Development Of Resonant And Non-Resonant MEMS Gyroscopes Using Commercial Foundry Process And Design Of Compensation Circuitry For Frequency Drift, Quadrature Error And Scale Factor Error

Abstract

MEMS based inertial sensors have found many applications in recent years and demand for robust and accurate sensors is increasing rapidly. MEMS gyroscopes in particular have found many applications from mobile phones to navigation systems and precision robotics, also, there is a need for highly accurate, robust and low-cost sensors. Resonant MEMS gyroscopes utilize the phenomenon of mode matching to achieve high sensitivity but are susceptible to environmental changes and fabrication imperfections. For achieving, the desired performance resonant gyroscopes need error compensation circuitry. Non-resonant gyroscopes use another approach in that they sacrifice the response sensitivity but remain accurate and robust even with drastic environmental changes and fabrication imperfections. Non-resonant gyroscopes can be further categorized based on the number of degree of freedoms in the operational modes and the different transduction mechanisms used. This work proposes a multi DoF non-resonant gyroscope design using electrostatic actuation and capacitive sensing based on the SOIMUMPs commercial microfabrication process. The non-resonant gyroscope was found to be robust in a temperature range of -40 to 100 C, it is also robust to fabrication imperfections and pressure changes. The sensitivity of the gyroscope is found to be 198.9 µV/(◦/s) with a low noise of 0.00328 rad/s/√Hz. In addition to the non-resonant gyroscope, this work also presents the design of resonant gyroscopes with error compensation techniques to minimize the performance loss. The resonant gyroscope has mechanical elements incorporated in the design to minimize frequency mismatch error, scale factor error and the quadrature error. These compensation mechanisms allow the gyroscope to maintain high performance in the presence of error source. Finally, a resonant MEMS gyroscope utilizing the concept of mode localization is presented. The design uses a novel technique for sensing the angular rate to achieve high resolution and is capable of measuring angular rates in micro degree per second which is much better compared to the previously reported designs. The design is also capable of angular rate measurement in the range of ±500 °/s.