Control of suspending force in novel permanent-magnet-biased bearingless switched reluctance motor

Recently, bearingless switched reluctance motor (BLSRM) has been received more and more attention. To realize the stable levitation and rotation, the corresponding suspending force and torque should be controlled. In this paper, different from the conventional bearingless SRM control, one independent control scheme for levitation force and torque is presented. In the control, a complex control algorithm based on a lookup table is not needed. Torque control is separated from radial force control, and each channel of radial force is independently controlled. Therefore, the control is very simple to be implemented. First, based on the brief introduction of the BLSRM structure and operating principle, the mathematical relationship of levitation force with respect to current and displacement is derived. Furthermore, the rotor dynamics model, in which levitation force in four degrees of freedom is considered, is established. Based on the given analysis, the digital control system, which includes torque and suspending force, is designed by means of TMS320F28335, and an experimental platform is established. According to the experimental results, the proposed BLSRM can be steadily levitated in the static and rotating conditions.