英文原文ResearchonaNovelParallelEngravingMachineanditsKeyTechnologiesAbstract:Inordertocompensatethedisadvantagesofconventionalengravingmachineandexerttheadvantagesofparallelmechanism,anovelparallelengravingmachineispresentedandsomekeytechnologiesarestudiedinthispaper.Mechanismperformancesareanalyzedintermsofthefirstandthesecondorderinfluencecoefficientmatrixfirstly.Sothesizesofmechanism,whicharebetterforalltheperformanceindicesofbothkinematicsanddynamics,canbeconfirmedandtherestrictionduetoconsideringonlythefirstorderinfluencecoefficientmatrixinthepastisbrokenthrough.Therefore,thetheorybasisfordesigningthemechanismsizeofnovelengravingmachinewithbetterperformancesisprovided.Inaddition,methodfortoolpathplanningandcontroltechnologyforengravingforceisalsostudiedinthepaper.Theproposedalgorithmfortoolpathplanningoncurvedsurfacecanbeappliedtoarbitraryspacialcurvedsurfaceintheory,controltechnologyforengravingforcebasedonfuzzyneuralnetwork(FNN)haswelladaptabilitytothechangingenvironment.ResearchonteleoperationforparallelengravingmachinebasedonB/Sarchitectureresolvesthekeyproblemssuchascontrolmode,sharingmechanismformultiuser,real-timecontrolforengravingjobandreal-timetransmissionforvideoinformation.Simulationresultsfurthershowthefeasibilityandvalidityoftheproposedmethods.Keywords:parallelmechanism,engravingmachine,influencecoefficient,performanceindices,toolpathplanning,forcecontrol,fuzzyneuralnetwork,teleoperation1IntroductionConventionalcomputerengravingmachinehasplayedanimportantroleinindustriessuchasmachinerymachining,printinganddyeingandentertainment,butithastheinherentdisadvantagessuchascuttingtoolcanbefedonlyalongthefixedguideway,lowerdegree-of-freedom(DOF)ofcuttingtool,lowerflexibilityandmobilityformachiningetc.Parallelmechanismhasthemeritssuchashighmechanicalstiffness,highloadcapacity,highprecision,gooddynamicperformanceetc(Zhen,H.；Ling-fu,K.&Yue-fa,F.,1997).Accordingtothecharacteristicsofparallelmechanism,ithasbeenahotresearchtopictoapplyparallelmechanismtothedomainoffuturemachining.Byapplyingparallelmechanismtoengravingdomain,itsinherentadvantagescanbefullyexertedandthedisadvantagesofconventionalengravingmachinecanbeovercomeorcompensated.Butasthespecialstructureofparallelmechanism,therelatedtheoryandtechnologyduringitsengravingisverydifferentfromthatofconventionalengravingmachine,anditisaundevelopedresearchtopicbynow.Inaddition,withthedevelopmentofcomputernetworktechnology,thenewconceptandmethodsuchasnetworkmachiningandmanufacturinghasbecomehotresearchtopic(GQ,Huang&K.L,Mak.,2001；Taylor,K.&Dalton,B.,2000；Ying-xue,Y.&Yong,L.,1999).Anovelparallelengravingmachinewithsix-axislinkageisproposedinthispaper,whichusesthe6-PUSparallelmechanismwith6-DOFastheprototype,andsomekeytechnologiessuchassizedesign,toolpathplanning,engravingforcecontrolandteleoperationarestudiedonthisbasis.2.Confirmingofmechanismtypeandengravingmachinessize2.1SelectionofmechanismandcoordinatesystemTheselectionofmechanismtypeisthefirststepfordesigningnovelengravingmachine,thefollowingreasonsmakeusselectthe6-PUSparallelmechanismfordesigningourengravingmachine.Comparingwithtraditionalmechanism,6-PUSparallelmechanismusesbaseplatform,threeuprightslayoutandhighrigidityframeworkstructureandhasthemeritssuchashighmodularization,highaccuracyandlowcost.ItsmodelisshowninFig.1.Fig.1.Themodelof6-PUSparallelmechanismAsshowninFig.1,6-PUSparallelmechanismconsistsofbaseplatform,dynamicplatformand6branchchainswithsamestructure,everybranchjoinswithbaseplatformthroughprismaticpairs(P),sliderofprismaticpairsjoinswithupendofthefixedlengthlinkthroughuniversaljoint(U),downendofthefixedlengthlinkjoinswithdynamicplatformthroughspherehinge(S),soitiscalled6-PUSparallelmechanism.Thecoordinatesystemof6-PUSparallelengravingmechanismisshowninFig.2.InFig.2,thegeometrycentersofbaseplatformanddynamicplatformplanearesupposedasOBandoprespectively.Ineverybranch,thecentersofprismaticpairs,universaljointandspherehingearemarkedwithAi,Bi,andCi(i=1,2,.,6)respectively.CoordinatesystemOB-XBYBZBisfixedonbaseplatform,takingBasbriefly.TheoriginofBliesongeometrycenterofbaseplatformsupplane,axisZBisverticalwithbaseplatformanddirectstoup,axisYBdirectstoanglebisectorofthefirstandsecondbranchleadscrewcenterline,andaxisXBcanbedeterminedwithright-handrule.Supposingthecoordinatesystemsetondynamicplatformisop-xpypzp,takingPasbriefly,itsoriginliesongeometrycenterofdynamicplatform,theinitialstateofdynamicplatformsystemisconsistentwiththatofbaseplatformsystemcompletely.Supposingthecoordinateofopis(0,0,Z)inB,thisconfigurationwithoutrelativerotationtoeveryaxisistheinitialconfigurationofthismechanism,andZchangingwithmechanismssize.Onthebasisofcoordinatesystemmentioned,weuseinfluencecoefficienttheoryandtheactualparametersofthismechanismtocalculatethefirstandthesecondorderinfluencecoefficientmatrixofeverybranchunderdifferentconfiguration.Then,wecangetthefirstandthesecondorderintegratedinfluencecoefficientmatrixHofthewholemechanism.和Thesignificanceanddetailedsolutionprocessforinfluencecoefficientmatrixisomittedhere,formoreinformationpleaserefer(Zhen,H.；Ling-fu,K.&Yue-fa,F.,1997).Fig.2.Coordinatesystemof6-PUSparallelengravingmechanism2.2MechanismperformanceanalysisbasedoninfluencecoefficientmatrixTheperformanceofengravingmachinewillchangewithitssize.Tofindoutthebettersizeforalltheperformanceindicesofbothkinematicsanddynamics,weobtainagroupofmechanismsbychangingitsparameters.Thesemechanismslengthoffixedlengthlinks(L)rangebetween45cmand55cm(stepis1cm),radiusofdynamicplatform(R)rangebetween10cmand20cm(Stepis1cm).Otherparametersofthemechanismisunchanging,soweget121mechanismstotally.Takingthesemechanismsasresearchobject,weconfirmthesamplepointforeverymechanisminitsworkspacewithalgorithmPerformanceAnalysis,thencalculatethefirstandthesecondorderinfluencecoefficientmatrixineverypoint.Furthermore,calculatealltheperformanceindicesineverysamplepointanddrawalltheglobalperformanceatlasof121mechanismsultimately.Todescribeconveniently,weabbreviatethefirstandthesecondorderintegratedinfluencecoefficientmatrixHqtoGandH,anduseG,HandG,Hastheangularvelocitysubmatrixandlinearvelocitysubmatrixofthefirstandthesecondorderintegratedinfluencecoefficientmatrixrespectively,namely,WecanchangemechanismsparametersandadjustvariablesstepinthealgorithmPerformanceAnalysistomeetactualanalysis.ThealgorithmisprogrammedwithMATLABandtheglobalperformanceatlasof6-PUSmechanismaredrawn(seeFig.3toFig.8),thenthemechanismsperformanceisanalyzedusingtheatlas.Table1showstheresultsofsamplepointnumber(abbr.toSPN)for121mechanismsrespectively,thefixedlinklengthofmechanismwithsequencenumber(abbr.toSN)1is45cm,itsradiusofdynamicplatformis10cm,thefixedlinklengthofmechanismwithSN121is55cm,itsradiumofdynamicplatformis20cm,therestmaybededucedbyanalogy.Inaddition,table2givestheperformanceindicesofsomemechanismonly,wherethemeanofSNissameasintable1.DescriptionforalgorithmPerformanceAnalysis:PerformanceAnalysisBeginForL=45To55/scopeoffixedlengthlinkForR=10To20/scopeofradiusofdynamicplatformSamplePointNumber=0；/initializationsamplepoin