A Micromechanical Mode-Matched Gyroscope Using Stiffness Nonlinearity and Electrostatic Tuning

This work reports design of a dual-mode decoupled single-mass micromechanical gyroscope with a fully symmetrical structure aiming to achieve mode-matching despite of fabrication errors and packaging stress imbalance. Mode-matching is done by combing the spring-hardening effect caused by the nonlinear stiffness of the elastic beam and the linear electrostatic stiffness by applying a DC voltage to dedicated linear electrostatic tuning electrodes set on the center mass of the gyroscope. First, the mode split between gyroscope drive mode and sense mode is narrowed by a coarse frequency tuning, which combines the spring-hardening effect based on adjusting the drive oscillation amplitude to a proper value, and the downward tuning effect caused by quadrature nulling electrode. Then mode matching is achieved by applying a DC voltage on the linear electrostatic tuning electrodes. Test results of the mode-matching gyroscope using aforementioned two-step tuning is also given. The gyroscope achieves an ARW of 0.011°/√h and BI of 0.229°/h under mode matching and with quadrature error suppressed by quadrature nulling electrode.