Indirect torque observer-based sensor-less efficient control of bearingless switched reluctance motor using global sliding mode and square currents control method

The Bearingless Switched Reluctance Motor (BSRM) is a new technology motor, which overcomes the problems of maintenances required associated with mechanical contacts and lubrication of rotor shaft effectively. In addition, it also improves the output power developed and rated speed. Hence, the BSRM can achieve high output power and super high speed with less size and cost. It has a considerable ripple in the net-torque due to its critical non-linearity and the salient pole structures of both stator and rotor poles. The resultant torque ripple, especially in these motors, causes the more vibrations and acoustic noises will affects the levitated rotor safety also. Practically at high-speed operations, the accurate measurement of the rotor position is complicated for conventional mechanical sensors. A new square currents control with global sliding mode control based sensorless torque observer is proposed to minimize the torque ripple and achieve a smooth, robust operation without using any mechanical sensors. The proposed controller is designed based on the error between the reference and measured torque values. The sliding mode torque observer measures the torque from the actual phase voltages, currents, and look-up tables. The simulation model has been modelled to validate the proposed methodology. From the simulation outputs, it is clear that the reduction of torque ripple by the proposed method shows improved than the conventional sliding mode controller. The overall system is more robust to the external disturbances, and it also gets efficient torque profile.