Linearized Model and Control Systems of Magnetic Bearings Composed of Six Electromagnets in the Shape of a Cone.

Abstract

To reduce the components, six electromagnets are applied to construct active magnetic bearings. The radial bearing is composed of three electromagnets, whose pole faces are in the shape of a cone, to generate the axial force ; the combination of the two radial bearings also has the function of a thrust bearing. A theoretical linearized model of the rigid-rotor motion is derived so that five control inputs can be decoupled into five motions when the electromagnets have similar dynamical characteristics. A method for designing an approximate decoupling control system is considered, and a relatively simple structure is presented to give actual input into the six electromagnets. The one freedom in giving the actual control input is considered in terms of the rate at which the two bearings take part in the thrust bearing. The results neglecting the thrust control are applicable to the similar radial bearings in the shape of a right cylinder.