Date of Award

12-2008

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Mechanical Engineering

Advisor

Li, Gang

Committee Member

Li , Gang

Committee Member

Thompson , Lonny

Committee Member

Daqaq , Mohammed

Abstract

Advances in micromachining technology have enabled the design and development of high performance microelectromechanical systems (MEMS). There is a pressing need for control techniques that can be used to improve the dynamic behavior of MEMS such as the response speed and precision. In MEMS applications, open-loop control is attractive as it computes a priori the required system input to achieve desired dynamic behavior without using feedback, thus eliminating the problems associated with closed-loop MEMS control. While the input-shaping control is attractive due to its simplicity, the effectiveness of this control approach depends on the accuracy of the model that is used to compute the input voltage. Accurate modeling of MEMS dynamics is critical in the input-shaping process. Input-shaping MEMS control algorithms based on analytical lumped models have been proposed. It has been shown that step-shaped input voltages can be used to control the structural vibration of MEMS. However, several questions remain to be answered: (1) What are the effects of the higher vibrational modes on the input-shaping control of MEMS? (2) Can the input-shaping technique be improved to control these effects?
In this work, a full 3-D computational code is developed for coupled electromechanical simulation and analysis of electrostatically actuated MEMS. The effect of higher vibrational modes on the input-shaping control of electrostatic micromirros is investigated. We show that, depending on the design of the micromirros, the bending mode of the micromirror structures can have significant effect on the dynamic behavior of the system, which is difficult to suppress by using the step-voltage open-loop control. We employ a numerical optimization procedure to shape the input voltage from the real time dynamic response of the mirror structures. The optimization procedure results in a periodic nonlinear input voltage design that can effectively suppress the bending mode effect.

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