Direct Suspension Force Control of Bearingless Permanent Magnet Synchronous Motor

The bearingless permanent magnet synchronous motor (BPMSM) is a strong-coupled nonlinear system. To solve the difficult problem of dynamic decoupling control among torque and suspension forces, the relationship between rotor radial suspension force and flux linkage are analyzed, the theory and method of direct torque control (DTC) are applied to the suspension control of the BPMSM in the paper. A double closed-loop control system, in which the inner closed-loop is radial suspension force loop and the outer closed-loop is rotor radial displacement loop, is constructed to control the radial suspension forces directly. The direct suspension force control (DSFC) algorithm based on space vector pulse width modulation (SVM) strategy is deduced, and the DSFC system for the BPMSM are designed and simulated using Matlab software. The simulation results show that the rotor can be suspended stability, torque and radial suspension forces can be controlled independently, the structure of control system is simple, and control system has strong robustness.