Inverse system modeling and decoupling control of bearingless induction motor based on air gap flux orientation

Abstract

Three-phase bearingless induction motor is a multivariable, nonlinear and strong coupling object, to achieve its decoupling control with high performance, an inverse system decoupling control strategy based on air gap flux orientation is proposed. Under the conditions of air gap flux orientation of torque system, the stator currents of torque winding and suspension winding are taken as input variables, and the inverse system mathematical model of bearingless induction motor is established; adopting the inverse system method, the bearingless induction motor is decoupled into four pseudo linear subsystems, include motor speed first-order integral subsystem, air gap flux-linkage first-order integral subsystem, α and β displacement components second-order integral subsystems. The structure of decoupling control system is presented also. From the simulation results, it is clear that not only the air gap flux-linkage of torque system can be controlled accurately and directly, but also the dynamic decoupling control between motor speed, air gap flux-linkage of torque system and two radial displacement components can be achieved; Meanwhile, the control system has the characteristics of small overshoot and fast response speed.