Closed-Loop Operation of a High-Q Silicon MEMS Quatrefoil Suspension Gyroscope

This paper reports on the closed-loop operation of a MEMS quatrefoil suspension gyroscope (QSG) using customized board-level electronics for readout, control, and signal conditioning. The gyroscopic operation is demonstrated by driving one of the secondary degenerate elliptical modes of the structure while forcing the in-phase and quadrature components of the other elliptical mode to zero at an operating frequency of ~426 kHz in a mode-matched configuration. Both modes demonstrate quality factors of over a million. The closed-loop operation overcomes the limitations of open-loop sense mode operation by extending the system bandwidth and dynamic range while enabling significant improvements in scale factor linearity relative to open-loop operation. An electrostatic frequency tuning method was used to implement mode matching. In closed-loop operation, the gyroscope demonstrates an angle random walk (ARW) of 0.09 °/√hr and bias instability (BI) of 0.25 °/hr, comparable with the specifications of other reported high-end MEMS gyroscopes.