A novel oscillation control for MEMS vibratory gyroscopes using a modified electromechanical amplitude modulation technique

Abstract

This paper reports a novel oscillation control algorithm for MEMS vibratory gyroscopes using a modified electromechanical amplitude modulation (MEAM) technique, which enhances the robustness against the frequency variation of the driving mode, compared to the conventional EAM (CEAM) scheme. In this approach, the carrier voltage exerted on the proof mass is frequency-modulated by the drive resonant frequency. Accordingly, the pick-up signal from the interface circuit involves a constant-frequency component that contains the amplitude and phase information of the vibration displacement. In other words, this informational detection signal is independent of the mechanical resonant frequency, which varies due to different batches, imprecise micro-fabrication and changing environmental temperature. In this paper, the automatic gain control loop together with the phase-locked loop are simultaneously analyzed using the averaging method and Routh–Hurwitz criterion, deriving the stability condition and the parameter optimization rules of the transient response. Then, a simulation model based on the real system is set up to evaluate the control algorithm. Further, the proposed MEAM method is tested using a field-programmable-gate-array based digital platform on a capacitive vibratory gyroscope. By optimizing the control parameters, the transient response of the drive amplitude reveals a settling time of 45.2 ms without overshoot, according well with the theoretical prediction and simulation results. The first measurement results show that the amplitude variance of the drive displacement is 12 ppm in an hour while the phase standard deviation is as low as 0.0004°. The mode-split gyroscope operating under atmospheric pressure demonstrates an outstanding performance. By virtue of the proposed MEAM method, the bias instability and angle random walk are measured to be 0.9° h−1 (improved by 2.4 times compared to the CEAM method) and 0.068° (√h)−1 (improved by 1.4 times), respectively.

Effect of circuit phase delay on bias stability of MEMS gyroscope under force rebalance detection and self-compensation method

“…Figure 2 shows a block diagram of the overall control system used in this paper, including an FPGA and analog circuitry. The drive mode control system consists of a classical automatic gain control (AGC) and PLL control [14]. AGC is used to keep the vibration displacement amplitude A x constant.…”

Novel on chip rotation detection based on the acousto-optic effect in surface acoustic wave gyroscopes

“…The expected theoretical values for the SFs can be obtained directly from Eqs. (8), (9) and (14) as SF PP-MZI = 58 nV / ( o /sec) and SF RT = 20 nV / ( o /sec). Since the two SAW resonators behave identically for both AOGs, the theoretically predicted ratio between the two SFs can be calculated as the ratio between the two gain factors (see Fig.…”

MEMS Gyroscope Automatic Real-Time Mode-Matching Method Based on Phase-Shifted 45° Additional Force Demodulation

“…There were two pairs of plate electrodes in the gyroscope sense mode; one pair was used as sense detection electrodes, one of the other pair was used as a tuning electrode, and the other was used to apply the 45° additional force signal . In addition, the drive-mode control system used the traditional PLL + AGC method [ 22 , 23 ], where the reference amplitude of the drive-mode displacement was set to 0.05 V. The Coriolis response detection method for the sense mode used open-loop detection. After relevant measurements, the value was set to 0.1 V, so that .…”