Research Of Mode-matching Control Methods For Silicon MEMS Resonant Gyroscope

Silicon MEMS gyroscope is an inertial sensors that used to measure angular velocity according to the Coriolis effect.With the development of MEMS technology,the gyroscope is widely used in many fields thanks to the advantages of small size,light weight,low cost,low power consumption,easy integration and mass production and so on.Due to the limitations of the micro-mechanical machined technology and the interference of environmental factors,there is a performances difference between theoretical designed and actual produced gyroscope,wherein the difference in resonant frequency will lead to gyroscope's mode-mismatch,which has a very large impact on the overall performance of the gyroscope.Therefore,mode-matching control is used to reduce the frequency difference between the drive and sense modes to achieve mode matching and improve the gyroscope's scale factor,bias instability,angular random walk(ARW)and other performance,which has significant research value.In this paper,a sixteen-sided gyroscope(cobweb-like DRG)with sense force feedback,quadrature stiffness suppressing and frequency tuning electrodes is selected.Various mode matching methods are proposed and corresponding control systems are designed.The main research work of this paper is as follows.After the principle analysis of mode matching method based on phase-frequency characteristics of quadrature error,an improved mode matching method based on combining quadrature stiffness suppressing and phase-frequency characteristics is proposed using the phase characteristics of quadrature error in mode-matching process.These control methods were simulated by the simulink model and tested by the FPGA digital control circuit.The stability experiment results show that the proposed improved method improves the stability of frequency tuning voltage by 3.8 times.A mode matching method based on resonant frequency difference is proposed.It is simulated by simulink model and tested by FPGA digital control circuit.The frequency difference within±0.05Hz is achieved and the tuning voltage settling time is only 0.6s through this mode-matching method.A real-time mode-matching method based on phase characteristics of virtual Coriolis force is designed to make the mode matching closed loop could work normally even when input angular rate is exist.In order to achieve a larger measurement range,the corresponding Coriolis force feedback closed loop based on this mode-matching method is also designed.The performance of the gyroscope is measured in three working modes:mode-mismatched open-loop detection,mode-matched open-loop detection,and mode-matched closed-loop detection.The results show that the best overall performance,that is,the scale factor is 76mV/°/s,the nonlinearity is 0.0517%,the measurable range is over±31°/s,the bias instability is as low as 2.3°/h,and the ARW is as low as 0.25°/Vh,which is acquired by the mode-matched closed-loop detection.