机械外文文献及翻译Word文档下载推荐.docx
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机械外文文献及翻译Word文档下载推荐.docx
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MultidisciplinaryDesignOptimization
ofModularIndustrialRobotsby
UtilizingHighLevelCADTemplates
1、Introduction
Inthedesignofcomplexandtightlyintegratedengineeringproducts,itisessentialtobeabletohandleinteractionsbetweendifferentsubsystemsofmultidisciplinarynature[1].Toachieveanoptimaldesign,aproductmustbetreatedasacompletesysteminsteadofdevelopingsubsystemsindependently[2].MDOhasbeenestablishedasaconvincingconcurrentdesignoptimizationtechniqueindevelopmentofsuchcomplexproducts[3,4].
Furthermore,ithasbeenpointedoutthat,regardlessofdiscipline,basicallyallanalysesrequireinformationthathastobeextractedfromageometrymodel[5].Hence,accordingtoBow-cutt[1],inordertoenableintegrateddesignanalysisandoptimizationitisofvitalimportancetobeabletointegrateanautomatedparametricgeometrygenerationsystemintothedesignframework.Theautomatedgeometrygenerationisakeyenablerforso-calledgeometry-in-the-loop[6]multidisciplinarydesignframeworks,wheretheCADgeometriescanserveasframeworkintegratorsforotherengineeringtools.
Toeliminatenoncreativework,methodsforcreationandautomaticgenerationofHLCthavebeensuggestedbyTarkian[7].TheprincipleofhighHLCtsissimilartohighlevelprimitives(HLP)suggestedbyLaRoccaandvanTooren[8],withtheexceptionthatHLCtsarecreatedandutilizedinaCADenvironment.Otherwise,thebasicsofbothHLPandHLCtcan,assuggestedbyLaRocca,becomparedtoparametricLEGOVRblockscontainingasetofdesignandanalysisparameters.Theseareproducedandstoredinlibraries,givingengineersoracomputeragentthepossibilitytofirsttopologicallyselectthetemplatesandthenmodifythemorphology,meaningthe
shape,ofeachtemplateparametrically.
2、MultidisciplinaryDesignFramework
MDOisa“systematicapproachtodesignspaceexploration”[17],theimplementationofwhichallowsthedesignertomaptheinterdisciplinaryrelationsthatexistinasystem.Inthiswork,theMDOframeworkconsistsofageometrymodel,afiniteelement(FE)model,adynamicmodelandabasiccostmodel.Thegeometrymodelprovidestheanalysistoolswithgeometricinput.Thedynamicmodelrequiresmasspropertiessuchasmass,centerofgravity,andinertia.TheFEmodelneedsthemeshedgeometryoftherobotaswellastheforceandtorqueinteractionsbasedonresultsofdynamicsimulations.
Highfidelitymodelsrequireanextensiveevaluationtimewhichhasbetakenintoaccount.ThisshortcomingisaddressedbyapplyingsurrogatemodelsfortheFEandtheCADmodels.Themodelsarebrieflypresentedbelow.
2.1HighLevelCADTemplate—GeometryModel
Traditionally,parametricCADismainlyfocusedonmorphologicalmodificationsofthegeometry.However,thereisalimittomorphologicalparameterizationasfollows:
•Thegeometriescannotberadicallymodified.
•Increasedgeometriccomplexitygreatlyincreasesparameterizationcomplexity.
ThegeometrymodeloftherobotisgeneratedwithpresavedHLCts,createdinCATIAV5.Thesearetopologicallyinstantiatedwithuniqueinternaldesignvariables.Topologicalparameterizationallowsdeletion,modification,andadditionofgeometricelementswhichleadstoamuchgreaterdesignspacecaptured.ThreetypesofHLCtsareusedtodefinetheindustrialrobottopologically;
DatumHLCtwhichincludeswireframereferencesrequiredforplacementfortheActuatorHLCTsandStructureHLCts,asseenFig.2.
Fig.2Anindustrialrobot(left)andamodularindustrialrobot(right)
ThenamesofthereferencesthatmustbeprovidedforeachHLCtinstantiationarestoredintheknowledgebase(seeAppen-dixA.4),whichissearchedthroughbytheinferenceengine.InAppendixA,pseudocodeexamplesdescribeshowthereferencesareretrievedandhowtheyarestoredintheknowledgebase.
Theprocessstartsbytheuserdefiningthenumberofdegreesoffreedom(DOF)oftherobot(seeFig.3)andisrepeateduntilthenumberofaxis(i)isequaltotheuserdefinedDOF.InordertoinstantiatethefirstStructureHLCt,twoDatumandtwoactuatorinstancesareneeded.ReferencesfromthetwoDatuminstanceshelporientingthestructureinspace,whilethegeometriesoftheactuatorinstances,atbothendsofthelink,areusedtoconstructtheactuatorattachments,asseeninFigs.2and3.Fortheremaininglinks,onlyonenewinstanceofbothdatumandactuatorHLCtsarerequired,sincethedatumandactuatorinstancesfromadjacentlinksarealreadyavailable.AppendixA.2showsapseudocodeexampleofaninstantiationfunction.ThefirstinstantiateddatumHLCtisdefinedwithreferencetotheabsolutecoordinatesystem.TheremainingdatumHLCtinstancesareplacedinasequentialorder,wherethecoordinatesystemofpreviousinstancesisusedasreferencefordefiningthe
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