Research And Relevant Design Of Vibrating Ring MEMS Gyroscope

Gyroscope is a kind of the inertial sensors using for measuring angular rate of rotating objects. Microelectro mechanical system (MEMS), which is becoming a more and more mature technology, has brought the revolutionary progress to inertial sensors. Due to the advantages of small volume, light weight, low power consumption, strong ability of resisting overload and low price, MEMS gyroscopes have been widely used in many fields such as the automobile electronics, consumer electronics, defense science and technologies. At the same time, various performance requirements have also been raised for MEMS gyroscopes.Mechanical structure, signal interface system and driving system are three main components of MEMS gyroscope, and the performance of MEMS gyroscope has been essentially restricted by electronic noises introduced in the signal interface and the driving system. Sigma-Delta modulation technology adopting the oversampling and noise-shaping techniques provides an effective approach for the noise optimization and digital signal processing loop realization.The mechanical characteristics of MEMS gyroscopes has been investigated in this thesis first. Based on the focused analysis of the mechanical structure and characteristics of MEMS vibrating ring gyroscope, the calculation model of the resonant frequency and the electronic model have been established, and some effective approaches for sensitivity improvement have also been presented. Then, a closed-loop Sigma–Delta force-feedback interface system has been presented, which contains the C/V readout circuit, the discrete-time transfor function of the mechanical structure, the stability of the system and the noise-shaping module. The driving system of MEMS gyroscopes has been studied finally. A third-order cascade Sigma-Delta modulator based on the CIFB structure has been successfully designed to solve the problems of the integrators saturation and the signal distortion, and can be used in the driving system. The behavioral simulation of the designed Sigma-Delta modulator was performed by using Matlab Simulink. At an oversampling rate of 128 and an input signal bandwidth of 50 KHz, the modulator achieves a signal-to-noise ratio of 102.9 dB and an accuracy of 16.80 bits, indicating that the designed Sigma-Delta modulator can meet the requirments of data processing in the driving system of MEMS gyroscopes.