14 November 1997 Laterally self-oscillated and force-balanced microvibratory gyroscope packaged in a vacuum package with a conditioning ASIC
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Abstract
A novel concept self-oscillator and dynamically tunable micro vibratory gyroscope, where oscillating, position- sensing and force-balancing take place on the wafer surface, has been developed. The gyroscope consists of: a grid-type planar mass which oscillates on the wafer surface; pairs of the differential capacitor type with LT shape position sense electrodes; a pair of force-balancing electrodes; oppositely placed comb-drive and comb-sensor for mass self-oscillation; fish hook shape springs to match the first and second modes with the mass oscillating and position sensing modes, respectively. The natural frequency of the position sensing mode is lowered and tuned by the DC bias voltage applied to the position sense electrodes and then finely tuned by DC bias on a pair of force-balancing electrodes. To reduce the mass exciting along the sensing direction, we drive the mass by the same DC and opposite AC driving voltage on the oppositely placed comb-drives. It also features that the position sensing electric interference ins reduced. The mass is self-oscillated by the condition of limit cycle, so the mass is always oscillated in the natural frequency even if the natural frequency is varied by the environment and/or it has displacement-force nonlinear behavior. The gyroscope is fabricated on the silicon wafer by surface micromachining technology and the polysilicon is used as an active structure. The gyroscope has an active size of 700 by 600 micro meters, the thickness of the structure is 7 micron meters and the proof mass of 1 micro gram. To improve the resolution of the gyro, it is packaged in the 50 mili-torr vacuum package with a conditioning ASIC. Experimental results show that the gyroscope has the equivalent noise level of 0.1 deg/sec at 2 Hz, the bandwidth of 100 Hz, linearity of 1 percent FS and the sensing range of 90 deg/sec.
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Kyu-Yeon Park, Kyu-Yeon Park, Chong-Won Lee, Chong-Won Lee, Yong-Soo Oh, Yong-Soo Oh, Byeungleul Lee, Byeungleul Lee, } "Laterally self-oscillated and force-balanced microvibratory gyroscope packaged in a vacuum package with a conditioning ASIC", Proc. SPIE 3242, Smart Electronics and MEMS, (14 November 1997); doi: 10.1117/12.293579; https://doi.org/10.1117/12.293579
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