A Low-Complexity In-Run Modal Frequency Tuning Method for MEMS Disk Gyroscopes Without Gain Calibration and Phase Shifting.

The approach of obtaining modal frequency split information using conventional sideband excitation signals requires gain calibration and compensation, and sense mode output signals as the frequency split decreases produce a phase shifting, which increases the complexity of the in-run modal frequency tuning method for MEMS gyroscope. In this paper, an in-run modal frequency tuning system based on multiple frequency sideband excitation signals and preset stiffness regulation voltages (quadrature stiffness correction and frequency tuning voltages) is designed and implemented. The frequencies of multiple frequency sideband excitation signals are proportional to the drive modal frequency, and eliminating the need for gain calibration of the modal frequency tuning system. The preset stiffness regulation voltages are adopted to control the initial frequency split within 0.1Hz, so that the phase of demodulation reference signals for sense mode remains fixed during the frequency tuning processing. Firstly, the conditions of modal frequency matching are analyzed based on the stiffness regulation electrodes. Secondly, the necessity of modal frequency matching is investigated from the perspectives of signal acquisition and mechanical sensitivity. Thirdly, the in-run modal frequency tuning system is designed. Finally, the static performance of the disk gyroscope before and after modal frequency matching is compared. Bias instability is reduced from 3.543°/h to 0.902°/h, and angular random walk is reduced from 0.646°/√ h to 0.049°/√ h, achieving the static performance of the tactical-grade gyroscope.