Sliding mode variable structure control for radial suspension forces of bearingless permanent magnet synchronous motor based on inverse system method

A bearingless permanent magnet synchronous motor (BPMSM) is a multi-variable, nonlinear and strong-coupled system. For closed-loop control, the decoupling control of radial forces is the key of stable suspension operation of the BPMSM. Based on basic electromagnetism theory, a radial force model of a BPMSM is given. The reversibility of the model is proved and an inverse system method is developed for the nonlinear, strongly coupled model, so that the system is decoupled into two decoupled linear subsystems. Furthermore, the sliding mode variable structure control (SMVSC) theory is applied to these subsystems to obtain the desired closed-loop response. The simulation results show that the proposed method is effective and the dynamic and static performance of the system is achieved.