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Y.Wu(Ed.):ICHCC2011,CCIS163,pp.269275,2011.Springer-VerlagBerlinHeidelberg2011Case-BasedDesignforHydraulicPowerCircuitChi-ManVong,Pak-KinWong,Weng-FaiIp,andZhi-XinYangFacultyofScienceandTechnology,UniversityofMacau,Macaucmvong,fstpkw,andyip,zxyangumac.moAbstract.Thispaperdescribesthedesignandimplementationofanautomatichydrauliccircuitdesignsystemusingcase-basedreasoning(CBR)asoneofthesuccessfulartificialintelligenceparadigms.Thedomainofcase-basedreasoningandhydrauliccircuitdesignarebrieflyreviewed.ThenaproposedmethodologyinautomaticcircuitdesignandlearningwiththeuseofCBRisdescribed.FinallyanapplicationexamplehasbeenselectedtoillustratetheusefulnessofapplyingCBRinindustrialhydrauliccircuitdesignwithlearning.Keywords:Case-basedreasoning(CBR),adaptationcase,hydrauliccircuitdesign.1IntroductionTheuseofcomputersinengineeringdesignhasbecomeamajortrendinindustry.Today,differentcommercialautomaticcomputer-aideddesign(CAD)softwareisavailabletoautomatethedesignprocessinmanyengineeringapplications.However,CADsoftwareinhydraulicsystemdesignisnotasprominentasinmanyotherareasofengineeringdesign.Thisismainlyduetothecomplexityofhydraulicanalysisandlackofagreementofthemostappropriateapproachtothedesignprocess.Inrecentyears,manyresearchesonintelligentCADorexpertsystemsforhydrauliccircuitshavebeenfoundintheliterature.MostoftheCADsystemsarebuiltfromproductionrules1fordesignknowledgerepresentationorintegratedrule-basedandobject-orientedtechnology2forreducingthecomplexityinhydraulicsub-circuitandcomponentrepresentation.Althoughtheapproachesareeffective,theacquisitionandmaintenanceofrulesaretheproblemsfacingbynotonlythesoftwareengineersbutalsothedesignersusingthesoftware.Moreover,staticlearning1isanotherissueoftraditionalrule-basedsystems.Toresolvetheproblemsinheritedfromconventionalrule-basedexpertsystems,theAIcommunityproposedanotherreasoningparadigmcalledcase-basedreasoning(CBR).CBRsupportslearninginthewaythatnewknowledgecanbeappendedtotheknowledgebasewithoutwiderrecompilationofthesystem.ThisisoneofmainadvantagesofCBRthatmaintenanceofknowledgetakesmuchlesstime.ThispaperstudiestheapplicationofCBRinhydraulicsystemdesignandaprototypeautomatichydrauliccircuitdesignsystemhasbeendevelopedtoverifythisproposedmethodology.1Whenevertherulesareupdated,thewholesystemhastoberecompiled.270C.Vongetal.2Review2.1Case-BasedReasoningCBR3isamethodologythatallowsdiscoveringanalogiesbetweenacurrentworkingsituationandpastexperiences(referencecases).CBRmakesdirectuseofpastexperiencestosolveanewproblembyrecognizingitssimilaritywithaspecificknownproblemandbyapplyingitssolutiontofindasolutionforthecurrentsituation.CBRhasbeenusedtodevelopmanysystemsappliedinavarietyofdomains4,5,6,7,8,9,10,includingmanufacturing,design,law,medicine,andplanning.BasicallyCBRisconstitutedwithfourREs3:RETRIEVEretrievesimilarpastcasematchedagainstcurrentproblemREUSEreusetosolvecurrentproblembasedonsolutionofpastcaseREVISErevisethepastsolutionifanycontradictionoccurswhenappliedtocurrentproblemRETAINretainthefinalsolutionalongwiththeproblemasacaseifthecaseisusefulinthefutureWhentheuserinputsaproblem,theproblemisinterpretedandconvertedasanewcaseintothespecificformatofthereasoningsystem.ThentheconvertednewcaseentersthestageofRETRIEVALwherethenewcaseismatchedagainstthepreviouscasesinthecaselibraryofthereasoningsystem.IntheretrievalstageofCBRusuallyasimplesimilarityfunctionisemployedtofindthenearestneighborforthecurrentproblemfromthereferencecases.Theformulaislistedin(1)wherewiistheimportanceofdimensioni,fiIandfiRarethevaluesforfeaturefiintheinputandretrievedcases,respectively.Forsymbolicvaluesoff,0if1ifIRIRiiiiIRiiffffff=.211()(,)nIRiiiIRiniiwffEffWw=.(1)2.2HydraulicCircuitDesignHydraulicpowerisoneofpowertransmissionsystemsandcontrol.Itconvertsmechanicalenergytohydraulicenergyforproducingusefulworksuchaspressingorlifting.Themaintaskofhydraulicpowersystemdesigniscircuitdesign.Thegeneralprocedureisshownasfollows:I.Thecircuitisdesignedaccordingtotheinformationprovidedbytheclientsuchasmaximumoperatingpressure,maximumload,speedofactuator,dutycycleandapplication,etc.II.Thesizesofthelinearorrotaryactuatorsaredeterminedaccordingtothemaximumoperatingpressure,maximumloadandloaddisplacement.III.Convertthecalculatedactuatorsizesintostandardsizes.Case-BasedDesignforHydraulicPowerCircuit271IV.Thesystemparameterssuchashydraulicoilflowrate,pressurechangeover,etc,aredetermined.V.Thesuitableactuatorsub-circuits,pumpandpumpsub-circuitisselectedbasedonthesystemparametersandthedesignspecifications.VI.Otherhydrauliccomponentsusedinthecircuitarefinallyselected.3ApplyingCBRinIndustrialHydraulicCircuitDesignInsection2.2stepV,hydraulicengineersareusuallyaccustomedtomodifyanexistingcircuitdesignintoanewonefordifferentsituationanduse.Itisbecausehydrauliccircuitdesignisusuallysimilarevenfordifferentsituation,sohydraulicengineershavetomanuallylookthroughmanyexistingeffectivecircuitsandthenselectasimilarandsuitableoneandperformmodification.Theprocessisrepetitiveandtediousinthestageofretrieving,becauseengineershavetoreviewthecircuitsonebyone.However,theprocessoftheretrievinganexistingcircuitandadaptingittofitbetterthecurrentsituationcanbestronglysupportedbyCBR.Iftheexistingcircuitsarecollectedinacomputerdatabase(caselibrary),andeachcircuitisstoredalongwithitsfunctionalandapplication-specificrequirementsoftheoutputs,theseparameterscanserveasthecase(circuitdesign)indexes.Wheneverthehydraulicengineerwantstoretrieveapastcasefromthecaselibrary,hejustneedstoinputthefunctionalandapplication-specificrequirements,andCBRuses(1)tocalculatethemostsimilarpastcase.Iftheengineerisnotsatisfiedwiththerecommendedcase,thenthenextmostsimilarpastcasewouldbeshown.Thiscouldbedonebecausethecasesarealreadyrankedwithdifferentsimilaritylevelinthecalculationofcasesimilarity.Afterthat,theengineercouldadaptormodifytheretrievedcasemanuallybytheaboveprocedureorbyapplyingtheadaptationrulessuppliedbyCBR.Thoseadaptationrulesarespecificproductionrulescapturedfromexpertsorfromtheengineersownexperience.Finallytheengineercandecideifthecaseisgoodenoughtostoreintothecaselibraryforfutureuse.Hydrauliccircuitdesignsdifferbynotonlythecircuitdiagrambutalsothefunctionalattributesalongwiththem.Forcircuitadaptation,ifsomecomponentsarereplaced,thentheattributeswillalsobemodifiedbyinsertingordeletingsomeofthem.CBRenablesstructuralmodificationofcases,sothatattributescanbeaddedordeletedaccordingly.Forexample,anengineerretrievesanpastcaseandperformsmodificationonthecircuitdesign,thenthenumberofattributeswouldbechangedaccordingto,whichsub-circuitsarerevisedbyaddingpredefinedattributesordeletingunnecessaryattributesinthesub-circuits.4ApplicationExampleThesystemimplementedisabletorecommendmostsimilarcircuitdesignbasedonthecircuitspecification.Theworkingenvironmentandfront-enduserinterfaceofthecircuitdesignsystemareshowninFig.1.Thelearningabilityofthesystemisillustratedinthispartwiththeaidofanexample.Table1showspartialattributesofthecaserepresentationforahydraulicsub-circuitshowninFig.2.272C.Vongetal.Fig.1.Workingenvironmentandfront-enduserinterfaceofthecircuitdesignsystemTable1.Partialattributesofahydraulicsub-circuitDrawingnameVar_1Max.Flow33L/minMax.Pressure630BarVariationstepsofspeed2Variationstepsofpressure1Wheneverapastsimilarcaseisretrieved,thecaseisadaptedinordertoreuseitforcurrentsituatio