Design and Development of Control Electronics for Coriolis Vibratory Gyroscopes

Abstract

Gyroscopes are physical sensors used to detect and measure the angular motion of an object with respect to an inertial frame of reference. In this paper, emphasis is given to vibratory gyro, which is based on vibration that occurs within the sensor. When an external force is applied to vibratory gyro, a new vibration is produced within the sensor in perpendicular direction, which helps us in calculating the angular rate. Ring Vibratory Gyro (RVG) falls under the category of Coriolis Vibratory Gyro (CVG). Due to piezoelectric effect, the beams of the gyro are activated and this helps to sense the vibrating ring in this novel gyroscope. The gyro structure consists of a substrate, eight supporting beams of thin shape and a vibrating ring. There are two modes of vibration that are coupled by the coriolis force dynamics - drive mode and sense mode. The drive mode comprises two sections - one to track the resonant frequency and the other to keep the vibration amplitude constant. The analog signals from piezo-electric elements are amplified and filtered to send them again to the sensor. The drive mode is excited by the excitation control loop, which keeps the amplitude constant. In the open-loop mode of operation, the drive mode is excited by a force of a prescribed amplitude. Inertial rotation about the input axis then results in the excitation of the second mode (the sense mode). The amplitude of the sense mode vibration is proportional to the input angular rate. The model of CVG is established in Simulink environment. In this paper, the control electronics for the drive mode of MEMS type CVG is presented. An amplitude controller is employed in the drive loop for maintaining constant amplitude and a frequency control loop for tracking frequency with the inclusion of a reliable scheme of demodulation.