Design and modeling for comb drive actuator with enlarged static displacement

New comb drives using high stiffness ratio springs are designed and modeled to provide capabilities of large static displacement and continuous motion for applications, such as micro XY stage, two dimensional lens scanner, variable optical attenuator, and optical switch, etc. The maximum static displacement of conventional comb drive is constrained by the side sticking effect of comb finger electrodes. Since the side sticking effect will become obvious and exhibit strong impact on actuator behavior in the case that the spring lateral stiffness is decreased when the static displacement is increased, and the rotation moment caused by unbalanced force between electrode fingers resulted from the environment disturbance and/or fabrication deviation will enhance the side pulling phenomena. The aforementioned sticking effect occurs at the static displacement smaller than the analytical results estimated by conventional stability criteria. Thus, a new stability criterion is proposed for providing more accurate predicted maximum static displacement. A new hybrid spring with an n-shaped joint for comb drive is developed and proposed in this paper as well. This new spring is capable of not only enhancing the lateral stiffness against to the lateral mechanical disturbance and shock, but also efficiently eliminating the rotation moment caused by the disturbance over the large displacement range. The design scheme is verified by the simulation results. (C) 2004 Elsevier B.V. All rights reserved.