Design and Analysis of a High-Gain and Robust Multi-DOF Electro-thermally Actuated MEMS Gyroscope

Abstract

This paper presents the design and analysis of a multi degree of freedom (DOF) electro-thermally actuated non-resonant MEMS gyroscope with a 3-DOF drive mode and 1-DOF sense mode system. The 3-DOF drive mode system consists of three masses coupled together using suspension beams. The 1-DOF system consists of a single mass whose motion is decoupled from the drive mode using a decoupling frame. The gyroscope is designed to be operated in the flat region between the first two resonant peaks in drive mode, thus minimizing the effect of environmental and fabrication process variations on device performance. The high gain in the flat operational region is achieved by tuning the suspension beams stiffness. A detailed analytical model, considering the dynamics of both the electro-thermal actuator and multi-mass system, is developed. A parametric optimization is carried out, considering the microfabrication process constraints of the Metal Multi-User MEMS Processes (MetalMUMPs), to achieve high gain. The stiffness of suspension beams is optimized such that the sense mode resonant frequency lies in the flat region between the first two resonant peaks in the drive mode. The results acquired through the developed analytical model are verified with the help of 3D finite element method (FEM)-based simulations. The first three resonant frequencies in the drive mode are designed to be 2.51 kHz, 3.68 kHz, and 5.77 kHz, respectively. The sense mode resonant frequency is designed to be 3.13 kHz. At an actuation voltage of 0.2 V, the dynamically amplified drive mode gain in the sense mass is obtained to be 18.6 µm. With this gain, a capacitive change of 28.11 fF and 862.13 fF is achieved corresponding to the sense mode amplitude of 0.15 sans-serifμnormalm and 4.5 sans-serifμnormalm at atmospheric air pressure and in a vacuum, respectively.

Review of Electrothermal Actuators and Applications

“…One more possible application of chevron actuators is the vibratory MEMS gyroscope designed recently in [85]. Electrothermal actuation, compared to electrostatic actuation traditionally used in such devices, was chosen because of the larger driving displacement achieved with significantly lower driving voltage.…”

A Dual-Mass Resonant MEMS Gyroscope Design with Electrostatic Tuning for Frequency Mismatch Compensation

“…However, matching the drive-and sense-mode resonant frequency in a MEMS gyroscope becomes challenging in the presence of microfabrication process tolerances and high-temperature operating conditions. To minimize the effect of external factors on the performance of MEMS gyroscopes, complex multi-degree of freedom (multi-DoF) mechanical structures, based on nonresonant operation, have been reported in the literature [7][8][9]. In addition to the structural complexity, the issue of low mechanical sensitivity is inherent to nonresonant MEMS gyroscope designs.…”

Microfabrication Process-Driven Design, FEM Analysis and System Modeling of 3-DoF Drive Mode and 2-DoF Sense Mode Thermally Stable Non-Resonant MEMS Gyroscope

“…The collider mass in this design approach transmits the dynamic energy from the drive mass to the final oscillating sense mass. Previously, the authors have presented the implementation of the collider mass concept, for the transfer of energy from drive mass to sense mass, for a 3-DoF drive and 1-DoF sense mode electrothermally actuated MEMS gyroscope [ 18 ]. The MEMS gyroscope was optimized considering the microfabrication process constraints of MetalMUMPs process with 20 μm thick structural layer of nickel.…”