Influence of Parametric Nonlinearities on Closed-Loop Operated MEMS Gyroscopes

The influence of parametric nonlinearities on the mode matching of closed-loop operated MEMS gyroscopes is investigated. Accurate resonance tuning of mechanical detection modes is essential for optimal noise suppression in closed-loop resonators. Large deflections of the drive mode lead to a geometric nonlinearity, which induces a phase-dependency in the mode-matching procedure. Those effects are known to amplify signal-to-noise ratio in open-loop vibratory MEMS gyroscopes. Predicted and measured tuning voltages and folded response of a sense mode in a prototype gyroscope are compared. Using simulations, it is shown that the pilottone with a 90° phase can confine the crosstalk of the Coriolis and quadrature channel to the quadrature channel exclusively. When applying a quadrature compensation in the simplified model, nonlinear amplification is prohibited in the output channel even for low gain of the force-to-rebalance loop. Furthermore, it is shown that in a simulation with idealized drive motion and demodulation signals the cross-coupling nonlinearity by itself does not have a major impact on standard noise suppression capabilities. [2021-0232]