塔式起重机有限元分析外文翻译.docx

FEMOptimizationforRobotStructureWangShijun,ZhaoJinjuan*DepartmentofMechanicalEngineering,Xi'anUniversityofTechnologyShaanxiProvince,People,sRepublicofChinaInstituteofPrintingandPackingEngineering,Xi'anUniversityofTechnologyAbstractInoptimaldesignforrobotstructures,designmodelsneedtohemodifiedandcomputedrepeatedly.Becausemodifyingusuallycannotautomaticallyberun,itconsumesalotoftime.ThispapergivesamethodthatusesAPDLlanguageofANSYS5.5softwaretogenerateanoptimalcontrolprogram,whichmikeoptimalprocedurerunautomaticallyandOptimalefficiencybeimproved.1) IntroductionIndustrialrobotisakindofmachine,whichisControlledbycomputers.Becauseefficiencyandmaneuverabilityarehigherthantraditionalmachines,industrialrobotisusedextensivelyinindustry.Forthesakeofefficiencyandmaneuverability,reducingmassandIncreasingstiffhessismoreimportantthantraditionalmachines,instructuredesignofindustrialrobot.Alotofmethodsareusedinoptimizationdesignofstructure.Finiteelementmethodisamucheffectivemethod.Ingeneral,modelingandmodiiyingaremanual,whichisfeasiblewhenmodelissimple.WhenmodeliScomplicated,optimizationtimeislonger.IntheIongeroptimizationtime,calculationtimeisusuallyverylittle,amajorityoftimeisusedformodelingandmodifying.Itiskeyofimprovingefficiencyofstructureoptimizationhowtoreducemodelingandmodifyingtime.APDLlanguageisaninteractivedevelopmenttool,whichisbasedonANSYSandisofferedtoprogramusers.APDLlanguagehastypicalfunctionofsomelargecomputerlanguages.Forexample,parameterdefinitionsimilartoconstantandvariabledefinition,branchandloopcontrol,andmacrocallsimilarIofunctionandsubroutinecall,etc.Besidesthese,ItpossessespowerfulcapabilityofITiathematicalcalcuIation.ThecapabilityofmathematicalCalculationincludesarithmeticcalculation,comparison,rounding,andtrigonometricfunction,exponentialfunctionandhyperbolafunctionofstandardFORTRANlanguage,etc.BymeansofAPDLlanguage,thedatacanbereadandthencalculated,whichisindatabaseofANSYSprogram,andrunningprocessofANSYSprogramcanbecontrolled.Fig.1showsthemainframeworkofaparallelrobotWiththreebars.Whenthelengthofthreebarsarechanged,conjunctendofthreebarscanfollowagiventrack,whererobothandisinstalled.Coreoftopbeamistriangle,owingtothreebarsusedinthedesign,whichisshowedinFig.2.UseofthreebarsmakestopBeamnonsymmetricalalongtheplanethatisdefinedbytwocolumns.AccordingtoaqualitativeanalysisfromFig.!,Stiffnessvaluesalongz-axisaredifferentatthreejointlocationsonthetopbeamandstiffnessatthelocationbetweenbar1andtopbeamislowest,whichisconfirmedbycomputingresultsoffiniteelement,too.Accordingtodesigngoal,stiffnessdifferenceatthreejointlocationsmusthewithinagiventolerance.Inconsistentofstiffnesswillhaveinfluenceonthemotionaccuracyofthemanipulatorunderhighload,soitisnecessarytofindtheaccuratelocationoftopbeamalongx-axis.Tothequestionspresentedabove,thegeneralsolutionistochangethelocationofthetopbeammanytimes,comparetheresultsandeventuallyfindaproperposition,Themodelwillbemodifiedaccordingtothelastcalculatingresulteachtime.Itisdifficulttoavoidmistakesiftheiterativeprocessiscontrolledmanuallyandtheiterativetimeistoolong.Theouterwallandinnerribshapesofthetopbeamwillbechangedafterthemodelismodified.TofindtheappropriateIocationoftopbeam,themodelneedstobemodifiedreetitiously.Fig.1SolutionofOriginalDesignThispapergivesanoptimizationsolutiontothepositionoptimizationquestionofthetopbeambyAPDLlanguageofANSYSprogram.Aftertheanalysismodelfirstfounded,theoptimizationcontrolprogramcanbeformedbymeansofmodelinginstructioninthelogfile.Thelateriterativeoptimizationprocesscanbefinishedbytheoptimizationcontrolprogramanddonotneedmanualcontrol.Thetimespentinmodifyingthemodelcanbedecreasedtotheignorableextent.Theefficiencyoftheoptimizationprocessisgreatlyimproved.2) ConstructionofmodelforanalysisThestructureshowninFig.1consistsofthreeparts:twocolumns,onebeamandthreedrivingbars.ThecolumnsandbeamarejoinedbytheboltsonthefirsthorizontalriblocatedontopofthecolumnsasshowninFig.!.BecausethedrivingbarsaresubstitutedbyequivalentforcesonIhejointpositions,theirstructureisignoredinthemodel.Thecoreofthetopbeamisthreejointsandaholewithspecialpurpose,whichcannotbechanged.TheOtherpartsofthebeammaybechangedifneeded.Fortheconvenienceofmodeling,thecoreofthebeamisfbrmedintoonecomponent.IntheprocessOfoptimization,onlythecorepositionofbeamalongxaxisischanged,thatistosay,shapeofbeamcoreisnotchanged.Itshouldbenoticedthat,intherestofbeam,onlyshapeischangedbutthetopologyisnotChangedandwhichcanautomaticallybeperformedbythecontrolprogram.Fig.l,sixboltsjointhebeamandtwocolumns.Thejointsurfacecannotbearthepullstressinthenon-boltjointpositions,inwhichitisbettertosetcontactelements.Whenthemodelincludescontactelements,nonlineariterativecalculationwillbeneededinIheprocessofsolutionandthecomputingtimewillquicklyincrease.Thetrialcomputingresultnotincludingcontactelementshowsthattheoutsideofbeambearspullingstressandtheinnerofbeambearsthepressstress.Consideringtheprimaryanalysisobjectisthejointpositionstiffnessbetweenthetopbeamandthethreedrivin