Adaptive Predefined-Time Compound Sliding Mode Control Based on Fractional-Order Theory for PMSM

In this article, an improved adaptive predefined-time fractional-order sliding mode control (PTFOSMC) approach with predefined-time disturbance observer (PTDO) is proposed for permanent magnet synchronous motor (PMSM) servo system. Firstly, to achieve the rapid and accuracy position control, an improved sliding mode control strategy with adaptive predefined-time reaching law (APRL) is proposed, and the convergence rate can be dynamically regulated. Meanwhile, the upper bound of convergence time is directly equal to the tunable parameter. Then, to further suppress the chattering, a fractional-order sliding mode surface is proposed, and the continuous and non-singular characteristic of control signal is guaranteed. The predefined time stability with the proposed PTFOSMC is also proven. Moreover, a predefined-time disturbance observer is designed to estimate the lumped disturbances, which is used for feed-forward compensation. Finally, the experimental results show that the state stabilization can be achieved swiftly by the proposed method while maintaining high control precision, fast transient response and strong anti-disturbance performance.