Background: In the existing inverse system decoupling methods of bearingless induction motor, the inverse system model is more complex, and it is not easy to realize the independent control of the magnetic suspension system. In this paper, in order to simplify its inverse system model, an independent inverse system decoupling control strategy is proposed.
Methods: Under the conditions of considering the current dynamics of torque windings, the state equations of torque system and those of magnetic suspension system are established, and the independent inverse system model of torque system and that of the magnetic suspension system are deduced. The air gap fluxlinkage of the torque system that is needed in the magnetic suspension system is identified by an independent voltage model. After the independent inverse model of torque system and that of magnetic suspension system are connected in parallel, they are connected in front of the original system of a bearingless induction motor. After this, the torque system is decoupled into two second-order integral subsystems, i.e. a fluxlinkage subsystem and a motor speed subsystem, while the magnetic suspension system is decoupled into another two second-order integral subsystems, i.e. the α- and β-displacement component subsystems. The design of the additional closed-loop controller is achieved through the pole assignment method.
Results: The obtained inverse model of the magnetic suspension system is independent of the fluxlinkage orientation mode of torque system, and thus the flexibility of the independent control for the torque system and magnetic suspension system is increased. The simulation results have shown that the system has good static- and dynamic-decoupling control performance.
Conclusion: The proposed independent inverse system decoupling control strategy is effective and feasible.