Adaptive Exponential Sliding Mode Control for a Bearingless Induction Motor Based on a Disturbance Observer

In the interest of solving the unsatisfactory control capability of a bearingless induction motor (BIM) under parameter variations, external disturbance, and load mutation, an adaptive exponential sliding mode controller and an extended sliding mode disturbance observer for on-line identification of system disturbance variables are designed. The first-order norm and switching function law is integrated into traditional reaching law, and an adaptive exponential reaching law is presented. The convergence rate can be adjusted adaptively according to the change of the sliding mode switch surface and the system state, so that the control system has the characteristics of low buffeting, excellent convergence performance, and good operation quality. In addition, the disturbance sliding mode observer takes the speed and the external disturbance of the BIM as the observation object. Meanwhile, the output of the disturbance sliding mode observer uses as the feed forward compensation for the system speed. The feedback speed can adjust operation condition adaptively with the speed error and reduce the influence of the disturbance. The simulation and experiment results indicate that the system has strong robustness to uncertainties as well as achieves the accurate identification of uncertain disturbance, the anti-disturbance ability, and the quality of operation for BIM control system can be improved, the chattering can also be inhibited simultaneously.