Application of the repulsive‑type magnetic bearing technology based on digital control implementation for manufacturing a micro‑mass measurement balance system
著者 Hussien Mahmoud Alaa Abdel Moneim
著者別名 ホセイン マハモド, アラー アブディル モーネイ
ム journal or
publication title
博士学位論文要旨 論文内容の要旨および論文審査 結果の要旨/金沢大学大学院自然科学研究科
volume 平成19年9月
page range 16‑30
year 2007‑09‑01
URL http://hdl.handle.net/2297/26679
AmAAABDELMONmMHUSSIENMOHAMUD 博士(工学)
博甲第841号 平成18年9月28日
課程博士(学位規則第4条第1項)
ApplicationoftheRepulsive-TypeMagneticBearinglbchnologyBasedon DigitalControllmplementationfbrManufblcturingaMicro-Mass
MeasurementBalanceSystem
.(極微小質量計測天秤へのデジタル制御反発形磁気軸受の応用に関する研究)
山田外史(自然計測応用研究センター・教授)
岩原正吉(自然科学研究科・教授),上杉喜彦(自然科学研究科・教授),
神谷好承(自然科学研究科・教授),滑川徹(自然科学研究科・助教授)
氏名 学位の種類 学位記番号 学位授与の日付 学位授与の要件 学位授与の題目
論文審査委員(主査)
論文審査委員(副主査)
学位論文要旨
Abstract
Therepulsive-typemagneticbearingtechnologyisbecomingattractivefbrmany applicationsinrecentyears,specially,fbrtllehighprecisionmstmnents・Themost importantfeatureofmagneticbearingingeneralisthecontact-丘eeoperation・Inaddition,
tllerepulsivetypespeciallyofferslnanyotlleradvantagessuchas,slnallnumberof electromagnetsandasmnplifiedschemeareneededfbrcontrol,italsohaveasoftand constantstifnesstothepassivecontrolaxis・so,tllistypeofbearingisriglltsuitedfbr lnanyapplications、Inthisthesis,tllerepulsivetypemagneticbearingbasedondigital controlilnplementationisemployedtomanufactureabalancesystemwhichcanmeasure nncrolnasses、Theproposedsystemconsistsofanaxialshaftandabalancebeam,tlleshaft islevitatedalongtlleradialdirectionbytllerepulsivefbrcesoftllelnagneticbearing sectionandalongtheaxialdirectionbyacontrolledelectromagnet・Thebeamiskeptatan eqUilibriumhorizontalpositionTheprincipleoperationdependsontransfeningtllelnass
valuetotllecurrentofacontrolledactuator・Thefimctionoftllesystelnasamass
measuringdeviceisconfirlnedbymeasunngsomesamplesandevaluatmgtllesystem lneasurelnentcharacteristicssuchassensitivity,controlcurrenthysteresisandlinearity.
1.Introduction
Itiswellknownthatelectronicsnowprovidetlle‘brams,fbrtoday,sadvancedsystems
andproducts,nncromechanicaldevicescanprovidetllesensorandactuator,tlleeycsand ears,handsandfeetwhichinterfacetotlleoutsideworld・Fordevelopmgbothelectronics andnlicrolnechanicalsystems,tllefieldofmaterialsciencehasgivenmuchofinterest、One oftlleimportanttopicsofmaterialscienceistllematerialcharacterizationwhichis perfbrlnedtospecifWllephysicalpropertiesoftllematerials・ThematerialCharacterization canbeachievedthroughsomechelnicalanalysissuchasdifferentialtllermalanalysis (DTA)andtllermogravetencanalysis(TGA).
Themassmeasurementdeviceswhichhavehighmeasunngsensitivitytodetectthelninute
changeofasa【nplemassarenecessaryfbrperfbrnmngsuchkindofmaterial characterizationanalysis・Insomeapplications,therangeofthatchangereachestlleorder of皿crogramsorevennano-grams・Theimportanttopictobeconsideredwllile lnanufacturinghighsCnsitivitymassmeasurementdevicesistllebearingmetllod、The repulsive-typemagneticbearingisanon-contactoperationmetllod,sonoproblcmanses 丘Cl、随ctionwhichusuallyaffectstllesystemsensitivity・Inaddition,itisasmgle-axis controlledsystelnsotllenumberofperipheraldeviccssuchassensorsandactuatorsare
-16-
reducedandasaresultsilnpleandsmallsizesystemdesignispossible、Anotllerimportant featureofthattypeOfbearingisthesoftandconstantstifnesstotllepassivecontrolaxis wllichensuresgoodlevitationstabilityalongtheradialdirection[1]-[3]、so,fbrtlle applicationsoftheearlierreqUirements,therepulsive-typemagneticbearingisrightsuited fbrnlanufacturingwhatiscalled“Repulsivctypemagneticbearingnucromass
lneasurementsystem.,,Inthistllesis,theconfigurationoftherepulsivetypemagneticbearingsectionandfbrces analysisisgivenThissectionisemployedfbrmanufacturingtlleproposedbalancesystem whichconsistsoftwomainparts,tlleaxialshaftpartandtllebalancebeampart・The completesetupoftlleproposedbalancesystemandtheoperatmgfeaturesaremcluded
ThesystemmathematicallmearizedmodeisobtamedandcontrollersfbrbothshaftandbeamareimplementedaroundaDSP、Theexperilnentalresultsfbrconfirn血gtllefUnction
oftllesystemasalnassmeasuremelltdeviceandevaluationofitScharacteristicssuchas
linearity,accuracy,andprecisionaregiven[4],[5].
2.Configurationoftlnerepulsivetypema窪neticlDearingsection
2.ISmJc"〃qハノjePMsecがo〃Thestructureoftherepulsive-typemagneticbeamgsectionisshowninFigl(a).It consistsoftwounits,eachunitconsistsofacylindricalstatormagnetandacylmdrical rotorlnagnetmade丘omNeodylniumIron-Boron(Nd-Fe-B)materialbecauseofits excellentmagneticpropertieswhicharementionedearlier,Thedimensionsofbothstator
androtormagnetsisalsoillustratedWhereapieceofmagneticmaterial(,Odeg)covers partoftllestatorlnagnetmordertoinlprovetllerepulsivefbrcecharacteristicsasitwillbe explainedlater・Thestatormagnetconsistsoftwopiecesattachedtogetller、TY1eradial repulsivefbrcesbetweentllestatorandrotormagnetslnaketllerotorlevitatedstablyalong
theradialdirectionwheretheaxialdirectionisunstableandneedsacontrolled electromagnetinordertostabilizetllerotor・Duetosolnemanufacturingdefectsor fabricationdifficulties,thereissomemagnetizationasymnetryofmagnetsandasaresult tllefnbricatedmagnetsOftllesamematerialanddimensionsarenotidentiCaLSo,befbre settingtllemodel,bothofthestatorandrotormagnetsshouldbeselectedtobesinlilari.e‘
manypiecesofrotorandstatormagnetsshouldbepreparedandthefluxdensity
distributionofeachpieceshouldbemeasuredmordertoselecttllerotorandstatorleftand rightmagnetsthathaveconstantfluxdensitydistributionaroundtllesurface,inaddition thefluxdensitiesvaluesofbothleftandrightmagnetsshouldbeascloseaspossibleto
eachotheH
22Fi"舵eノe川e"/αM)ノID応q/rノカePMsecがo"伽〃
TheFEMmodeloftllePMsectionisshowninFig、1(b)Theaxialrepulsivefbrcesare calculatedusmgtlleMaxwell3-Dprogrammordertousetllisdatafbrdesigningtlle electrolnagnetusedfbrcontrollmgtlleunstabledirectionHowever,theradialfblCesare calculatedinordertoensuretllestabilizationalongtllatdirection.Asshownmthenlodel,
bothoftheleftandri=htstatorconsistsoftwopiecesofNd-Fe-Bperlnanentmagnetand
tllestatoriscOveredbyamagneticshuntmateriaL
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X↓
Mag j、 s)
JUdeK
傅鳴.
nlI
Unit:m、
S MaOcrialDimcnsIons
圏…Ⅷ(…‘…
NStatorPM,Nd-Fe-B,‘`×,‘X8 MagneIicmntcri別IIron(S45C)ノ6,XI4dXB
=
《otorma四
Ⅱほに臣h、IHI【
magnet
(a)Structureofthesection (b)FEMmodelofthesection
Fig.lConfigurationandFEMmodelofthePMrepulsivetypelnagneticbearing
Thecalculatedaxialrepulsivefbrcesmcaseofusingonepieceandtwopiecesstatorsare showninFig.Z(a)nisclearfiPomtllecalculateddatatllattlleaxialfbrcemcaseofusing twopieceSstatorislessthanthefbrcemcaseofusingonepiece・Inadditiontllerangeof fbrcclmearityiswiderwitlltwopieces・Sotllestatorisdesignedastwopiecesbecausein tlliscasethefbrceneededfbrcontrollingtllatdirectionwillbelesstllanthefbrcemthe caseofusingonepiece,tllatmeanssmallandsnpleelectromagnetdesignisreqUired・Thc surfaceofthe叩perpartofthestatoriscoveredwithironshuntmaterialwithdifIerent centerangles・TWocenteranglesaresimulated,g0degreeand360degree、Attachmgsuch shuntmaterialaffectsbotllaxialandradialfbrcecharacteristics・I、Fig.2(b),theaxial repulsivefbrcewithoutattachmgtheironshuntandwithironshuntofcenterangles90 degrceand360degreeisshownTheironshuntofbotllcenteranglesdecreasestheaxial fiorcc,but90degreeispreferablebecauseofbetterlinearity・Decreasingtlleaxialrepulsive fbrceisdesirablefbrasimplecontroldesign・Furtllerlnore,tllisshuntincreasestlleradial repulsivefbrcealongz-directionandmakesitalwayspositivewhichisdesirablefbrbetter stability・Thisisclearlyillustratedin]Fig.3(a)Wheretlleradialrepulsivefbrcewithout attachingtheshuntandwith90degreeofironshuntisshown、Thenegativegradientofthe radialfbrcecharacteristics(i、e、positivestiffiless)contributetopassivestability・Theradial repulsivefbrcealongy-dircctionisalsocalculatedmbothcases(witllandwitlloutshunt)
andshownmFig、3(b)They当directionfbrcechangeslinearlywillltlledisplacelnentand
lncreasesalittlewhenthestatoriscoveredwithtllemagneticshunt.
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Axialdi印k四CmemMmlm)
AxialdispkmcmantOnlm0
(a)Usingoneandtwopiecesstator (b)Withoutandwithmagneticshunt Fi9.2CalculatedaxialrepulsivefbrcescharacteristicsofthePMsection
6
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52515052100(巴三国田富②。』巳。昌已三壱塁 284048100心心Ce一一【田冨の自己の彦窃己(読昌呵弓飼国
-11 0.8-04 -..、…△・・-1.Z-U、8-0.400.40.8、-4 と1.2-1.2 -0.8 -0.4
Z-dircctiondisplacement(m、)Y白diIcctiondisplacement(m[I0
lZ-dilectionfbrcecharacteristics (b)Y-directionfbrcecharacteristics
Fig.3CalculatedradialrepulsivefbrcescharacteristicsofthePMsection.
Z-dircctiondisplacementOnm) 1.2
(a)Zdilectionfbrcecharacteristics
Pannanent controlled
e
JnIP a回nEt
Gapsensor
uapsensor
Stopperplate
Fig4Configurationoftlleaxialshaftpart、
3.Configurationoftheaxialslmftpart
TheconfIgurationoftheaxialshaftisshownmFig4,Wherethetwounitsoftlle
permanentmagnetsareinstalledaroundthecenterpoint;tllestructureoftllissectionis
explainedearlier.BasedonEarnshawtheorem,theaxialshaftisunstablealongtheaxial direction,soacontrolledelectromagnetismstalledtogenerateanattractiveforce,This fbrceismodulatedthroughacontrolsystemwhichreceivestheshaftpositionmfbnnation fomagapsensormstalledtotheleftsideoftheshaft・Theexplanationofeachpart mdividuallyisgivenmtllenextsUbsections、Astopperplateisplacedinordertostopthe
movementoftheshaftwhilenooperationFurtllennoreabalanceweigI1tisplacedatthe otllerendoftheshaftinordertokeCpitmeqUilibriumposition
3・IEルc加川cJg7zeM己Sig7z
TheEarnshawtlleoremstatesthat,atleast,onedirectionshouldbeactivelycontrolledin ordertoachieveastablenon-contactlevitationmmagnetstatic・so,anelectrolnagnet
deviceismstalledbesideanironplatefixedintlleshaft・Thedetailsstructureofboth E1ectromagnetandironplateareshowninFig4TheEMconsistsofanironcoreand0.6
,mndiametercoppercoilof683turn,8.91ohmresistanceandO・O6Z4henerymductance・
Thisdeviceisusedtogeneratetherequiredstabilizingfblce,IIlfact,theelectromagnet causestheflUxtocirculatemalnagneticloopWhenanalyzingsuchmagneticloop,an
-19-
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exacttheoreticalcomputationofthefieldisrarelypossibleandseldomreqUired・One usuallyworkswitllanalyticmetllodsOfapproximation,basedontllesimplifj/ing assumptionthattlleflux,exceptfbrintheairgap,runsentirelythrouglltlleironSmcetlle permeabilityofironisconsiderablylargerthanthatofair,tllemagneticfieldlinesleave theironalmostperpendicularly・TheEMfbrcecanbeexpressedasfbllows
涙―だ
K一一涙一万
。〃α42N0匹’一乎一一FwhereN,iaretheNoofturnsandcurrentofthecoilrespectively,xistheaxialgap,Aairis tlleareaoftheairgapbetweentheEMandironplate,川istllepemeabilityoftheair.
↓_
+L
4のLノ⑪
npl
』鼎佃
X1】Iに
Unit:、、
(b)Ironplate (a)ControlledEM
Fig、4ConfigurationoftheEMandIronplate.
5352515032L0(庭)8衿&]①[助ロ日○垣。①[四
Lb
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u--口---口--乱
Axialgap(m、)
●
(a)FEMmodeloftlleEM (b)EMfbrcecharacteristics
Fig・SThecontrolledEMmodelandfbrcecharacteristiCs.
ThefiniteelementlnodeloftheelectrolnagnetdeviceisshowninFi9.5(a)wherethe attractivefbrceiscalculatedasafimctionoftheairgapandthecoilcurrentusingMaxwell 3-Dsoftware・TheEMfbrcevs・axialairgapcharacteristicsfbrdifferentcoilcurrentsare
showninFig5(b).TheaxialairgapchangesfieolnOto2mnandthefbrceiscalculatedat 0.24A,0.48Aand0.72Acurrent、TllefbrceisinverselyproportiOnalwiththeairgapand directlyproportionalwitllcoilcurrent、Inordertoachieveastablenon-contactlevitation,
theEMfiDrcecharacteristicsiscomparedwiththePMrepulsivefbrcecharacteristicsfbr
deterIniningtllesteadystateoperatingcurrentandgapThisinfbrlnationisneededfbr implementationofthecontrolsystemwhichisemployedtoadjustthecoilcurrentattlle
-20-
steadystateoperatingpoint・TheEMsteadystateoperatingcurrcntissetatO48Aandif fbranyreason,tlleairgapischanged,tllecoilcurrentshouldbealsochangedmorderto keeptlleEMfbrceconstantallthetimefbrachievingstablelevitation
3.2dxjZJノg叩Sc"so7
Theopticalsensorisfastandhasagoodsensitivity;maddition,itismagnetically mdependent,simpleandcheap、Fortllesereasons,aphotosensorisusedfbrdetectingthe displacementoftheaxialshaft・ThestructureoftllephotosensorisshowninFig、6(a),
whereitconsistsofaliglltemittingdiode(LED)(GL513F)andaphotodiode(PD)(MI- 33H2D).TheLEDemitsUlelightandtllesllutterobstructstllelight・TheqUantityoftlle
Lightreceptionside 05 V 01
iVI2 ゴISectlonphot⑥。、。[
4⑪ 300s成碗冒画[団{の。凶旦〔旨・目。、
-.ご=,------,.
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---…・----6-.---…田---………----…ず---… ̄
l⑪nuZ■ⅡⅡ四回qmKn上
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~ ̄ ̄豆一一一一一・●・・.●。.●● ̄ ̄ ̄ ̄ ̄・・「●---●-.-■----...◆
●CCCロー■0■'■~~口PCCCc●●●--1■-■--●●●~●●-●。。■'--■■CC-C--・-勺一一■-■の。一・・●0 ■ ひし・-----■--.sし。。●-.こ=----
、--T,--
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DiSpIacenmtOmD
JnSDlaCemeT 2
(a)Sensorstructure
(b)Outputcharacteristics Fig、6thephotogapsensorstructureandoutputcharacteristics.
incidentliglltonthebisectionphotodiodeischangedasthepositionoftheshaftis changedandasaresulttlledifferentialoutputvoltageischangedaswelLTllesensor
characteristicsisshowninFig6(b)
4.COnfHgurationoftllebalmncelDeam
イ.IBam"ce6eα〃WiZノbelecかo川ag7zetcMWam7
ThefirsttrailofmanufacturingoftllebalancebeamisshowninFig、7Itconsistsofabrass bar,atonofitsends,anironballisattachedandaMheotherend,analunmnumSample holderisplacedAsmalls]mtterisfixedattheholdersidewhereaverticaldisplacement sensorisalrangedandinstalledbesidetlleholderinordertodetectthedisplacementofthe bearnwhentllesampleisaddedtotlleholder・TY1issensoristllesametypeofUleaxialgap sensorusedfbrdetectingtheaxialshaftdisplacement,butitisonlyarrangedmdifferent waytodetecttheverticaldisplacement・ThemfbrlnationofthebeampoSitionistransfelred mmtllegapsensortoacontrolsysteminordertoadjusttlleattractionfbrceofan electrolnagnetwithironcoremstalledundertheironbalLThisEMattractionfbrCeis
changedaSthepositionofthebearnischangedinordertolKeeptllebeamlnequilibrium
horizontalposition、Asitisexplamedearlier,tlleEMreluclancefbrceneededfior stabilizmgtheaxialshaftisdirectlyprOportionalwiththesqUareoftheEMcurrentanditis
samefbrtheEMusedfbrkeepingthebeamhorizontaL
●
-21-
eraneT
JnpallLonIrollec naHnBLRb囮凹uuI
Hunk nct
一冨冒=…-=---杯一一=--L`騨轤
Jean nnqi囮Iuhu
__’
Fig.7BalancebeamwithEMactuator,
Avoicecoilmotor(VCM)actuatorissuggestedtoreplacetheEMwherethestabilizing fbrceisproportionallmearlywithcurrent・ReplacingtheEMwiththisdevicewillincrease thesystemsensitivitywhichisdesiredfbrmeasuringtheslnallsamples・Anotherimportant aspectistllesaturationofEMironcoreandthemagnetichysteresis,itmcreasesthe
measurementerror.
イ.2Baノ[J"ce6ea川wjZZlvojcecoノノ川om7
TllemodifiedbalancebeamconfigurationisshownmFig、8.TheEMandironballare
replacedbyavoicecoillnotorastllebeamactuatortoavoidthedifficultiesmthedesign
andcontroLSomeofthesedifficultiesarethenonlinearityoftlleEMreluctancefbrce,tlle
colnplexdistributionoftllefluxintlleairgap,andthesaturationoftheEMcoremateriaL
TlleVCMattractionfbrceislmearlyproportionalwitlltllecoilcurrentandasaresult,tlle
systemmeasurementsensitivityisbeconlinghigherthanintllecaseofusmgEMwheretlle
fbrceisproportionaltotllesquareoftllecurrent.
手.38J'wc〃eqノンノieFCMα"cMie抑jMC川ilリノ伽伽〃o〃
TheconfigurationoftheVCMisshowninFig.9(a)itconsistsofanironyoke,afigureof eigImtcoppercOiloflOturnsand0.61mndiameter,andtwopiecesofpennanentmagnets areattachedtotheinternalsidesoftlleyoke・Thepemanentmagnetisconsideredasa sourceofastationeryflux,Thefbrceexertedonthecoilisgivenby
Fc.〃=B、/、lVj
WhereBistllefluxdensityinsidetllegap,Mstllenumberofcoiltums,ノistllelengtllof thepartoftllecoilwllichliesinsidetllegap,andjistllecoilcurrent、AsillustratedmFig、
9(a),thedirectionofthefbrceexertedonthecoilis叩wardaccordmgtolefthandrule・But becausethecoilisfixedandtheyokeisfiPee,tllereisareactiondownwardfbrceexertedon
theyokeasgivcnintheeqUatiOnbelow・Thisattractionfbrceexertedontheyokekeepsthe
balanceofthebeam.
F,、=F"庭=-F・ojl
TllesimulatedlnagneticfileddistributionoftlleVCMmodelbyMaxwell2-Dsoftwareis shownmFig.,(b).T11efluxdensityattllelmeW11ichliesmthemiddleoftlleairgap insidetheyokeiscalcUlatedusingtlle2-Dfiniteelementmetllod・Itisclear丘or、Fig.3-14
thatthefluxdensityattllatlmeisparabolic.
lermanCm
Jermancm okc
aIZnI TaEnCISCUL1uL
Fi窪.SBalancebeamwitllvoicecoilmotor、
-22-
Balanccbeam
mDI
、
(伊日)、{目呂旨逼
“し
澪、
DiSplacemBntOnllD
(aWCMconfiguration 化)F1uxdensitydistribution
Fig・DVCMstructureandfluxdensitydistributioninsidetllegapatthecenter 5.ConfigumtionofthecompletesystemandprincipleolDeration
ThetOpviewoftllecompletesetupoftllerepulsivetypemagneticbearingbalancesystem isshowninFiglO・Theaxialshaftandtllebalancebealnareattachedtogetllerattl1e centerpoint・Thehybridlnagneticbearingsystemwhichincludestllepennanentlnagnet unitsandtheelectromagnetwithactivecontrolhelpsthesettobelevitatedstablywitllout
contact・ThelnostconⅡnonproblelnarisesmallconventionalbeambalanceistlleEiction atthefillcnⅡ、;thisproblemdecreasestheequiplnentsensitivity・Thenon-contactlevitation oftheproposedsystemovercomesthefiictionproblemseckingfbrbettersensitivity・
Tlleproposedmagneticlevitationmassmeasurelnentsystenlisbasedoninstallinga controlledbalancebeamandusesitasthemeasuringdevice,sotllemeasuremem sensitivityishigherthanthatoftlleconventionalmechanicalbearingsystelns・Also,tllis systemcanbeusedtodetecttherelativevaluewhichismassWheretheeffectofgravityis elinnatedlnsomeapplications,itisneededtodetectthelnasschangeofasamplewhere
tllischangeisresultingffomheatingorpressurizationSincethebalancebeamofthe systemisdesignedsothatthesampleholderandtheactuatoraredistantenough,itis convementtobeusedasathermobalancewhichiswidelyusedfbrthechenlicalanalysis・
Someoftlleseanalysissuchasdifferentialthennalanalysis(DTA)andthenno-gravimetric analysis(TGA)areusehlfbrmaterialcharacterizationapplicationS
TY1eprincmleoperationoftlleproposedsystemdependsontransfelTingtheadditionalnlass tothcactuatorcontrolcurrent・Whentllesampleisaddedtotlleholder,tllebeamis
distUrbedanditspositionischangedTheverticaldisplacementofthebeamisdetectedby thegapsensormstalledbesidetlleholderandbythehemofdigitallyilnplementedcontrol system;tlleactuatorcontrolcurrentischangedinordertogeneratetllefbrcenecdedto keeptllebeamatitsorigmalposition
TllefimctionofmassmeaSuringisconfirmedbyaddingsomesalnplestotheholderand noticingtllevoicecoilcmrentchange、Inordertoprovetllattllesystemmeasurestlle colTectsamplemass,somesamplesofknownmassesarealsomeasuredaftercalibrating thesystemThedetailsofexperimentalresultsofmeasurementandtlleevaluationoftlle systemmeasurementperfbnnanccssuchaslincarity,accuracy,precisionandrepeatability
willbegivenlater.
-23-
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L------------------0Fi9.10Topviewoftllecompletesetupoftlleproposedbalaj【lcesystem.
6.Systemmodelingandcontroldesign
匝皿"αノゥノがcα/伽6!bLFqハノiMxjaMq/iα"α6α伽ceDea川
TlledynalnicmodeloftheaxialshaftisshownmFig、11(a).Forderivingasimple
ThedynalnicmodeloftheaxialshaftisshownmFigll(a).Forderivmgasnmplesystem model,someidealconditionsareassumed,Theseconditionsmcludenoleakageflux,no DCmagneticsaturationorllysteresismtlleelectrolnagnet,however,tlleperlneabilityof thecoreisassumedtobeinfinity・Tlledifferentialequationswhichdescribethemotionof thelevitatmgohjectarederivedasfbllows:
〃超一F(x)-Eh(x,j) ,Rj+LjLe
wh…(皇)肌川薑αX+〃
Theanalyticallnodeloftllebalancebcamshouldbealsoderivedinordertodesignthe beamcontroller・Thepllysicallawswhichgoverntllemotionoftllebeamareinvestigated WherethelnodelisshowninFigll(b)
川,jE二o
lRi+LjLe
川,雌川29-川,g-Fim(z,i)
WhercE,=jWBL
-24-
LevitatingobjectControlledelectmmagnet
「
DluⅡ[ 、、ニーア霧夛
腕2
(a)Shaftmodel (b)Beamlnodel
Fi窪.11Analyticalmodelsofshaftandbeam 52αO"肋ノノl27j"!P/e川e"ZZZrjO〃
Aftertheanalyticalmodelsofbothshaftandbeamarederivedandtllestatespace equationsareobtained,thecontrollersaredesignedusingthelinearquadraticoptimal controltechniquewheretheblockdiagrarnofshaftandbearncontrolsystemsareshownin Figl2.TheblockdiagramofthewholesystemwithcontrolisgiveninFig、13where4- channel,12bit,25KHzanalog-to-digitalconverterreceivesthevoltagesignalsfromboth oftheaxialandradialgapsensorswhichexpressthedisplacementofbothshaftandbearn Thesevoltagesignalsarefedtothecontrollerafieritisbeingconvertedintodisplacement signalsThecontrolleroutputispassedtothedigital-to-analogconverterandthenthe controlsignalsarefedtothernagneticbearingactuators(EMandVCM)throughpower
amplifiercircuits・
ThecontrolprocessstartswithrunningtheMTALABprogramtocalculatethecontroller feedbackmatricesandthengeneratingthereal-timecontrolsignalsbyexecutingthe
MTALBSIMULmKcontrollermodeLBythehelpofルpasssoftware,theexecuteddata iSsubmittedtotheDSPandafterthatthemagneticbearingsystemisoperatedltis
confirmedtllatthepreviouslydesignedcontrollerscouldachievestablelevitationofthe systemalongtheaxialdirectionwherethebeamCouldbekeptatanequilibriumhorizontal positionevenafteritissubjectedtoextemaldisturbance.
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-25-
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7.MassmeasurementmdevaluationofthesystempermrmmcesAfterthesystemismanufacturedandtllecontrollersaredCsignedandimplementedaround aDSP,theexperimentsarecarriedoutonthesystemtoconfinnthefimctionofmass measuringandevaluatetlleperfbrmances・Intllefirstexperiment,somesamplesofequal rnassesareaddedgraduallytotllemassholderandremovedbythesarneway、Ineachtime
tllecontrolcurrentisnoticed,Tllecontrolculrentvs、samplemasscharacteristicsisshown
inFigl4(a)wherethebeamactuatorisanEMwitllironcore・Thecontrolcurrent variationismcreasedasthesamplemassinsidetheholderisincreasedAsshownmFigl4
〔b),tlledifferencemtllecontrolcurrentbetweentllemcreasingdirectionanddecreaslng whichisdefinedbythellysteresisisinvestigatedbyzoomingintoFigl4(a).Itisfbund tllatthesensitivityisqUitelowandtllevalueoftllellysteresisiseqUivalentto730}L9.and thenon-lmearityerroroftllecharacteristicsisabout5%ofthefilllscalecurrent.
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8.ImprovementoftlleWstemmeasurementclmracteristics 8・IR印mcmgZノbeEM6eα'Mc伽加'6〕′αMcecojJ伽〃
BecausetheEMfbrceisproportionaltotllesqllareofthecoilcurrentandlheproblelns arisehomironcoresaturation,thesystemmeasurementcharacteristicsarenotsatisfactory・
nleEMisreplacedbyvoicecoilmotordevicewheretllefbrceisproportionaltothecoil culrentandthesourceofthefluxispennanentmagnets(PM,s)hlordertokeepunifbnn fluxdensitymsidetlleyokegapfbrcertainrangealongtllecenter,sonlepennalloyfilnls areattachedtothesurfaceofthePM,s;thishemfbrdecreasingthecmremhsteresisBy lllesamewaytlleexpemnentsarecarriedoutontllesystenlandsamplesofeqUalmasses areaddedglHduallyandremoved・Thecontrolcurentvs、samplemasscharacteristicsis showninFig、15(a).Itisfbundtllatthesystemsensitivityismcreasedtomoretllantwo times;tllellystersisisdecreasedtolOl』gandthenonlmearityerrortoabout1%・A1sothe readabilityoftlleSystemwasabout751LgasillustratedmFigl5(b).
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Inordertomcreasethesystemreadabilityandsensitivitywllichistllemainobjectivefbr proposedsystemtheeqUalbrassbeambrassbeamiSreplacedbyunequalambeammade 丘omDuralun血wllichisliglltandstiffmateriaLTheannlengtlltotheholdersideis becon血gdoubletheamlengtllattheactuatorside,andtlleflatmassholderisreplacedby aknife-edgeone・Aftertllismodification,thesystemsensitivityisdoUbledasshownmfIg andtllenonlmearityerrorisdecreasedto0.2%asshowninFig、16(a)Wheretllereadability rcached3OILgasshownmFigl6(b).AnotllereXperilnentiscaneiedOutontllesystemto evaluateitsaccuracyandprecisionWherethereadingofthesystemiscomparedbytlle readingofaMattlerToledobalanceAB204-s(2209×0.1mg).Intllisexpelimentsome samplCofdifferentmassesintllerange金omO-100mgarepreparedandmeasure,firstby MettlerTolcdobalanceandthenbytlleproposedsystenl・AsshownmFig、17(a),the maxnnumdifferencemthereadingbetweenthetwosystelnswas0.2mg、hanother experimenteachsampleismeasuledbytheproposedsystemlnanytinlesandtllestandard deviationiscalculated・Itisfbundthatthemaxinmndeviationwasabout0.1mgasgiven
inFigl7(b).
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Fi巴.17Evaluationoftlleperfbrmancesoftlleproposedsystem(accuracyandprecision)
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Forthecontrolsystemswhichinvolveanintegratorattllefeedfbrwardpath,theproblem ofintegrationwindupariseswhereani叩utconstraintisincludedtoprotectthesystem TheintegrationwindupaffectsthesystemperfbrInancesanddecreasestlleabilityoftlle systemtorejecttheexternaldisturbancesWhichsometilnesleadstomsatiability、Ananti windupschelneisaddedtothebeamcontrolsystelnasshownmFi9.18(a).
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Afteraddingtheanti-windupscheInc,tllesystemcouldrejectlargedisturbancesandtllis helpstomcreasetllelneasurementcapacityofthebalancesystem・Theexperimentsare carriedoutonthesystemanditisfbundtllatsystemcapacitycanreachlgasshowninFi9.
18(b).
9.Conclusi皿
T11erepulsivetypemagneticbearingisriglltsuitedfbrmanufacturingsuchsystenlbecause ofitsnon-contactoperationW11ichmakestllesystelnmoresensitivethantlleconventional bearingbalances、Moreover,itissmgleaxiscontrolledandasresult,asimplifiedcontrol schemeisneededfbrcompletelystablelevitation、Thedesignprincipledependsonusmga balancebeamwitlltwoendsfbrtllemeasunng,whereatoneend,themassholderis locatedandanactuatorislocatedontheother・Ihisenablestheusertoclinmnatetheeffect
ofgravityandasaresult,measuresthelnassoftllesanlple・Thebalancebeamisdesigned sotllattllesampleholderandtheactuatoraredistant;sotllissystemcanbeusedtodetect tllechangemtllelnassofasampleasafimctionofacontrolledtemperatureand/ortinle wllichisknownastllerlnogravimetericanalysis(TGA).Theexperimentalresults confirlnedtllatthesystemcanmeasuretllemassofthesanlpleswitllsatisfactory
measurementperfbnnances.
hfilture,tlleplanofworkwillconcernwitllusinganothercontroldesignteclmiqUesuch asH-oocontrolWhichconsiderstllemodeluncertaintysuchasumnodeledhigh丘eqUency dynanmcs,neglectednon-1inearties,andplantparameterperturbationsdueto environmentalfactors・Usingsuchcontro1teclmiqUewillincreasetllesystelnlDbustness
andinlprovetllesystelnperfbrmancesandasaresulttllemeasurementerrordecreases.
References
[1]A・Hussien,T,Okada,TOhji,S・Yamada,andM、Iawhara,“Arepulsive-type magneticbearingnncro-massmeasurelnentsystemandmeasurementofresolution",
Tm"Mがo"q/・伽MZgMjcSbcjel1WMW",voL4,no、2,pp51-55,2004
[2]AlaaA・Hussien,TomotadaOkada,TakallisaOllji,SotoshiYamadaandMasayoshi IWallara,“Investigationoftheconfigurationandcontrolofarepulsive-typemagnetic levitationsystemusedfbrlnicro-massmeasurement"P'wee伽gQかABI砂SE4,.,
JUne2004,Kyushu,Japan
[3]T、Okada,A1aaA・Hussien,T・Ohji,S・Yamada,andlnasayoshilwallara"APennanent Ma印etRepulsiveTypeMagneticbearingBalanceSystem,,ProceedingsqMbe3〃
・ノZIPα〃AzJMJノメα,jVbwZba伽肌ノb〃比〃"〃o'MZ2pノjcaがo"sq/Eノcc加川cJgMic Pノbe"o〃e"αj〃Eノecmcaノα"αMCCA〃jcaノ&〕入y花川.pp53-57,January2004,Auckland,
NewZealand.
[4]A,Hussien,T・Okada,T・Ollji,M,Iawhara,andS,Yamada"Improvelnentoftlle meamenlentcharacteristicsofaInagneticbearingbalancesystenf,,Z7wzMcがo〃q/、伽 MJg7zeZjcSbcjel【W/〔ノヒZpα",vol、5,no、2,pp.,7-100,ZOO5.
[5]A1aaA・Hussien,S、Yamada,andMIawhara,T,Okada,andT、O11ji"Applicationof tllerepulsive-typemagneticbearingfbrmanufactulingmcromassmeasurement balanceequipment,,,」EEE伽"Mcがo〃Q/MJg7ze伽,vol41,nolO,pp3802-3804
0ct2005.
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学位論文審査結果の要旨
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