Research Papers

Mechanically Amplified 3-DoF Nonresonant Microelectromechanical Systems Gyroscope Fabricated in Low Cost MetalMUMPs Process

[+] Author and Article Information
Rana I. Shakoor1

Nano-Devices Group,  National Institute of Lasers and Optronics (NILOP), Islamabad, 45650 Pakistanrana.iqtidar@gmail.com

Shafaat A. Bazaz

Department of Computer Science,  Center for Advanced Studies in Engineering (CASE), 19-Attaturk Avenue, G-5/1, Islamabad, Pakistanbazaz@case.edu.pk

M. Mubasher Saleem

 GIK Institute of Engineering Sciences and Technology, Topi, Khyber Pakhtunkhaw, Pakistanmubasher@giki.edu.pk


Corresponding author.

J. Mech. Des 133(11), 111002 (Nov 11, 2011) (8 pages) doi:10.1115/1.4004790 History: Received February 02, 2010; Revised July 15, 2011; Published November 11, 2011; Online November 11, 2011

This paper introduces the design implementation of 3-DoF Microelectromechanical Systems (MEMS) based gyroscope concept, which allows shaping up the dynamic response without using advance control system strategies, with less compromise in performance. The proposed architecture utilizes an active–passive mass configuration in order to achieve the dynamic amplification of the oscillation in 2-DoF drive-mode. A comprehensive theoretical description, dynamics, and mechanical design configuration of the proposed gyroscope design are discussed in detail. A complete test methodology has also been devised for the proposed nonresonant 3-DoF gyroscope. A cost effective commercially available metal-multi user MEMS process is used to fabricate a 20 μm thick nickel based micromachined vibratory gyroscope with an overall chip size of 2.2 mm × 2.6 mm. A good agreement is found between the tested and the simulated results. The experimental characterization demonstrated that the wide bandwidth frequency response of the 2-DoF drive-mode oscillator consists of two resonant peaks at 754 Hz and 2.170 kHz, respectively, with a flat region of 1.4 kHz between the peaks, defining the operational frequency region. The sense-mode resonant frequency lies within this region at 1.868 kHz allowing the amplitude of the response to be insensitive to structural parameter and damping variations, with improved robustness against such variations. The passive mass achieved a dynamic amplification of three times at first resonant peak of 754 Hz and five times at the second resonant peak of 2.170 kHz in comparison with the active mass, resulting in improved sensitivity in response to the Coriolis torque induced due to rotation.

Copyright © 2011 by American Society of Mechanical Engineers
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Figure 1

Operating principal of resonant micromachined vibratory gyroscope

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Figure 2

3-DoF design concept with 2-DoF drive and 1-DoF sense-mode oscillators

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Figure 3

The scanning electron microscope (SEM) image of the prototype fabricated using MetalMUMPs. The insets show the enlarged images of the driving comb and the sensing parallel plates.

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Figure 4

Representation of position vectors of the proof masses m1 and m2 of the gyroscope relative to the rotating gyroscope frame B

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Figure 5

Suspension system of 2-DoF drive- and 1-DoF sense-mode oscillator of proposed microgyroscope

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Figure 6

(a) Lumped mass-spring-damper model for 2-DoF drive-mode oscillator and (b) Lumped mass-spring-damper model for the 1-DoF sense-mode oscillator of 3-DoF microgyroscope

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Figure 7

Process flow for the fabrication of microgyroscope using MetalMUMPs in MEMSPro (a) N-type < 100 > silicon wafer, (b) 2 μm thick isolation oxide layer, (c) patterning of 0.35 μm thick silicon nitride layers, (d) patterning of 0.7 μm thick Polysilicon layer, (e) patterning of anchor metal layer, and (f) patterning of 20 μm electroplated structural layer of Ni and trench etch in the substrate

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Figure 8

The drive-mode response, showing flat operating region under varying pressure conditions

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Figure 9

3-DoF MEMS gyroscope active and passive mass drive-mode response at 60 V dc and 10 V ac with a constant pressure of 4 Torr

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Figure 10

Microsystem Analyzer MSA-400 used to characterize the microgyroscope

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Figure 11

(a) 3-DoF microgyroscope drive-mode response (first resonant frequency) (b) 3-DoF microgyroscope drive-mode response (second resonant frequency), and (c) 3-DoF microgyroscope sense-mode response



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