Please use this identifier to cite or link to this item: http://scholarbank.nus.edu.sg/handle/10635/15767
Title: Linearization and control of dual-axis micromirror
Authors: ZHAO YI
Keywords: MEMS, Dual-Axis Micromirror, Electrostatic Actuation, Scanning Nonlinearity, Lineariztion, Pull-in Instability
Issue Date: 29-Dec-2006
Source: ZHAO YI (2006-12-29). Linearization and control of dual-axis micromirror. ScholarBank@NUS Repository.
Abstract: The electrostatically actuated dual-axis micromirror based on MEMS technology has attracted much attention. However, the intrinsic nonlinearity of the electrostatic torques results in two problems. One is the scanning distortion within the stable range. Another is the scanning instability, known as "pull-in" problem, which greatly limits the scanning range of the device.The objectives of this study are (1) to investigate the scanning nonlinearity of a dual-axis micromirror and subsequently to propose some methods to linearize the distorted scanning fields, and (2) to stabilize the device beyond the pull-in point thereby extending its useful scanning range. Two linearization methods, i.e. RBF neural network (NN) and Delaunay triangulation (DT) are proposed to reduce or eliminate scanning nonlinearity, thus correcting the distorted scanning field. A position feedback integral sliding mode control (ISMC) algorithm is applied to stabilize the micromirror beyond its pull-in point.Experiments carried out in the static mode of the micro-mirror indicated that the scanning field is severely distorted by the nonlinear electrostatic torques, the distortion rates being about 30% for x-axis and y-axis scanning. By applying the RBF NN or DT method, the distortion rates are found to be suppressed to less than 5%.The original pull-in observed occurred whenever the two driving voltages exceeded 3 V. After applying ISMC, the device exhibits an extended stable range, which is more than 30% bigger than the original one. The closed-loop system also demonstrates improved transient performance, such as shortened setting time and eliminated overshoot.
URI: http://scholarbank.nus.edu.sg/handle/10635/15767
Appears in Collections:Ph.D Theses (Open)

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