Improved Non-Singular Fast Terminal Sliding Mode Control with Sliding Mode Disturbance Observer for PMSM Drives

To further improve the dynamic response and disturbance rejection performance of Permanent Magnet Synchronous Motor (PMSM) drive systems, a composite control strategy is proposed in this paper, integrating an enhanced Non-Singular Fast Terminal Sliding Mode Controller (NFTSMC) with a Sliding Mode Disturbance Observer (SMDO). The primary challenge addressed is the inherent chattering problem commonly encountered in traditional NFTSMC methods, particularly when striving for fast response. To mitigate this issue, a Novel Sliding Mode Reaching Law (NSMRL) is introduced. This reaching law is designed to adapt to the variations in the system's state, effectively suppressing chattering in the control output, while maintaining the controller's high-precision tracking performance. In addition, to further improve the disturbance rejection capability of the control system, SMDO is employed to estimate load disturbances in real-time. The estimated disturbances are then incorporated into the output of the improved NFTSMC as a feedforward compensation term, thereby enhancing the system's ability to reject disturbances. The effectiveness of this composite control approach is demonstrated through simulation results, which show superior performance in terms of fast dynamic response, efficient chattering suppression, and strong disturbance rejection in PMSM drive systems.