Multi-Axis Maglev Positioner With High Resolution Over Large Travel Range
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This paper presents a novel multi-axis 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 6-axis force generation with just 3 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 3 laser interferometers and 3 capacitance sensors to sense the 6-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 feedback linearization was applied to cancel the nonlinearity of the actuators over the large travel range. Various experiments were conducted to test positioning, loading, and vibration-isolation capabilities. This maglev stage has a moving mass of 0.267 kg. Its position resolution is 4 nm over a travel range of 5 × 5 mm in the x-y plane. It can carry and precisely position an additional payload of 2 kg. Its potential applications include semiconductor manufacturing, micro-fabrication and assembly, nanoscale profiling, and nano-indentation. Copyright © 2005 by ASME.
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