Design of a micro magnetic bearing actuator

A micro magnetic bearing actuator, with an outside diameter of 2.6 mm, is being fabricated at RMIT. The rotor of the bearing actuator is structured to operate with active control in the radial directions while being supported passively in the axial direction. This paper addresses the design problem for micro magnetic bearing actuators. The key issue in the design is the evaluation of magnetic forces. By applying the "fringing range method" developed by the authors, a magnetic circuit model is developed for this actuator, which is used for calculating the flux densities at key locations and the magnetic forces on the rotor. Expressions for magnetic forces have been developed previously and a design procedure is proposed in this paper. It is found by using these expressions and the proposed procedure, that we can easily investigate the influence of design parameters on actuator performance. Design results for the micro magnetic bearing are given in detail.