This paper presents the design, fabrication, and testing of an 80-/spl mu/m-thick, 1.1 mm in diameter high aspect-ratio (20:1) polysilicon ring gyroscope (PRG). The vibrating ring gyroscope was fabricated through the high aspect-ratio combined poly and single-crystal silicon MEMS technology (HARPSS). This all-silicon single-wafer technology is capable of producing electrically isolated vertical electrodes as tall as the main body structure (50 to 100's (/spl mu/m tall)) with various size air-gaps ranging from submicron to tens of microns. A detailed analysis has been performed to determine the overall sensitivity of the vibrating ring gyroscope and identify its scaling limits. An open-loop sensitivity of 200 /spl mu/V/deg/s in a dynamic range of /spl plusmn/250 deg/s was measured under low vacuum level for a prototype device tested in hybrid format. The resolution for a PRG with a quality factor (Q) of 1200, drive amplitude of 0.15 /spl mu/m, and sense node parasitic capacitances of 2 pF was measured to be less than 1 deg/s in 1 Hz bandwidth, limited by the noise from the circuitry. Elimination of the parasitic capacitances and improvement in the quality factor of the ring structure are expected to reduce the resolution to 0.01 deg/s/(Hz)/sup 0.5/.

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A HARPSS polysilicon vibrating ring gyroscope

This review provides a summary of the work completed to date on the nonlinear dynamics of resonant micro- and nanoelectromechanical systems (MEMS/NEMS). This research area, which has been active for approximately a decade, involves the study of nonlinear behaviors arising in small scale, vibratory, mechanical devices that are typically integrated with electronics for use in signal processing, actuation, and sensing applications. The inherent nature of these devices, which includes low damping, desired resonant operation, and the presence of nonlinear potential fields, sets an ideal stage for the appearance of nonlinear behavior, and this allows engineers to beneficially leverage nonlinear dynamics in the course of device design. This work provides an overview of the fundamental research on nonlinear behaviors arising in micro/nanoresonators, including direct and parametric resonances, parametric amplification, impacts, selfexcited oscillations, and collective behaviors, such as localization and synchronization, which arise in coupled resonator arrays. In addition, the work describes the active exploitation of nonlinear dynamics in the development of resonant mass sensors, inertial sensors, and electromechanical signal processing systems. The paper closes with some brief remarks about important ongoing developments in the field.

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Nonlinear Dynamics and Its Applications in Micro- and Nanoresonators

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 describes a procedure for identifying mass and stiffness imperfections present in a microring gyroscope. In general mass and stiffness imperfections will be present as a result of fabrication variances and will contribute to mistuning of the gyroscope. Both mass and stiffness imperfections are treated as perturbations of the ideal isotropic mass and stiffness. The mass and stiffness perturbations are combined to form a structural imperfection, which is shown to be determinable from Nyquist plots of the frequency response functions. An analysis of electrostatic "tuning" is presented and demonstrates that the nonlinear negative spring component produced from a particular arrangement of capacitive electrodes is capable of removing such structural imperfections. If uncorrected the structural imperfections would otherwise result in anisoinertia and anisoelasticity. A comparison between the theoretically predicted tuning voltage and the experimentally derived value is made and shown to be in agreement. The major advantage of electrostatic tuning is that it may be implemented on-chip during operation thus providing active tuning. This is in contrast to the trimming techniques employing laser ablation or focussed ion beam, which may only be done prepackaging.

/pdf/electrostatic-correction-of-structural-imperfections-present-22c84zq5bx.pdf

Electrostatic correction of structural imperfections present in a microring gyroscope

This review provides a summary of the work completed to date on the nonlinear dynamics of resonant micro- and nanoelectromechanical systems (MEMS/NEMS). This research area, which has been active for approximately a decade, involves the study of nonlinear behaviors arising in small scale, vibratory, mechanical devices that are typically integrated with electronics for use in signal processing, actuation, and sensing applications. The inherent nature of these devices, which includes low damping, desired resonant operation, and the presence of nonlinear potential fields, sets an ideal stage for the appearance of nonlinear behavior, and this allows engineers to beneficially leverage nonlinear dynamics in the course of device design. This work provides an overview of the fundamental research on nonlinear behaviors arising in micro/nanoresonators, including direct and parametric resonances, parametric amplification, impacts, selfexcited oscillations, and collective behaviors, such as localization and synchronization, which arise in coupled resonator arrays. In addition, the work describes the active exploitation of nonlinear dynamics in the development of resonant mass sensors, inertial sensors, and electromechanical signal processing systems. The paper closes with some brief remarks about important ongoing developments in the field.Copyright © 2008 by ASME

In this paper, a method employing both parametric excitation and harmonic forcing is applied to the excitation of a micro-ring gyroscope in order to improve its rate resolution performance. A multiple scales perturbation method is used to propose a methodology and this demonstrates the significance of the parametric instability boundary in facilitating the design of the required control strategies. The analysis shows that the 'effective' quality factor of any mode of vibration of the resonator may be increased arbitrarily through parametric excitation. This scheme, when applied to the primary motion of the gyroscope, allows forcing levels to be reduced by several orders of magnitude whilst sustaining the response amplitude. As the parametric excitation and forcing are at different frequencies the excitation scheme proposed minimizes the unwanted effect of electrical 'feedthrough' at the forcing frequency, resulting from parasitic capacitances. Simulation of the oscillator scheme, which is highly nonlinear, is achieved using MATLAB-Simulink and this validates the perturbation analysis. Agreement between the models within 8% is demonstrated. The excitation scheme proposed may be readily applied to many resonant MEMS/NEMS sensors.

A control scheme for a MEMS electrostatic resonant gyroscope excited using combined parametric excitation and harmonic forcing

The principal features of a three-axis ring gyroscope are described. The equations of motion, the response to constant rates of turn, and the relationships between the modes of vibration are derived. Tuned and untuned cases are considered.

Principles of a three-axis vibrating gyroscope

This paper investigates laser ablation as a mechanism for fine tuning the flexural modes of vibration of a slightly imperfect suspended ring. A theoretical analysis of the effect of ablation on the natural frequencies of both in-plane and out-of-plane flexural modes is developed. Contributions made to the frequency shift from the reduced mechanical stiffness and reduced mass, as a result of ablation, are included. A specific cyclic symmetric relationship between the modes of vibration and the ablation configuration permitting multimodal tuning is developed. This relationship is expanded for the particular case of flexural modes of order 2 and 3, which are commonly used in vibrating ring gyroscope designs. For vibrating ring gyroscopes, tuning between certain flexural modes of vibration greatly increases the sensitivity of the device to applied rates of rotation. Therefore, a fine-tuning mechanism is highly desirable.An experimental examination of multimodal tuning using laser ablation is performed...

Multimodal tuning of a vibrating ring using laser ablation

This paper reports the experimental results of parametric amplification applied to a harmonically forced resonant MEMS sensor. In this work parametric amplification of the forced response at resonance in the range 10–100 is investigated for an electrostatically actuated and sensed gyroscopic sensor. Several important factors pertinent to practical exploitation are highlighted. The main obstacle to high gain parametric amplification is the nonlinearity of the electrostatic force which becomes significant for high amplitude vibration. By significantly reducing the harmonic forcing level to just above the noise threshold, parametric amplification of the resonant response by a factor of 80 has been achieved whilst maintaining linear response characteristics. It is shown that parametric amplification modifies the shape of the Nyquist plot of the frequency response function from the conventional circle to that of a pronounced ellipse. This is shown to be due to generally unequal contributions to both the real and imaginary parts of the frequency response function and is related to the relative phase between the two harmonic excitations. Furthermore, the phase transition around resonance is shown to be slower for the parametrically amplified resonator. The relationship between the Q-factor and the bandwidth for the parametrically amplified resonator is investigated and is shown to be significantly different from that of a linear resonator with constant coefficients. A linearized theoretical model is used to confirm and understand these experimental findings. Further experimental tests have also been conducted to investigate the relationship between parametric gain and parametric excitation at the onset of nonlinear dynamic response.

JS Burdess

Papers

Electrostatic correction of structural imperfections present in a microring gyroscope

A control scheme for a MEMS electrostatic resonant gyroscope excited using combined parametric excitation and harmonic forcing

Principles of a three-axis vibrating gyroscope

Multimodal tuning of a vibrating ring using laser ablation

An experimental study of high gain parametric amplification in MEMS