Research On The Stability Of Closed-loop Oscillation System For Micro Silicon Resonant Accelerometer

Micro Silicon resonant accelerometer is a new type of micro inertial device which based on MEMS technology. It has the features such as small volume, low power consumption, high sensitivity, and large dynamic range and so on, which is suitable for high precision navigation system. Thus it has a wide application prospect.The research based on the stability of oscillation circuit for micro silicon resonant accelerometer has carried out in this paper, which includes the modeling of electromechanical interface for accelerometer, the approach to control the amplitude of the closed-loop oscillation circuit based on nonlinear control theory, the analysis of phase stability for oscillator and circuit design.Firstly, the operating principle of Micro Silicon micro resonant accelerometer has been analyzed, which described the transformation mechanism for the signals of accelerometer, and derived the equivalent circuit parameters for the resonator. Based on the analysis of the parasitic capacitance which has the influence on the accelerometer, the circular diode interface circuit was applied to instead the traditional cross resistance type interface circuit, which has improved the interface circuit. On this basis, the equivalent model establishment for the electromechanical interface of the accelerometer has completed based on Cadence software, which achieved the closed-loop simulation of accelerometer and the oscillator circuit.Secondly, the approach to control the amplitude of the closed-loop oscillation circuit based on nonlinear control theory has been studied. According to the interface circuit based on the displacement control, the main factors which affected the amplitude have been analyzed, and the close loop control model on amplitude for the entire oscillator circuit has been established. It has study the concrete realization approach for the amplitude control based on the principle of the automatic gain control has been studied, while its effect on the noise of the amplitude has been analyzed.Thirdly, the mechanism of electrical noise to the phase interference of the carrier signal has been expounded. The linear and nonlinear factors which influenced the oscillator phase noise have been analyzed. The noise from the interface and the resonator amplitude that affect the phase noise have been verified by the experiment, which further guide the design of oscillating circuit.Finally, based on the aforementioned research content, the optimal design of the silicon micro-accelerometer resonant oscillation circuit has achieved, and the performance tests have carried out for the SRA measurement system according to IEEE standard of accelerometer. The test results show that the1σ bias stability for the designed accelerometer is 51.2μg, the scale stability is 28.2ppm, the zero bias stability is 4.8μg, and the resolution is 15.9μg/Hz while the bandwidth is within 100Hz. Through the comprehensive performance test, the performance parameters obtaining for the SRA measurement system has realized, which provides the evidence for the subsequent improvement design.