Self-oscillation loop design and measurement for an MEMS resonant accelerometer

摘要

This paper provides detailed information about the dynamic model and closed-loop control theory of resonant accelerometer based on electrostatic stiffness. After the resonant accelerometer principle based on electrostatic stiffness has been analyzed, a dynamic model was built. According to the requirement of constant stable vibration amplitude for a different applied acceleration, control equations based on self-sustained oscillation loop technology were also developed for the whole system. By applying the averaging method, the system behaviors were analyzed, and equilibria for the vibration amplitude were achieved. Theoretical analysis and simulation showed that the vibration amplitude became stable and attractive only when the stable criterion was satisfied. Using a PI controller, constant level vibrating amplitude can be achieved when the input acceleration changes. A resonant accelerometer was fabricated using bulk-silicon dissolved process. Under the aforementioned conditions, the accelerometer was driven and tested using a self-sustained oscillation loop. When the sensing voltage was 5 V, the sensitivity was 58 Hz/g, and the resolution was 3.5 mg for a single vibrating beam.