The Sliding-Mode Control Based on a Novel Reaching Technique for Permanent Magnet Synchronous Motors

In order to improve the robustness, disturbance rejection and dynamic response performance of permanent magnet synchronous motor (PMSM) speed servo system, a novel sliding mode control (NSMC) strategy is adopted to replace the traditional proportion integral (PI) regulator in the design of speed controller. The mathematical model of PMSM is analyzed and a sliding mode controller based on a novel reaching technique is proposed. The integral of speed error is introduced into sliding mode surface to avoid the requirements of acceleration signal and reduced the steady-state error of the system. Meanwhile, a variable speed reaching method is imported to make the approaching speed correlate with the change of system state |s|, so as to improve the dynamic quality. In addition, the sigmoid function is used to replace the sign function in the conventional SMC, which further reduces chattering phenomena. Simulation and experimental results show that the proposed NSMC method based on the new reaching technique can realize precise speed control. Compared with the conventional PI and SMC control, this method not only achieves a fastest and best response speed, but also has a strongest robustness of resisting the external disturbance.