthedesignfield.Ref:•Magrab,1997,IntegratedProductandProcessDesignandDevelopment,CRC

2、Press.•NamPSuh,1990,ThePrinciplesofDesign,OxfordUniversityPress1Definitions•AnAxiomisafundamentaltruththatisalwaysobservedtobevalid.•Axiomsmaybehypothesizedfromalargenumberofobservationsbynotingthecommonphenomenasharedbyallcases;theycannotbeprovenorderived,buttheycanbeinvalid

3、atedbycounter-examples.2Definitions•AnTheorem/Principleisapropositionthatmaynotbeself-evidentbutthatcanbeprovedfromacceptedaxioms.•ACorollary/DesignRuleisapropositionthatfollowsfromaxiomsortheorems.3DesignFunctionalRequirement(FR)andDesignParameter(DP)•FRsistheminimumsetofind

4、ependentrequirementsthatcharacterizethefunctionalneedsoftheproductdesign.•EachFRisindependentofotherFRs.•DPsarethekeyphysicalvariablesthatcharacterizethedesignobjecttofulfiltheFRs.•MathematicalRepresentationoftheIndependenceAxiom:DesignEquationWhenm=n,designmatrixisasquaremat

5、rix.4Twodesignaxiomstomakegooddesign•Axiom1•TheIndependenceAxiom:Maintaintheindependenceoffunctionalrequirements(FRs).•Axiom1statesthatduringthedesignprocess,aswegofromtheFRsinthefunctionaldomainwithdesignparameters(DP)inthephysicaldomain,themappingmustbesuchthataperturbation

6、inaparticularDPmustaffectonlyitsreferentFR.5Axiom1canberestatedas:•AnoptimaldesignalwaysmaintainstheindependenceofFRs.•Inanacceptabledesign,theDPsandtheFRsarerelatedinsuchawaythatspecificDPcanbeadjustedtosatisfyitscorrespondingFRwithoutaffectingotherFRs.63cases:1.Theuncoupled

7、design-simplestcaseofdesign:72.Thecoupleddesign-undesirable83.Decoupleddesign–thedesignmatrixAisatriangularmatrixTheindependenceofFRscanbeassuredifweadjusttheDPsinaparticularorder.9Example:•Two-knobFaucet(WaterTap)FRs:FR1=ObtainwaterflowrateFR2=ObtainwatertemperatureDPs:DP1=M

8、eanstoadjustcoldwaterflowDP2=MeanstoadjusthotwaterflowPossibleDesign