Reduced-order observer-based robust control for cold rolling mill HAGC system with measurement delay

In view of the case that time-delay arises in the output measurements and system states are not all measurable for the hydraulic automation gauge control (HAGC) system in cold strip rolling mills, the reduced-order observer-based robust control strategy is proposed to improve the accuracy of the strip thickness in practice. Based on Lyapunov-Krasovskii functional stability theory, a sufficient condition is first given under which there exists an asymptotically stable reduced-order observer and a robust stabilizing controller for the uncertain nonlinear system with output delay. And then, with the help of this result, a robust output feedback stabilizing controller is designed for the HAGC system in cold strip rolling mills. Moreover, simulation results in a real cold strip rolling mill are given to show the effectiveness of the proposed control scheme.