Anti-windup design of active disturbance rejection control for sampled systems with input delay

A novel anti-windup design of active disturbance rejection control (ADRC) is proposed for industrial sampled systems with input delay and saturation. By using a generalized predictor to estimate the delay-free system output, a modified extended state observer is designed to simultaneously estimate the system state and disturbance, which could become an anti-windup compensator when the input saturation occurs. Accordingly, a feedback controller is analytically designed for disturbance rejection. By proposing the desired closed-loop transfer function for the set-point tracking, a prefilter is designed to tune the tracking performance while guaranteeing no steady-state output tracking error. A sufficient condition for the closed-loop system stability is established with proof for practical application subject to the input delay variation. Illustrative examples from the literature are used to demonstrate the effectiveness and merit of the proposed control design.