A robust triangular-electrode based capacitive detection method for MEMS gyroscopes
This paper presents a robust triangular-electrode based (TEB) capacitive detection method for MEMS gyroscopes. The TEB method utilizes the inherent nonlinearity of TEB variable-area sense capacitor to measure the amplitude and the phase of mechanical motion, and the derived amplitude and phase are independent of such system parameters as the carrier voltage, the nominal sense capacitance, the gain or phase shift in C/V circuit. As a result, gyroscope outputs and their scale factor are robust to system parameter fluctuations using TEB method. Working principles and robustness are compared between linear-EAM method and TEB method to manifest the superiority of TEB method. Finally, the TEB method is implemented in an FPGA-based PCB with a MEMS gyroscope. Experimental results verify the theoretical analysis and demonstrate that the sensitivity of the scale factor on carrier voltage variations is highly suppressed up to 99.77% using TEB method. In addition, the offset drift of gyroscope output on circuit phase shift variations is greatly suppressed up to 99.96% by virtue of TEB control. Allan variance analysis demonstrates a bias instability of 4.0 °/h, and an ARW of 0.32 °/√h at atmosphere.