Direct control of torque and levitation force for dual-winding bearingless switched reluctance motor

- The torque and levitation force are separately regulated with simple implementation.
- The torque ripple can be greatly reduced.
- The levitation forces can be effectively generated.
- The rotor radial displacement can be slightly decreased.

In dual-winding bearingless switched reluctance motors (BSRMs), an additional winding is placed on the stator poles in conventional switched reluctance motors (SRMs), which is mainly to achieve the function of levitation. Due to the hysteresis current control in existing control strategies for dual-winding BSRMs, the complicated derivation of winding-current expression was necessary, and some constraints were also introduced that increased the difficulties on designing the current control algorithm. In order to solve these problems, the direct control concept of torque and levitation forces is proposed and developed in this paper, named as direct torque control (DTC) and direct force control (DFC). Moreover, the torque ripple can also be reduced greatly. Firstly, the space voltage vectors of dual-winding BSRMs are defined for the main and levitation windings, respectively. After that, the rules and procedures for selecting the space voltage vectors are demonstrated in detail, and the system control block is also presented to facilitate the implementation of proposed control strategy. Finally, experimental results are provided to demonstrate the performance.