Control of a 5DOF magnetically levitated positioning stage

A high-precision, magnetically levitated, five degree-of-freedom (5DOF) positioning stage is presented. Four independently controlled iron-cored permanent magnet linear synchronous motors are used to translate the stage and rotate it about the two horizontal axes. Six optical encoders with 10 mum resolution, mounted on linear guides, are used to measure displacements and rotations. A partially control-affine model is presented, which is sufficient for the purposes of control. Nonlinear tracking controllers are developed for the 5DOF system using feedback linearization and internal model regulation for step and sinusoidal references.