Research on Robust Control Strategy of Permanent Magnet Linear Synchronous Motor

Research on Robust Control Strategy of Permanent Magnet Linear Synchronous Motor
　　The paper is supported by National Natural Science Foundation of China“Research of High-precision Micro feed PMLSM AC Servo System”(NO.59875061). The paper researched on the permanent magnet linear synchronous motor (PMLSM) servo system used in modern advanced NC machine tool. For the characteristic of direct drive and the requirements of robustness and tracking performance for the servo system in NC machine tools, this paper focused on the control issues for the PMLSM servo system with the uncertainties of parameter changes and load disturbances. Main contents of the paper are stated as the follows.Based on analyzing the uncertainties of the Neodymium magnets permanent magnet linear synchronous motor servo system, for the uncertainty of PMLSM specific caused by strong end effect disturbance, a robust tracking control strategy was put forward in which the Quantitative Feedback Theory (QFT) is applied in PMLSM robust servo system. Frequency-domain theory is used to design the QFT robust controller, which is adopted as the speed controller. In addition, the uncertain scope of the object and system performance index were used in a quantitative manner to form the boundary in the Nichols chart, so as to conduct system design and shaping on the Nichols chart under the condition that the open-loop frequency curve of the reference object meets the boundary conditions, The pre-filter was designed to compensate for the dynamic performance of the system. Simulation results show that the control scheme can effectively suppress the impact on the servo performance motor, which results from the uncertainties such as parameters change and other disturbances, enhance the dynamic tracking performance, as well as improve the accuracy of the system to a great degree.The traditional design of QFT needs to conduct loop shaping on the Nichols chart so as to obtain a controller, which causes some inconvenience in the design.
　　Therefore, this paper proposed H_∞control method instead of charting to obtain a controller. By means of the rational selections of the uncertainty weighting function, the high-frequency noise suppression weight function and the sensitivity weight function, H_∞control is used to obtain QFT speed controller based on linear matrix inequalities. The proposed method not only simplifies the QFT design steps, but also guarantees that a pre-filter makes the system output response satisfy the performance requirements. Simulation results show that the robust tracking controller for PMLSM based on combing QFT and H_∞control method improves the performance of the system greatly.In order to further increase tracking performance and robust performance of the linear motor servo system, the control method combing the H_∞robust control and sliding mode control(SMC) Neodymium magnets was applied to permanent magnet linear synchronous motor servo system. Sliding mode controller ensures fast tracking performance, while the H_∞robust controller suppresses a variety of disturbances within the closed-loop system and improves the performance. Simulation results show that the robust tracking controller combing the sliding mode and H_∞control method for permanent magnet linear synchronous motor shows good tracking performance, and presents strong robustness on the changes in http://www.chinamagnets.biz/Neodymium/Ball-Neodymium-Magnets.php system parameters.PMLSM experimental system platform was built on the dual-linear motor loading scheme. PID control method, QFT/ H_∞control method and sliding mode/ H_∞robust control method were compared in the experiments under the circumstances of the speed loop sudden loaded and parameters change. The comparative experimental results verifie the validity of control strategies proposed in theoretical analysis and simulation.