Disturbance-observer-based adaptive finite-time dynamic surface control for PMSM with time-varying asymmetric output constraint

This article presents a disturbance-observer-based adaptive finite-time dynamic surface control scheme, capable of guaranteeing transient behavior for the PMSM with arbitrary asymmetric time-varying output constraint and unmatched external disturbance. The major challenge of this paper is devising efficient strategies to tackle the nonsymmetric output restraints with arbitrary characteristics and unmatched external perturbation for the system under the finite-time backstepping framework. Given this, a nonlinear transformation function is adopted to coordinate from the output-constrained dynamic model to an uncontained one, and a finite-time disturbance observer is introduced to evaluate the unmatched external perturbation. Then, a dynamic surface control approach having adaptive properties for PMSM is conceived by combing a neural network to evaluate the nonlinear functions and a first-order filter to handle the "explosion of complexity." Additionally, it is proved that the signals in the closed-loop system can narrow down to a bounded region and the tracking error can merge in a limited time to tiny vicinity of zero by employing a fast finite-time stability principle. Eventually, simulation cases and contrast results reveal the tracking performance and immunity to the disturbance of the devised controller.