Adaptive convergence second order sliding mode speed controller for PMSM with a disturbance observer based on a novel sliding mode reaching law

Abstract

Permanent magnet synchronous motors (PMSMs) have attracted extensive attention owing to their high-power density, efficiency, and excellent dynamic performance. Sliding mode control (SMC) is widely used to enhance PMSM speed regulation. However, chattering and implementation difficulties often make conventional SMC less effective and harder to deploy in practice than proportional–integral–derivative (PID) control. This paper proposed an improved adaptive convergence second-order sliding mode control (I-SOSMC) based on PID type sliding mode surface, which exhibits improved dynamic performance, reduced chattering, and simple implementation. To further improve disturbance rejection, an improved sliding mode disturbance observer (I-SMDO) based on a novel sliding mode reaching law (SMRL) is integrated with the I-SOSMC to enhance the disturbance rejection in the PMSM drive. Moreover, the adaptive convergence mechanism in the I-SOSMC adjusts the convergence parameter online according to the estimated disturbance level, thereby strengthening disturbance rejection while further suppressing chattering. Preliminary simulations show that the proposed I-SOSMC reduces settling time from 56.39 ms to 1.41 ms and limits the maximum speed drop from 11.32% to 0.46%, corresponding to about 97.5% faster settling and 96% smaller speed sag. These results indicate that the proposed I-SOSMC achieves faster convergence, smaller speed fluctuations, and superior disturbance rejection, making it a promising solution for high-performance PMSM drives.