The Realization Of Vibratory MEMS Gyroscope Digital Signal Processing System

MEMS vibratory gyroscope which is used to sense angular velocity, is widely used in many fields for its small size, light weight and low cost. With the development of the MEMS technology, the requirements to the performance of gyroscope improves too. The technique of gyroscope signal processing is maturity. The noise and temperature drift of analog processing circuit itself, have limited the usage of MEMS gyroscope. To overcome these shortcomings, digital processing is researched and accepted.In this paper, digital processing is selected to realize the gyroscope signal processing in FPGA and DSP, based on the analog processing circuit. The major work of this thesis contains:(1)Digital processing system of vibratory gyroscope output signal contains two modes, drive feedback mode and angular velocity demodulation mode. The drive feedback mode is used to keep the amplitude and frequency of the feedback signal used as the input of the vibratory gyroscope. The angular velocity demodulation mode realizes the demodulation of the input modulated signal and outputs the input angular velocity. This paper analyses the principle of these two modes, and gives the way of realization.(2)The digital system realizes the carrier wave, drive feedback demodulation and sense demodulation based on FPGA. The carrier wave is accomplished by improved CORD1C algorithm, with phase precision of 32 bits. Drive feedback demodulation and sense demodulation are accomplished using the CORDIC carrier wave .Through a series of MATLAB simulations, the improved bandpass filter, lowpass filter, phase filter, auto gain control part and angular velocity demodulation part are attained in DSP.(3)The performance of every part of the digital processing system is tested, containing the carrier wave, the signal before and after drive feedback demodulation, the signal before and after angular velocity demodulation and the feedback drive signal.(4)Test result of the SNR of the carrier wave is above 104dB, the SNR improvement of the drive feedback demodulation is 14.5dB and the SNR improvement of the sense demodulation is 11.225dB. The scale factor of the tested gyroscope is 2.9398mV/deg/sec, and the zero input bias instability is about 329deg/h.