Development of an end-effector mounted tracking methodology for feedback control of high precision 3-DOF planar motions

This paper presents the development of a methodology for laser interferometry based pose measurement of a three degree of freedom (DOF) planar nanopositioning stage, and its use for tracking control over a large workspace. The proposed methodology employs a miniature pure rotation scanner mounted atop the stage's end effector to provide compensation for any sensor misalignment introduced through motion of the yaw axis, thereby reducing the impact of geometric errors. A feedforward-feedback compound controller is established for both the misalignment compensation and tracking aspects of operation, and experimentation is performed which demonstrates high precision positioning. Sensor positioning considerations are shown to have a crucial impact on tracking performance.