Design, fabrication and operation of MEMS gimbal gyroscope

In this paper, we present an MEMS gyroscope with double gimbal structure. The device has inner- and outer-gimbals with independent coils (inner- and outer-coils), and the gimbals are perpendicularly supported by torsion bars. In the parallel magnetic field, the reference vibration of the inner-gimbal is introduced by electromagnetic force from the inner-coil and displacement of the outer-gimbal by the Coriolis force is detected by electromotive force at the outer-coil. The device has no critical parts such as narrow gaps or comb drivers, and it requires less accurate alignment of the magnetic field. Since the device can operate in atmospheric pressure, a hermetic seal is not required. For stable operation, the device was combined with a semi-digital control circuit. The circuit has an overtone PLL oscillator, time-shared driving/detecting logic, a kind of adaptive band pass filters. The system showed excellent performance for angular rate detection. Additionally, the characteristics of the device operating in vacuum were also examined.