An In-Run Automatic Mode-Matching Method for N = 3 MEMS Disk Resonator Gyroscope

This paper demonstrates an in-run automatic mode-matching method for a Micro-Electro-Mechanical systems (MEMS) disk resonator gyroscope (DRG) operating in the n = 3 wineglass mode. In proposed method, two sideband signals whose frequencies are located at both sides of the drive mode symmetrically, are used to excite the gyroscope, and the response of the gyroscope in the Coriolis force channel is demodulated to obtain the indicator of the frequency split for mode-matching. The input angle rate can still be measured when the proposed mode-matching loop works normally. However, due to the asymmetry of the amplitude of the double-sideband response of the sense mode, there is a tuning error, which leads to a shift of the matching frequency. To eliminate the tuning error and achieve perfect mode-matching, a novel compensation method for the amplitude correction is proposed. The theories of electrostatic tuning of the MEMS DRG, the proposed mode-matching method and the compensation method are analyzed and introduced. The simulation results show that this method can achieve in-run automatic closed-loop mode matching for gyroscopes, and the compensation method can effectively eliminate the tuning error and reduce the frequency split from ~0.5 Hz to < 0.01 Hz. The experimental results show that the bias instability (BI) and the angle random walk (ARW) is improved by 5.8 times and 1.7 times, respectively, under mode-matching. After the tuning error is eliminated with compensation method, the BI and ARW are further reduced to 1.36 °/h and 0.1562 °/
$\surd \text{h}$
, respectively.