Inertial Sensor and Its Applicati

on for Space Fundamental Expe

riments

Ze-Bing Zhou (周泽兵 ), Jun Luo (罗俊 )

zhouzb@mail.hust.edu.cn

Center for Gravitational Experiment,

Huazhong University of Science and Techn

ology

3rd ASTROD, 14-17 July, 2006, Beijing

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OutlineOutline

Principle of inertial SensorPrinciple of inertial Sensor

Space application of inertial sensorSpace application of inertial sensor

Progress of inertial sensor in HUSTProgress of inertial sensor in HUST

SummarySummary

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11 、、 Principle of Accelerometer/Inertial Principle of Accelerometer/Inertial SensorSensor

2r 0 rx x y

0 2r 0/x y

xr =

x -

y

k

m

y

x If 10 210 m/s / Hzy

Hz10 f r 2.5pm/ Hzx

To 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

)( yxkxm

0 /k m

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Accelerometer Structure

TestMass

Senor Open-Output

TestMass Actuator Controller Closed-

Output

Sensor

Linkage：Mechanic, Electrostatic, Magnetic, Optical

Position Sensor: Optical, Capacitance, SQUID

Force Actuator: Electromagnetic, Electrostatic, Piezo-

Control Unit: simulative, digital, mixed

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Electrostatic Suspension/Space Accelerometer

•Capacitance transducer + Electrostatic Actuator

•One Proof Mass with Six degree-of-freedom measurement

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Superconducting Inertial Sensor

•SQUID technique

Optical Suspension

Inertial Sensor

• Optical read out (phase)

and control (power)

Inertial sensor with atom-interferometer

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Acceleration Acceleration

MeasurementMeasurement

ModelModel

Inertial Inertial

ReferenceReference

ModelModel

(Geodesic)(Geodesic)

Test mass tracks

with spacecraft

Spacecraft tracks

with test mass

Operation modes in space applicationsOperation modes in space applications

2、 Space Application of Inertial Sensor

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1975 CACTUS

1996 ASTRE: µgravity survey

2000 STAR : CHAMP

2002 SuperSTAR : GRACE

2006? GRADIO GOCE

2009 ?MICROSCOPE

2015 LISA

Ref. ONERA

Space Application of Inertial Sensor

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CHAMP GFZ,Germany

2000.7.15

GRACENASA/GFZ

2002.3.19

Projects of EGF Measurement

3*10-9 m/s2 3*10-10 m/s2

Accelerometer provided by P. Touboul, ONERA, France

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MICROSCOPE (ONERA-ESA 2009?)

Proof-mass material :

Platinum - Titanium

Pt/Pt - 186g/500g

Pt/Ti - 186g/106g

Expected Precision: 5*10-15 m/s2

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Predicted Accelerometer Noise: 3×10-15 m/s2/Hz1/2

0.1mHz ~1mHz

Inertial Sensor for LISA

Univ. Trento, Italy, 2003

2*10-13 m/s2/Hz1/2 at 3mHz

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3、 Development of inertial sensor in HUST

Member of ASTROD-1: Inertial sensor research

TISS: Test of Inverse-law Square in Space

proposed by Prof. Jun Luo

Background:

Present status:

Preliminary progress of CESA on ground

(Chinese Electrostatic Suspension/Space Accelerometer)

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Terrestrial Scheme for Electrostatic Suspension Inertial Sensor/Accelerometer

ONERA, 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 Suspension

Main difficulty: 1g Earth’s gravity acceleration limit

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Fiber Suspension

Electrostatic feedback

CESA Scheme

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Turntable

Probe

Fiber

Experimental setup

Vacuum: 100Pa. Position in center of

+10um Preamplifier in

vacuum Digital PID Control

Original prototype

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Experimental parameters

Proof Mass M Al, 319.47+0.05 g ; (58.03+0.03) *(47.9

7+0.07) *(40.11+0.02) mm3

Inertial moment I (1.471+0.005)*10-4 kg m2

Suspension fiber Tungsten, Φ50um *(960+1)mm

Torsion constant Kf (9.14+0.11) *10-8 Nmrad-1

Free period T0 252.1+1.9 s

Quality factor Q ≈382 (about 100Pa)

Capacitance electrode 19.5mm*40.1mm, gap: 0.81±0.10 mm;

Capacitance in balance C0 8.7+1.1 pF

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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 e

lectrostatic torque on the test mass;

(3) The test mass follows the capacitive electrodes, and its rotational a

ngle is simultaneously monitored by an optical level.

* In this case, the electrostatic torque is equal to the fibre

restoring one. feedback fiber fS V k

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Sensitivity:

Calibration Result

Feedback voltage variety (0.170V)Angle variation (5.173mrad)

8f / (3.61 0.29) 10 V/NmMS Γ V

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Preliminary Result (8th July,2006)

Resolution: 3*10-12 Nm/Hz1/2 at 1mHz

2.4*10-10 m/s2/Hz1/2 at 1mHz

1SD=1.5mV

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Dynamic range: ++ 2.8*10 2.8*10-8 -8 NmNm

Dynamic range measurement

Feedback voltage Error signal

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Predicted of Inertial sensor for ASTROD-1

Capacitance 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 1mHz

If the capacitance sensor

keeps same resolution

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b

mdS

AV

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Disturbance model

2pm,d n n a pm,n pm cp p a/ ( )a x V H F m K X X

Fsp,g

Fsp,ng Xsxa

Fpm,g

Fpm,n

Capacitance Transducer Hs

Controller Hc

Electrostatic Actuator Ha

Coupling Kcp

VfedVn

Coupling Kcp

Xn

Verr

TMSC

Thruster Ht

Tn

•Intrinsic noise

•Disturbance on TM

•Coupling between

TM and SC

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Key of further research:

•To add translation control

•To improve the vacuum

•To add vibration isolation

•To analyse and test the disturbance effects

•To change probe parameters for ASTROD-1

condition:

TM material, capacitance gap….

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•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

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Thank you very much!