Date of Award

Spring 2009

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical & Aerospace Engineering

Program/Concentration

Mechanical Engineering

Committee Director

Zhili Hao

Committee Member

Jen K. Huang

Committee Member

Shirshak Dhali

Call Number for Print

Special Collections; LD4331.E56 D87 2009

Abstract

Over the past two decades, micromachined gyroscopes fabricated using MicroElectroMechanical Systems (MEMS) technology have attracted a great deal of attention from various industrial and military sectors due to their significant advantages over traditional bulky gyroscopes, including small size, batch fabrication, low power consumption, and low cost. Among the various micromachined gyroscopes developed so far, tuning-fork gyroscopes with integrated electrostatic transducers have been extremely attractive because of their significant advantages over other structural forms and other types of transducers., including larger proof mass, large vibration amplitude in the drive-mode, and relative ease of fabrication.

This thesis presents the advanced design and performance characterization of a new tuning-fork gyroscope with high Quality Factors (Qs). This gyroscope design is comprised of a tuning-fork mechanical structure with high. Qs in both its drive-mode and sense-mode, comb-drive transducers for excitation of the drive-mode vibrations, parallel-plate sense electrodes for detection of a rotation rate signal, and tuning electrodes for minimizing the frequency difference between the two operation modes. The detailed finite element analysis of the tuning-fork structure is conducted in ANSYS. Through the use of an electrical analogy, the overall dynamic behavior of the tuning-fork structure and its integrated transducers is modeled as an equivalent electrical circuit model in P-SPICE. This design is fabricated using a one-mask fabrication technology based on silicon-on-insulator (SOI) wafers. The fabrication process consists of two steps: 1) a Deep-Reactive-Ion-Etching (DRlE) step of an aspect ratio of 10:1 and 2) a Hydrogen fluoride (HF) etching step. One batch of 30µm-thick gyroscopes is fabricated. These fabricated devices are tested under a vacuum in a two-port configuration using an Agilent 4395A network analyzer to characterize the frequency response of the drive-mode and sense-mode. The measured best Qs of a fabricated gyroscope are 106,000 for the drive-mode and 102,000 for the sense-mode. Since the gyroscope design is based on matched mode operation, a DC bias voltage applied to the device is adjusted in order to minimize the frequency difference between the drive-mode and the sense-mode. A minimum frequency difference of 4Hz over l 9.49kHz is achieved. However, due to the presence of Quadrature error, the rate sensitivity of the gyroscope is not successfully measured. In addition, due to the critical importance of minimizing frequency difference, a preliminary study on mode coupling and its associated dynamics of the gyroscope is also conducted.

Rights

In Copyright. URI: http://rightsstatements.org/vocab/InC/1.0/ This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).

DOI

10.25777/w9xr-1w27

Share

COinS