Multiaxis Maglev Positioner With Nanometer Resolution Over Extended Travel Range

Abstract

This paper presents a novel multiaxis positioner that operates on the magnetic-levitation (maglev) principle. This maglev stage is capable of positioning at the resolution of a few nanometers over a planar travel range of several millimeters. A novel actuation scheme was developed for the compact design of this stage that enables six-axis force generation with just three permanent magnets. We calculated the forces with electromagnetic analysis over the whole travel range and experimentally verified them with a unit actuator. The single-moving part, namely, the platen, is modeled as a pure mass due to the negligible effect of magnetic spring and damping. There are three laser interferometers and three capacitance sensors to sense the six-axis position/rotation of the platen. A lead-lag compensator was designed and implemented to control each axis. A nonlinear model of the force was developed by electromagnetic analysis, and input current linearization was applied to cancel the nonlinearity of the actuators over the extended travel range. Various experiments were conducted to test positioning and loading capabilities. The 0.267kg single-moving platen can carry and precisely position an additional payload of 2kg. Its potential applications include semiconductor manufacturing, microfabrication and assembly, nanoscale profiling, and nanoindentation.