Design of a MEMS Gyroscope for Absolute Angle Measurement

University Of Minnesota-Twin Cities, Minneapolis MN

Investigators

Abstract

MEMS gyroscopes are typically designed to measure angular rate of rotation. A measurement of the angle itself is useful in many applications but cannot be obtained by integrating the angular rate due to the presence of bias errors which cause a drift. This project develops an innovative design for a vibrating gyroscope that can directly measure both angle and angular rate. The proposed design is based on the principle of measuring the angle of free vibration of a suspended mass with respect to the casing of the gyroscope. The design incorporates a nonlinear feedback control system in order to address two critical challenges. First, the control system compensates for dissipative forces and keeps the mass vibrating at a constant level of energy. Second, the control system compensates for the rotary cross-coupling that occurs due to the non-ideal nature of the suspending springs. The control system is carefully designed so that it does not affect the free vibration nature of the mass and does not alter the Coriolis forces which play an important role in the measurement of angular rate. The project includes a three-phase work plan for design and in-house fabrication of the vibratory gyroscope in the University of Minnesota's Microtechnology Laboratory (MTL). The significance of the project is that it breaks new ground by introducing sophisticated control systems into the MEMS domain. The use of advanced control techniques leads to a new sensor making the measurement of a new variable (absolute angle) possible. On a lesser note, several techniques developed in the project have wide applicability to vibratory sensor design in general and would lead to technical improvements in accelerometers, rate gyroscopes and microbalances. The educational objectives of the project include curriculum development, promotion of cross-disciplinary skills, and development of benchmark models for web-based education.