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

Journal of Sensors, Oct 2016

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.

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

Sliding Mode Control for Bearingless Induction Motor Based on a Novel Load Torque Observer Zebin Yang,1 Ling Wan,1 Xiaodong Sun,2 Lin Chen,1 and Zheng Chen1 1School of Electrical and Information Engineering, Jiangsu University, Zhenjiang 212013, China 2Automotive Engineering Research Institute, Jiangsu University, Zhenjiang 212013, China Received 11 June 2016; Revised 26 August 2016; Accepted 6 September 2016 Academic Editor: Rafael Morales Copyright © 2016 Zebin Yang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract 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. 1. Introduction Based on the similarity principles of magnetic bearing and alternating current (AC) motor stator structure, BIM is formed. Two sets of windings are embedded in the stator slot of BIM, which can separately produce electromagnetic torque and radial levitation force. BIM achieves the integration of rapid rotation and stable suspension of rotor by changing the currents in the windings and avoids the mechanical bearing friction, wear and tear, and lubrication. It breaks the bottleneck of traditional asynchronous motor developing towards the higher precision and higher speed direction [1–5]. BIM has many better advantages than the traditional asynchronous motor, such as simple structure, uniform air gap, high mechanical strength, high speed, and ultrahigh speed running in the corrosion or other special environments. Therefore, it shows broad development prospect in medical equipment, transportation, national defense, and so forth [6–9]. However, BIM has the characteristics of nonlinearity, multivariability, and strong coupling. The traditional PI controller cannot acquire high-performance control for BIM when the control system is disturbed by load torque [10]. Sliding mode variable structure control, as a kind of special nonlinear control, can operate in accordance with the trajectory designed by people and purposefully adjust operation according to the system status, which can gain excellent control performance. Due to the fact that the sliding mode control not only can be set by people, but also does not need high precision mathematical model and has strong robustness to disturbances, it is becoming a hot research topic [11–15], and it is gradually applied in the AC servo system. In [16], a new reaching law was designed to improve the operation quality of sliding mode. At the same time, it was applied in the speed control, which effectively enhanced the robustness of permanent magnet synchronous motor (PMSM) system. In [17], the sliding mode control combining with model reference adaptive was used to obtain the speed. The results showed that it increased the estimation precision of rotor velocity for PMSM and decreased the chattering. In [18], the sliding mode control was used in a generator based on the exercise equipment with nonlinear - characteristic curves. The amount of generator input current harmonic is greatly reduced. In [19], the conventional sliding mode control was united with the adaptive fuzzy backstepping scheme. The simulation proved that this method improved the performance of mismatched uncertain system. In [20], the sliding mode control dealt with the difficult problem of obtaining the counterelectromotive force, and it finally implemented the direct torque control of brushless direct current motor. In [21], the sliding mode control was used to detect the speed and position for PMSM. The experimental results proved the validity of the proposed sliding mode observer. In [22], based on the nonsingular terminal sliding mode algorithm and backstepping metho (...truncated)


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Zebin Yang, Ling Wan, Xiaodong Sun, Lin Chen, Zheng Chen. Sliding Mode Control for Bearingless Induction Motor Based on a Novel Load Torque Observer, Journal of Sensors, 2016, 2016, DOI: 10.1155/2016/8567429