A new repulsive magnetic levitation approach using permanent magnets and air-core electromagnets

This paper introduces a new repulsive magnetic levitation approach using permanent magnets and air-core electromagnets as primary actuating components. The permanent magnets, which are attached to the bottom of a carrier, are repulsively levitated above and by oblong shaped electromagnets, which constitute one part of the guide tracks. Due to the lateral unstable nature of repulsive levitation, the stability of the levitated permanent magnets is regulated by another part of the guide tracks, electromagnetic stabilizers, which are strands of straight wires running through the entire length of the guide tracks above the levitation coils. A state feedback controller with integral compensator is designed for the stability control. The entire levitation system is divided into three subsystems: levitation, stabilization and propulsion. All the control works with respect to each subsystem are executed extrinsic to the carrier, i.e., there is no electrical circuit on board the carrier. The feasibility of this new levitation approach is confirmed successfully by a small scale demonstration system designed to transport a single silicon wafer in a microelectronic fabrication line. The wafer carrier is stably levitated 1.5 mm above the track surface with lateral air-gaps of 0.5 mm. Its maximum velocity is 22.2 cm/sec and the traveling range is 1 m