航天器姿态确定和姿态控制课件.docx

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1、航天器姿态确定和姿态控制课件pointthetelescopeDesiredAttitudeActualAttitudedeterminesthedesiredtorques,andsendelectricalcommandsappliesthedesiredtorquestakethemeasurementsEstimatedAttitudeEstimatesthecurrentattitudeACS:SingleSpinTheentirespacecraftspins,whichprovidesinertial3C3PlatformRotorAACAAACS:MomentumBias:Th

2、emomentumbiassatelliteisavariationofthedualspinconceptthatovercomesmomentumusuallyspunbyelectriccontrolledmomentumwheelcomethereforehowmuchangularmomentumofchangesitaboutTwomagnetictorquersinteractACSmethods:ActivePropellantReactionwheelswithSensorsThetypesofsensorsusedforattitudedeterminationare:1.

3、horizonsensors(orconicalEarthscanners),2.sunsensors,3.starsensors,4.magnetometers,5.inertialreferenceunits(IMUorattitudereferenceunitsARU),and6.GPSreceivers.Horizonsensorsmeasurepitchandrolltoanaccuracyofabout0.1-0.5deg.Anaccuracylessthan0.05degcanbeachievedbyextensivecalibrationandaccountingforthee

4、quatorialbulge.Sunandstarsensorsprovidedirections.Anhorizonsensordoesnotprovideyawinformation(formomentumbiassystemsitisnotnecessarytomeasureyaw).Onewide-FOVortwonarrow-FOVstarsensorsareneededtoprovideattitude.SincethestarsensorscannotprovidecontinuousattitudemeasurementsanIMU/ARUisneededtoprovideth

5、eattitudebetweenmeasurements.IMUssufferfromdriftandbiasesandneedfrequentupdateswhichareprovidedbythestarsensors.MagnetometersmeasureEarthsmagnetic.Accuraciesnobetterthan1degcanbeobtained.TheGPSreceiversareusedinaninterferometermodetodetermineattitude.Accuraciesasgoodas0.01degareexpectedusingGPS.Pres

6、enceSunSensorsEntranceslitGridslitPhotocellatthebase(belowtheslit)SunraysPhotocellShadowareaShadowrodPresencesunsensorsprovidethcrossingtimeonly,orthesunpresencewithinthesensorFOVUsedtosynchronizepulsedcommand(spin-up,spin-down)tomaneuvretoturnon/offonboardexperimentsinstrumentation.PhotocellsMirror

7、ImageplanemaskSunimageLensAperturePhotocell1Photocell2T()(0)(0)cosIIdnI?=?AnalogicSunSensorsPhotocell#2Photocell#1NormalSunraysNormalPhotocellsMaskReferenceaxisNormalSensor1Sensor2SunraysNormalPhotocellSensor#2Sensor#1Angle(deg)OutputcurrentMeasurementCommandMeasurementommandmmand:sunpresenceMeasure

8、ment(4parts):ATA,Signbit,Codebits,Interpolatingbits.DigitalsensorPhotocellsGridslitsBinarycodeGraycodeSunangleBinaryGrayDecimalBinaryGray0110111001011101111000100110100111101101111011001100110111111112131415161718192021101111001101111011111000010001100101001110100101011110101010111001100011000110011

9、1011110101111011111Graycodeconsistsofthefactthatthebitstring,whichtheanglemeasure,changesonebitonlyateachdigitalstep.BinaryandGraycodePhotocellsDoubleDigitalSunSensor2Bestrange:14-16ofCO(lesshighaltitudecloudscontr.)Relativeradiance400(IR)and30,000(visible)allowtoevaluatetheNadirdirection.HotMoonHar

10、dhorizonHotareaforcoldMoonHotareaforhotMoonColdMoonHothorizonpositionColdhorizonpositionMooncenterdistanceRelativeradianceMoonhorizonsensorMoontemperaturerange:240degto+30degMeridianslitInclinedslitSatelliteequatorDisplacementangle(deg)Earth/SunsensorsforspinningS/CStarsensorforspinningS/COpticalaxi

11、sElevationslitAzimuthslit文档视界航天器姿态确定和姿态控制课件航天器姿态确定和姿态控制课件FocalPlaneArcheopsKiruna2002StarTrackersElectronicsPhotomultiplierOpticalsystemBaffleStarGridSensorsElectronicunitSignalprocessingandAnalogtodigitalconverterTelemetryLinkSmallprecisionisassociatedwiththefactthattheEMFModelsarenotsoaccurate.Biasesnotnegligeable(residualsofmagneticfieldscausedbyonboardcircuits)TypicalGN&CSensors(Wertz)AttitudeDeterminationSystems