Enhanced Active Disturbance Rejection Control for Time-Delay Systems

In this paper, a further enhanced active disturbance rejection control method is proposed for time-delay systems, which can be generally applied for open-loop stable, integrating and unstable processes. The plant model is adopted to design an extended state observer (ESO) such that both the disturbance and the unknown plant dynamics could be estimated. Then a prediction filter is designed to estimate the delay-free output response for control design, while satisfying the asymptotic stability constraints. A notable merit is that there is a single tuning parameter in the proposed ESO or controllers, which can be monotonically tuned to achieve a good trade-off between the control performance and robustness. The robust stability constraint of the closed-loop system is derived in terms of the linear matrix inequality and the Wirtinger inequality. An illustrative example is given to demonstrate the effectiveness of the proposed method.