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外文翻译--数控机床的编程演变.doc

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外文翻译--数控机床的编程演变.doc

英文原文EvolutionaryprogrammingofCNCmachinesAbstractThepaperproposesanewconceptforprogrammingofCNCmachines.TheconceptbasedongeneticalgorithmsassuresevolutionarygenerationandoptimizationofNCprogramsonthebasisofCADmodelsofmanufacturingenvironment.Thestructure,undergoingsimulatedevolution,isthepopulationofNCprograms.TheNCprogramscontrolthemachinewhichperformssimpleelementarymotions.Duringtheevolutionthemachinemovementbecomesmoreandmorecomplexandintelligentsolutionsemergegraduallyasaresultoftheinteractionbetweenmachinemovementsandmanufacturingenvironment.TheexamplesofevolutionaryprogrammingofCNClatheandCNCmillingmachinetoolfordifferentcomplexitiesoftheblanksandproductsarepresented.Theproposedconceptshowedahighdegreeofuniversality,efficiency,andreliabilityanditcanbealsosimplyadoptedtootherCNCmachines.©2005ElsevierB.V.Allrightsreserved.KeywordsManufacturingsystemsNCprogrammingCNCmachinesGeneticalgorithm.1.IntroductionSincetheCNCmachinesarealreadypresentinalmostallmanufacturingsystems,theautomaticprogrammingofCNCmachinesbecamewidespreadinthelasttwodecades1,4,6,7.Thus,nowadaysnumerouscommercialprogrammingsolutions,includingautomaticgenerationofNCprograms,areavailable.Thesolutionsdifferinreliability,efficiency,flexibilityanduniversality.Sofar,ithasnotbeenpossibletotraceauniversalsolutionfortheprogrammingofNCmachines.InthispaperweusedthegeneticalgorithmsGA2basedapproachforprogrammingofCNClatheandmillingmachinetool.TheproposedconceptcanbeadoptedalsotootherCNCmachinesforexamplecoordinatemeasuringmachines5,weldingmachines,laserandplasmacuttingmachines4,robotsandmanipulators.Theconceptimitatesthenaturalevolutionoflivingorganisms,whereinthestrugglefornaturalresourcesthesuccessfulindividualsgraduallybecomemoreandmoredominant,andadaptabletotheenvironmentinwhichtheylive,whereasthelesssuccessfulonesarepresentinthenextgenerationsrarely.IntheproposedconcepttheNCprograms,representedasweightedgraphs,undergoadaptation.DuringthesimulatedevolutionmoreandmoresuccessfulorganismstheNCprogramsemergeonthebasisofgivendataonmanufacturingenvironment.Researcheshaveshownthattheproposedconceptisuniversal,flexible,reliable,andefficient.ForthepapertobeselfcontainedthebasictermsonturningandmillingprocessesarestatedinthebeginningoftheSection2.Afterwardstheideaoftheproposedconceptispresented.Thecodingi.e.,genotypeoftheindividualNCprogramorganism,theevaluationoforganisms,andthegeneticoperationsusedaredescribed.Sections3and4showfunctioningoftheproposedsystem.TheexamplesofprogrammingofCNClatheandCNCmillingmachinetoolfordifferentcombinationsofexactingnessoftheblankandproductaregiven.Section5summarizesthemaincontributionsoftheperformedresearchandalsogivesguidelinesforfurtherresearches.2.ProgrammingofCNClatheandmillingmachinetoolwithGATheobjectiveofturningandmillingprocessistoassurerelativemotionofthetoolwithrespecttotheworkpiece.Theconsequenceoftherelativemotionismovingofthetoolreferencepointand,consequently,formingofthedesiredshapeoftheproduct.Thetoolmovementconsistsoftheworkingandfeedingmotions.Machiningofmaterialtakesplaceinseveralcutswhoseoptimumsequenceisknowningeneralonlyforverysimpleproducts.Eachworkingmotiontakesoffacertainquantityofmaterialandthusitproducesthecuttings.2.1.MainalgorithmThebasicideaoftheproposedconceptwillbedemonstratedonsimpleexamples.Figs.1and2showtheblank,productandtherelevantchipsinturningandmillingprocess,respectively.Theareaofthepossibletoolblademotionisdiscretizedintosquaresincaseofturningandboxesincaseofmilling.Thetoolofonesquarethicknessinturningcanmovediscretelyup,down,toleftandtoright,whereasitcutsonlytorightordownwards.Incaseofmillingthetoolcanmoveandcutinthepositiveandnegativedirectionsofaxesx,yandz.DuetothediscretizationofthemachiningfieldthetoolreferencepointisinthemiddlebottomofthecuttingtoolFigs.1and2.Thematerialtobetakenoffisdividedintoseveralcutsconsistingofchips.Forexample,thecut1inthebottomdiagramofFig.1consistsofninechips,thecut2andthecut3consistoffourchipseach,thecut4oftwochips,etc.DiagramsattherightofFig.1showthetypesofmachining.Duetothediscretenatureofthesystemitispossibletoselecthorizontal,verticalorcombinedcuts.Fig.3showsthemainalgorithmforprogrammingoftheCNCmachinetoolinthepseudocode.Firstitisnecessarytoenterthedataontheblankandproduct.Intheproposedconceptenteringiseffectedautomatically,directlyfromtheCADmodulesoftheblankandproduct.Theinputofthedesiredtypeofmachiningfollows.Thenthesystemdividesthemachiningareaintothedesirednumberofsquaresturningorboxesmilling.Attheendofthedatainputitisnecessarytodefinethestartingandfinalpointofthetoolmotionandthetoolreferencepoint.FromnowonthesystemiscapableofautonomousgeneticallybasedgeneratingandoptimizingtheNCprogramsthroughseveralgenerationst.TheBooleanvariableknownNCprogramdecideswhetherthesolutionfrommachiningpreviouslyperformedshouldbeusedfortheinitialpopulationortheinitialpopulationshouldbeinitializedcompletelyatrandom.EachchromosomeorganisminthepopulationPtrepresentsacollisionfreeoranoncollisionfreeNCprogram.Ofcourse,intheinitialgenerationmostoftheprogramsarenoncollisionfree.EachNCprogramconsistsoffeedingmotionbetweentheinitialpointandtheinitialcut,feedingandworkingmotionsbetweencutsandfeedingmotionbetweenthefinalcutandfinalpointofthetool.Theevolutionarydevelopmentofsolutionstarts,whenthechromosomeshavebeenevaluated.Greaterprobabilityofparticipatinginthegeneticoperationsofselectionandchangingisassignedtothesolutionsbettersolvingtheproblem.Selectionassuressurvivalofmoresuccessfulmembersofpopulationandtheirprogressinunchangedformintothenextgeneration.Changinginfluencesoneorseveralorganismsandcreatesfromthemtheiroffspring.Afterselectionandchanginganewgenerationisobtainedwhichhastobeevaluated,too.Theprocessisrepeateduntiltheterminationconditionoftheprocesshasbeenfulfilled.Thatcanbethegreatestspecifiednumberofgenerationsorsufficientqualityofsolutions.2.2.InitialstructurecodingofNCprogramTherandomlygeneratedcollisionfreeandnoncollisionfreei.e.feasibleandinfeasibleNCprogramscanberepresentedbyaweightedgraphFig.4.Theverticesofthegraphsareworkingmotionscuts,andtheedgesbetweenthepointsarethefeedingmotions.Eachvertexofthegraphisconnectedtoallotherverticesofthegraph.Thepointsandcorrectionsinthegraphareweighted.Thesequenceofgenesi.e.cutsrepresentstheblademotionfromcuttocut.Inthegraphthetwopermanentgenesverticesaretheinitialandfinalpointoftheblademotion,markedwithSandE,respectively.Theintermediateverticese.g.cut1,cut4representthecutssubjectedtomachining.Atfirst,thetoolmoveswiththefeedingmotionfromtheinitialpointSuptothefirstcut,thenitproceedswiththefeedingmotionuptothenextcut,itmachinesitandsoon,untilithasmachinedallcuts.Finally,withthefeedingcutitreachesthefinalpointE.TherandomlygeneratedNCprogramsdifferinthenumberoftherequiredtoolstepsandinthenumberofcollisionsbetweenthetoolandtheworkpiece.Beforeintroducingletusdefinetwoimportanttermsconsistencyofcutsandconsistencyofchips.Acutisconsistentifatleastonechipinthecutstickstotheworkpiece.Achipisconsistentifitstillstickstotheworkpiecei.e.totheconsistentcut.Verifyingofcutsandchipsisveryimportant,sinceduetofastlychangingenvironmenti.e.workpieceitisnecessarytocheckcontinuouslywhichworkpieceareashavealreadybeenmachinedornot.2.3.EvaluationofpopulationTheaimofthecombinatorytaskistofindsuchapaththroughtheweightedgraphwiththeinitialpointSandfinalpointEthatwillcontainallpointsinthegraphandsothatthesumofweightsattheedgesandverticesandofweightednumberofcollisionswillbeminimum.InotherwordsthismeansthatitisnecessarytofindtheoptimumcollisionfreeNCprogram.If,forexample,thepaththroughthegraphinFig.4isequaltothelistS,cut1,cut2,cut3,cut4,cut5,cut6,cut7andE,thesumoftheweightsatconnectionsandpointsisasfollowsEvalNCx_wNCxwS1wcut1w12wcut2w23wcut3w34wcut4w45wcut5w56wcut6w67wcut7w7EfH,1whereNCxisthexthNCprogram,wS1thelengthoffeedingmotionfrominitialpointSuptothefirstcuttingofcut1,wcut1thelengthofworkingmotionofconsistentcut1,wijthelengthoffeedingmotionbetweentheconsistentcut1,wiEthelengthofworkingmotionfromthelastcuttingofthelastconsistentcutiuptopointE,ftheimpactfactor,andHthenumberofcollisions.ThemostdemandingoperationoftheevaluationoftheNCprogramisthedeterminationofthetoolpathlength,consistencyofcutsandcuttingsandnumberofcollisions.Duetochangingoftheworkpieceshapeduringmachiningconsequentlyalsothetoolpathlengthchanges.Duringthefeedingandworkingmotionofthetoolthesystemcarefullyfollowsuptheblademovement,itcontinuouslyverifiestheconsistencyofcutsandthepossiblecollisions.Fig.5showsthenonconsistencyofcutsandcollisionduringturningandmilling.Fig.6describestheprocedureevaluation,whichcontributesmosttocomplexityofprogrammingoftheCNClatheandmillingmachinetoolbygeneticalgorithms.Theprocedureincludesfourmostimportantfunctionscheckconsistence,checkcollision,moveandcuttakingcareofverifyingtheundesirablecollisionofthetoolwiththeworkpiece.Thefunctioncheckconsistencesupervisesseparationofcuttingsfromworkpieceandthusverifiestheconsistenceofcuts.Thefunctionsmoveandcutareintendedforsimulationofthetoolworkingandfeedingmotions.Theevaluationofthechromosomestartsbycallingthefunctionscheckconsistenceandcheckcollisionwhichcontinuouslyfollowsupeverystepoftheblade

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