外文翻译--激光切割机的传动控制可变结构系统.doc

徐州工程学院毕业设计外文翻译学生姓名学院名称机电工程学院专业名称机械设计制造及其自动化指导教师VSSmotioncontrolforalaser-cuttingmachineAlesHace,KarelJezernik*,MartinTerbucUniversityofMaribor,FacultyofElectricalEngineeringandComputerSciences,InstituteofRobotics,Smetanovaul.17,SI-2000Maribor,SloveniaReceived18October1999；accepted2June2000AbstractAnadvancedposition-trackingcontrolalgorithmhasbeendevelopedandappliedtoaCNCmotioncontrollerinalaser-cuttingmachine.Thedrivetrainsofthelaser-cuttingmachinearecomposedofbelt-drives.Theelasticservomechanismcanbedescribedbyatwo-masssysteminterconnectedbyaspring.Owingtothepresenceofelasticity,frictionanddisturbances,theclosed-loopperformanceusingaconventionalcontrolapproachislimited.Therefore,themotioncontrolalgorithmisderivedusingthevariablesystemstructurecontroltheory.Itisshownthattheproposedcontrole!ectivelysuppressesthemechanicalvibrationsandensurescompensationofthesystemuncertainties.Thus,accuratepositiontrackingisguaranteed.(2001ElsevierScience¸td.Allrightsreserved.)Keywords:Positioncontrol；Drives；Servomechanisms；Vibrations；Variablestructurecontrol；Chattering；Disturbancerejection；Robustcontrol1.IntroductionFormanyindustrialdrives,theperformanceofmotioncontrolisofparticularimportance.Rapiddynamicbehaviourandaccuratepositiontrajectorytrackingareofthehighestinterest.Applicationssuchasmachinetoolshavetosatisfythesehighdemands.Rapidmovementwithhighaccuracyathighspeedisdemandedforlasercuttingmachinestoo.Thispaperdescribesmotioncontrolalgorithmforalow-costlaser-cuttingmachinethathasbeenbuiltonthebaseofaplanarCartesiantablewithtwodegrees-of-freedom(Fig.1).Thedrivetrainsofthelaser-cuttingmachinearecomposedofbelt-driveswithatimingbelt.Theuseoftimingbeltsinthedrivesystemisattractivebecauseoftheirhighspeed,highefficiency,longtravellengthsandlow-cost(Haus,1996).Ontheotherhand,theyyieldmoreuncertaindynamicsandahighertransmissionerror(Kagotani,Koyama&Ueda,1993).Consequently,belt-drivessufferfromlowerrepeatabilityandaccuracy.Moreover,thebelt-drivedynamicsincludemoreresonancefrequencies,whichareadestabilisingfactorinafeedbackcontrol(Moon,1997).Therefore,aconventionalcontrolapproachlikePI,PDorPIDcontrolfailstoachieveacceptableperformance.Plantparametervariations,uncertaindynamicsandloadtorquedisturbances,aswellasmechanicalvibrations,arefactorsthathavetobeaddressedtoguaranteerobustsystemstabilityandthehighperformanceofthesystem.Anadvancedrobustmotioncontrolschemeisintroducedinthispaper,whichdealswiththeissuesrelatedtomotioncontrolofthedriveswithtimingbelts.ThecontrolschemeisdevelopedonthebasisofthemotioncontrolalgorithmintroducedbyJezernik,CurkandHarnik(1994).Itpossessesrobustpropertiesagainstthedisturbancesthatareassociatedwithanominalplantmodel,asithasbeendevelopedwiththeuseofthevariablestructuresystem(VSS)theory(Utkin,1992).Thecrucialpartofthecontrolschemeistheasymptoticdisturbanceestimator.However,asshowninthispaper,itfailstostabiliseresonantbeltdynamics,sinceitwasdevelopedforarigidrobotmechanism.Therefore,thispaperintroducesanimprovedmotioncontrolscheme,whichsuppressesthevibrationsthatwouldariseduetothenon-rigid,elasticdrive.Consequently,arapidresponsewithlowpositiontrackingerrorisguaranteed.Thepaperissetoutasfollows.Thelaser-cuttingmachineispresentedandthecontrolplantmodelofthemachinedrivesisdevelopedinSection2.InSection3,theVSScontrolregardingtheelasticservomechanismisdiscussedandthederivationofthemotioncontrolschemeisdescribed.Section4presentstheexperimentalresultsandafollow-updiscussion.ThepaperissummarizedandconcludedinSection5.2.Thecontrolplant2.1.ThemachinedescriptionThelaser-cuttingmachineconsistsoftheXYhorizontaltableandalasersystem(Fig.1).Thefundamentalcomponentsofthelasersystemare:thepowersupplyunit,whichisplacedoffthetableandthusisnotconsideredinthemotioncontroldesign；thelaser-beamsource,whichgeneratesthelaserbeam(thelaser-generator)；thelaser-head,whichdirectsthelaserbeamontothedesiredpositioninthecuttingplane.Fig.1.Themachineandthecontrollerhardware.Thetablehastomoveandpositionthelaserheadinahorizontalplane.Thisisachievedbythemeansofadrivesystemwithtwoindependentmotionaxes.TheyprovidemovementalongtheCartesiansXYaxesof2and1m,respectively.TheX-driveprovidesthemotionofthelaser-headinX-direction.Thedriveandthelaser-headaswellasthelaser-generatorareplacedonthebridgetoensureahigh-qualityopticalpathforthelaser-beam.ThemovementofthebridgealongtheY-axisisprovidedbytheY-drive.Thelaser-headrepresentstheX-driveload,whiletheY-driveisloadedbythebridge,whichcarriesthecompleteX-drivesystem,thelaser-head,andthelaser-generator.Theloadsslideoverthefrictionlessslidesurface.Thepositioningsystemconsistsofthemotioncontroller,theamplifiers,theDC-motorsandthedrivetrains.TheX-drivetrainiscomposedofagearboxandabelt-drive(Fig.2).Thegearboxreducesthemotorspeed,whilethebelt-driveconvertsrotarymotionintolinearmotion.Thebelt-driveconsistsofatimingbeltandoftwopulleys:adrivingpulleyandadrivenpulleythatstretchthebelt.TheY-drivetrainismorecomplex.Theheavybridgeisdrivenbytwoparallelbelt-drives；eachbridge-sideisconnectedtooneofthebelt-drives.Thedrivingpulleysofthebelt-drivesarelinkedtothedrivingaxis,whichisdrivenviatheadditionalbelt-driveandthegearboxisusedtoreducethespeedofthemotor.