Input-output linearizing control for levitated rotating motors

A model is derived, in which FEM (finite element method) is employed, for an induction-type bearingless motor that has conventional four-pole stator windings for the torque and additional two-pole windings for controlling the radial displacements. A decoupling control strategy based on feedback linearization is presented so that subsystems of the rotor speed and rotor displacements of the bearingless motor are linearized, thus they can be controlled easily, and better performance can be obtained also. Linear system method then is utilized to synthesize these linearizing subsystems. Some simulations are employed. Satisfactory performance is obtained.