Sliding Mode Control for Bearingless Induction Motor Based on a Novel Load Torque Observer

For the problem of low control performance of Bearingless Induction Motor (BIM) control system in the presence of large load disturbance, a novel load torque sliding mode observer is proposed on the basis of establishing sliding mode speed control system. The load observer chooses the speed and load torque of the BIM control system as the observed objects, uses the speed error to design the integral sliding mode surface, and adds the low-pass filter to reduce the torque observation error. Meanwhile, the output of the load torque is used as the feedforward compensation for the control system, which can provide the required current for load changes and reduce the adverse influence of disturbance on system performance. Besides, considering that the load changes lead to the varying rotational inertia, the integral identification method is adopted to identify the rotational inertia of BIM, and the rotational inertia can be updated to the load observer in real time. The simulation and experiment results all show that the proposed method can track load torque accurately, improve the ability to resist disturbances, and ameliorate the operation quality of BIM control system. The chattering of sliding mode also is suppressed effectively

Vector control for a bearingless induction motor based on nonsingular terminal sliding mode structure

© 2017 IEEE. To improve the performance of the bearingless induction motor (BIM) under disturbances, a nonsingular fast terminal sliding mode control (NFTSMC) strategy is proposed. The sliding mode surface is designed as a combination of linear sliding mode and nonsingular terminal sliding mode. Besides, considering the power function of the state variables, which make the approaching speed correlate with the state variables, so as to improve convergence performance of the linear sliding mode and solve the singularity of terminal sliding mode. Meanwhile, current signal and radial force are extracted by the electromagnetic torque and the equation of levitation force. Therefore, the convergence speed of system can be accelerated during the whole process, which contributes to chattering-free operating. The simulation and experiment results indicate that the proposed method can not only track the given value of the speed and radial displacement quickly, but also improve the operation quality and enhance the system robustness

A Bearingless Induction Motor Direct Torque Control and Suspension Force Control Based on Sliding Mode Variable Structure

Aiming at the problems of the large torque ripple and unstable suspension performance in traditional direct torque control (DTC) for a bearingless induction motor (BIM), a new method of DTC is proposed based on sliding mode variable structure (SMVS). The sliding mode switching surface of the torque and flux linkage controller are constructed by torque error and flux error, and the exponential reaching law is used to design the SMVS direct torque controller. On the basis of the radial suspension force mathematical model of the BIM, a radial suspension force closed-loop control method is proposed by utilizing the inverse system theory and SMVS. The simulation models of traditional DTC and the new DTC method based on SMVS of the BIM are set up in the MATLAB/Simulink toolbox. On this basis, the experiments are carried out. Simulation and experiment results showed that the stable suspension operation of the BIM can be achieved with small torque ripple and flux ripple. Besides, the dynamic response and suspension performance of the motor are improved by the proposed method