Magnetic Levitation System for Linear Direct Drives based on Lorentz Forces

Linear rolling and plain bearings are established and proven in Mechanical Engineering. However, for highest requirements concerning stiffness, dynamics and durability, as well as in dust-free and vacuum rooms, usage of magnetically levitated linear bearings can be economically worthwhile. Existent magnetic levitation systems are designed in greater dimensions, especially for purposes of passenger transportation like the German Transrapid and for usage in machine tools [2] [1]. Furthermore, they are mostly based on electromagnets, what is firstly attended by damping effects due to eddy currents and hysteresis losses and secondly attended by need for complex closed-loop control algorithms. In this paper an innovative magnetic levitation system for linear direct drives is presented, that is exclusively based on Lorentz forces and which is designed in dimensions for application in precision engineering systems [3]. Permanent magnets are arranged similar to a Halbach array within the guideway and thereby establish a magnetic field for the levitation and guidance coils. The comparatively low weight of the moving part and its lack of eddy currents allow for highest dynamics. Moreover, easy and efficient closed-loop algorithms can be implemented because of the linear correlation of Lorentz force and current. Finally, the performance of the levitation system is shown using the example of an existing prototype.