Negating self-induced parametric excitation in capacitive ring-based MEMS Coriolis vibrating gyroscopes

Rate sensing performance of ring-based capacitive Coriolis Vibratory Gyroscopes (CVGs) is degraded by the presence of imperfections and self-induced parametric excitation caused by electrostatic nonlinearities as the drive amplitude increases. This paper investigates the feasibility of using electrostatic forces to negate self-induced parametric excitation for a ring based CVG having 8 electrodes uniformly spaced inside and outside the ring. A mathematical model is developed to describe sensor dynamics under operating conditions and negation of self-induced parametric excitation is achieved by including additional parametric pumping voltages that generate electrostatic forces in antiphase with the self-induced parametric excitation. Numerical results are obtained for the rate sensitivity, bias rate and quadrature error of the sense output as the drive amplitude is increased and it is found that negating self-induced parametric excitation can enhance device performance under specific conditions by enabling nonlinear frequency matching. The proposed approach is more effective for larger electrode spans and improves the linearity of the rate sensing performance with drive amplitude. Numerical results are presented which include a comparison with results obtained using the Finite Element method to validate the proposed approach.