Laterally oscillated and force-balanced micro vibratory rate gyroscope supported by fish-hook-shaped springs

A new concept for a micro vibratory rate gyroscope supported by fish-hook-shaped springs, where the oscillating position sensing and force balancing take place on the wafer surface, has been developed. The gyroscope consists of a grid-type planar mass, LT-shaped position-sensing electrodes to detect the Coriolis motion, pairs of force-balancing electrodes to improve the linearity and dynamic range, prominence-shaped comb-drive electrodes to improve the resolution by increasing the oscillating displacement, and fish-hook-shaped springs to match the first and second modes with the mass oscillating and position-sensing modes, respectively. Due to the relatively high stiffness of the proposed fish-hook-shaped springs except in the desired directions, the gyroscope tends to be quite insensitive to environmental vibrations or shocks, maintaining the electromechanical stability. Also the resonance frequencies associated with lateral vibration modes are independent of the change in thickness of the polysilicon structure, which guarantees a uniform sensitivity of the products. Experimental results show that the gyroscope has an equivalent noise level of 0.1 degrees s(-1) at 2 Hz, a bandwidth of 100 Hz, and a dynamic range of 90 degrees s(-1). (C) 1998 Elsevier Science S.A.