Inertial Sensor and Its Application for Space Fundamental Experiments Ze-Bing Zhou ( ‘¨³½…µ ), Jun Luo ( ç½— ) Center for Gravitational

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  • Inertial Sensor and Its Application for Space Fundamental Experiments

    Ze-Bing Zhou (), Jun Luo () for Gravitational Experiment, Huazhong University of Science and Technology 3rd ASTROD, 14-17 July, 2006, Beijing

  • Outline Principle of inertial Sensor Space application of inertial sensor Progress of inertial sensor in HUST Summary

  • 1Principle of Accelerometer/Inertial SensorIfTo obtain the acceleration of the mobile objects by monitoring the relative motion of the proof mass w.r.t. it; Lower of natural frequency (softer linkage), higher sensitivity

  • Accelerometer StructureTestMassSenorOpen-OutputTestMassActuatorControllerClosed-OutputSensorLinkageMechanic, Electrostatic, Magnetic, OpticalPosition Sensor: Optical, Capacitance, SQUIDForce Actuator: Electromagnetic, Electrostatic, Piezo-Control Unit: simulative, digital, mixed

  • Electrostatic Suspension/Space AccelerometerCapacitance transducer + Electrostatic ActuatorOne Proof Mass with Six degree-of-freedom measurement

  • Superconducting Inertial SensorSQUID techniqueOptical Suspension Inertial Sensor Optical read out (phase) and control (power)Inertial sensor with atom-interferometer

  • Acceleration Measurement ModelInertial ReferenceModel(Geodesic)Test mass tracks with spacecraftSpacecraft tracks with test massOperation modes in space applications2Space Application of Inertial Sensor

  • 1975 CACTUS1996 ASTRE: gravity survey2000 STAR : CHAMP2002 SuperSTAR : GRACE2006? GRADIO GOCE2009 ?MICROSCOPE2015 LISARef. ONERASpace Application of Inertial Sensor

  • CHAMP GFZ,Germany2000.7.15GRACENASA/GFZ2002.3.19Projects of EGF Measurement3*10-9 m/s23*10-10 m/s2Accelerometer provided by P. Touboul, ONERA, France

  • MICROSCOPE (ONERA-ESA 2009?)Proof-mass material : Platinum - Titanium Pt/Pt - 186g/500gPt/Ti - 186g/106gExpected Precision: 5*10-15 m/s2

  • Predicted Accelerometer Noise: 310-15 m/s2/Hz1/2 0.1mHz ~1mHzInertial Sensor for LISAUniv. Trento, Italy, 20032*10-13 m/s2/Hz1/2 at 3mHz

  • 3Development of inertial sensor in HUST Member of ASTROD-1: Inertial sensor research TISS: Test of Inverse-law Square in Space proposed by Prof. Jun LuoBackground:Present status:Preliminary progress of CESA on ground(Chinese Electrostatic Suspension/Space Accelerometer)

  • Terrestrial Scheme for Electrostatic Suspension Inertial Sensor/AccelerometerONERA, France, 20002*10-10 m/s2/Hz1/2[RSI 71 2000 302]Univ. Trento, Italy, 200310-13 m/s2/Hz1/2[PRL 91 2003 151101]High-Voltage Suspension Fiber SuspensionMain difficulty: 1g Earths gravity acceleration limit

  • Fiber SuspensionElectrostatic feedbackCESA Scheme

  • Vacuum: 100Pa.Position in center of +10umPreamplifier in vacuumDigital PID ControlTurntableProbeFiberExperimental setupOriginal prototype

  • Free motion of the torsion pendulum

  • Experimental parameters

    Proof Mass M Al, 319.47+0.05 g ; (58.03+0.03) *(47.97+0.07) *(40.11+0.02) mm3Inertial moment I (1.471+0.005)*10-4 kg m2Suspension fiber Tungsten, 50um *(960+1)mmTorsion constant Kf (9.14+0.11) *10-8 Nmrad-1Free period T0 252.1+1.9 sQuality factor Q 382 (about 100Pa)Capacitance electrode 19.5mm*40.1mm, gap: 0.810.10 mm; Capacitance in balance C0 8.7+1.1 pF

  • Calibration steps: (1) To change the capacitive electrodes position with respect to the test mass by the rotate table; (2) The capacitive sensor detects the relative motion, and then acts an electrostatic torque on the test mass; (3) The test mass follows the capacitive electrodes, and its rotational angle is simultaneously monitored by an optical level. * In this case, the electrostatic torque is equal to the fibre restoring one.

  • Sensitivity:Calibration ResultFeedback voltage variety (0.170V)Angle variation (5.173mrad)

  • Preliminary Result (8th July,2006)Resolution: 3*10-12 Nm/Hz1/2 at 1mHz2.4*10-10 m/s2/Hz1/2 at 1mHz1SD=1.5mV

  • Dynamic range: + 2.8*10-8 NmDynamic range measurementFeedback voltage Error signal

  • Predicted of Inertial sensor for ASTROD-1Capacitance gap: 0.8 mm 1 cm (156 times)TM: 320g (Al) 1.68 kg (5*5*3.5cm3, Au-Pt)3*10-13 m/s2/Hz1/2(5 times)2.4*10-10 m/s2/Hz1/2 at 1mHzIf the capacitance sensor keeps same resolution

  • Disturbance modelIntrinsic noise Disturbance on TM Coupling between TM and SC

  • Key of further research:To add translation controlTo improve the vacuumTo add vibration isolationTo analyse and test the disturbance effectsTo change probe parameters for ASTROD-1 condition: TM material, capacitance gap.

  • Inertial Sensor/Accelerometer is one of key technologies for space fundamental experiments. It will be developed with the requirement of space mission, and inversely then it will push the space mission.Electrostatic suspension/space accelerometer has been studied for over 30 years, and succeed to be used in space.CESA should be studied step by step, too much disturbances need be analyzed, tested, and suppressed.4. Summary

  • Thank you very much!