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 detailed mathematical model is developed and nonlinear tracking controllers are designed for the 5DOF system using feedback linearization, output regulation, and antiwindup compensation for step and sinusoidal references.