Study Of Digital Detection Technology For Piezoelectric Micromachined Modal Gyroscope Based On FPGA

Piezoelectric Micromachined Modal Gyroscope(PMMG)researched in this paper is a kind of solid-state angular rate sensor,which is based on high order resonant mode of a piezoelectric body as its reference vibration.It utilizes the piezoelectric effect as detection principle and the inverse one as driving principle.Compared with the general vibratory micro gyroscope,PMMG not only can resist shock and shake,but also has no specifically requirement for vacuum packaging.So it can be widely used in many fields.In the study of the PMMG,driving and detection are the two important aspects.Based on the working principle of the PMMG,the closed-loop driving circuit board is optimized.The optimization mainly includes bandpass filter circuit and single-to-differential amplifier circuit.The whole driving circuit PCB board is also redesigned,which can track working frequency fast and provide sinusoidal driving signal with a stable amplitude.To meet the requirement of data acquisition and algorithm of PMMG,firstly building the PMMG output signals model and verifying the validity of the detection algorithmin in resonance condition by Matlab.The results from Matlab is useful for FPGA programming.A design of digital detection system with both high precision and high sampling rate based on FPGA is completed.The principle and approach are presented,which include hardware circuits design,AD sampling sequences control,digital signal processing based on FPGA and the realization of RS-232 communication protocol etc.The whole detection system is simulated by Modelsim.The main control chip is FPGA chip XC6SLX25 from Xlinx and the AD chip is AD7960(18-Bit,5MSPS)from ADI.Experiment results show that the system can acquire three output signals of the gyroscope at the same time,and send the processed data to PC for displaying and storing.The measured frequencies stabilize around 349.89 kHz.The fluctuating range is 8 Hz.The mean square error of reference voltage Vpp is 0.004 V.The detection system is stable and precise.This digital detection circuit can be well applied for MEMS microgyroscope signal processing and enhance the stability and anti-jamming of microgyroscope.