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Proceedings Paper

Closed-loop adaptive control for torsional micromirrors
Author(s): Ke-Min Liao; Yi-Chih Wang; Chih-Hsien Yeh; Rongshun Chen
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Paper Abstract

An adaptive control scheme to achieve accurate positioning and trajectory tracking of torsional micromirror is presented in this study. The torsional micromirror is fabricated by using surface micromachining processes, in which phosphorusdoped polysilicon is employed as the structure layer as well as the bottom electrode. Generally, every fabrication step contributes to imperfections in micromirror. The proposed adaptive self-tuning controller has advantages of on-line compensating parameter variations or model uncertainty of the torsional micromirror, resulting from fabrication imperfections that produce asymmetric structures, misalignment of actuation mechanism, and deviations of the center of mass from the geometric center. In our design, the amount of detection of differential capacitance between the left and right electrodes at the femtofarad (fF) level is utilized as feedback signals. Simulation results show that the designed controller has better transient response compared to the PID control scheme. The micromirror can follow the reference trajectory (5 kHz) with acceptable error in several microseconds, thus the convergence of the controller is confirmed. Furthermore, the unknown model parameters can be identified correctly while the so-called persistent excitation condition is satisfied.

Paper Details

Date Published: 24 January 2004
PDF: 9 pages
Proc. SPIE 5346, MOEMS and Miniaturized Systems IV, (24 January 2004); doi: 10.1117/12.524691
Show Author Affiliations
Ke-Min Liao, National Tsing Hua Univ. (Taiwan)
Yi-Chih Wang, National Tsing Hua Univ. (Taiwan)
Chih-Hsien Yeh, National Tsing Hua Univ. (Taiwan)
Rongshun Chen, National Tsing Hua Univ. (Taiwan)

Published in SPIE Proceedings Vol. 5346:
MOEMS and Miniaturized Systems IV
Ayman El-Fatatry, Editor(s)

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