A Novel Technique for Controlling Speed and Position of Bearingless Switched Reluctance Motor Employing Sensorless Sliding Mode Observer

Abstract

High-speed motors working in harsh environments such as high temperatures, radiation, and poisonous substances are limited because of motor breakdown due to vibrations of mechanical bearings. The concept of magnetic bearings is an alternative to the issues of slide or ball bearings because of its advantages of friction-free, negligible thermal problems, and lubrication free. Rotor vibration control during start-up, acceleration and deceleration phases are one of the key problems besides stable levitation, in high-speed applications of bearingless switched reluctance motor (BSRM). The use of linear control strategies alone is not effective in suppressing vibration due to residual unbalance and external disturbances. In this paper, a global sliding mode controller (GSMC) is proposed to control the speed and position of BSRM and also sensorless operation with sliding mode observer. In this method, rotor displacement tracking error functions are used in the sliding mode switching functions and the new sliding mode displacement control and speed tracking equations are obtained with an extra exponential fast decaying nonlinear function along with conventional linear sliding mode switching surface. Simulation is carried on 12/14 BSRM with the proposed controller and observer and the results of rotor displacements and speed are presented. In addition to the improvement of performance characteristics when compared to sliding mode controller, GSMC cancels the reaching mode, reduce the chatting, and overcome the disturbance and the time delay.