塔式起重机有限元分析外文翻译.docx

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1、FEMOptimizationforRobotStructureWangShijun,ZhaoJinjuan*DepartmentofMechanicalEngineering,XianUniversityofTechnologyShaanxiProvince,People,sRepublicofChinaInstituteofPrintingandPackingEngineering,XianUniversityofTechnologyAbstractInoptimaldesignforrobotstructures,designmodelsneedtohemodifiedandcomput

2、edrepeatedly.Becausemodifyingusuallycannotautomaticallyberun,itconsumesalotoftime.ThispapergivesamethodthatusesAPDLlanguageofANSYS5.5softwaretogenerateanoptimalcontrolprogram,whichmikeoptimalprocedurerunautomaticallyandOptimalefficiencybeimproved.1) IntroductionIndustrialrobotisakindofmachine,whichi

3、sControlledbycomputers.Becauseefficiencyandmaneuverabilityarehigherthantraditionalmachines,industrialrobotisusedextensivelyinindustry.Forthesakeofefficiencyandmaneuverability,reducingmassandIncreasingstiffhessismoreimportantthantraditionalmachines,instructuredesignofindustrialrobot.Alotofmethodsareu

4、sedinoptimizationdesignofstructure.Finiteelementmethodisamucheffectivemethod.Ingeneral,modelingandmodiiyingaremanual,whichisfeasiblewhenmodelissimple.WhenmodeliScomplicated,optimizationtimeislonger.IntheIongeroptimizationtime,calculationtimeisusuallyverylittle,amajorityoftimeisusedformodelingandmodi

5、fying.Itiskeyofimprovingefficiencyofstructureoptimizationhowtoreducemodelingandmodifyingtime.APDLlanguageisaninteractivedevelopmenttool,whichisbasedonANSYSandisofferedtoprogramusers.APDLlanguagehastypicalfunctionofsomelargecomputerlanguages.Forexample,parameterdefinitionsimilartoconstantandvariabled

6、efinition,branchandloopcontrol,andmacrocallsimilarIofunctionandsubroutinecall,etc.Besidesthese,ItpossessespowerfulcapabilityofITiathematicalcalcuIation.ThecapabilityofmathematicalCalculationincludesarithmeticcalculation,comparison,rounding,andtrigonometricfunction,exponentialfunctionandhyperbolafunc

7、tionofstandardFORTRANlanguage,etc.BymeansofAPDLlanguage,thedatacanbereadandthencalculated,whichisindatabaseofANSYSprogram,andrunningprocessofANSYSprogramcanbecontrolled.Fig.1showsthemainframeworkofaparallelrobotWiththreebars.Whenthelengthofthreebarsarechanged,conjunctendofthreebarscanfollowagiventra

8、ck,whererobothandisinstalled.Coreoftopbeamistriangle,owingtothreebarsusedinthedesign,whichisshowedinFig.2.UseofthreebarsmakestopBeamnonsymmetricalalongtheplanethatisdefinedbytwocolumns.AccordingtoaqualitativeanalysisfromFig.!,Stiffnessvaluesalongz-axisaredifferentatthreejointlocationsonthetopbeamand

9、stiffnessatthelocationbetweenbar1andtopbeamislowest,whichisconfirmedbycomputingresultsoffiniteelement,too.Accordingtodesigngoal,stiffnessdifferenceatthreejointlocationsmusthewithinagiventolerance.Inconsistentofstiffnesswillhaveinfluenceonthemotionaccuracyofthemanipulatorunderhighload,soitisnecessary

10、tofindtheaccuratelocationoftopbeamalongx-axis.Tothequestionspresentedabove,thegeneralsolutionistochangethelocationofthetopbeammanytimes,comparetheresultsandeventuallyfindaproperposition,Themodelwillbemodifiedaccordingtothelastcalculatingresulteachtime.Itisdifficulttoavoidmistakesiftheiterativeproces

11、siscontrolledmanuallyandtheiterativetimeistoolong.Theouterwallandinnerribshapesofthetopbeamwillbechangedafterthemodelismodified.TofindtheappropriateIocationoftopbeam,themodelneedstobemodifiedreetitiously.Fig.1SolutionofOriginalDesignThispapergivesanoptimizationsolutiontothepositionoptimizationquesti

12、onofthetopbeambyAPDLlanguageofANSYSprogram.Aftertheanalysismodelfirstfounded,theoptimizationcontrolprogramcanbeformedbymeansofmodelinginstructioninthelogfile.Thelateriterativeoptimizationprocesscanbefinishedbytheoptimizationcontrolprogramanddonotneedmanualcontrol.Thetimespentinmodifyingthemodelcanbe

13、decreasedtotheignorableextent.Theefficiencyoftheoptimizationprocessisgreatlyimproved.2) ConstructionofmodelforanalysisThestructureshowninFig.1consistsofthreeparts:twocolumns,onebeamandthreedrivingbars.ThecolumnsandbeamarejoinedbytheboltsonthefirsthorizontalriblocatedontopofthecolumnsasshowninFig.!.B

14、ecausethedrivingbarsaresubstitutedbyequivalentforcesonIhejointpositions,theirstructureisignoredinthemodel.Thecoreofthetopbeamisthreejointsandaholewithspecialpurpose,whichcannotbechanged.TheOtherpartsofthebeammaybechangedifneeded.Fortheconvenienceofmodeling,thecoreofthebeamisfbrmedintoonecomponent.In

15、theprocessOfoptimization,onlythecorepositionofbeamalongxaxisischanged,thatistosay,shapeofbeamcoreisnotchanged.Itshouldbenoticedthat,intherestofbeam,onlyshapeischangedbutthetopologyisnotChangedandwhichcanautomaticallybeperformedbythecontrolprogram.Fig.l,sixboltsjointhebeamandtwocolumns.Thejointsurfac

16、ecannotbearthepullstressinthenon-boltjointpositions,inwhichitisbettertosetcontactelements.Whenthemodelincludescontactelements,nonlineariterativecalculationwillbeneededinIheprocessofsolutionandthecomputingtimewillquicklyincrease.Thetrialcomputingresultnotincludingcontactelementshowsthattheoutsideofbeambearspullingstressandtheinnerofbeambearsthepressstress.Consideringtheprimaryanalysisobjectisthejointpositionstiffnessbetweenthetopbeamandthethreedrivin