Digital Closed-Loop Control Based on Adaptive Filter for Drive Mode of a MEMS Gyroscope

This paper describes the design of a digital closed drive loop for a MEMS vibratory, vacuum packaged gyroscope. The displacement of the gyroscope is demodulated by the adaptive filter-least mean square (LMS) though which the amplitude and phase of the displacement are separated for respective control. The amplitude is kept constant by the automatic gain control (AGC) method with a proportion-integral (PI) controller while the phase is controlled by phase locked loop (PLL). Results of experiments carried out on field-programmed-gate-array (FPGA) with a doubly decoupled bulk gyroscope are shown to be in close agreement with simulation results. The amplitude variance of the detect signal of drive mode is 28ppm in half an hour while the phase variance is 770ppm.