机械专业毕业设计外文翻译外文文献

AMulti-DOFUltrasonicMotorUsingIn-planeDeformationofPZTElementsandItsDrivingCircuitMinghuiZhang,MantianLiandLiningSunRoboticsInstituteHarbinInstituteofTechnologyHarbin,HeilongjiangProvince,ChinaAbstract-DuetotheincreasingnumberofDOFsofsystemsandthereducingthevolumeandweightofthedevices,multi-degrees-of-freedom(DOFactuatorshavebecomemoreusefulinthefieldofrobotics.Andthegeneralfeaturesofultrasonicmotorsarealsosuitableforconstructingadirect-drivemulti-DOFactuator.So,anewmulti-DOFultrasonicmotorusingin-planedeformationofPZTelementsisintroducedinthispaper.Thenitsworkingprincipleandrequirementfordrivingcircuitareanalyzed.Atlast,adrivingcircuitisproposedaccordinglywhichgeneratessinusoidalactuatingsignalswithaFPGApart(aDirectDigitalSynthesizer(DDSarrayissynthesizedinitandamplifiesthemwithhighvoltagepoweroperationalamplifiers.Itischaracteristicofindependentadjustmentofamplitudeandfrequencyforeachoutputsignalandindependentadjustmentphasebetweenanytwoofoutputsignals.Thecircuitmeetstherequirementofthemotor.IndexTerms-ultrasonicmotor;multi-degreeoffreedom;in-planedeformation;drivingcircuitI.INTRODUCTIONMulti-DOFultrasonicmotorisanewkindofmulti-DOFactuator.Withitorothermulti-DOFactuators,dexterousmulti-DOFcanbegeneratedeasily,andatthesametimethevolumeandweightofthedevicesarealsoreducedgreatly.Andcomparingtoothermulti-DOFactuators,multi-DOFultrasonicmotorscanbeeasilyminiaturized.What’smore,theyalsohavemanyotherexcellentcharacteristicssuchashightorqueatlowspeed,highstationarylimitingtorque,absenceofelectromagneticradiation,lessnoise,andsimplicityofdesign.Someofthecharacteristicsassurecapabilityofultrasonicmotorsasmulti-DOFactuators,usableasdirect-driveactuators.Especially,amulti-DOFultrasonicmotorwithcompactstatorandsimpledrivingcircuitisverysuitableforroboteyecontrol,laserhandling,andotherapplications[1].Therefore,manymulti-DOFactuatorsbasedontheprincipleofultrasonicmotorshavebeenproposedinthepast.Toyamadevelopedasphericalultrasonicmotorinwhichthreeorfourring-shapedvibratorsarearrangedaroundasphericalrotor[2].Takfumidesignedanultrasonicactuatorwithmulti-degreeoffreedomusingbendingandlongitudinalvibrationofasinglestator,whichhasbeenappliedinanauditorytele-existencerobot[3,4].Takemuraproposedabar-shapedultrasonicmotorcapableofgeneratingthree-DOFmotionandaplatetypemulti-DOFultrasonicmotorwhoserotorwaslargerinthesizeofvolume[5,6].Otokawaconstructedanarrayed-typemulti-DOFultrasonicmotorbasedonaselectionofreciprocatingvibrationmodes[7].Almostallthesemulti-DOFultrasonicmotorsgeneratevibrationbyexpandingandcontractingwiththecouplingcommonlyassociatedwiththepiezoelectricd33(strainore33,(stresscoefficients.Inordertoobtaintheoptimumworkingcharacter,adrivingcircuitfortheultrasonicmotorshouldbedeveloped.Andtostudythemulti-DOFultrasonicmotordirectlyandeasily,itisbetterthatthedrivingfrequencyandvoltageoftheoutputsignalmustbeadjustable,andthephasebetweentheoutputsshouldalsobecontrollable[8,9].Takemurahaveproposedaself-oscillationdrivingcircuitfortheplatetypemulti-DOFultrasonicmotortheydeveloped.Experimentalresultsconfirmtherotorcanberotatedusingtheself-oscillationdrivingcircuitandthemaximumrotationalspeedoftherotorisabout70rpm[6].AndKingLonghasalsodesignedthreekindsofdrivingcircuitsforathree-degreefreedomofsphericalpiezoelectricultrasonicmotor[10].Inthispaper,anewmulti-DOFultrasonicmotorisintroduced,whichgeneratesvibrationwiththecouplingassociatedwiththepiezoelectricd31(strainore31,(stresscoefficientsandthepiezoelectricd15(strainore15,(stresscoefficients.Then,aspecialdrivingcircuitbasedonDDSisdeveloped.ThesinusoidaldrivingsignalsaregeneratedfromtheDDSarraysynthesizedaFPGApartandamplifiedbyhighvoltagepoweroperationalamplifiers.Thefrequencyandamplitudeofthefouroutputsignalsfromthedrivingcircuitarealladjustableindependently;andthephasebetweenanyofthemcanalsobeadjusted.II.STRUCTUREANDPRINCIPLEA.StructureofthestatorAsquarebeamhastwobendingmodeswhoseresonancefrequenciesareequaltoeachother.Andwithcalculateddimensions,itmayhaveonelongitudinalmodewhichisorthogonaltothemanditsresonancefrequencyalsocorrespondstothem.Thesecondbendingmodefrequenciesinanydirectionforcircularcylindersareequaltoeachotherandthefirstlongitudinalmodefrequencycanbeveryclosetothem.Thestatorofthemotorpresentedinthisstudycombinesthecircularandsquarecrosssections.Theoutsidesurfaceofahollowmetalcylinderisflattenedonfoursidesat90degreestoeachotherandfourrectangularpiezoelectricplatesarebondedontothesefourflattenedProceedingsofthe2007IEEEInternationalConferenceonMechatronicsandAutomationAugust5-8,2007,Harbin,Chinasurfaces[Fig.1].ThePZTplatehasfiveelectrodes;fouraredepositedonthetopsurfacewhilethefifthoneisdepositedonthebottomsurfaceofthePZTplates.OnthetopofPZTplates,twoelectrodesareconnectedacrosscornersasoneinput,andtheinputsonthesymmetricpositionsofthestatoraredefinedasoneinputelectrodegroup.AndthebottomsofPZTplatesareelectrodeduniformlyandtheyareground.Withtheapplicationofanalternatingcurrent(ACvoltagepotentialacrossthethicknessofthepiezoelectricplate,theplatewillexpandandflexduetothecouplingcommonlyassociatedwiththepiezoelectricd31(strainore31,(stresscoefficientsandthepiezoelectricd15(strainore15,(stresscoefficients[11,12].Withtheconfigurationshown,theplatedeformsin-planeandmakeslongitudinalandbendingvibrationofthebase.(a(bFig.1Structureofthestator.(aorthographicview;(btopviewB.VibrationmodesFig.2showsthedrivingprincipleofthemulti-DOFultrasonicmotor.Therotorcanrotatearoundthreeperpendicularaxes.AlongitudinalvibrationandtwobendingvibrationsofthestatorareusedasshowninFig.2.Fig.2(ashowsthenaturalvibrationmodesofthestatorthatareusedwhentherotorrotatesaroundthezaxis.Figs.iandiiishowthesecondbendingmodeofthestatorinthex-zplane(modeA,andFigs.iiandivshowthesecondbendingmodeofthestatorinthey-zplane(modeB.Whenthesetwonaturalvibrationmodes,AandB,arecombinedataphasedifferenceof90°,thetipofthestatorrotatesaroundthezaxis.Then,thesphericalrotorincontactwiththestator’sheadalsorotatesaroundthezaxisbyfrictionalforce.Fig.2(bshowsthenaturalvibrationmodesusedwhentherotorrotatesaroundthexaxis.Figs.iandiiishowthefirstlongitudinalmodeofthestatoralongthezaxis(modeC,andFigs.iiandivshowthemodeB.whenanelectricalexcitationisimposedbetweenelectrodegroup‘A’or‘B’andground,thesetwonaturalvibrationmodes,BandC,arecombinedataphasedifferenceof90°,andthetipofthestatorrotatesaroundthexaxis.Then,thesphericalrotoralsorotatesaroundthexaxisduetofrictionalforce.Excitationofinputelectrodegroup‘A’andgroundwillcausethecounterclockwiserotationbyright-handrule,whileexcitationofinputelectrodegroup‘B’andgroundwillcausetheclockwiserotation.TherotorrotatesaroundtheyaxiswhenthemodeAandthemodeCarecombinedinthesamewayasthecaseofFig.2(b.Thepointtonoticeisthatthenaturalfrequenciesofthesethreenaturalvibrationmodes,A,B,andC,shouldbeascloseaspossible.TableIshowstheinputphasesforthePZTplatesneededforexcitationeachrotation.(a(bFig.2Drivingprincipleofthemulti-DOFultrasonicmotor.(aaroundzaxis;(baroundxaxisWhenadrivingvoltageisappliedonelectrodesA1andA2,vibrationmodesBandCcanbeexcitedthesametime.Accordingly,thetipofthestatorrotatesaroundthexaxiscounterclockwise.Then,thesphericalrotorincontactwiththestator’sheadalsorotatesaroundthexaxiscounterclockwisebyfrictionalforce.Similarly,thesphericalrotorrotatesaroundthexaxisclockwise,whenadrivingvoltageisappliedonelectrodesB1andB2.AndtheexcitationonelectrodesC1andC2willcausethecounterclockwiserotationoftherotorandheexcitationonelectrodesD1andD2willcausetheclockwiserotationoftherotor,aswell.TherotorwillrotatearoundzaxiscounterclockwisewithelectrodesA1andC1beingexcitedsimultaneouslyataphasedifferenceof90°androtatearoundzaxisclockwisewithelectrodesB1andD1beingexcitedsimultaneouslyataphasedifferenceof90°.C.GeometrySincethedesigniscomplicated,finiteelementanalysismethodisusedtoconductmodalandharmonicanalysisoftheultrasonicmotor,includingthelinearizedpiezoelectricmaterialproperties.Inthisway,afeasibledesigncanbedevelopedfromtheconceptwithreasonableassurancethattheresultsoftheanalysiswouldresemblethebehaviorofanactualactuator.Fig.3(aand(bshowthecalculatedfirstlongitudinalmodeandthecalculatedsecondbendingmodeofthestator,respectively.Thecalculatednaturalfrequenciesofthesemodesareveryclose,about57kHz[TableI].(a(bFig.3Vibratingmodesofstator.(asecondbendingmode;(bfirstlongitudinalmodeTABLEINATURALFREQUENCIESOFTHESTATORVibratingmodeNaturalfrequency(KHzFirstlongitudinalmodealongzaxis(L156.7Secondbendingmodeinthex-zplane(B256.6Secondbendingmodeinthey-zplane(B256.6ThebasicconfigurationofthemotorisshowninFig.4.Therotorismadeofstainlesssteel.Thestatoroftheprototypemotorconsistsofahollowmetaltube(brasswithanouterdiameterof10mmandinnerdiameterof6mm,lengthof16mm,andfourrectangularpiezoelectricplateswithdimensions,16mminlength,8mminwidth,and1mminthickness.Theoutsidesurfaceofthemetalcylinderisonfoursidesat90degreestoeachother.ThePZTplates(PZT4,KunshanJingfengElectricCorp.,Ltd.,whicharepoledinthethicknessdirection,arebondedontototheflatorthogonalsurfacesofthecylinderusingaconductiveepoxy[Fig.1(b].Thestatorisheldonthebasewithfourscrews.Andthesupportingpointsareonthenodalplane.Fig.4AssemblydiagramofMDOFUSMIII.DRIVINGCIRCUITA.StructureFordrivingultrasonicmotors,agenerationofthedesirednaturalvibrationofthestatorisoneofthemostimportantpoints.Consideringtherequirementforexcitationofeachrotation,weproposeadrivingcircuitformulti-DOFultrasonicmotorswhichcangeneratefourindependentalternatingexcitationsignals.Theamplitudeandfrequencyofeachsignalcanbeadjustedindividually;thephasebetweenanytwoofthefourexcitationscanbeadjustedindividually,aswell.Fig.5showstheschematicdiagramofthedrivingcircuit.ThecircuitincludestheDSPcontroller,theFPGApartinwhichaDDSarrayaresynthesized,D/Amodules,lowpassfilters(LPFandpoweramplifiers(PA.TheDSPcontrollerreceivescommands,encodervaluesandotherfeedbacks,andthencontrolsthedigitalpotentiometerandtheFPGApartcorrespondingly.TheDSPcontrollercommunicateswiththeFPGApartthroughadualportRAM.ThefrequencyandphaseinformationforeachoutputiswritteninRAMbyDSPcontrollerandreadbytheFPGApartwhichusesitastheparameterfortheDDSarray.ThefourDDSmodulesintheDDSarraygeneratethefourexcitationoutputsrespectively.Actually,theoutputsignalofDDSmoduleiscodedsinusoidalsignal,andmustbetransformedtostepsinusoidalwavebyD/Amoduleandsmoothedbylowpassfilter.Afteramplifiedbythepoweramplifier,thesmoothultrasonicsinusoidwaveservesastheexcitationsignal.Fig.5SchematicdiagramofthedrivingcircuitB.WorkingprincipleSincetheoutputvoltageoftheD/AmoduleisproportionaltoitsreferencevoltageandtheamplitudeofthedrivingcircuitoutputisalsoproportionaltotheoutputvoltageoftheD/Amodule,theamplitudeofthedrivingcircuitoutputcanbeadjustedbysettingthereferencevoltageoftheD/Amodule.Digitalpotentiometersareusedtomodifythereferencevoltage.AlldigitalpotentiometersgettheirvaluesfromtheDSPcontrollerandupdatethevaluessimultaneouslywiththeuniquechipselectsignal.TheadjustmentofthefrequencyoftheoutputsandphasebetweenoutputsisrealizedbyDDSanddescribedasthefollows.Fig.6showstheschematicdiagramofaDDS,whereKisthefrequencycontrolword,fcisthefrequencyoftheinputclocksignal,NisthedigitalcapacityofDDS.Ateveryrisingedgeofinputclock,theaccumulatoraccumulatesinsteplengthofK.TheoutputofaccumulatorisaddedwithPanditsresultactsastheaddressofthewavepatternROM.AlltheinformationofwaveisstoredintheROM.TheoutputofROMisturnedintostepwaveinD/Aconverter[13].Afterpassingthelowpassfilter,thestepwaveissmoothedandalltheharmoniccomponentsareremoved.IntheDDSsystem,theaccumulator,theadderandtheROMintheimaginarylineblockaresynthesizedinFPGA,whileotherspartsareindividualelectricalcomponents.ThefrequencyoftheDDSoutputsignalis:KffNcout2wherefoutisthefrequencyoftheoutput.ThefrequencyisinratioofthefrequencycontrolwordK,sofoutcanbeadjustedproportionallybychangingthevalueofK.ThusthefrequencyrangeofDDSoutputisfromfc/2Ntofc/2,whenthefrequencycontrolwordisinaspanfrom‘1’to‘N-1’.Butinordertoguaranteetheoutputaccuracy,thereatleastneedtobefoursamplingpointsinoneperiod.ThemaximumofKisN-2,thatis,thehighestfrequencyoftheDDSoutputisfc/4.Fig.6SchematicdiagramofDDSIntheimplementprocessofDDS,thephasecontrolwordPisaddedwiththeresultofthefrequencyaccumulatorateveryrisingedgeoftheinputclock.Consequently,ashiftof2ʌ•P/2Nisgeneratedintheoutputwave.Thus,thephasesofoutputsignalscanbeeasilyadjustedwithmodifyingthephasecontrolwordandtheresolutionofphaseadjustmentis2ʌ/2N.C.PoweramplifierInordertogeneratecontinuousoutputinultrasonicrange,highvoltagepoweroperationalamplifiers(ApexMicrotechnologyCorp.areadaptedtorealizepoweramplification.Theyarecharacteristicofhighvoltage,highoutputcurrentoutput,highslewrateandlowquiescentcurrent.Sotheyareveryappropriatetodrivepiezoelectricelements.Thehighvoltagepoweroperationalamplifiercanbeusedjustlikeordinaryoperationalamplifier(RF=5kȍ,RIN=150kȍ,RCL=3.3ȍ,asshowedinFig.7,whereRCListhecurrentlimitresistor.Andconsideringthecapacityloadsandclosedloopstability,thetypeofhighvoltagepoweroperationalamplifierisPA90.Andthequalificationofthepoweramplifiercircuitisasfollows:theclosedloopgainis30;themaximumpeak-to-peakamplitudeoftheoutputis300V;thehighestfrequencyis100KHzwith2.2nFcapacityloads.Fig.7PoweramplifierInordertodemonstratethedrivingcircuit,a2.2nFcapacitiveloadisaddedtothedrivingcircuit.Actually,thecapacityofthepiezoelectricplatesislessthan2.2nF.Fig.8showstheoutputsignalofthedrivingcircuitmeasuredbytheDS5102Coscilloscope,adigitaloscilloscopeofRigolElectricCorp..Allthefiguresarecapturedwith50V/div(yaxisand5ȝs/div(xaxis.Fig.8(ashowsthatthevoltageofoutputcanbeadjustedfrom0to300V.Fig.8(bshowsthatthefrequencyofoutputcanbeadjustedfrom0to100kHz.Andfig.8(cshowsthatthephaseoftwooutputsalsocanbeadjusted.(a(b(cFig.8Outputsignalsofthedrivingcircuit.(aamplitudeadjustment(bfrequencyadjustment(cphaseadjustmentIV.CONCLUSIONSInthisstudy,thedrivingprincipleforamulti-DOFultrasonicmotorusingin-planedeformationofthePZTelementsisproposed.Anditsrequirementforthedrivingcircuitisalsoanalyzed.Accordingly,thedrivingcircuitbasedonDDSisdevelopedwhichconsistsoftheDSPcontroller,theFPGApartinwhichaDDSarrayaresynthesized,D/Amodules,lowpassfiltersandpoweramplifiers.Thedrivingcircuitischaracteristicoftheamplitudeandfrequencyofeachoutput,andthephasebetweenanytwooftheoutputscanbeadjustedcontinuouslyandindependently.Soitcanbeusedintheexperimentalstudyofmulti-DOFultrasonicmotors.ACKNOWLEDGMENTThisstudyissupportedbytheNationalNaturalScienceFoundationofChina#50575056.AuthorsalsowouldliketothankthestaffofKunshanJingfengElectricCorp..fortheirhelpinmanufacturingthepiezoelectricceramics.REFERENCES[1]K.Takemura,T.Maeno.“Designandcontrolofanultrasonicmotorcapableofgeneratingmulti-DOFmotion”.IEEE/ASMETransactionsonMechatranoics,vol.6,no.4,pp.499-506,2001[2]T.Shigeki,S.ShigeruandZ.Guoqiang.“Multidegreeoffreedomsphericalultrasonicmotor”.ProceedingsofIEEEInternationalconferenceonroboticsandautomation,pp.2935-2940,1995[3]T.Amano,Takaakiishii,K.NakamuraandS.Ueha.“Anultrasonicactuatorwithmulti-degreeoffreedomusingbendingandlongitudinalvibrationofasinglestator”.ProceedingsofIEEEUltrasonicssymposium,pp.667-670,1997[4]H.Kawano,H.AndoandT.Hirahara,etal.“Applicationofamulti-DOFultrasonicservomotorinanauditorytele-existencer