A novel narrow-band force rebalance control method for the sense mode of MEMS vibratory gyroscopes

• We present a novel narrow-band force rebalance control method for MEMS gyroscopes.
• There is no demodulation and modulation components in the control loop.
• Coriolis and quadrature forces are rebalanced simultaneously in one control loop.
• A BPF is adopted as a feedback controller, and the system is stable and robust.
• The bias instability is 5.1 deg/h, bandwidth is 97.2 Hz and nonlinearity is 0.06%.

In this paper, a novel narrow-band force rebalance control method for the sense mode of a MEMS vibratory gyroscope is presented in detail. There is no demodulation and modulation components in the control loop, and a band pass filter is applied as a controller to accomplish the feedback control. The proposed approach possesses the following advantages: (1) the Coriolis force and quadrature force are rebalanced simultaneously in only one control loop; (2) the loop’s noise is suppressed much by the band pass filter; (3) the control system is linear and very simple to realize. Detailed theoretical analyses are performed to acquire the frequency response models of the closed loop system. Experimental results in the frequency domain of force demonstrate that the phase margins approximate to 60 deg, gain margins are larger than 43 dB, sensitivity margins are smaller than 2.5 dB, and the bandwidth is about 97.2 Hz, which accord with those of simulation. Besides, the overshoot of step response is smaller than 10%, and settling time is less than 15 ms. All these stability indexes in frequency domain and time domain verify that the control system is actually feasible and very robust. The scale factor of the MEMS gyroscope with closed loop controlled sense mode is measured to be 71.9 mV/deg/s with nonlinearity of 0.06%, and the bias instability and angle random walk are evaluated to be 5.1 deg/h and 0.21 deg/√h, respectively.

Force rebalance control schematic for the sense.Figure optionsDownload as PowerPoint slide