Design and control of active magnetic bearing system with Lorentz force-type axial actuator

As the size of five-axes active magnetic bearing (AMB) system gets smaller, the space limitation for installation of axial magnetic bearing unit and the eddy current induced braking of radial magnetic bearing unit become a stringent design concern. In this paper, a new type of compact, high-performance five-axes AMB with solid cores and rotor is proposed, which consists of four permanent magnets, four U-shaped cores and 16 control coils. It features that the radial and axial magnetic bearing units are integrated for compact design and that the homo-polar type configuration of poles with optimized pitch length is adopted to minimize the eddy current induced braking force. The proposed homo-polar AMB system is levitated by the Lorentz-type axial as well as Maxwell-type radial forces. Based on the magnetic flux distribution analysis, the control algorithm is designed to account for the coupled effect between the radial and axial control fluxes. Experiments are also carried out with a prototype AMB system to validate the new design concept. (C) 2005 Elsevier Ltd. All rights reserved.