Sensorless Control Strategy for Permanent Magnet Synchronous Motor Based on a Novel Power-Exponential Reaching Law

To address the issues of slow convergence, significant chattering, and poor suppression of high-frequency interference in sliding mode observer(SMO) for sensorless control of permanent magnet synchronous motors, this paper proposes a novel sliding mode control strategy that integrates an exponential reaching law with a power reaching law, referred to as the power-exponential reaching-law. A second-order low-pass filter is also introduced to enhance the accuracy of system state observation. First, a sigmoid function is employed to replace the traditional sign function, thereby enhancing the smoothness of sliding mode switching. Second, the second-order low-pass filter is used to more effectively attenuate high-frequency disturbances and enhance noise immunity. Finally, a new power-exponential reaching law is designed to balance fast convergence with effective chattering suppression. A simulation model is developed in MATLAB/Simulink, and experimental validation is conducted on a physical test platform. The results demonstrate that the improved SMO significantly enhances dynamic response speed and steady-state accuracy, reduces speed and position estimation errors, and effectively suppresses chattering. This confirms the feasibility and superiority of the proposed method in high-speed sensorless control applications.