Predictor-based disturbance rejection control design for low-order stable and integrating processes with time delay

In this paper, a novel predictor-based disturbance rejection control scheme is proposed for industrial stable and integrating processes with time delay. Two realizable differentiators with finite gain are first introduced to estimate the derivatives of the delay-free output response given by a generalized predictor. Then, a predicted disturbance response is constructed for feedforward compensation by using the input signal along with the delay-free output response and its estimated derivatives. By specifying the desired closed-loop poles, the feedback controller is derived analytically. A prominent advantage of the proposed control scheme lies in that a trade-off between the control performance and its robustness against process uncertainties can be made by monotonically tuning the adjustable parameters in the prediction filter, differentiator and feedback controller, respectively. The necessary and sufficient condition for robust stability of the closed-loop system is established based on the small gain theorem. Two illustrative examples from the literature are adopted to demonstrate the effectiveness and superiority of the proposed control scheme.