Enhancement of disturbance-rejection performance of uncertain input-delay systems: A disturbance predictor approach

To suppress disturbances in uncertain tracking control systems with an input-delay, a disturbance predictor based on a high-order generalised extended-state observer is devised in this study. A smooth enough approximation of the disturbance is first made, then the approximation ahead of delay-time is predicted. The construction of the disturbance predictor is based on a truncated Taylor polynomial. To facilitate the analysis and design of the closed-loop control system, control gains for the nominal plant are designed in advance. Then the stability analysis for the closed-loop system is conducted, which yields a robust stability condition. As the disturbance predictor takes into consideration the influence of the input-delay, the presented method enables the enhancement of the disturbance-rejection performance. Finally, comparisons of the developed method with major methods in this field are conducted to validate the developed method and to demonstrate its advantages.