A Pendulum Bench Based On Translation-tilt Compensation Principle For Accelerometer Performance Investigation On The Ground

The electrostatic accelerometer plays an important role in space science missions such as the satellite Earth's gravity measurement,the test of equivalence principle,the space-borne gravitational wave detection mission and so on.The electrostatic accelerometer is based on capacitive displacement sensing and electrostatic feedback control techniques.It has the characteristics of extremely high resolution and six degrees of freedom(DOFs)measurements simultaneously but very low dynamic range.In order to evaluate the performance of the electrostatic accelerometer on the ground,the Earth's gravity must be counteract.The high-voltage levitation method is different from the fiber suspension method and free-falling method,which realized the six DOFs measurements simultaneously.The high-voltage levitation scheme is suitable to test the engineering prototype,but the performance is limited by the seismic noise.The high-voltage levitation electrostatic accelerometer has been developed in our laboratory and realized six Do Fs(degrees of freedom)measurements simultaneously.The translation noise of the accelerometer has reached 4×10^-8m/s²/Hz^1/2at 0.1Hz,and the measurement noise is higher than its estimated intrinsic noise due to the seismic noise.So the vibration isolation system should be taken into consideration.For tranditional passive vibration isolation systems,their vibration isolation bandwidth are usually above 1Hz due to the resonant frequency limitations,which can not cover the measurement bandwidth of accelerometers.A pendulum bench has been proposed in our group for accelerometer performance investigation on the ground,on which the accelerometer is insensitive to the horizontal vibration at low frequency.The theory of the electrostatic accelerometer and the high-voltage levitation measurement scheme have been introduced firstly.Besides the seismic noise of the measurement bandwidth,the measure-ment noise of the accelerometer is also influenced by the high-frequency vibration noise out of the measurement bandwidth and the rotational cross-coupling noise of the measurement bandwidth.To improve the meaurement performance,a pendulum bench based on translation-tilt compensation has been carefully modeled and analyzed.Combined with the center of percussion theory,we found that both the high frequency down conversion and the cross-coupling from rotational axis are related to the relative position of the test mass of the accelerometer,and it has been verified by a series of experi-ments.A vibration isolation bench has been designed and a tilt adjustment scheme has been proposed in the need of the accelerometer measurement on the ground.In order to avoid the impact of the cir-cuit of electrostatic accelerometers,we separated the circuit from the sensor head and put it out of the bench.The noise of the horizontal acceleration of the accelerometer which is placed on the bench has reached 3×10^-9m/s²/Hz^1/2around 0.2Hz.Comparing with the experimental level measured on the ground,it has been reduced by one orders of magnitude,so the vibration isolation ability of the bench has been fully verified.The work of the thesis is meaningful for improving the measurement level of electrostatic accelerometers on the ground,and it can provide an reliable environment for the test of the next generation electrostatic accelerometer.