A Large-Stroke 3DOF Stage With Integrated Feedback in MEMS

Abstract

In this paper, we design, fabricate, and validate a large-stroke 3-degree-of-freedom (DOF) positioning stage with integrated displacement sensors for feedback control in a single-mask microelectromechanical systems (MEMS) fabrication process. Three equal shuttles exactly define the position of the stage in $x$ , $y$ , and $R_{z}$ . The kinematic relation between the shuttle positions and the stage position is given by the geometric transfer function. By increasing the order of this geometric transfer function, the stage error can be reduced. Each shuttle consists of a flexure mechanism, a position sensor, and electrostatic comb drive actuators for actuation along a straight line. The range of motion of the stage is limited by electrostatic pull-in of these comb drives. Three parameters of the stage, the leafspring length, the eccentricity, and the tangential arm, have been varied to find their influence on the stage range of motion. These simulation results can be used to design stages with different specifications. Position control of the individual shuttles is applied to control the position of the stage. The stroke of the 3DOF stage is verified up to 161 $\mu \text{m}$ in $x$ , 175 $\mu \text{m}$ in $y$ , and 325 mrad in $R_{z}$ . This exceeds the range of motion of existing stages. [2014-0314]