This review surveys micromachined gyroscope structure and circuitry technology The principle of micromachined gyroscopes is first introduced Then, different kinds of MEMS gyroscope structures, materials and fabrication technologies are illustrated Micromachined gyroscopes are mainly categorized into micromachined vibrating gyroscopes (MVGs), piezoelectric vibrating gyroscopes (PVGs), surface acoustic wave (SAW) gyroscopes, bulk acoustic wave (BAW) gyroscopes, micromachined electrostatically suspended gyroscopes (MESGs), magnetically suspended gyroscopes (MSGs), micro fiber optic gyroscopes (MFOGs), micro fluid gyroscopes (MFGs), micro atom gyroscopes (MAGs), and special micromachined gyroscopes Next, the control electronics of micromachined gyroscopes are analyzed The control circuits are categorized into typical circuitry and special circuitry technologies The typical circuitry technologies include typical analog circuitry and digital circuitry, while the special circuitry consists of sigma delta, mode matching, temperature/quadrature compensation and novel special technologies Finally, the characteristics of various typical gyroscopes and their development tendency are discussed and investigated in detail

The Development of Micromachined Gyroscope Structure and Circuitry Technology

This paper investigates a novel method for the mode-matched control of a microelectromechanical systems (MEMS) vibratory gyroscope through a phase-domain analysis. Compared with the previous works, the proposed method presents a simple and robust automatic mode tuning scheme for sensitivity enhancement. In designing the mode-matched control loop, the resonant characteristics of the driving axis are used as the reference mode. Then, the phase difference between sense and drive modes at the resonant frequency of drive mode is used to generate a control signal for phase error regulation. For the control loop design, a linear phase-locked loop is adapted. Through the simulation using practical MEMS gyroscope parameters, the mode-matching performance and robustness of the designed control loop is demonstrated. It is also shown that coupling effect yields no degradation of output sensitivity. Finally, the experimental results obtained by implementing the electronics of mode-matched control verify the feasibility of the proposed method.

On the Mode-Matched Control of MEMS Vibratory Gyroscope via Phase-Domain Analysis and Design

A MEMS gyroscope includes: a microstructure having a fixed structure, a driving mass, movable with respect to the fixed structure according to a driving axis, and a sensing mass, mechanically coupled to the driving mass so as to be drawn in motion according to the driving axis and movable with respect to the driving mass according to a sensing axis, in response to rotations of the microstructure; and a driving device, for keeping the driving mass in oscillation with a driving frequency. The driving device includes a discrete-time sensing interface, for detecting a position of the driving mass with respect to the driving axis and a control stage for controlling the driving frequency on the basis of the position of the driving mass.

Microelectromechanical gyroscope with position control driving and method for controlling a microelectromechanical gyroscope

Analog-to-digital converters based on sigma–delta modulators ( $\Sigma \Delta {\mathrm{ M}}$ ) are a popular choice for high resolution conversion from the analog to the digital domain. With relatively small modifications, they can also be used as electromechanical $\Sigma \Delta {\mathrm{ M}}$ (EM- $\Sigma \Delta {\mathrm{ M}}$ ) force feedback interfaces for capacitive micro-electromechanical systems (MEMSs) inertial sensors. Such interfaces are able to combine the benefits of force feedback and analog-to-digital conversion at relatively modest circuit cost. This paper provides a comprehensive review of EM- $\Sigma \Delta {\mathrm{ M}}$ interfaces for capacitive MEMS inertial sensors. The principle and the design methodology of EM- $\Sigma \Delta {\mathrm{ M}}$ interfaces are introduced. A classification of EM- $\Sigma \Delta {\mathrm{ M}}$ accelerometers and gyroscopes is presented, and a detailed analysis of different EM- $\Sigma \Delta {\mathrm{ M}}$ architectures is given. The most representative EM- $\Sigma \Delta {\mathrm{ M}}$ inertial sensors systems are discussed and compared with regard to their performance characteristics. In particular, the properties of various discrete and continuous-time techniques and a system parameter optimization methodology are illustrated through specific examples. Finally, current challenges and future development trends of EM- $\Sigma \Delta {\mathrm{ M}}$ interfaces for inertial sensors have been identified.

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Electromechanical Sigma–Delta Modulators ( $\Sigma \Delta {\mathrm{ M}}$ ) Force Feedback Interfaces for Capacitive MEMS Inertial Sensors: A Review

In the current times, microelectromechanical systems and nanoelectromechanical systems form a major interdisciplinary area of research involving science, engineering, and technology. A lot of work has been reported in the area of modeling and control of these devices, with the aim of better understanding their behavior and improving their performance. This paper presents a review of the emerging advances in the modeling and control of these micro- and nanoscale devices and converges on the exciting research in on-chip control , with a mechatronics and controls perspective and concludes by projecting future trends.

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A Survey of Modeling and Control Techniques for Micro- and Nanoelectromechanical Systems

This paper describes the design of the control loops in a z-axis, MEMS vibrational gyroscope operating in a vacuum enclosure. In this device, a silicon mass is driven through electrostatic actuator so that it has a sinusoidal linear motion, with a controlled speed. The design of a suitable controller, capable of maintaining the required speed and with prescribed restoring capabilities after shocks is briefly described in the paper. Attached to the driving mass, a second mass, free to move in the direction orthogonal to the motion of the first mass, is subjected to a Coriolis force, proportional to the product of the first mass speed by z-axis rotational speed. The sensing of the Coriolis force and, in turn, of the z-axis rotational speed, is performed in closed loop fashion, with a 1-bit quantized actuation. The restoring force that brings the motion of the second mass to zero is equivalent to the output bit stream of a band-pass sigma-delta converter and contains the information of the Coriolis force. The design of this second control loop and a detailed analysis on the signal-to-noise ratio achievable with the proposed design is reported.

G.S. Durante

Papers

Control of a Z-axis MEMS vibrational gyroscope