Dynamics of Symmetric Active Magnetic Bearing Systems Composed of Solid Magnet Cores in the Shape of a Cone

Abstract

A generally noninteracting control system is designed for active magnetic bearing systems, which are composed of magnet cores in the shape of a cone, to have both functions of radial and thrust bearings. The structure of the bearing system is symmetric with respect to the gravity center of the rotor : the magnet cores are made of solid steel and the electromagnets have similar dynamical characteristics. The dynamics of the magnetic control force are modeled by the sum of two second-order time-lag systems, and unknown parameters are estimated experimentally. Experimental results are obtained for frequency responses of the rotor motion to disturbance inputs and for responses to impact to the rotor. The former responses are compared with the numerical results using the dynamics of the control force with the estimated parameters. The results show the effectiveness of the model and the usefulness of the method for designing the control system.