A dynamic convergence second-order sliding mode control structure for PMSM with an observer based on a novel sliding mode reaching law

Sliding mode control (SMC) is widely used to improve the speed control performance of permanent magnet synchronous motors (PMSMs). However, challenges such as chattering and implementation difficulties often make traditional SMC ineffective and difficult to implement in practice. This paper proposes a dynamic convergence second-order sliding mode control (SOSMC) structure to solve these problems. This method reduces the reliance on sufficiently large switching gains, effectively addressing the conflict between disturbance rejection and chattering reduction. Specifically, this proposed method outlines principles for dynamically adjusting the convergence process and enhance disturbance rejection capability. Furthermore, it contains an adaptive switching gain influenced by the convergence of the system state to enhance its overall performance. Compared to conventional methods, this approach demonstrates significant improvements in speed drop reduction and settling time, achieving 97.3% and 86.9% of the performance of the controller with disturbance observer (DOB), respectively. To verify the effectiveness of the proposed structure, a fuzzy-based adaptive method is designed and integrated with the control structure. Apart from the proposed SOSMC structure, a sliding mode disturbance observer (SMDO) is designed with a novel sliding mode reaching law (SMRL) to reduce chattering issue and improve disturbance rejection in PMSM systems, showing faster convergence and greater accuracy compared with traditional SMRLs. Finally, both simulation and experimental results are conducted to demonstrate the effectiveness of the proposed methods.