1)science.pdf

TECHNIQUEKEYWORDSFORANGULARTHEPRIMARYFIELDUSINGTHEFINITEELEMENTRESULTS,APPROPRIATESHAPEANDSIZEOFFERROMAGAPPLICATISENSORPERFORMANCEANDONEIMPORTANTTRENDINSENSORRESEARCHHASBEENINTOTHEAREAOFSENSORSYSTEMS2INGDISTANCEBETWEENFERROMAGNETICCOMPONENTANDGMRSENSORCHIPSURFACE,WHICHISUSUALLY15MMORMORE68NOTETHATIFTHEWORKINGDISTANCEISSMALLER,THEMAGNETICINTENSITYGENERATEDBYTHEFERROMAGNETICCOMPONENTISUSUALLYSOSTRONGTHATITCANUPSETITSPINNEDLAYER,THUSPERMANENTLYDAMAGINGTHESENSORELEMENTFURTHERMORE,THEGMRSENSORBRIDGEINFACTCONVERTSANYFIELDDIRECTIONTOTWOCOMPONENTSIGNALS,INDEPENDENTOFTHEIRSOURCE02632241/SEEFRONTMATTERC2112009ELSEVIERLTDALLRIGHTSRESERVEDCORRESPONDINGAUTHORADDRESSSTATEKEYLABORATORYOFROBOTICSANDSYSTEMHIT,HARBIN,PRCHINATEL8645186412042FAX8645186418306EMAILADDRESSESLANTIANHIT163COMTLAN,HONGLIUDLRDEHLIUMEASUREMENT42200910111016CONTENTSLISTSAVAILABLEATSCIENCEDIRECTMEASUREMJOURNALHOMEPAGEWWWELSEVIERDOI101016/JMEASUREMENT200903002WHENDEVELOPINGSENSORSFORMEASURINGANGULARSIGNALINMINIATURESYSTEMS,ITBECOMESOBVIOUSTHATTHEBASICSENSORHASMANYLIMITATIONSANDIMPERFECTIONSEGSIZE,WORKINGDISTANCE,ACCURACYANDOFFSETWHICHPREVENTTHEDESIGNERFROMACHIEVINGTHEREQUIREDSPECIFICATIONSTOIMPROVETHEBASICSENSORPERFORMANCE,ONEOPTIONISTOTRYANDREFINETHESENSORITSELFUSINGBETTERMATERIALS,PRODUCTIONMETHODS,ETCTHISCHOICEISGENERALLYANEXPENSIVEONEANOTHEROPTIONISTOINCORPORATETHESENSORINTOASYSTEMWHICHHASTHEUNIQUEOBJECTIVEOFIMPROVINGTHEBASICKEYADVANTAGESEGHIGHSENSITIVITY,MINIATURESIZE,CONTACTLESSINSTALLANDWEARFREEWORKOVEROTHERKINDSOFSENSORS3,4HOWEVER,MAGNETICFIELDSENSORSYSTEMSFORDEMANDINGAPPLICATIONSINEVITABLYCONTAINFERROMAGNETICPARTS5THESEFERROMAGNETICCOMPONENTSARECURRENTLYUSEDASAPARTOFTHESENSORITSELF,LIKEINGMRSENSORTHESTRUCTUREOFSUCHSENSORSYSTEMSISRATHERCOMPLEX,RENDERINGDIFFICULTTHEIRINTEGRATIONINTHECASEOFGMRSENSORS,THEISSUESINCLUDETHEMOUNTINGOFTHEFERROMAGNETICCOMPONENTINLIMITEDASSEMBLYSPACE,ANDTHEWORKMAGNETICSENSORFINITEELEMENTTECHNIQUES3DSTATICMAGNETICANALYSISGMRSENSORMEMS1INTRODUCTIONINGENERAL,FURTHERSYSTEMMINIATURIZATICREATEDEMANDSFORACONTINUOUSDOWNSCALINGFUNCTIONSINAVARIETYOFDIFFERENTNETICCOMPONENTISCOMPAREDANDOPTIMIZEDASIMPLIFIEDSIGNALPROCESSINGCIRCUITISALSOGIVENFORTHEULTRAMINIATUREGMRSENSORSYSTEMFINALLYEXPERIMENTALRESULTSSHOWANANGULARACCURACYOFLESSTHANC61C14WITHONLYTHERESIDUALOFFSETCOMPENSATIONOFULTRAMINIATUREGMRSENSORSYSTEMISOBTAINEDINTEGRATIONEXPERIENCESREVEALTHECHALLENGESASSOCIATEDWITHOBTAININGTHEREQUIREDCAPABILITIESWITHINTHEDESIREDSIZEC2112009ELSEVIERLTDALLRIGHTSRESERVEDONWILLCERTAINLYOFSENSORONFIELDS1ACCORDINGLY,FURTHERSCALINGOFSENSORSYSTEMS,ISMANDATORYFORALLAPPLICATIONSWHEREULTRAMINIATURESIZEENABLESTHEINTEGRATIONOFMEMSANDOTHERHIGHLYINTEGRATEDSYSTEMSASAMAGNETICFIELDSENSOR,GMRSENSOROFFERSSEVERALTEROUSROBOTHANDA3DSTATICMAGNETICANALYSISMODELINGISUSEDTOAVOIDSENSORDAMAGEBYTHEEXCESSIVEMAGNETICINTENSITYANDDISORIENTATIONWHENOTHERMAGNETICFIELDSDISTURBSTUDYOFULTRAMINIATUREGIANTMAGNETOBASEDON3DSTATICMAGNETICANALYSISTLANA,YWLIUA,MHJINA,SWFANA,ZPCHENASTATEKEYLABORATORYOFROBOTICSANDSYSTEMHIT,HARBIN,PRCHINABINSTITUTEOFROBOTICSANDSYSTEMDYNAMICS,GERMANAEROSPACECENTER,GERMANYARTICLEINFOARTICLEHISTORYRECEIVED27NOVEMBER2008ACCEPTED3MARCH2009AVAILABLEONLINE12MARCH2009ABSTRACTINTHISSTUDY,AMETHODGIANTMAGNETORESISTANCEDESIGNAPPROPRIATERESISTANCESENSORSYSTEMA,HLIUA,B,THEMODELINGOFFERROMAGNETICCOMPONENTOFANULTRAMINIATUREGMRSENSORSYSTEMISPRESENTEDTHEGOALOFTHEMODELINGISTOSENSORSYSTEMFORTHEHIGHLYINTEGRATEDDLR/HITII5FINGERDEXENTCOM/LOCATE/MEASUREMENT9WHENASECONDMAGNETICFIELDISADDTOTHEPRIMARYFIELD,THERESULTINGFIELDISASUPERPOSEDSUMOFBOTHFIELDSANDITMAYLEADTOSEVEREDISORIENTATIONOFTHEANGULARMEASUREMENTTHESETWOCONSTRAINTSOBSTRUCTTHEAPPLICATIONOFGMRSENSORINHIGHLYINTEGRATEDFIELDINTHISSTUDY,THEULTRAMINIATUREGMRSENSORSYSTEMWITHONLY05MMWORKINGDISTANCEISDEVELOPED,ANDTHEDISORIENTATIONBYOTHERMAGNETICFIELDISAVOIDEDANDCOMPENSATEDALSOBASEDON3DSTATICMAGNETICANALYSISTECHNIQUETHISPAPERFIRSTLYINTRODUCESTHECONCEPTOFGMRSENSORANDFINITEELEMENTMODELINGSECONDLY,THESHAPEANDSIZEOFFERROMAGNETICCOMPONENTARECOMPAREDANDOPTIMIZEDBYUSINGTHE3DSTATICMAGNETICANALYSISRESULTSTHENASIMPLIFIEDSIGNALPROCESSINGCIRCUITISALSOGIVENFINALLYTHEEXPERIMENTALRESULTSOBTAINEDWITHTHEDEVELOPEDMETHODARECOMPAREDWITHTHEORETICALRESULTS2GMRSENSORCONCEPT1012TLANETAL/MEASUREMENT42200910111016GIANTMAGNETORESISTANCEMEANSTHEVERYLARGECHANGEINRESISTANCEINULTRATHINMAGNETICMULTILAYERFILMSTHEBASICGMRMATERIALCONSTRUCTIONINCLUDESAPINNEDLAYERANDAFREELAYERTHEFREELAYERCANBEINFLUENCEDBYANEXTERNALMAGNETICFIELDANAPPLIEDMAGNETICFIELDOFADEQUATEMAGNITUDE,INTHERANGEGREATERTHANTHESATURATIONFIELDFORTHEFREELAYERANDSMALLERTHANTHESTANDOFFFIELDFORTHEPINNEDLAYER,WILLFORCETHEFREELAYERMAGNETIZATIONTOFOLLOWTHEFIELDWHENITROTATESWITHAFIXEDREFERENCELAYERMAGNETIZATION,ANDANINSTEPFOLLOWINGOFTHEFREELAYERMAGNETIZATION,MAGNETORESISTANCEISASIMPLECOSINEFUNCTIONOFTHEANGLEOFTHEROTORRELATIVETOTHESTATIONARYSENSORANDTHERESISTANCEROFASPINVALVEISRELATEDTOTHEANGLEHBETWEENTHEFREEANDTHEPINNEDLAYERMAGNETIZATIONSINTHEFOLLOWINGEQUATIONRRP112GMR1C0COSH1WHERETHERPISTHELOWESTRESISTANCEWHENTHETWOMAGNETIZATIONSAREPARALLEL,ANDTHEGMRISTHEMAXIMUMPERCENTAGEMAGNETORESISTANCETHEANGLESENSORISUSEDINCOMBINATIONWITHAPLANARPERMANENTMAGNETATTACHEDTOALIVESHAFTROTOR,ASSHOWNINFIG1THEPERMANENTMAGNETISMAGNETIZEDINFIG1SCHEMATICOFANANGLESENSORPERMANENTMAGNETROTOR7PLANTHUSCREATINGAFIELDTHATISINTHEPLANEOFTHESENSORCHIPANDROTATINGWITHTHESHAFTTHISFIELDFORCESTHEFREELAYERMAGNETIZATIONTOROTATEINPHASEWITHITANDTHEROTORTHEREFORETHEOUTPUTSIGNALISASINUSOIDALFUNCTIONOFTHEANGLEWITHTHEPERMANENTMAGNET,SENSORDESIGN,ANDTHEIRAXIALCONFIGURATIONTHESAME,THEDISTANCEBETWEENTHEMAGNETANDTHESENSOR,ORWORKINGDISTANCE,DETERMINESTHEMAGNITUDEANDDISTRIBUTIONOFTHEMAGNETICFIELDACTINGONTHEFREELAYEROFTHESVRESISTORSTHEBASICREQUIREMENTFORTHEWORKINGDISTANCEISTHATTHELOWESTFIELDACTINGONTHEFREELAYERISLARGEENOUGHTOSATURATEIT,ANDTHEHIGHESTFIELDDOESNOTDISTORTTHEREFERENCELAYER73FINITEELEMENTMODELINGFEMTHEMETHODOFFINITEELEMENTMODELINGISBASEDONADISCRETIZATIONOFTHESOLUTIONDOMAININTOSMALLREGIONSTHEPROGRAMUSESMAXWELLSEQUATIONSASTHEBASISFORELECTROMAGNETICFIELDANALYSISINMAGNETOSTATICPROBLEMS,THEUNKNOWNQUANTITYDEGREEOFFREEDOMISUSUALLYTHEMAGNETICVECTORPOTENTIAL,ANDISAPPROXIMATEDBYMEANSOFPOLYNOMIALSHAPEFUNCTIONSOTHERMAGNETICFIELDQUANTITIESSUCHASMAGNETICFIELDFLUXDENSITY,MAGNETICINTENSITY,CURRENTDENSITY,ENERGY,FORCES,LOSS,INDUCTANCE,ANDCAPACITANCEAREDERIVEDFROMTHEDEGREEOFFREEDOM10THESIZEOFELEMENTSMUSTBESMALLENOUGHTOPROVIDESUFFICIENTACCURACY11INTHISWAY,THEDIFFERENTIALEQUATIONSOFTHECONTINUOUSPROBLEMCANBETRANSFORMEDINTOASYSTEMOFALGEBRAICEQUATIONSFORTHEDISCRETEPROBLEMTHEPRACTICALPROBLEMSNECESSITATEUSUALLYSEVERALTHOUSANDSOFUNKNOWNSHOWEVER,APPROPRIATENUMERICALTECHNIQUESHAVEBEENDEVELOPED,ENABLINGTOOBTAINTHESOLUTIONOFSUCHSYSTEMSWITHINREASONABLETIME,EVENWHENPERSONALCOMPUTERSAREUSEDASAHIGHLYINTEGRATEDELECTROMECHANICALSYSTEM,ROBOTHANDNEEDSTOCOMPLETECOMPLEXTASKS,LIKEFINEMANIPULATION,ITISOFTENNECESSARYTOGETENOUGHACCURATEANGULARSIGNALSTOIMPLEMENTSOMECONTROLSTRATEGY12THEREFOREANGULARSENSORPLAYSASAVERYIMPORTANTROLEINTHESENSORSYSTEMANDITSSIGNALACCURACYAFFECTSCONTROLEFFECTDIRECTLYWITHHIGHSENSITIVITYANDMINIATURESIZE,GMRSENSORISVERYAPPROPRIATEFORHIGHLYINTEGRATEDSYSTEM,LIKEDLR/HITII5FINGERDEXTEROUSROBOTHANDASABOVESTATED,INSPITEOFTHEBENEFITSWHICHGMRSENSORHAS,THEREARESTILLSOMEIMPERFECTIONSINHIGHLYINTEGRATEDAPPLICATIONBECAUSEINHIGHLYINTEGRATEDSYSTEM,ITDOESNOTHAVEENOUGHSPACETOINSTALLTHESENSORANDPERMANENTMAGNET,THENTHESENSORSYSTEMSHOULDBEDESIGNEDTOMAKETHEBESTUSEOFTHELIMITEDSPACEFOREXAMPLE,INTHEDLR/HITIIDEXTEROUSROBOTHAND,THEDISTANCEBETWEENSHAFTENDANDGMRSENSORCHIPSURFACEISONLY05MMASSHOWNINFIG2BYTHELIMITATIONOFMACHINESTRUCTURE,THEREARETWOTYPESOFPERMANENTMAGNETCANBEEMBEDDEDINTOTHESHAFTENDONEISCYLINDER,THEOTHERISCUBEINORDERTOENSUREENOUGHSTRENGTHANDAVOIDINTERFERENCE,THEDIAMETEROFTHECYLINDERPERMANENTMAGNETSHOULDBELESSTHANOREQUALTO25MM,THELENGTHOFTHECUBEPERMANENTMAGNETSHOULDBELESSTHANOREQUALTO6MM,ANDBOTHTHETHICKNESSSHOULDBELESSTHANOREQUALTO1MMFACETHEPROBLEMSOFTHELIMITEDSPACEANDTHEDEMANDOFPRECISEANGULARSIGNALS,ANDCONSIDERCOSTANDTIMEOFSENSORDEVELOPMENT,ITISUNACCEPTEDTHATFIRSTMANUFACTUREPERMANENTMAGNETANDTHENMEASUREITBYMEASURINGAPPARATUSTHEREFORE,WEPRESENTAVALIDMETHODTHATUSES3DSTATICMAGNETICANALYSISTECHNIQUEFORDESIGNINGTHETYPEOFTHEPERMANENTMAGNETTOGUARANTEEAPPROPRIATEDIRECTIONANDMAGNITUDEOFTHEMAGNETICFIELDTHE3DFINITEELEMENTANALYSISMODELOFACYLINDERPERMANENTMAGNETANDACUBEPERMANENTMAGNETAREBUILTRESPECTIVELY,ANDTHEIRSPATIALMAGNETIZATIONVECTORDISTRIBUTIONSAREALSOSHOWNFIG3ASHOWSASPATIALMAGNETIZATIONVECTORDISTRIBUTIONSGENERATEDBYACYLINDERPERMANENTMAGNETU25C21MM,ANDFIG3BREPRESENTSASPATIALMAGNETIZATIONVECTORDISTRIBUTIONSGENERATEDBYACUBEPERMANENTMAGNET6C22C21MMFROMTHEFIGURE,ITCANBESEENTHATTHEMAGNETIZATIONVECTORSGENERATEDBYTHECUBEPERMANENTMAGNETAREMOREPLANARTHANTHOSEOFTHECYLINDERPERMANENTMAGNETITISBECAUSETHELENGTHOFTHECUBEPERMANENTMAGNETISBIGGERTHANTHECYLINDERPERMANENTMAGNETWHEREASGMRSENSORCHIPISONLYSENSITIVEINTHEPARALLELPLANEOFTHECHIP,RATHERTHANORTHOGONALLYTOTHECHIP,SOTHECUBEPERMANENTMAGNETISBETTERTHANTHECYLINDERPERMANENTMAGNETFORAPPLICATIONOFGMRSENSORINTHISPAPERHOWEVER,GMRMATERIALSNOTONLYREQUIRETHEDIRECTIONOFMAGNETIZATIONVECTOR,BUTALSONEEDTHEMAGNITUDEOFMAGNETICINTENSITYINITSWORKINGRANGETOAVOIDTHESENSORELEMENTDAMAGEANDSIGNALDISTORTIONTHEREFORETHEDISTRIBUTIONOFTHEMAGNETICINTENSITYINTHELIMITEDSPACEISMUSTBEACHIEVEDFORTUNATELY,3DSTATICMAGNETICANALYSISTECHNOLOGYCANMAKETHESEPROBLEMSEASYTOBESOLVEDWITHTHEHELPOF3DFEMSOFTWARE,WEACQUIRE3DMAGNETICFIELDDISTRIBUTIONOFDIFFERENTPERMANENTMAGNETTYPEFIGS4AND5FROMTHEDATESHEETOFGMRSENSORCHIP,WEKNOWFIG2APPLICATIONOFTHEGMRSENSORIN5FINGERDEXTEROUSROBOTHANDTLANETAL/MEASUREMENT422009101110161013INORDERTOREJECTDISTURBANCEOFMAGNETICFIELD,THELIVESHAFTISMADEOFNONMAGNETICSTAINLESSSTEELMATERIALTHENTHEMODELCANBESIMPLIFIEDANDONLYTHEPERMANENTMAGNETISANALYZED,SOTHEBURDENOFANALYSISCALCULATIONISLIGHTENEDGREATLYTHEPERMANENTMAGNETSANALYZEDINTHISPAPERAREMADEOFNDFEB35MATERIALANDHAVEREMANENCEEQUALTO12340TANDCOERCIVEFORCEEQUALTO11339A/MFIG3ASPATIALMAGNETIZATIONVECTORDISTRIBUTIONSGENERATEDBYACYLINDER6C22C21MMTHEWORKINGRA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NGULARERRORSOLIDCURVEISLESSTHANC61C14,WHICHFULFILLSTHEREQUIREMENTSOFANGULARMEASUREMENTINDLR/HITII5FINGERDEXTEROUSROBOTHANDANDMANYOTHERAPPLICATIONS6CONCLUSIONSBASEDON3DSTATICMAGNETICANALYSISTECHNIQUE,THEULTRAMINIATUREGMRSENSORSYSTEMWITHONLY05MMALLOFWHICHMAKESUPFORTHESHORTCOMINGSOFTRADITIONALMEASUREMENTSENSORS,SUCHASBULK,COMPLEXITY,HIGHCOST,STRICTDEMANDTOWORKINGENVIRONMENTANDASSEMBLYDIFFICULTYTHISWORKALSOHASESTABLISHEDAGOODBASEFORFURTHERSTUDYOFMAGNETICSENSORFORMICROSENSORSYSTEMSOFMEMSANDHIGHLYINTEGRATEDSYSTEMSACKNOWLEDGEMENTSTHISPROJECTISSUPPORTEDBYTHENATIONALHIGHTECHNOLOGYRESEARCHANDDEVELOPMENTPROGRAMOFCHINA863PROGRAMNO2006AA04Z255ANDSELFPLANNEDTASKNOSKLR200801A01OFSTATEKEYLABORATORYOFROBOTICSANDSYSTEMHIT1016TLANETAL/MEASUREMENT42200910111016FIG9THEERRORSBETWEENMEASUREDVALUESANDTHEORETICALVALUESWORKINGDISTANCEISNEWLYDEVELOPEDFORHIGHLYINTEGRATEDDLR/HITII5FINGERDEXTEROUSROBOTHANDTHROUGHTHEEXPERIMENTRESULTSMENTIONEDABOVE,THEOUTPUTCHARACTERISTICSOFTHEGMRSENSORSYSTEMHAVEBEENOBTAINEDSUCHASTHEMEASUREMENTRANGE,ACCURACY,WORKINGDISTANCEANDTHEREPEATABILITYITALSOHASTHEQUALITIESOFULTRA