Precise Positioning of Electrostatic MEMS: A Non-Contacting Approach

Previously, precise positioning of electrostatic MEMS devices has been achieved using mechanical contact between movable and fixed components. A disadvantage of this approach is that stiction at the contact may eventually lead to device failure. This paper presents an alternative approach, whereby a desired configuration is defined by the intersection of two comb structures—one movable and the other fixed. Extremum-seeking control drives the movable electrode to this desired configuration by maximizing the mutual capacitance between the two comb structures. As in the case of mechanical contact, the device structure primarily determines the actuated configuration rather than precise sensing or actuation. However, because the comb structures never physically contact each other, stiction failure is eliminated.