A Multiaxis, Large-Output, Sensing Framework of Integrating Linear Optical Encoders for Nanopositioning Systems

Abstract

Linear optical encoders have been widely applied in nanopositioning systems when combined with compliant mechanisms to provide feedback control. A linear encoder can offer large-range nanometric sensing quality by a noncontact frictionless operation, with affordable cost and no dynamic range limitation. Traditionally, linear encoders are guided by translational compliant mechanisms to measure the single-axis input or output. In a multiaxis large-range nanopositioning system, the linear encoder is not feasible to directly measure the multiaxis output motion, since the required large-range lateral motion (perpendicular to the measuring direction or primary direction) will make it disabled when sensing the motion in the intended primary direction. This letter proposes a multiaxis large-output sensing framework that only uses linear optical encoders to provide feedback, which is based on the closed-loop kinematic decoupling principle. An XY compliant stage system with only two linear encoders is proposed to explain the multiaxis output sensing approach for nanopositioning applications.