Micro Electro Mechanical Gyroscope Based on Thermal Principles

Peer reviewed: 
No, item is not peer reviewed.
Scholarly level: 
Graduate student (PhD)
Date created: 
Angular velocity
Coriolis effect
Inertial sensors
Linear acceleration
Thermal gyroscope

Four variants of a novel single-axis thermal gyroscope were designed, microfabricated, and characterized in this thesis. Unlike conventional gyroscopes that use a solid seismic mass, the thermal gyroscope utilizes a particulate proof mass. The operating principle of the device is differential temperature detection due to the Coriolis effect on an oscillatory gas stream, in response to rotation. The stream is created by alternate expansion and contraction of the gas particles through activation of two or multiple microheaters in a confined volume. The miniature device structure includes multiple temperature detectors symmetrically arranged with respect to the microheaters. Thermocouples and resistive temperature detectors are exclusively used in the designs. Three versions of the device possess planar structures, whereas the other version forms an out-of-plane structure relying on a compliant platform and a locking mechanism. The fabrication process of the device is based on a variety of bulk or surface micromachining technologies on silicon substrates using polyimide and/or silicon dioxide structural layers. As the designs progress, the microstructures are freely suspended over a cavity etched into the substrate or within the volume above the substrate, with minimal structural support.

A precision rotary stage was constructed to accurately measure the device performance. Two variants of the device showed extremely low sensitivities. However, two other versions exhibited excellent linearity within the tested ±1260 °/s, and they demonstrated sensitivities of 0.947 and 1.287 mV/°/s where 20 mW of power was supplied to the heaters. The bandwidths of the devices were measured to be 20 and 40 Hz. The robustness of the devices was validated by the drop shocks of 2722 to 16 398 g (9.81 m/s^2). Despite the ability of rejecting linear accelerations, the devices showed comparable sensitivities to the linear accelerations. A systematic study of the device acceleration sensitivity, with a variety of low- to high-density gases at high pressures, confirmed that the acceleration signal was induced due to low degrees of rotational symmetry in the device topology. An analytical correction factor was developed capable of 5.8-fold nonlinearity compensation. A novel device configuration was also constructed proving 16 times more effective in rejecting the linear acceleration signal.



Supplemental video available - MEMS Out of Plane Thermal Gyroscope. 

Appendix C: Simulated structure of the designed OOP Gyro

Document type: 
This thesis may be printed or downloaded for non-commercial research and scholarly purposes. Copyright remains with the author.
Carlo Menon
Applied Sciences: School of Engineering Science
Thesis type: 
(Thesis) Ph.D.