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外文翻译--高速数控齿轮磨床的一种无噪音磨削主轴 英文版.pdf

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外文翻译--高速数控齿轮磨床的一种无噪音磨削主轴 英文版.pdf

ANoiseFreeServoSpindleforHighspeedNCGearGrindingMachinesTakashiEmura,LeiWang,HisashiNakamura,MasashiYamanakaandYasushiTeshigawaraDepartmentofMechatronicsandPrecisionEngineering,TohokuUniversityAoba,Aramaki,Aobaks,Sendai,98077JapanAbstractTheauthorsdevelopedaproductivetypeNCNumericallyControlledgeargrindingmachineforautomobileplants,ThisNCmachinerequireshighaccuracysynchronizationbetweenthegrindingspindleandworkspindle.Wemustusehighpowerservomotorsandservoamplifierstosatisfythespecificationrequiredforhighspeedgrinding.However,sincethehighpowerservoamplifiercausesverylargerippleofmotorcurrentatPWMPulseWidthModulationfrequencyandinducesstrongnoise,itbecomesdifficulttogetthestablesynchronousrotationamongspindles.Therefore,theauthorstriedtousetwophasetypePUtoachievenoisefreehighspeedsynchronousspindlesandtoreducethenoisecausedbythecurrentripplewithakindofcurrentfilter.Inthispaper,anapproachforsuppressingthenoiseandexperimentalresultsaredescrlbed.I.INTRODUCTIONGeargrindingtakesextremelylonggrindingtimeanditpreventsincreasingtheproductivityinmassproductionofgears.Thus,theauthorsdevelopedaproductivetypeNCgeargrindingmachineforautomobileplants,whicharethemostproductiveplantsofgears.Thismachinerequirestwolargepowerservospindlesforitsgrindingspindleandworkspindle.heseservospindlesalsohavetobesynchronouslycontrolledwithhighprecisionevenrotatingatahighspeed.Theauthorsusedhighpowerandhighspeedservomotorstodrivethespindles.Forexample,theservomotorforgrindingspindlehasaratedpowerof22kW,ratedoutputtorqueof22Nmandmaximumrotaryspeedof10000r/min.Theservomotorforworkspindlehasaratedpowerof16kW,ratedoutputtorqueof82N.mandmaximumrotaryspeedof2000r/min.TheseservomotorsaredrivenbyPWMPulseWidthModulationtypeservoamplifiers,andthePWMtypeamplifieroflargepowercausesaverylargerippleinmotorcurrentwhichappearsatPWMfrequency.Sincethislargecurrentrippleinducesastrongnoisewhichcausestroubletocontrolsystems,itisdifficulttorealizesynchronouscontrolofhighaccuracy.Therefore,theauthorstriedtousetwophasetypePLLPhaseLockedLooptogetnoisefreehighspeedsynchronousspindlesandtriedtouseakindofcurrentfiltertoreducetherippleofmotorcurrent.Experimentswerecarriedouttoconfirmtheeffectivenessofthenoisefreesystems.Inthispaper,anapproachforsuppressingthenoiseandgettingthehighspeedandhighprecisionsynchronousspindlesisdescribedwithexperimentalresults.11.NOISECAUSEDBYPWMProblemsofnoiseofthegrindingspindleismoreseverethanthatoftheworkspindlebecausetheratedpowerofthegrindingspindleislargerthanthatoftheworkspindle.Thuswemainly07803302691954.0001995IEEEdescribeaboutthecaseofgrindingspindleinthefollowings.Thegrindingspindleisdrivenbyahighpowerbrushlessservomotor.Sincethemaximumoutputvoltageoftheservoamplifierislimitedto200Vandtheratedpoweroftheservomotoris22kW,thecurrentoffieldcoilhastobemorethan200Aatapeakload.Forthislargecurrent,awirediameteroffieldcoilbecamelarge,andthenumberofturnsbecameafewbecauseofthelimitationofwindingspace.Thusinductanceofthefieldcoilwasconstrainedtoaverysmallvalue.Themeasuredinductanceofonephaseisabout30pHatlkHzanditisreducedtoverysmallvalueoflessthan1.5pHat25kHzofPWMfrequency.Sincethecoilinductanceisextremelysmalllikethis,itselectricaltimeconstantisverysmall.Thismeansthatwecangetagoodcontrolcharacteristics.However,theextremelyshorttimeconstantcausesverylargecurrentrippleatPWMfrequency,andthiscurrentrippleinducesthestrongnoise.Thestrongnoisegivesseriousproblemstocontrolsystems.Inordertoanalyzetheripplecurrent,numericalsimulationofmotorcurrentwascarriedout.Fig.laissimplifiedmodelofsynchronousmotorforsimulation,wherecoilinductanceLis1.44pH,coilresistanceRis0.15SZandvoltageofDClineEis200V.PWMoutputvoltageEu,EvandEwofservoamplifieraresuppliedonterminalofthreephasesU,V,W.PWMpatternshowninFig.lbaregeneratedbycomparingreferencevoltageeu,eVandewwithtrianglewaveegofwhichfrequencyis25kHz.Fig.2aisanexampleofsimulatedresults,wheretheoutputfrequencyoftheservoamplifieris300Hz.AsshowninFig.2a,motorcurrentisoverlappedbylargenoise.Fig.2bgivesthedetailsituationbyconiparingsimulatedandmeasuredresultsofcoilcurrent,wheresimulatedresultsagreedwiththemeasuredresults.ThusthesimulatedresultsshowsthatthemotorcurrenthasverylargecurrentrippleatPWMfrequency.Thissimulationshowsclearlythattheservomotorandpoweramplifiergenerateverystrongnoisesforthesakeofsmallnessofcoilinductance.Thecoilinductancedecreasessharplyathighswitchingfrequencyinsuchlargepowermotorbecauseofthemagneticcharacteristicoffieldcore.ThenoisescausedbyswitchingisaverysevereprobleminthisNCmachineandhastobeovercomeinordertoachievethehighprecisionsynchronouscontrol.Therefore,thefollowingsectionsdescribetwodifferentapproachesforovercomingswitchingnoiseproblem.SectionHIpresentsasynchronouscontrolmethodoftwophasetypePLLwhichenablesthesystemengageahighprecisionandhigh692UEvWEUEVEWbFig.1.Vu,V,,V,arebackEMFelectromotiveforceMotormodelfornumericalsimulation.I,,I,,I,arelinecurrentandn3EsUEV.I,I1001I.....I........I........I.......II0123TimemsaSimulatedmotorcurrent.InITime2OpddivbComparisonofsimulatedandmeasuredresults.Fig.2.Rippleofmotorcurrent.speedsynchronouscontrolunderstrongnoisesituation.SectionIVgivesdiscussionofusinglargepowerfiltertosuppressswitchingnoiseandtheexperimentalresults.111.SYNCHRONOUSSYSTEMBYTWOPHASETYPEPLLThedevelopedgeargrindingmachinerequireshighspeedsynchronouscontrolwithhighaccuracy.Thehighspeedandhighprecisionsynchronouscontrolsystemsarerealizedusuallybyusingahighresolutionandhighspeedencoderwhoseoutputistwophasesinusoidalwave.However,thevoltageofthesinusoidalwavesisusuallyverysmall,anditisdifficulttodetectthissmallvoltagewithoutproblemsofthenoiseunderthestrongnoisesurroundings.Thismeansthatwecannotusetheconventionalcontrolmethodofhighprecisionsynchronization.Therefore,theauthorsusedtwophasetypePLLinthissynchronoussystem.ThetwophasetypePLLwasfirstproposedbyEmuralanditsnoiserejectionabilitywasalreadyverified24.Fig.3isblockdiagramofthehighspeedsynchronoussystembetweengrindingspindleandworkspindleoftheNCgeargrindingmachine.BothoftheservospindleswerecontrolledbytwophasetypePLL.Acommandpulsegeneratorgeneratestwopulsetrainswhosefrequencyratioisthevelocityratioofgrindingspindletoworkspindle.PositioncontrollersoftwophasetypePLLcontrolthespindlessoasforthemtofolloweachcommandpulseaccurately.ByusingtwophasetypePLL,highspeedandhighprecisionsynchronouscontrolwasrealized.TwointerpolatorsoftwophasetypePLLinterpolateencodersignalwithhighresolutionandtheinterpolatedoutputpulsesofrotationalanglearesenttoservoamplifiers.A.HighresolutiondetectionofrotaryanglewithinterpolatoroftwophasetypePLLTheservoamplifierswhichweusedthistimerequireatwophaserectangularsignalforgeneratingthethreephasefieldcurrentthatsynchronizeswithrotorangle.However,wecouldnotusetheconventionalinterpolatorsofcomparatortypebecauseofthenoiseinducedbytheripplecurrent.Therefore,theauthorsdesignedspecialinterpolatorswhichusetwophasetypePLLasshowninFig.4todetectrotaryanglesofspindles.Circuitsofthisinterpolatorwasdesignedmainlyaccordingtothedescriptionin3,andsotheyareonlybrieflydescribedinthefollowing.Inputsignalisatwophasesinusoidalwavesin,cosBiobtainedfromencoder.Atrackingsignaloftwophasesinusoidalwavesine,,cos0,isgeneratedbyavoltagecontrolledoscillatorVCO.ThisVCOiscontrolledsoastotracktheinputsignal.PhasedifferenceofinputsignalandtrackingsignaliscalculatedbyphasedetectorPD.LoopfilterLFremoveshighfrequencycomponentsofoutputofPDandoutputtoVCO.V/FconvertercontainedinVCOgeneratespulsetrain693Commandpulsegeneratorpulsedistributorr1IcontrollerWorkoieceOpticalencoder/.Fig.3.AhighspxdsynchoussystemforNCgeagrindingmachines.InputFig.4.Blockdiagramofinterpolatorusingtwphasetype.PLL.withthefrequencyproportionaltoinputvoltage.Thepulsetrainsiscountedwithabinarycounter,andtheoutputofcounterisfedtoaROM.TwophasesinusoidalwaveindigitalvalueiswrittenintheROManditisoutputwhenaddressed.D/AconvertersconverttheROMoutputtoanalogvoltage.Thesinusoidalwaveiscontrolledsoastotrackinputoftwophasesinusoidalsignalbycontrollingthephasedifferenceto0,thismeansthatPLLisinlockedstate.Underthelockedstate,pulsefromV/Fbecomestotheinterpolatedpulseofinputsignalwhichistherotaryangleofencoder.ThemostsignificantdifferenceoftwophasetypePLLfromconventionalPLListhatwecanalwaysobtainthetrue2phasesinusoidalwavewhichtracksinputsignal.Thismeansthatithasexcellentnoisesuppressioncharacteristicsandwiderangeofinputfrequency.Thiscircuitcanalsolockwhenmotorchangesitsrotarydirection.Opticalencodersofveryhighprecisionareusedtodetectrotaryangleofshaft.Numberofopticalslitsis1800forgrindingspindleand9000forworkspindle.Wecanget2phasesinusoidalwavesfromtheencoders.Thedevelopedinterpolatordividesthemby128timesandoutput2phaserectangularpulsesignal.Hencetheresolutionis5.6and1.1respectively,andthemaximumfrequencybecomesupto38.4MHz.Thepulsesarefedtopoweramplifiersandaswellusedtomonitorsynchronouscontrol.In3,amagneticscalewithinductiontypeheadwasusedastherotarysensor.Becauseinductiontypeheadcannotworkatlowspeed,theinterpolatorcouldnotworkatrotaryspeedbelow300r/min.However,thenewlydevelopedsystemcanworkatanyspeedbelow10000r/mforgrindingspindleandbelow2000r/minforworkspindle.Ofcourse,wecangivereversiblerotationstothespindles.Ingeneral,detectionwithsohighaccuracyandhighfrequencyiscriticallyaffectedbynoisesanditisverydifficulttorealizestablecontrol.However,thenewinterpolatorscandetecttherotorangleswithoutmisoperation.Fig.5illustratesanexampleofexperimentalresults.InFig.5,inputsignalmeanssignalobtainedfromencoderandtrackingsignalmeansthesinusoidalwaveofVCO.AsshowninFig.5,signalfromencoderisdistortedbystrongnoise.However,thesinusoidalwavewhichispreciselytrackingtheinputsignalhasnodistortion,becauseitisgeneratedbyVCOwhoseoutputwaveformistruesinusoidalwave.WecangettheinterpolatedpulsesfromtheoutputpulsesofV/Fconverter,bywhichthetrackingsinusoidalwaveswereconstructed.B.ServoControllerwithTwoPhaseTypePLLServocontrollerusesthetwophasetypePLLmethodaswell.TheschematicisshowninFig.6.Aservoerrorde694TimeFig.5.ExperimentalresultsofinterpolatoroftwophasetypePLL.Workspindle,500rhninsine,Asine,ServoServof1amplifierIMotor6sine,Fig.6.SchematicofservomechanismoftwophasetypePLL.tectoroftwophasetypePLLisusedtodetectservoerrorwithveryhighprecision.PIDcontrollercontrolsthemotortorquetomaketheservoerrorto0.Referencesignalofthisloopisapairoftwophasesinusoidalwavessin8,cose,andtheirphaseiscomparedwiththetwophasesinusoidalwavesobtainedfromencoderbythefollowingvectorphaseoperation.cos8icos8,sin8sin0,cos8dcos8sin8,sin8cos8,sin8d}1HencewecangetapairoftwophasesinusoidalwavesofwhichargumentisphasedifferenceBd88,.Sincewecandetectthephasedifference8dwiththesameprincipleastheinterpolatormentionedpreviously,theservoerrordetectoroftwophasetypePLLdetectstheservoerrorwithhighresolutionandhighaccuracy.Anotherfeatureofthisloopisthattheservoerrordetectorisabletodetectangularvelocityerrorwithhighaccuracy.ThisisbasedontheexcellentcapabilityofPLLinfrequencydetectionasknown.Byfeedbackoftheangularvelocityerrorobtainedfromthephasedetector,wecouldrealizetheservocontrollerwhoseDgainishighenoughandconsequentlywhosestabilityissignificantlyhigh.Theresolutionandmaximumspeedare11.25and10000r/minforgrindingspindleand1.125tStepdisplacementCommand10.6IIII00.20.4TimeSIFig.7.Stepresponseofgrindingspindleel18bitBRMROMsUsin/costables11converterstTogrindingspindleToothoraxisROMssin/costables4D/AconvertersToworkspindleFig.8.ReferencesignalgeneratorforsynchronouscontrolsystemoftwophasetypePLLand2000r/minforworkspindlerespectively.Thesevaluesareextremelyexcellentvaluesthathaveneverbeenrealized.Fig.7ashowsastepresponseofgrindingspindle.FromFig.7,itisknownthatthegrindingspindletrackscommandplusespreciselyevenundertheexistenceofstrongnoise.C.ReferenceSignalGeneratorBothofworkspindleandgrindingspindlecontrolledbytheabovementionedtwophasetypePLLispositioningservomechanism.Theirpositioningcommandisgivenconsequentlytwophasesinusoidalwaveofwhichangularfrequencyisdecidedbythespecificationsofworkpieceandtool.ThestructureofreferencesignalgeneratorissimpleasshowninFig.8.AsshowninFig.8,theoutputpulsefrequencyofareferencepulsegeneratorisdecreasedbyBRMBinaryRateMultiplier,ofwhichdecreasingrateisdecidedbytherotaryspeed695

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