Multi-Element Disturbance Observer for Separately Estimating Periodic and Nonperiodic Disturbances in PMSM Control Systems

In high-precision servo systems, the vibration and noise generated by the periodic disturbances have a significant impact on the accuracy and smoothness of permanent magnet synchronous motors. The usually high frequency of the periodic disturbances and the presence of unknown disturbances in the control system make the estimation and compensation of the periodic disturbances challenging. For this reason, a multi-element disturbance observer (MEDOB) is proposed in this article. The rotor position is averaged into a number of intervals, and the corresponding periodic disturbances for each interval can be estimated independently by the MEDOB. As the number of intervals increases, the estimates will approximate the actual periodic disturbances. Separate estimation of periodic and nonperiodic disturbances is realized with the help of the MEDOB. In addition, a single-loop sliding mode speed controller is designed with the disturbance estimates. Lyapunov theory is used to analyze the convergence of the proposed method. Simulations and experiments are implemented, and the results show that the proposed method is competitive in terms of accuracy, response, and robustness.