A compound control method of improving speed tracking accuracy for permanent magnet synchronous motor

To address the challenge of achieving precise tracking control in permanent magnet synchronous motor (PMSM), owing to the presence of periodic torque ripple and non-periodic disturbances, a compound controller combining iterative learning control (ILC) and improved nonsingular fast terminal sliding mode control (INFTSMC) is introduced. First, the state space equations of the PMSM are formulated to incorporate the unmodelled periodic functions and non-periodic disturbances that need to be learned. Second, a novel nonsingular fast terminal sliding mode surface is developed, in which the variable function related to the error is introduced, thereby enhancing robustness against disturbances while ensuring rapid convergence. To suppress the effect of periodic torque ripple, the ILC is designed to approximate the unmodeled periodic function. With the aim of weakening the chattering phenomenon, fuzzy control is utilized to update the switching gain in real time. Finally, the experimental results reveal that the developed control strategy significantly weakens disturbances and improves both the tracking performance and capacity of resisting disturbance for PMSM servo system.