Self-sensing-control-of-piezoelectric-positioning-stage

SensorsandActuatorsA226(2015)76–80

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SensorsandActuatorsA:Physical

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Self-sensingcontrolofpiezoelectricpositioningstagebydetectingpermittivity

KatsuhiroSaigusa ,TakeshiMorita

GraduateSchoolofFrontierScience,TheUniversityofTokyo,Kashiwa,Chiba277-8563,Japan

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abstract

Articlehistory:

Received15August2014

Receivedinrevisedform26January2015Accepted16February2015

Availableonline23February2015

Keywords:

PiezoelectricactuatorHysteresis

PermittivitydetectionSelf-sensingcontrol

Piezoelectricdisplacementcontainshysteresisandcreepproperties.Therefore,adisplacementsensorisindispensableinprecisepositioningdevices;however,theadditionalspaceandcostareproblems.Ontheotherhand,self-sensingmethodsthatutilizethepiezoelectricactuatoritselfasthedisplacementsensorhavebeenproposed.Withtheseself-sensingmethods,precisepositioningbecomespossiblewith-outanadditionaldisplacementsensor.Wedevelopedaself-sensingmethodutilizingthenon-hysteresisrelationshipbetweenthepermittivitychangeandthepiezoelectricdisplacement.Furthermore,adiffer-entialcurrentmeasurementmethodusingtwopiezoelectricelementswithabimorphactuatorcouldimprovethepositioningaccuracy.Inthisstudy,weexaminethecontrolofapositioningstageusingtwomultilayeredpiezoelectricactuatorsbyapplyingthedifferentialcurrentmeasurementmethodforself-sensingcontrol.Theresultsindicatethatthedifferentialcurrentmeasurementmethodiseffectiveforprecisepositioningcontrol.Thepositioningerrorsduetohysteresisdecreasedfrom0.8 mto0.1 mfora10 mdisplacementrange.Inaddition,permittivityfeedbackcontrolcouldcompensateforthecreepproperty.

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1.Introduction

Piezoelectricmaterialshavetheadvantagesofaccuracyandrapidresponse.Therefore,theyareusedinhigh-precisiondevicesasactuators.Forexample,apiezoscannerofAFMoradeformablemirrorforatelescopeadoptspiezoelectricactuators[1,2].How-ever,piezoelectricdisplacementcontainshysteresisandcreepproperties,andthesepropertieshavebeenstudiedfromvariousviewpoints[3–5].Toeliminatethehysteresispropertyofapiezo-electricactuatorforprecisepositioningcontrol,adisplacementsensor,suchasacapacitivesensororalaserinterferometer,isindis-pensable.However,foralow-costandsimplesystem,self-sensingmethodsthatutilizethepiezoelectricactuatoritselfasadisplace-mentsensorarerequired[6–9].Forexample,aself-sensingmethodbasedonthenon-hysteresisrelationshipbetweenthepiezoelectricdisplacementandtheelectricchargewasproposed[6,7].How-ever,thismethodisnotstableinthequasi-staticstate,becausetheelectricchargeisdif culttoholdandtheoffsetchargesignalaccumulates,duetotheintegrationofthecurrentsignal.

Ontheotherhand,wehavereportedthenon-hysteresisrelationshipbetweenthepiezoelectricdisplacementandtheper-mittivityofpiezoelectricactuators.Thisrelationshipwasutilizedfortheself-sensingmethodfordetectingthepiezoelectricdisplace-mentfromthepermittivitychange.Byapplyingthismethod,thepiezoelectricdisplacementofthebimorphactuatorwascontrolledwithina0.4 merrorforan80 mdisplacementrange[10–12].Inthisstudy,weexamineourself-sensingmethodforthepositioningstageusingmultilayeredactuators,whicharemainlyutilizedinprecisepositioningdevices.Inaddition,thedifferentialcurrentmeasurementmethod,whichwasquiteusefulinourpre-viousstudyusingthebimorphmechanism[12],isappliedtothepositioningstagefortheimprovementofthepermittivitydetectionaccuracy.

2.Experimentalsetup

2.1.Permittivitydetection

Correspondingauthor.Tel.:+81471364615.

E-mailaddress:saigusa@ems.k.u-tokyo.ac.jp(K.Saigusa).

Self-sensingcontrolbydetectingpermittivityisbasedonthenon-hysteresisrelationshipbetweenthepiezoelectricdisplace-mentandthepermittivitychange.Thisisrelatedtothefactthatthepermittivityfollowsasimilarbutter ycurvetothatofthepiezo-electricdisplacementversusinputvoltage,asshowninFig.1.It

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