Decoupling Control for Bearingless Induction Motor with a-th Order Inverse System Theory

A 5 degrees of freedom bearingless induction motor is a multi-variable, nonlinear and strong-coupled system. In order to achieve rotor suspension and operation steadily, it is necessary to realize dynamic decoupling control between torque force and suspension forces. In the paper, a method based on a-th order inverse system theory is used to study on dynamic decoupling control of bearingless induction motors. Firstly, the working principles of 3 degrees of freedom magnetic bearing and 2 degrees of freedom bearingless induction motor are analysed, the radial-axial force equations of 3 degrees of freedom magnetic bearing and the electromagnetic torque equation and radial force equations of the 2 degrees of freedom bearingless induction motor are given, and then the state equations of the 5 degrees of freedom bearingless induction motor are set up. Secondly, feasibility of decoupling control based on dynamic inverse theory for bearingless induction motor is discussed in detail, and the dynamic feedback linearization method is used to decouple and linearize the system. Finally, linear control system techniques are applied to these linearization subsystems to synthesize and simulate. The simulation results have shown that this kind of control strategy can realize dynamic decoupling control between torque force and suspension forces of the 5 degrees of freedom bearingless induction motor, and the control system has good dynamic and static performance.