Study On Performance Improvements Of Measurement And Control Circuit Of Silicon Resonant Micro-accelerometer

Silicon resonant micro-accelerometer is a high-precision MEMS sensor,it can convert the acceleration signal directly to the frequency signal.Based on the principle prototype of silicon resonant micro-accelerometer developed by the laboratory,this paper analyzes its working principle and improves the circuit,and the task and goal is to improve the overall performance of the prototype.The main research contents include the following aspects:(1)Based on the silicon resonant micro-accelerometer,the basic theory is analyzed and its dynamic model is established.The electrostatic driving mode of the accelerometer structure is analyzed.The principle of phase-locked loop phase control and loop start-up principle in closed-loop control circuit are discussed,and the transfer function of automatic gain control loop is deduced.(2)According to the principle of electrostatic operation of the prototype,the unilateral detection and bilateral detection are analyzed and compared.The feasibility of bilateral signal detection is determined for the weak detection signal and the influence of coupling capacitance.At the same time,a reasonable interface circuit is designed to extract the vibration displacement signal,and the interface detection circuit is analyzed and optimized,and the rationality is verified by experiments.(3)According to the principle of regulated power supply,the switching regulator and linear regulation are compared to determine the basic scheme of the secondary power supply.The power supply circuit is selected and designed according to the requirements of the measurement and control circuit.The interference of the power supply to the monitoring and control circuit is analyzed.Aiming at the ripple and current surges existing in the DC regulated power supply,the pre-filter circuit and the post-filter circuit are designed by the Multisim and the MATLAB simulation is carried out and verified experimentally.(4)Based on the analysis of the mechanical thermal noise and electrical noise existing in the prototype of the current accelerometer,the basic noise model of the components is established.Based on this,the noise model of the interface circuit is established and analyzed.The phase noise of each module is analyzed and the phase-locked loop noise transmission model is established.(5)In this paper,the improvement of the measurement and control circuit is applied to the prototype of the laboratory development.According to the test conditions of the domestic"vibration beam accelerometer test",the whole silicon micro resonant accelerometer prototype is tested,the test results are as follows:the bias repeatability increased from 20.95μg to 16.08μg;the bias stability increased from 34.26μg to 17.92μg;and the stability of 1g increased from 41.46μto 16.83μg;scale factor stability increased from 35.33ppm to 15.29ppm;scale factor repeatability increased from 52.76ppm to 39.43ppm;the forward and reverse scale factor nonlinearity were 681.97ppm and 629.79ppm in the range of ± 20g,while temperature performance improved is better than before.