Design and performance test of a MEMS vibratory gyroscope with a novel AGC force rebalance control

Abstract

In this paper, the development and performance test results of a laterally oscillating MEMS gyroscope using a novel force rebalance control strategy are presented. The micromachined structure and electrodes are fabricated using the deep reactive ion etching (DRIE) and anodic wafer bonding process. The high quality factor required for the resonance-based sensor is achieved using a vacuum-sealed device package. A systematic design approach of the force rebalance control is applied via a modified automatic gain control (AGC) method. The rebalance control design takes advantages of a novel AGC loop modification, which allows the approximation of the system's dynamics into a simple linear form. Using the proposed modification of AGC and the rebalance strategy that maintains a biased oscillation, a number of performance improvements including bandwidth extension and widened operating range were observed to be achieved. Finally, the experimental results of the gyroscope's practical application verify the feasibility and performance of the developed sensor.

A novel control loop design and its application to the force balance of vibratory rate sensor

“…In order to compensate for this, a nonlinear function η(⋅) is employed in the inner feedback loop as shown in Fig. 3 [13]. The characteristic of η(⋅) is to normalize the amplitude of an input oscillating signal with a unit gain with no input-output deviation on frequency and phase terms.…”

“…There has been a number of works to adopt the force balance strategy into angular rate sensor developments and during last decades, it has been succeedingly applied to micromachined vibratory rate sensors. Various papers addressing force balance control of vibratory rate sensors have been published [1][2][3][4][5][6][7][8][9][10][11][12][13]. For instance, the control algorithm is implemented in an adaptive control scheme in [4,5].…”

“…In this background, it was fortified a motivation to attain a simple realization of the control loop for vibratory rate sensors. For a simple implementation, in particular, the studies in [3,13] adopted automatic gain control (AGC) scheme for the rate sensor's dynamics control. Through a comprehensive adaptation of AGC technique to vibratory rate senror [3,17], [13] presented seminal results regarding operating principle, control strategy, fabrication and experiment.…”

“…In this paper, a continued work to incorporate the AGC scheme to a vibratory rate sensor is done by considering further essential factors that are untouched in [13]. First, noise effect on the loop is considered since the control circuit is composed of several highly nonlinear elements.…”

Modeling Of Structural And Environmental Effects On Microelectromechanical (Mems) Vibratory Gyroscopes

“…Usually gyroscope displacement measurement varies under open loop scheme which can cause undesirable performance characteristics such as scale factor nonlinearity, limited dynamic range and narrow bandwidth [9]. In MEMS gyroscopes, manufacturing imperfection and noises often exist which negatively influence the resolution and performance.…”