Abstract
A miniature vacuum-packaged silicon microgyroscope (SMG) with symmetrical and decoupled structure was designed to prevent unintended coupling between drive and sense modes. To ensure high resonant stability and strong disturbance resisting capacity, a self-oscillating closed-loop circuit including an automatic gain control (AGC) loop based on electrostatic force feedback is adopted in drive mode, while, dual-channel decomposition and reconstruction closed loops are applied in sense mode. Moreover, the temperature effect on its zero bias was characterized experimentally and a practical compensation method is given. The testing results demonstrate that the useful signal and quadrature signal will not interact with each other because their phases are decoupled. Under a scale factor condition of 9.6 mV/°/s, in full measurement range of ± 300 deg/s, the zero bias stability reaches 15°/h with worse-case nonlinearity of 400 ppm, and the temperature variation trend of the SMG bias is thus largely eliminated, so that the maximum bias value is reduced to one tenth of the original after compensation from -40 °C to 80 °C.
Highlights
The silicon microgyroscope (SMG) is an important kind of sensor found in inertial instruments that are widely used in aerospace measurement, balance control, and vehicle navigation systems
A SMG with the structure of changing-area capacitor detection is adopted in this paper, and the quality factor of a SMG in two modes is above 10,000, so its sense mode detection essentially attains better linear performance and high sensitivity
The bandwidth of SMG is approximately decided by the designed frequency difference between drive and sense modes
Summary
The silicon microgyroscope (SMG) is an important kind of sensor found in inertial instruments that are widely used in aerospace measurement, balance control, and vehicle navigation systems. In most of the literature drive mode circuitry designs of AGC and PLL (Phase Lock Loop) modules have been independently or simultaneously used to attain a certain performance [4,5,6]. On this basis, a simplified drive circuit with a combination of AGC and modulation technologies was investigated to achieve a high SNR (Signal Noise Ratio) and good performance. Open-loop detection is favorable for design simplification and to accomplish the integration and miniaturization of the measurement-control circuit, which can basically meet the specification requirements of low-precision SMGs, and has been successfully applied in many reports [2,3]. Though some gyroscopes in the literature [7,8] use single channel closed-loops or double-channel closed-loops without modulation of high frequency carrier signal, it is very difficult for a separate charge amplifier to measure a minor varying signal due to some large existing unquenchable parasite signals
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