A laterally driven symmetric micro-resonator for gyroscopic applications

Abstract

Conventional microgyroscopes of the vibrating type require resonant frequency tuning of the driving and sensing modes to achieve high sensitivity. These tuning conditions depend on each microgyroscope fabricated, even though the microgyroscopes are identically designed. A new micromachined resonator, which is applicable to microgyroscopes with self-tuning characteristics, is presented. Since the laterally driven two-degrees-of-freedom resonator was designed as a symmetric structure with identical stiffness in two orthogonal axes, the resonator is applicable to vibrating microgyroscopes, which do not need mode tuning. A dynamic model of the resonator was derived considering gyroscopic applications. The dynamic model was evaluated by experimental comparison with fabricated resonators. The resonators were fabricated using a simple process of a single polysilicon layer deposited on an insulator layer. The feasibility of the resonator as a vibrating microgyroscope with self-tuning capability is discussed. The fabricated resonators of a particular design have process-induced non-uniformities that cause different resonant frequencies. For several resonators, the standard deviations of the driving and sensing resonant frequencies were as high as 1232 and 1214 Hz, whereas the experimental average detuning frequency was 91.75 Hz. The minimum detuned frequency was 68 Hz with 0.034 mV s −1 sensitivity. The sensitivity of the microgyroscope was low due to process-induced non-uniformity; however, the angular rate bandwidth was wide. This resonator could be successfully applicable to a vibrating microgyroscope with high sensitivity, if improvements in uniformity of the fabrication process are achieved. Further developments in improved integrated circuits are expected to lower the noise level even more.

Read-out calibration of a SOI capacitive transducer using the pull-in voltage

“…A Maple worksheet is used to solve a set of equations that integrally model the concurrent effect of over-etching on the spring stiffness and the capacitor values (i.e. equations (1), (2), (7) and (8) with added over-etching variable). In doing so, the maple worksheet finds the amount of over-etching that corresponds to the measured pull-in voltage.…”

“…Variations in dimensions of 10% are not uncommon [1,2]. This limits the usefulness of models based on mask dimensions, since actual dimensions will always deviate from mask dimensions, thereby causing changes in key parameters such as resonance frequency [2][3][4], sensitivity, displacement range and damping coefficient.…”

Structural design and experimental characterization of torsional micromachined gyroscopes with non-resonant drive mode

“…To enhance the sensitivity further, the device is packaged in high vacuum, minimizing energy dissipation due to viscous effects of air surrounding the mechanical structure. Extensive research has been focused on the design of symmetric suspensions and resonator systems for mode matching and minimizing temperature dependence [8,9]. However, especially for lightly-damped devices, the requirement for mode matching is well beyond fabrication tolerances, and none of the symmetric designs can provide the required degree of mode matching without feedback control [10,11].…”

Improved Differential Evolution Based on Stochastic Ranking for Robust Layout Synthesis of MEMS Components

“…For example, it is reported in [9] that the width of a typical suspension beam has a fabrication tolerance of about 10%. How to design MEMS that is most insensitive to fabrication process variation is therefore an important issue in MEMS design.…”