Improved Sliding Mode Control with Disturbance Rejection for Load Torque Observation of Permanent Magnet Synchronous Motors

To address issues like large chattering and slow response in traditional sliding mode control of permanent magnet synchronous motors (PMSMs), a new type of reaching law is designed. This approach incorporates a conventional exponential reaching law with an adaptable proportionality coefficient, system state variables, and the power term of the sliding mode surface to mitigate chattering while enhancing convergence speed. To avoid introducing differential terms of speed error and reduce high-frequency chattering in the system, an integral sliding mode surface is used to design an improved PMSM speed controller. To address the issue of reduced control accuracy and increased chattering in the control system caused by load disturbance fluctuations, a novel saturation function-based extended state observer (ESO) is devised. This ESO is utilized to estimate the load disturbance and the estimated disturbance value is fed forward to the improved sliding mode controller to further enhance the system1 s disturbance rejection capability. The numerical simulation results demonstrate that the proposed control strategy substantially improves the dynamic performance and disturbance rejection of the motor. When the motor is affected by load torque fluctuations, compared to PI control, the proposed control strategy reduces overshoot by about 23.1% and increases response speed by 62.5%. Compared to traditional sliding mode control, the proposed control strategy reduces overshoot by about 15.3% and increases response speed by 50%. The new sliding mode reaching law can effectively reduce sliding mode chattering. Compared to traditional sliding mode controllers, the improved sliding mode controller reduces motor chattering by about 50%. © 2024 Xi'an Jiaotong University. All rights reserved.