关于机械手的中英文翻译文档格式.docx

关于机械手的中英文翻译文档格式.docx

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学院名称

专业名称

指导教师

20**年

5月

27日

COMBINATIONOFROBOTCONTROLANDASSEMBLYPLANNINGFORAPRECISIONMANIPULATOOR

Abstract

Thispaperresearcheshowtorealizetheautomaticassemblyoperationonatwo-fingerprecisionmanipulator.Amulti-layerassemblysupportsystemisproposed.Atthetask-planninglayer,basedonthecomputer-aideddesign（CAD）model,theassemblysequenceisfirstgenerated,andtheinformationnecessaryforskilldecompositionisalsoderived.Then,theassemblysequenceisdecomposedintorobotskillsattheskill-decompositionlayer.Thesegeneratedskillsaremanagedandexecutedattherobotcontrollayer.Experimentalresultsshowthefeasibilityandefficiencyoftheproposedsystem.

KeywordsManipulatorAssemblyplanningSkilldecompositionAutomatedassembly

1Introduction

Owingtothemicro-electro-mechanicalsystems（MEMS）techniques,manyproductsarebecomingverysmallandcomplex,suchasmicrophones,micro-opticalcomponents,andmicrofluidicbiomedicaldevices,whichcreatesincreasingneedsfortechnologiesandsystemsfortheautomatedprecisionassemblyofminiatureparts.Manyeffortsaimingatsemi-automatedorautomatedassemblyhavebeenfocusedonmicroassemblytechnologies.However,microassemblytechniquesofhighflexibility,efficiency,andreliabilitystillopentofurtherresearch.Thispaperresearcheshowtorealizetheautomaticassemblyoperationonatwo-fingermicromanipulator.Amulti-layerassemblysupportsystemisproposed.

Automaticassemblyisacomplexproblemwhichmayinvolvemanydifferentissues,suchastaskplanning,assemblysequencesgeneration,execution,andcontrol,etc.Itcanbesimplydividedintotwophases;

theassemblyplanningandtherobotcontrol.Attheassembly-planningphase,theinformationnecessaryforassemblyoperations,suchastheassemblysequence,isgenerated.Attherobotcontrolphase,therobotisdrivenbasedontheinformationgeneratedattheassembly-planningphase,andtheassemblyoperationsareconducted.Skillprimitivescanworkastheinterfaceofassemblyplanningtorobotcontrol.Severalrobotsystemsbasedonskillprimitiveshavebeenreported.Thebasicideabehindthesesystemsistherobotprogramming.Robotmovementsarespecifiedasskillprimitives,basedonwhichtheassemblytaskismanuallycodedintoprograms.Withtheprograms,therobotiscontrolledtofulfillassemblytasksautomatically.

Askill-basedmicromanipulationsystemhasbeendevelopedintheauthors’lab,anditcanrealizemanymicromanipulationoperations.Inthesystem,theassemblytaskismanuallydiscomposedintoskillsequencesandcompiledintoafile.Afterimportingthefileintothesystem,thesystemcanautomaticallyexecutetheassemblytask.Thispaperattemptstoexploreauser-friendly,andatthesametimeeasy,sequence-generationmethod,torelievetheburdenofmanuallyprogrammingtheskill

sequence.

Itisaneffectivemethodtodeterminetheassemblysequencefromgeometriccomputer-aideddesign（CAD）models.Manyapproacheshavebeenproposed.Thispaperappliesasimpleapproachtogeneratetheassemblysequence.Itisnotinvolvedwiththelow-leveldatastructureoftheCADmodel,andcanberealizedwiththeapplicationprogramminginterface（API）functionsthatmanycommercialCADsoftwarepackagesprovide.Intheproposedapproach,arelationsgraphamongdifferentcomponentsisfirstconstructedbyanalyzingtheassemblymodel,andthen,possiblesequencesaresearched,basedonthegraph.Accordingtocertaincriterion,theoptimalsequenceisfinallyobtained.

Todecomposetheassemblysequenceintorobotskillsequences,someworkshavebeenreported.InNnajietal.’swork,theassemblytaskcommandsareexpandedtomoredetailedcommands,whichcanbeseenasrobotskills,accordingtoapredefinedformat.ThedecompositionapproachofMosemannandWahlisbasedontheanalysisofhyperarcsofAND/ORgraphsrepresentingtheautomaticallygeneratedassemblyplans.Thispaperproposesamethodtoguidetheskilldecomposition.Theassemblyprocessesofpartsaregroupedintodifferentphases,andpartsareatdifferentstates.Specificworkflowspushforwardpartsfromonestatetoanotherstate.Eachworkflowisassociatedwithaskillgenerator.Accordingtothedifferentstartstateandtargetstateoftheworkflow,theskillgeneratorcreatesaseriesofskillsthatcanpromotetheparttoitstargetstate.

Thehierarchyofthesystemproposedhere,theassemblyinformationonhowtoassembleaproductistransferredtotherobotthroughmultiplelayers.Thetoplayerisfortheassembly-taskplanning.TheinformationneededforthetaskplanningandskillgenerationareextractedfromtheCADmodelandaresavedinthedatabase.BasedontheCADmodel,theassemblytasksequencesaregenerated.Attheskill-decompositionlayer,tasksaredecomposedintoskillsequences.Thegeneratedskillsaremanagedandexecutedattherobotcontrollayer.

2Taskplanning

Skillsarenotuseddirectlyattheassembly-planningphase.Instead,theconceptofataskisused.Ataskcanfulfillaseriesofassemblyoperations,forexample,fromlocatingapart,throughmovingthepart,tofixingitwithanotherpart.Inotherwords,onetaskincludesmanyfunctionsthatmaybefulfilledbyseveraldifferentskills.Ataskisdefinedas:

T=（BasePart;

AssemblyPart;

Operation）

Base_PartandAssembly_Partaretwopartsthatareassembledtogether.Base_Partisfixedontheworktable,whileAssembly_Partishandledbyrobot’send-effectorandassembledontotheBase_Part.OperationdescribeshowtheAssembly_PartisassembledwiththeBase_Part;

Operation∈{Insertion_T,screw_T,align_T,...}.

Thestructureofmicropartsisusuallyuncomplicated,andtheycanbemodeledbytheconstructivesolidgeometry（CSG）method.Currently,manycommercialCADsoftwarepackagescansupport3DCSGmodeling.Theassemblymodelisrepresentedasanobjectthatconsistsoftwopartswithcertainassemblyrelationsthatdefinehow

thepartsaretobeassembled.IntheCADmodel,therelationsaredefinedbygeometricconstraints.Thegeometricinformationcannotbeuseddirectlytoguidetheassemblyoperation—wehavetoderivetheinformationnecessaryforassemblyoperationsfromtheCADmodel.

Throughsearchingtheassemblytreeandgeometricrelations（mates’relations）definedintheassembly’sCADmodel,wecangeneratearelationgraphamongparts,forexample,Inthegraph,thenodesrepresenttheparts.Ifnodesareconnected,itmeansthatthereareassemblyrelationsamongtheseconnectednodes（parts）.

2.1Matingdirection

InCSG,therelationsoftwoparts,geometricconstraints,arefinallyrepresentedasrelationsbetweenplanesandlines,suchascollinear,coplanar,tangential,perpendicular,etc.Forexample,ashaftisassembledinahole.TheassemblyrelationsbetweenthetwopartsmayconsistofsuchtwoconstraintsascollinearbetweenthecenterlineofshaftLc_shaftandthecenterlineofholeLc_holeandcoplanarbetweentheplaneP_ShaftandtheplaneP_Hole.Thematingdirectionisakeyissueforanassemblyoperation.Thispaperappliesthefollowingapproachtocomputethepossiblematingdirectionbasedonthegeometricconstraints（theshaft-in-holeoperationofFig.3istakenasanexample）:

1.Forapartintherelationgraph,calculateitsremainingdegreesoffreedom,alsocalleddegreesofseparation,ofeachgeometricconstraint.

Forthecoplanarconstraint,theremainingdegreesoffreedomare

.Forthecollinearconstraint,theremainingdegreesoffreedomare

.

and

canalsoberepresentedas

and

.Here,1meansthatthereisadegreeofseparationbetweenthetwoparts.

andso,thedegreeoffreedomaroundthezaxiswillbeignoredinthefollowingsteps.

Inthecasethatthereisaloopintherelationgraph,suchaspartsPart5,Part6,andPart7inFig.2,theloophastobebrokenbeforethematingdirectioniscalculated.UndertheassumptionthatallpartsintheCADmodelarefullyconstrainedandnotover-constrained,thefollowingsimpleapproachisadopted.Fortheparttintheloop,calculatethenumberof1sin

;

where

istheremainingdegreesoffreedomofconstraintkbyparti.Forexample,inFig.2,giventhatthenumberof1sin

islargerthan

respectively,thenitcanberegardedthatthepositionofPart7isdeterminedbyconstraintswithbothPart5andPart6,whilePart5andPart6canbefullyconstrainedbyconstraintsbetweenPart5andPart6.WecanunitePart5andPart6asonenodeintherelationgraph,alsocalledacompositenode,asshowninFig.2b.Thecompositenodewillberegardedasasinglepart,butitisobviousthatthecompositenodeimpliesanassemblysequence.

2.Calculatematingdirectionsforallnodesintherelationgraph.Again,beginningatthestatethattheshaftandtheholeareassembled,separatethepartinonedegreeofseparationbyacertaindistance（largerthanthemaximumtolerance）,andthencheckifinterferenceoccurs.Separationinboth±

xaxisand±

yaxisofR1causestheinterferencebetweentheshaftandthehole.Separationinthe+zdirectionraisesnointerference.Then,selectthe+zdirectionasthematingdirection,whichisrepresentedasavectorMmeasuredinthecoordinatesystemofthe

assembly.Itshouldbenotedthat,insomecases,theremaybeseveralpossiblematingdirectionsforapart.Theconditionforassemblyoperationinthematingdirectiontobeendedshouldbegiven.Whencontactoccursbetweenpartsinthematingdirectionattheassembledstate,whichcanbecheckedsimplywithgeometricconstraints,theendconditionismeasuredb