机械专业英文文献向理想的机械工程设计支持系统.docx
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机械专业英文文献向理想的机械工程设计支持系统.docx
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机械专业英文文献向理想的机械工程设计支持系统
Towardtheidealmechanicalengineeringdesignsupportsystem
DavidG.Ullman
AbstractThispaperdetailstheprogresstowardthedevelopmentoftheidealmechanicalengineeringdesignsupportsystem.ItattemptstolookatthegapbetweentheneedsofamechanicalengineerandwhatiscurrentlyavailableonCADsystemsSincethetern:
CADemphasizesthatthecomputerisanaidtothehumandesigner,thispaperisdesignercentricitisbasedheavi~ontheactivitiesperformedbydesignersandthetypesofinformationdevelopedbythen:
SeventeengoalsfortheidealmechanicaldesignsupportsystemarelistedThesearedirectedatthetypesofinformationdevelopedduringthedesignprocessandtheactivitiesusedtodevelopthemForeachoftheseventeen,backgroundinformation,thecurrentstateoftheart,andopportunitiesforfuturedevelopmentareitemized
KeywordsMechanicalengineeringdesign,CAD,Supportsystem
1
Introduction
ThispapersummarizestheprogressmadetowardthedevelopmentoftheidealmechanicalengineeringdesignsupportsystemFornearly30years,computeraideddesign(CAD)systemshavebeentoutedbytheirdevelopersassystemsthatsupportengineeringdesignersdevelopingproductsCADsystemshavehadamajorimpactonhowdesignisaccomplishedintheworkplaceThisbeingsaid,thereisamazinglylittleibrmalresearchontheeffectsofthesesystemsonthedesignersandonthefinalproducts’Thispaperpresentsastructurefordiscussingtheseeffects
Indoingso、ltsummarizeswhatisknownandwhatneedscobestudiedFinally、itdiscusseshowCADsystemshaveevoh,edtosupportincreasingportionsoftheactivitiesthatareusedtodevelopproducts.
ThetermCADemphasizesthatthecomputerlsanaidtothehumandesigner,sothispaperisdesignercentricitisbasedheavilyontheactivitiespertbrmedbydesignersandthetypesofintbrmationdevelopedbytheminmanyways,thisisanupdateoftwoearlierpapers,‘‘Theimportanceofdrawinginthemechanicaldesignprocess”[29Jand“issuescriticaltothedevelopmentofdesignhistory,designrationaleanddesignintentsystems”【311Thelatterpaperdeveloped13outstandingissuesthatneededtoberesolvedtorealizethecaptureandqueryofengineeringdesignintormationasapotentiallorlmprovmgthedesignprocess
andthereuseofdesignIntormation.
ThetbundationforthefirstpaperwasthestudyofthemarksmadeonpaperbynvemechanicaldesignengineersofvaryingbackgroundsandexperienceTheywereeachgiventheinitialspecificationstbroneoftwot~irlysimple,yetrealistic,mechanicaldesignproblemstakenfromprofessionalpracticeTheengineerswererequestedtothinkaloudastheysoh,edtheproblemsTheirverbalreports、drawings,andgestureswerevideoandaudiotapedforaperiodof610hThetapeddatawerethentranscribedtoobtaina‘‘protocol”ofthedesignsessionEachdesignermadenumerousdrawingsduringhisorhersolutionoftheproblemA110fthesewereonpaperCADsystemswerenotusedinthestudgbecausenoneofthedesignersusedCADlntheirdailypractice,anditsusewouldhaveaddedanothervariabletoanalreadycomplexexperiment.
Fromthemorethan40hofdatataken,15sectionswereselectedthatrepresentedtypicalconceptual,layout,detailandselectiondesignforeachsubjectThe15sectionsofprotocoldataconsistedof174rainofdataThedatawereanalyzedtoexploretheobservationsthatdrawingsare
usedto:
1Archivethegeometrictormofthedesign
2Communicateldeasbetweendesignersandbetweenthedesignersandmanufacturingpersonnel
3ActasananalysistoolOften,missingdimensionsandtolerancesarecalculatedonthedrawingasitlsdeveloped
4Simulatethedesign
5ServeasacompletenesscheckerAssketchesorotherdrawingsarebeingmade,thedetailslefttobedesignedbecomeapparenttothedesignerThis,inett)ct,helpsestablishanagendaofdesigntasksleLtoaccomplish
6Actasanextensionofthedesigner’sshorttermmemoryDesignersoftenunconsciouslvmakesketchestohelpthemrememberldeasthattheymightotherwisetorget
The1990paperrefinedandsupportedtheseobservationsAdditionalIv,althoughthesubiectsdidnotuseCADsystems,theresuhssuggestedthat:
1CADsysternsnl[istallowtbrsketchinglnput
2CADsysternsnlustallowforavarietyofInterfacestbrthedesignerThisdoesnotmeanmorewaystodefineacircle、butaneftorttomatchtheinterfaceandtheimageontheCADsystemtothatneededbythedesigner
3CADsystemsiiltlStrecognizedomaindependentfeaturesandtreatthemasentities
4CADtoolsneedtobeabletomanageconstraints(evenabstractandtkmctionalconstraints)andensuretheirsatistaction、asitisevidentthathumandesignersarecognitivelylimitedinthisability
Sincethatpaperwaswritten,CADsysternshavematuredandhaveaddressed、atleasttosomedegree、all南uroftheconclusionsiIowever,eventhemostrecentsystemsareaongwaytbomtheidealmechanicalengineeringdesignsupportsystemInthispaper,theidealsystemwillbedescribedandprogresstowardthisldealdiscussed
2
Amodelofdesignproblemsolving
itmaysomedaybepossibleforadesignertoputona‘‘thinkingcap”thatcantakehisorherthoughtsanddeelopahardwarereDresen【atlonResearchonunderstandingcognitiveprocesses,CAD,andrapidprototypinglscertainlymovinglnthatdirectionThisidealimpliesthatwecantbrmtflateconceptsJnourheadsthataresumcientlywelltormedtowarranthardwareItalsoassumesthatCADsystemsaresuflicientlgdevelopedtotakeourthoughtsandmanagetheevolutionofpartsandassembliesCADsystemdevelopmentwillrequireantinderstandingofthecognitiveworkingsofdesignerssothatthetransitiontbomthoughttorepresentationispossible
Toexplorewhatlsknownaboutthislink、considertherelationshipbetweenthehumanproblemsoh,erandtheexternalenvironmentshowninFig1ThisfigurelsbasedonthemodeldevelopedbvNewellandSimon『20landlscalledtheinformationprocessingsystem(IPS)Thefigureisasimple‘‘map’’ofwhereinformationaboutthedesignisdevelopedandstoredThefigureshowsaninternal,humanproblemsolvingenvironment(insidethemindofthedesigner)andanexternalenvironment(outsidethemindofthedesigner)Withinthedesigner,twolocationscorrespondtothetwodifferentkindsofmemory:
shorttermmemory(STM)andlongtermmemory(LTM)Externaltothedesigner,therearemany‘‘designstoragelocations”includinggraphicalrepresentationmediasuchaspiecesofpaperandCADtools,aswellasothermediasuchastextualnotes,handbooks,andcolleaguesEachlocationhascertainpropertiesthataffecthowitcanbe
usedindesign
DetailonthecharacLeris【icsoftheSTMandtheLTMlsbasedonNewellandSimon’smodel[20JExtensionshavebeenmadetoitforvisualimagery【1l,12,13Jandefforts
havebeenmadetocodil~~it【21itmustberealizedthatthecontentsofthemodelgivenherearenotfollyagreedtointhecognitivepsychologycommunity,butthe),arecertainlysecureenoughtoprovideabasisfordiscussingtheroleofCADinmechanicaldesign
2.1
Short-termmemoryShorttern:
memorglsvervfastandpowerfulThecontentsoftheSTMaretheinformationweareawareof,thatis,ourconsciousmindAlldesignoperations(。
g,visualperceptionanddrawingcreation)arebasedoninformationintheSTMUnfortunately,theSTMhaslimitedcapacityStudiesshowthatitislimitedtoapproximatelysevencognitiveunitsorchunksofinformationDuringdesign,thesechunksarevisualimagesofforn:
s,informationaboutfonction,mentaln:
odelsoffit,stepstorepresentanideainaCADsystem,orotherdiscretepiecesofinformationAlthoughlimitedincapacity,theSTMisafastprocessorwithprocessingtimesontheorderof100nls[41
2.2
Long。
termmemoryThelongtermmemory,ontheotherhand,hasessentiallyinfinitecapacity,butaccessisslowAccesstoLTMisalsonotdirectMemoriesrntlStbetriggeredbysomecueor
retrievalstrategybasedonintbrmationinSTMDuringdesign,partsofthedesignarestoredinLTMThesearerelativelyeasytocuebecause,atanytime,currentlyin:
portantpartsofthedesignareintheSTMandcanactaspointersfortheknowledgeintheLTM
2.3
ExternaIenvironment
intheexperimentsrunin1990[291,itwasclearthatmanydrawingactionswerenotusedtodocumenttheresultsofthedesignactivitybutwerepartofthedesignprocessitselgifthesubjectscouldbareperformedtheseactivitiesintheirheadstheywouldhavedonesowithoutmakingthesketches,notes,andcalculationsonpaperThus,itisconcludedthattheexternalenvironmentlsoftenusedasanextensionoftheSTMandLTMitlscriticalthatthemediausedinthisenvironmentsupportthedesigner’scognitionItemizingthematchormismatchbetweenthemediaandhumancognitionisoneoftheobjectivesofthispaper
Theapproachtakeninthispaperistofirstdescribethetypesot'informationmanaged(Sect3)andthendiscusstheactivitiesperformedbytheexternalenvironmentsupportingthedesigner(Sect4)ThetypesofinformationandactivitiesaredevelopedintermsofthecapabilitiesofanidealsystemEachsubsectionbeginswithstatementsaboutwhattheidealengineeringdesignsupportsystemshoulddoSupportinginformationfollowsthesestatementsNext,thereisadescriptionofhowpaperandpencil,2DCADsystems,solidmodelingsystems,parametricsystems,andothersupporttoolsmeettheidealEachsubsectionconcludeswith0DD0r【unlLlesforlmprovement
3
Informationmanagedbyanidealmechanicalengineeringdesignsuppo~system
Mechanicalengineersmanageabroadrangeofinformationinthissection,theXarioustypesofinformationwillbeitemized,beginningwiththemostbasicandprogressingtothemostdemanding
3.1
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