Disturbance Observer based Repetitive Controller for Time-Delay Systems

This paper presents a discrete control design for time-delay systems subjected to the periodical command signal or exogenous disturbances. Unlike other dead-time compensators (DTC), we take profit of the system components to construct an internal model. In addition, a novel disturbance observer is developed to compensate the effect of disturbances, and thus to achieve tracking and disturbance rejection simultaneously. The possible fractional delay from discretization is also handled by using a fractional delay filter. The stability conditions and robustness analysis under model uncertainties are provided. Two numerical examples including a supply chain management (SCM) is provided to illustrate the feasibility of the results.