Smart Sensor Systems: Emerging Technologies and Applications

Chapter 5Low-Power Vibratory Gyroscope Readout

Chinwuba Ezekwe¹ and Bernhard Boser²

¹Robert Bosch, Palo Alto, California, USA

²Berkeley Sensor & Actuator Center, University of California, Berkeley, USA

5.1 Introduction

Inexpensive MEMS gyroscopes are enabling a wide range of automotive and consumer applications. Examples include image stabilization in cameras, game consoles, and improving vehicle handling on challenging terrain. Many of these applications impose very stringent requirements on power dissipation. For continued expansion into new applications it is imperative to reduce power consumption of present devices by an order-of-magnitude.

Gyroscopes infer angular rate from measuring the Coriolis force exerted on a vibrating or rotating mass. For typical designs and inputs, this signal is extremely small, requiring ultralow noise pickup electronic circuits. This low noise requirement directly translates into excessive power dissipation.

This chapter describes a solution that exploits mechanical signal amplification using a technique called mode-matching. The electronic circuit continuously senses the resonance frequency of the mechanical sense element and electrically tunes it to maximize the output signal. A new and robust feedback controller is used to accurately control the scaling factor and bandwidth of the gyroscope while at the same time guaranteeing stability in the presence of undesired parasitic resonances.

5.2 Power-Efficient Coriolis Sensing

After a brief ...