Experimental Research On The Digitized Driving Circuit And Vibration Characteristics Of MEMS Vibrating Gyroscope

With the advances in micro-electromechanical systems(MEMS)technology,inertial sensing devices has been greatly developed and become one of the most widely used MEMS devices.MEMS vibrating gyroscope is one of the mainstream types of inertial sensors.This kind of MEMS gyroscope can be used to measure the acceleration of the system.The velocity and displacement of the system can be further calculated to realize the precise positioning.It is widely applicated in aerospace,military and consumer electronics fields.MEMS vibrating gyroscopes works in a resonant mode.Obtaining working resonant mode with high quality is key to improve the performance of MEMS vibrating gyroscope.Therefore,high frequency resolution of driving signal is requested to find the accurate resonant frequency.And stable and adjustable amplitude of the driving signal is requested as well to ensure that the gyroscope generates large enough vibration.In this dissertation,the driving method and principle of MEMS vibrating gyroscope are studied and explained.A PZT piezoelectric gyroscope is studied as the research object.A driving circuit is designed according to the gyroscope driving principle.The driving circuit is combined with the digital control of Field Programmable Gate Array(FPGA)embedded system.And the direct digital synthesis(DDS)and automatic gain control technology(AGC)technology are used to achieve the output signal frequency and amplitude accurately adjustable in the driving circuit.According to the working principle of MEMS vibrating gyroscope,the driving signal required by the gyroscope can be generated from DDS block and the signal frequency can be adjusted accurately with the digital signal control of FPGA.By changing the DDS frequency control bits through the FPGA,the resolution of signal frequency can reach 0.1Hz.The amplitude of the driving signal is controlled by AGC.The resolution of signal amplitude can reach 0.01 V and the gain time can be 0.1.The DAC block is controlled by FPGA to change the AGC gain control voltage,thereby controlling the amplitude of driving signal.The precise and adjustable driving signals are transmitted to the driving electrodes of MEMS gyroscope,which will excite a vibration mode of gyroscope.The induced charge is generated by the sensing electrodes of the gyroscope and amplified by the charge amplifiers to observe the vibration of the gyroscope.Based on the MEMS vibration gyroscope driving circuit designed and implemented in this paper,the vibration characteristics of MEMS vibration gyroscope is experimentally studied.And the influence of the driving signal on the vibration quality factor and linearity of the gyroscope are obtained.In this paper,the characteristics about the resonance frequency,quality factor and linearity of the MEMS vibrating gyroscope were analyzed through the driving experiments.In the experiment,the resonance frequency of the gyroscope is between 330-332 kHz,which changes according to the driving signal.The resonance frequency decreases with the increase of the amplitude of driving signal.The amplitude of the driving signal has a linear relationship with the induced charge of the gyroscope.The quality factor of the gyroscope decreases first and then increases with the amplitude of driving voltage increases in this experiment.The optimized driving scheme for MEMS vibrating gyroscope and vibration characteristics are obtained in this paper.The research results provide a theoretical reference for the proper excitation of MEMS vibrating gyroscope.