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Electrostatic (ES) force is one of the most important actuation mechanisms for microelectromechanical systems (MEMS) devices. However, residual vibration of microstructures induced by ES actuation can bring various problems that degrade dynamic performance and device longevity, such as long settling time, dynamic pull-in, and contact fatigue. By suppressing this undesirable effect, it is expected that both the dynamic performance and device reliability can be effectively enhanced. This paper presents a command-shaping-based scheme with experiment validation for both fast positioning and reduced contact impact of MEMS devices by the suppression of motion-induced vibrations. The scheme was developed by applying energy conservation, force equilibrium, and elliptical integrals. Simulink simulations indicate that both the impact force and settling time can be effectively reduced. In order to count the possible parameter variation and unmodeled dynamics, an online tuning scheme is also proposed and verified through simulation. Finally, spring-plate specimens fabricated using SU-8 with a metallic coating and a test bed containing a laser positioning sensor and a high voltage source are designed to further demonstrate the performance of the proposed scheme; the test results indicate that the proposed approach can effectively enhance the dynamic performance of MEMS devices such as grating light valves and RF switches.
Date of Publication: Feb. 2011