Robust model-free super-twisting sliding-mode control method based on extended sliding-mode disturbance observer for PMSM drive system

Unknown disturbances such as parameter perturbations, PM demagnetization fault, and external disturbances degrade the control performance of a permanent magnet synchronous motor (PMSM) drive system. This paper presents a novel model-free super-twisting sliding-mode control (MFSTSMC) method based on an extended sliding-mode disturbance observer (ESMDO) for a PMSM drive system. First, a novel model-free ultra-local model (ULM) is presented for PMSM with unknown disturbances. Next, the speed loop and d−q axis current loops controllers are designed by using the MFSTSMC method. This control strategy drives the system state quickly converges to the reference value in finite time. Then, an ESMDO is constructed to estimate the unknown parts of the novel model-free ULM. The estimated unknown part is fed back to the MFSTSMC controller to perform feedforward compensation, which effectively eliminates the influence caused by unknown disturbances. Moreover, the stability of the designed observer-based controller is discussed using a quasi-quadratic Lyapunov approach. Finally, comparisons with other methods demonstrate that the presented method improves the dynamic response, anti-disturbance, and robustness of the PMSM drive system.