In this paper, we introduce two position control scheme; the lead-lag control and the sliding mode control for a stage system, which is levitated and driven by electric magnetic actuators. This consists of a levitating object (called platen) with 4 permanent magnetic linear synchronous motors in parallel. Each motor generates vertical force for suspension against gravity and propulsion force horizontally as well. This stage can generate six degrees of freedom motion by the vertical and horizontal forces. Dynamic equations of the stage system are derived simply. The sliding mode control algorithm is more effective than the lead-lag control algorithm to reduce effects from movements and disturbances of other axis.
-In this paper, a conceptual design and a detailed design of novel cylindrical magnetic levitation stage is introduced. This is came from planar-typed magnetic levitation stage. The proposed stage is composed of cylinder-typed permanent magnet array and semi-cylinder-typed 3 phase winding module. When a proper current is induced at winding module, a magnetic levitation force between the permanent magnet array and winding module is generated. The proposed stage can precisely move the cylinder to rotations and translations as well as levitations with the magnetic levitation force. This advantage is useful to make a nano patterning on the surface of cylindrical specimen by using electron beam lithography under vacuum. Two methods are used to calculate required magnetic levitation forces. The one is 2D FEM analysis, the other is mathematical modeling. This paper shown that results of two methods are similar. An assistant plate is introduced to reduce required currents of winding module for levitations in vacuum. The mathematical model of cylindrical magnetic levitation stage is used for dynamic simulation of magnetic levitations. A lead-lag compensator is used for control of the model. Simulation results shown that the detail designed model of the cylindrical magnetic levitation stage with the assistant plate can be controlled very well.
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