Strong-Robustness Sliding Mode Torque Observer With Frequency Adaptive Filter Integrated for PMSMs

Accurate estimation of load torque is critical for optimizing the control performance of permanent-magnet synchronous motor (PMSM) drives. This paper first establishes a mathematical model of the PMSM using coordinate transformation theory. Then, a non-singular terminal sliding mode load torque observer (NTSMLO) is developed to precisely estimate load torque during motor operation, taking advantage of the non-singular terminal sliding mode to achieve rapid response times and minimize chattering effects. However, traditional low-pass filters have problems with phase distortion and low roll-off rates, which limits their adaptability in dealing with external disturbances and time-varying parameters. To improve observation accuracy and enhance robustness, a frequency adaptive observer (FAO) is integrated into the NTSMLO, forming the adaptive non-singular terminal sliding mode load torque observer. Finally, the effectiveness of the proposed observer is validated through numerical simulations and experimental tests. Experimental results demonstrate significant improvements in both speed and parameter robustness over traditional sliding mode observers.