Robust UDE-based control of uncertain nonlinear state-delay systems

In this paper, a robust control strategy for uncertain nonlinear continuous-time plants with disturbances and state delays is proposed. The strategy is based on the uncertainty and disturbance estimator (UDE). Both cases with known and unknown delay are considered. In the case of an unknown time delay, the term with the delay is treated as an additional disturbance to the system. Both nonlinear and linear control algorithms are proposed. The algorithms show excellent tracking and disturbance rejection performance. Simulations are given to show the effectiveness of the UDE-based control.