Closed loop control design for the sense mode of micromachined vibratory gyroscopes

Abstract

This paper presents a novel design method of force rebalance control for the sense mode of micromachined vibratory gyroscopes. Specific theoretical deductions are performed to identify a precise linear model of the open loop system of the sense mode, which is crucial for the PI controller design. The frequency responses obtained by experimental tests agree well with those calculated with the theoretical model, indicating the accuracy of the theoretical analyses. Experimental results demonstrate that the bandwidth of the closed loop is extended to 94.8 Hz from 2.3 Hz in the open loop and the quadrature signal is suppressed by about 64 dBV in the closed loop system. The overshoot and stable time in the step response of the closed loop system are measured to be about 15% and 35 ms, respectively. The mode-splitting gyroscope with the closed loop controlled sense mode achieves a scale factor of 41.0 mV/deg/s with nonlinearity of 0.09% and asymmetry of 1%, and a bias instability of 4.0 °/h with angle random walk of 0.171 deg/h1/2.