Constant-frequency oscillation control for vibratory micro-machined gyroscopes

This paper proposes a new oscillation control algorithm for vibratory micro-machined gyroscope system. The control algorithm tunes the resonant frequency of the gyroscope to the specified resonant frequency and maintains the specified amplitude of oscillation by altering the gyroscope dynamics. Feedback control is designed to achieve frequency tuning in the presence of time-delay. The stability of the control system is analyzed using the averaging method. Based on the real system, simulation models were set up to evaluate the control algorithm. Further, the algorithm mainly implemented using a field-programmable-gate-array (FPGA) is tested on a capacitive vibrational gyroscope operating at atmospheric pressure. First measurement results of the novel digital prototype show the phase variance of the detected signal of drive axis is 13 ppm in an hour while the amplitude variance is 22 ppm. A bias instability value of 6°/h is achieved using this new oscillation control loop.