ai-aerospace/ams_data_full_2000-2020 huggingface dataset:
Design of"Super-flat" StrainWaveGearing Thestrainwavegearing principle isuniqueintransmitting hightorquethrough anelastically deformable component. Thegearhasjustthreeconcentric elements: •TheCircular Spline(CS)isasolidcylindrical ringwithinternal gearteeth• •TheFlexspline (FS)isanon-rigid, thincylindrical cupwithexternal teethattheopenendofthecup. Theclosedendofthecupisprovided withamounting flangeforconnecting machine elements. •TheWaveGenerator (WG)iscomprised ofathin-raced ballbearing fittedontoanelliptical plug, serving asahighefficiency torqueconverter. CircularSpline Flexspline WaveGenerator Figure2.Basicgearcomponents Toreducetheoveralllengthofthegear,anewsuper-flat shapeFSandthinWGbearing weredesigned. ThewidthoftheCSwasalsoreduced tofittotheFStoothwidth.Figure3showsacomparison between designdimensions oftheconventional model(CS-type), thecurrentmodel(CSF-type), andCSD-type gear. Allgearsaresize20.Thisnewtypeofgearisapproximately 50%ofthelengthoftheCSF-type gearand 30%oftheCS-type gear.Thereweremanyissuestoberesolved inordertorealizethesuper-flat design. ¢70 ¢70 • ' Figure3.Dimensions ofCS-type, CSF-type andCSD-type gear 110
Technical Challenges Related totheSuper-flat Design andtheirSolutions Fati.que stren,qth ofFStoothbed Toreducetheoveralllengthofthegear,anew50%shorter FSwasdesigned. Thetoothwidthitselfwas reduced by50%compared totheCSF-type. Thereduction oftoothwidthcauses decreasing fatigue strength oftheFStoothbed.Thiswasconfirmed bytheresultsofprototype testingattheearlystagesof development. TheCSF-type FStoothshapewasdesigned withtoothrelieftoprevent toothinterference. Figure4shows anexample ofthetoothshapewithrelieving. Indesigning theCSD-type FS,therelieving waseliminated to increase toothcontact areaasmuchaspossible. Amethod otherthantoothreliefwasusedtosolvetooth interference, aswillbediscussed later.Thesuccess ofthisdesignwasconfirmed bytheresultofprototype testing. Flexspline ____ diaphragm j_---,,  I.___ __IConin_________ !ang Z:i,_'/ WG " i_"_,!majoraxis CSD_ CSF-type\ Figure4.Relieving Figure5.Coning ofFlexspline Fatique stren,qth ofFSdiaphraqm WhentheFSandWGareassembled, theFSiselastically deformed intoaconical shapebytheelliptical shapeoftheWG.Thiselasticdeformation iscalled"coning". Theconingangleincreases astheFSlengthis shortened. (Figure 5).Theincrease intheconinganglewillcauseanincrease intherepeated bending stressatthediaphragm andareduction inthefatigue strength. Furthermore, asshowninFigure6,a substantial effectonthefatiguestrength isalsoanticipated ifthereisamounting error. Basedonthestressvaluesobtained byfiniteelement analysis, thelimitformounting errorsfortheFSasa function ofthefatiguefracture ofthediaphragm werecalculated. Figure7showsanexample ofagearsize 50withgearratio100:1.Thiscalculation confirmed thattheallowable mounting error,whenconsidering repeated peaktorque,exceeds therecommended assembly tolerance ofthegear.Thisprovides evidence oftherobustness oftheCSD-type design. Startinq torque Thelargerconing angleposesachallenge tosmooth rotation ofthegearduetoincreased tooth interference andadecrease ofthegapwithinthebearing raceway. Thiscauses thestarting torqueofthe geartoincrease. Toprevent toothinterference, anewelliptical shapefortheWGplughasbeendeveloped. Thisnewshapeisoptimized fortheCSD-type gear.Thenewelliptical shapeadjusts amoving locusofthe FStooth.Itwassuccessfully applied totheCSD-type gearofsize50andratio100:1withthislargerconing angle. 111
TheconingoftheFSdeformstheouterraceoftheWGbearing,withlargerconinganglescausinglarger conicaldeformations. Thisdeformation generatesanaxialtranslationbetweentheWGouterraceandthe innerracecausinginterference betweentheracesandballs.Thistendstoincreasethestartingtorqueof thegear.Topreventthisundesiredeffectofconing,theradialclearanceofthebearingwasoptimizedforthe CSD-typegear.Asaresultoftheseoptimizations, theincreaseofstartingtorquewaskeptataminimum. Inclination DeviationE E E o 7 £30.3 0.2 0.1CSD-50-100  repeated peaktorque Recommended /_elerance forassembly _ _IIIII"_I 00.10.20.30.40.50.6 Inclination0.7 [deg.] Figure6.Mounting errorofFlexspline Figure7.Misalignment limitforFlexspline Torsional stiffness Thelargerconinganglerequires largerclearances between theinsideoftheFSandtheoutside oftheWG bearing. Thisaccommodates thelargerconical deformation oftheFS.Additionally, theWGbearing hasa largerradialclearance optimized fortheCSD-type gear.Theseclearances haveaninfluence onthe torsional stiffness ofthegear.Whenatorqueisapplied tothegear,theclearances withinthegearare reduced astheresultofelasticdeformation ofeachelement ofthegear. I -8002.0E-03 ._o 0 _-1.0E-03 J 1'3PLr___ J_, -4o  -l.0E-03 -2.0E-03 Figure8.I I 400 800 Torque(NT1) Torque-torsion CurveofCSD-50-100 Figure8showsthetorsional characteristics viewed fromthelowspeedshaftwhentheloadtorqueis applied tothelow-speed shaftwiththehigh-speed shaftfixed.Thereisnonoticeable decrease instiffness inthelowtorqueregion.Thisshowsthatoptimizing theclearances withintheWGfortheCSD-type gear doesnotdegrade thetorsional stiffness. 112
Durability Figure9showsanexample ofadurability testfortheCSD-type gearsize50,ratio100:1.Thetestwas performed underasinusoidal loadtorqueof+686Nm andinputspeedof3000rpm.Harmonic drivegrease 4BNo.2wasusedforlubrication. Thedurability wasevaluated bymeasuring theincrease inlostmotion against thetotalnumber ofrevolutions oftheWG. Thevalueofthelostmotion isthetorsional angleviewed fromthelowspeedshaftwhenasmalltorque (approximately 4%oftheratedtorque) isapplied tothelow-speed shaftwiththehigh-speed shaftfixed.The angles measured byperforming thistestintheclockwise andcounterclockwise directions areadded together. Byreviewing theincrease inthetrendoflostmotionversusthenumber ofWGrevolutions, itis possible topredictthesubsequent wearwithadditional WGrevolutions. Astheresultofthetest,virtually no increase inthelostmotionvaluewasfoundatthetotalof4X108WGrevolutions. Thetestresultsillustrate thehighdurability oftheCSD-type gearunderconditions indicated. Wearlifeofthegeardepends ontheoperating condition andlubrication. Inspaceapplications, aspecial vacuum-suitable lubricant isnormally used.Thesedurability testresultscannotbeapplied directly tospace applications. Instead, extensive testing mustbeconducted toverifythesuitability ofothergreases and underotheroperating conditions. Thesedurability testsshould beconducted forboththegearsetand spacecraft asawhole. 1.0E-03"D v --8.0E-04 "6 6.0E-04 tj t4.0E-04 2.0E-04 0.0E+00 1.0E+06CSD-50-100-2A-GR Lubricant: Harmonic Grease4BNo.2 Loadtorque:+/-686Nm (sinusoidal) Inputspeed:3000rpm 1.0E+07 Figure9.1.0E+08 1.0E+09 W/Gtotalrevbtution Durability testresult Further Development TheCSD-type gearwasdesigned tohaveanaxiallengththatisasshortaspossible. Thenextstepin developing lightweight andcompact gearsinvolves theutilization ofanaluminum alloyfortheWGplugand CS.TheCScanconsist entirely ofanaluminum alloyorfeature acomposite designusingaluminum and eithercastironorstainless steel.Thiswouldgreatlyimprove powerdensity byreducing weight.Aversion of thisgearisunderdevelopment forindustrial applications. Aprototype withanaluminum alloyWGplugand acomposite CSmadefromaluminum alloyandcastironhasachieved anequalwearlifeasthecurrent modelofthesamesize.Aversion forspaceapplications wouldfeature aCScomposite usinganaluminum alloyandstainless steel.However, therearetechnical issuestoberesolved forjoiningstainless steeland aluminum components. Theseissuesareleftasafurtherdevelopment subject. Conclusion CSD-type strainwavegearing realizes anexceedingly flatshapethathasneverbeenseenbeforeina precision speedreducer. Despite manytechnical challenges toachieving thisflatdesign, thedecrease of 113
torquecapacitycanbeheldto30%incomparison withCSF-type. However,theadvantages in compactness andweightsavingsarestillmaintained. Figure10showstherelationship betweenvolume andratedtorque.Figure11showstherelationship betweenmassandratedtorqueforeachtypeofstrain wavegearing.TheCSD-typeisapproximately 27%smallerthantheCSF-typeandapproximately 60% smallerthantheCS-typeinvolume.Itisalsoapproximately 20%lighterthantheCSF-typeand approximately 37%lighterthantheCS-typeinmassperratedtorque.Theseresultsshowthatthepower densityofCSD-typeishigherthantheothertypesofstrainwavegearing. Thesizeandmasssavings willbe amplified whenthedesignoftheentirespacecraft isconsidered. Thisnewgearwillallowanewgeneration ofsolararraydrivesandantenna pointing devices tobedeveloped. 1.0E-03 Ev E > 1.0E-04 t.0E-05 10 Figure10. lO 0.1 10&cs iCSF ®CSD & A •• &Jl• A ,,i® o 100 1000 RatedTorque (Nm) Relationship between volume andratedtorque &CS ..... •CSF.... OCSD .... 11 0 I 1O0 1000 RatedTorque(Nm) Figure 11.Relationship between massandratedtorque References 1.Kiyosawa, Y.,Sasahara, M.,andIshikawa, S.,"Performance ofaStrainWaveGearing usingaNew ToothProfile", ASME, Proc.International PowerTransmission andGearing Conference, April1989, Vo1.11,pp.607-612. 2.Kiyosawa, Y.,Takizawa, N.,Ohkura, T.andYamamoto, Y."ANewStrainWaveGearing: Performance Evaluation", JSMEProc.MPT,'91 International Conference onMotion andPowerTransmissions, November 1991,P.1132-1136 3.KeijiUeura,Dr.RolfSlatter"Development oftheharmonic drivegearforspaceapplications", ESAProc. 8thEuropean SpaceMechanisms andTribology Symposium, September 1999,pp.259-264 114
Table 1.ZeroPlayHinge Latch Results andMeasurements fromTestontheZeroPlayHingeLatch PlayIntheDirection ofRotation Side1Pla_'attheendoftheZeroPlayHincjeLatchfrom30_lmforce Side2Pla_/attheendoftheZeroPlayHin_leLatchfrom309mforce Side1LatchPinOutsideDiameter Side1LatchPinHoleInsideDiameter Side1LatchPin/Latch PinHoleClearance Side1HingeAxleOutside Diameter Side1Hincje_HoleInsideDiameter Side1DoubleHin_leAxleHoleInsideDiameter SideIHingeAxle/Hinge HoleplusHingeA,de/Double HinaeHoleClearancemm(inI <.00254 (<.0001/ <.00381 (<.00015) 6.322(0.24891 6.388(0.2515/ 0.066/0.0026 ) 6.337(0.2495) 6.363f0.2505 } 6.388(0.2515 / 0.077(0.003) Side2LatchPinOutside Diameter 6.337t0.2495) Side2LatchPinHoleInsideDiameter 6.38810.2515) Side2LatchPin/Latch PinHoleClearance 0.051(0.002/ Side2HingeAxleOutsideDiameter Side2HingeAdeHoleInsideDiameter Side2DoubleHingeAxleHoleInsideDiameter Side2Hingehode/Hin_le HoleplusHir_leAxle/Double HingeHoleClearance Calculated amountofplayw_thoutthewedging actionduetoloosefitbetween axles,pinsandholesin therotational direction at35.56mm(1.4inIfromaxlea_s. PlayPerpendicular totheDirection ofRotation Side1PlayattheendoftheZeroPla_/Hinge Latchfrom30_lmforce Side2PlayattheendoftheZeroPlayHingeLatchfrom30_mforce A,,dalSpaceBetween Side1HingeandtheDoubleHinge A_alSpaceBetween Side2Hin_leandtheDoubleI_n_le Measured thencalculated amountofplayfromoneendtotheotherwithoutthewedging actiondueto loosefitbetween thepartsandtheholesandaxlesat35.56mmtl.4in)fromaxleaxis.6.33710.2495/ 6.363(0.2505/ 6.363t0.2505 ) 0.052(0.002/ 1.27(.050) <.00508 (<.0002) <.00508 (<.0002) .3175(0.0125 / .2413(0.0095/ 1.1684(0.046) ZeroPlayHingeLatches / /\ ,= Figure1.FGBEnclosure 17FramewithZeroPlayHingeLatches 118
t.atch PinScrew L_t_l,ei_Grip_ SpringPin___r' -¢- /Retaining Rin_ Hinge Latch PinHoles -- _. / Hinge .AxleHoles ...... _ ublcHinge Double }tin_c Backstop  _-'_--,_,_- _lt/"/._. Tapered Latch pinLatch PinSpring _. - _ _ Single Hinge Figure 2,ZeroPlayIlinge Latch -Exploded andAssembled Viev,'s Clam_crew r Clam [_ ZeoPlayHinge Latch Assembly recision V-blo% - Dial_ir =Precision FlatTable Stand Figure 3.Zero Play Hinge Latch Test Assembly. Rotational Direction 119
/ Non-Metallic HoldDownandRelease foranRFAntenna DavidJ.Hernandez Jr." Abstract Quickrelease mechanisms typically usemetallic rodsaspreload-carrying members. Thisisoftennota viablesolution forrestraint andrelease components thatareconnected toanRFAntenna. Thisis because metalextensions remaining afterrelease caninterfere withtheantenna's communications signals. Astrium Ltd.(formerly MatraMarconi Space) required anantenna release mechanism thatincorporates a quickrelease withnegligible source shockoutput. However, themechanism couldnotdisrupt the antenna's transmission aftertheantenna wasreleased fromthestowed position. Inaddition, atensile preload hadtobemaintained fora6-month periodwitharodelongation nottoexceed 5%oftherod length. NEAmettheserequirements byintegrating aGlassFiber/Epoxy Laminate 10G/40 ("Tufnol") rodintothe NEA-patented split-spool holddownandrelease mechanism. Thecombination ofthenon-metallic rod andthesplit-spool device(SSD)provides aneffective method ofapplying andmaintaining thenecessary preload forlaunchaswellasproviding a"virtually" shock-free release. Introduction Release mechanisms aredevices thatallowrelease ofadevicethatisinitiallystowed duringlaunchand, later,tobedeployed wheninspace. These devices include, among others, solararrays, reflectors, various instruments, coversorantennas. Astrium Ltd.required sucharelease devicetobeusedinconjunction withthedeployable antennas for theMetOp spacecraft. Twodifferent tensile preloads forantenna restraint, andthelocation ofthehold downpoints,forcedthedevelopment oftworelease systems. Apreload of3700Nwastobeapplied attheelbowoftheantenna. Atthislocation theantenna was restrained byaSSDintegrated withatitanium rod.Atensilepreload of2000Nwastobeapplied atthe antenna end.Atthislocation theantenna wasrestrained byaSSDintegrated withaTufnolrod.The antenna andtheholddownpointsareshowninFigure1.Inthefigure,release assembly (RA)001refers tothelocation oftheSSDwiththetitanium rodandIRA002referstothelocation oftheSSDwithaTufnol rod. A4.5-amp current pulseoveraduration of35milliseconds wasrequired toactivate bothSSDs. Furthermore, theconfiguration ofeachmechanism hadtoremain identical pertheAstrium specification. Theabilitytoincorporate bothtitanium andTufnolrodsispossible withtheSSDrelease mechanism. The SSD'spreload-carrying capability varieswiththediameter andmaterial oftherodusedinconjunction with themechanism. TheSSD'sstrength capability isimportant. Withitspresent designtheModel9101PSSD,independent of theroddiameter androdmaterial, willwithstand upto20000N.Consequently, anypotential creepfrom theSSDwouldcomedirectly fromtherod.Thisisbecause theSSDisusedatafraction ofitsload carrying capability (lessthan25%). "NEAElectronics, Inc.,Chatsworth, CA Proceedings ofthe35thAerospace Mechanisms Symposium, AmesResearch Center,May9-1I,2001 121
OO 0 ,0 A Figure1.Antenna HoldDownPoints Mechanism Actuation Therelease ofthemechanism requires activation through afusewireinitiator assembly. Therelease time ofthefusewireisapproximated bythefollowing equation: Ws>cppV.._ *1.25 W=Watts(I2*R) s=Timeinseconds toactuate cp=Thermal Capacitance offusewire p=Density offusewire Vwire "Volume offusewirebetween contacts Whenthevalueoftheleftsideoftheequation exceeds themelting pointvalueontheright,theactuation timecanbeapproximated within2milliseconds. The25%additional thermal mass(1.25coefficient) accounts foranypotential lossesfromconduction, convection, andradiation. Whilethewiredoesnotmelt duringactuation, itdoesreachtemperatures closetothemelting point.Itisthepulloftherestraining wire onthefusewirethatseparates oropensthefusewirecircuit.Foranalysis indetermining themechanism actuation timeitissafetoassume themelting temperature ofthewire.Atthistemperature thewirewould nolongerbeasolidcapable ofresisting theforceoftherestraining wire. Thefusewirelengthusedinthismechanism wasoptimized. Itwasoptimized toallowforamargin of greater than10milliseconds tothelowesttimetheactuation current wassupplied bytheMetOppower supply. 122
SSDShockOutput Thesource shockfromthemechanism's release oftherodwasalsoanimportant requirement. The mounting andlocation oftheholddownpoints,inaddition totheantenna's sensitivity, necessitated avery lowshockoutput. Astrium Ltd.required thattheSSDmechanism emitshocklevelslessthan0.8x frequency ofemission. Theshockwastobemeasured byaccelerometers (10-10000Hz)intheZaxis ona61cmx61cmx19mm(2'x2'x¾")aluminum plateat127mm(5inches) and254mm(10inches) fromthesource. During actuation thesource shockproduced apeaklevelof160g'sat7000Hzusinga42-mm long Tufnolrod.Thetensilepreload ontherodwas2500N.Thenegligible source shockisattributed tothe split-spool restraint andrelease principal. Thetestdatademonstrated thatthemechanism withtheTufnol rodexhibited agreater shockemission thantheirtitanium counterparts. Itisbelieved thatthereasonfor thegreater shockemission isbecause theTufnolmaterial hasahigherelasticmodulus thanthetitanium. NEAengineers assume thattheslowrelease oftherod'sstrainenergy isthereason fortheoverall negligible shockemitted. Themeasured preload dropovertimeinmilliseconds afteractuation would seemtoconfirm thishypothesis. Non-Metallic RodDevelopment Asignificant challenge forNEAindeveloping theHold-Down andRelease Mechanism forAstrium Ltd. wasselection ofthenon-metallic rodmaterial. Theproperties thatareimportant inthematerial selection include: •Hightensilestrength •Highelectrical resistance •RFtransparency •Highmodulus ofelasticity •Lowcreepcharacteristics Themorecommon non-metallic materials usedinspacewereeliminated because theydidnotsufficiently meettherequirements above. Thesematerials include butarenotlimitedtoULTEM, Delrin,TORLON andPEEK. Afterathorough reviewoftheaboveparameters, Astrium Ltd.recommended usingamaterial named Tufnol. Aroddiameter of7.95mm,withatensile strength of300MPa,wasmorethancapable of withstanding the4000-N maximum preload requirement. Theoperational preload of2000Nwouldbe maintained attheMetOpspacecraft levelbymeansofaflexureplateasshownintheAstrium designin Figure2.Whatremained wasthecreepbehavior oftheTufnolunderpreload overanextended periodof time. Inthisconfiguration theflexure platemaintains thepreload viabending. Forthisreason elongation in excess of0.18mmwouldcauseanunacceptable non-preload condition. Thepractical application fortheSSDmechanism istopreload itduringassembly oftheMetOp satellite busandstowitforaperiodofsixmonths. Itwasnecessary forAstrium Ltd.tospecifythattheTufnolrod survive apreload ofapproximately 2500Nforthissix-month period. Furthermore, Astrium addeda temperature requirement of30°C+5°C/-0°C forthesix-month condition. Thiswouldrepresent the conditions thattheMetOpbuswouldbestowed in. NEAconstructed atesttosimulate thestowed conditions. Assembled inhardware madetotheflight configuration, theTufnolrodwaspreloaded toapproximately 2450N.Thisloadwasthemaximum operational preload caseinambient conditions (roomtemperature of15°Cto20°C). 123
Support StructureTension Rod Ejection PistonHardContact Point Release Actuator Figure2.MetOpAntenna Configuration WhentheSSDmechanism wasplacedintheoven,thepreload increased toapproximately 2465N.The preload wasadjusted tomaintain aconstant load.However, thetimeforadjusting theconstant loadwas foraperiod of60days. Afterthattime,theloadwasallowed todecayatitsownratewithout adjustments. Agraphdepicting theloadasmeasured byaloadcellincompression isshowninFigure3. 2500 2480 2460 2440 2420 2400 2380 2380 2340 2320\ \ 2300 0 20 40 60 80 100 120 140 160 180 Oay$ Figure 3.TufnolRodLoadvs.Time 124
Theelongationovertime,whileunderload,showsatotalcreepof0.076mmoverthefinalfour(4)month period.Oncetheloadwasremovedandtherodexamined,itwasfoundthattherodlengthhadincreased 0.05mminplasticdeformation. AsseeninFigure4,therodlengthincreasedatincreasingtimeintervals.Thebehavioroftherodwas expectedtobeinthiscondition,reachinganasymptote-like curve.Althoughthecreeptestwasscheduled torunfortwomonths,NEAcontinuedthetestforanotherfourmonths.Afteroneyear,theelongationof therodunderconstantloadwouldapproach0.11mm,wellwithintheelongationrequirement ofAstrium's flexureplate. 01 009 0o8 007 EE006 .E 005 o "='0C_ (].03 002 001 0 0 20 40 60 80 100 120 140 160 Dayl Figure 4.Elongation ofTufnol Rodvs.Time Conclusion Therelease mechanism, integrated withaTufnolrod,succeeded inholding aconstant loadoveran extended timewithminimal creep.Theco-action ofaglasscomposite rodandametallic restraining devicetoretainaloadoveranextended timehasprovensuccessful tobothAstrium Ltd.andNEA. Plasticdeformation oftheTufnolrodoccursatloadsabove2400N,whilemaintaining anultimate loadof approximately 14000N.UsesoftheTufnol rodintension overextended periods oftimeshould be possible whenthenominal forceisbetween 14and17%ofthecomposite material's ultimate strength. Shockemissions fromthemechanism maybeminimized usingrelease rodsofhigher modulus of elasticity. Provided therodmaterial doesnotinterfere withtheapplication oneshould consider usinga lesselasticmaterial. Fusewireassembly provides consistent actuation. Theanalytical modelprovides aconsistent meansof predicting theactuation time.Depending ontheamount ofpoweravailable foractuation, thecorrectwire diameter andlengthcanbeutilizedtofittheneedsofdifferent applications. Acknowledgements Stephen Bamford, Astrium Ltd.,forproviding theapplication responsible fortheantenna andholddown design. A.M.Kiley,Astrium Ltd.,fortheholddownconcept andTufnolroddesign. 125
Conclusions Insummary, asfarasacontroller gainvaluesetofproportion, integration, andderivative ofaPID controller iswithinastabilitylimit,anycombination ofthethreestablegainsguaranteed tospintherotor uptothemaximum allowable speedofthefault-tolerant magnetic bearing testrig.Foravarietyof multiple component (coilsandamplifiers) failures, theintegrator ofaPIDcontroller generated autonomous corrective forcestocompensate thosefailedsituations. Also,thecontroller doesn'trequire anyoperator's inputtochangethegainvaluesetforfailedsituations. Thedemonstration washighlighted whenusingonlytwoactivecoilsandamplifiers fromeachradialbearing(thatis,twelveoutofsixteen coilsandamplifiers werefailed)levitated therotorandspunitwithoutlosingstabilityanddesiredposition uptothemaximum allowable speedof20,000rpm. Thisvaluable demonstration provedthatasafefault-tolerant bearingdesignispossible andanoil-free magnetic bearing canhavemultiple coilor/andamplifiers failures beforecausing anentiresystem shutdown. Thisworkhelpedtoeliminate thecontroversial safetyissueofusingamagnetic suspended turbomachinery forfutureengines tocarrypeoplesafely. Thefutureworkwillincludeacomplete dynamic analysis ofafault-tolerant bearingsystemanddevelop amoreenhanced PIDcontroller byusingaKalman filter,whichcanestimate statevariables to overcome thesensornoiseandunknown process noise. Acknowledgements Thisworkwascarriedoutunderafund,whichwasmainlyprovided bytheTurbomachinery and Combustion Technology Program (RobertCorrigan, Program Manager), andalsoinpartbytheFlywheel andEnergyStorage SystemProgram. References 1.Chen,H.M.,2000,"ASelf-Healing Magnetic Bearing," 5t"International Symposium onMagnetic Suspension Technology, pp.25-34,July. 2.Fedigan, S.J.,Williams, R.D.,Shen,D.,andRoss,R.A.,1997,"Design andImplementation ofa FaultTolerant Magnetic Bearings Controller," Proceedings oftheFifthInternational Symposium on Magnetic Bearings, Kanazawa, Japan,pp.307-312. 3.Field,R.J.,lannello, V.,1998,"AReliable Magnetic BearingSystemforTurbomachinery," Proc.6th Int.Symp.Magn.Bearings, Cambridge, MA,pp.42-51,August. 4.Lyons,J.P.,Preston, M.A.,Gurumoorthy, R.,andSzczesny, P.M.,1994,"Design andControlofa Fault-Tolerant ActiveMagnetic Bearings SystemforAircraftEngine," Proceedings oftheFourth Internaltional Sysmposium onMagnetic Bearings, ETHZurich,pp.449-454. 5.Maslen, E.H.,Meeker, D.C.,1995,"FaultTolerance ofMagnetic Bearings byGeneralized Bias CurrentLinearization," IEEETransactions onMagnetics, Vol.31,No.3,pp.2304-2314, May. 6.Meeker, D.C.,1996,=Optimal Solutions totheInverseProblem inQuadratic Magnetic Actuators," Ph.D.Dissertation, Mechanical Engineering, University ofVirginia, May. 7.Na,U.J.,Palazzolo, A.,2000,"Optimized Realization ofFault-Tolerant Heteropolar Magnetic Bearings," ASMEJournalofVibrations, Vol.122,pp.209-221, July. 130