Attenuation of roll eccentric disturbance by modified repetitive controllers for steel strip process with transport time delay

In this paper, we propose a new modified repetitive controller to attenuate roll eccentric disturbance in a steel strip rolling process with a transport time delay in control. A conventional modified repetitive controller cannot address the transport delay adequately. To overcome this difficulty, we propose a new mechanism which cancels such a delay in a closed loop. Furthermore, the transport time delay has a fluctuation which causes adverse effects on a performance of the disturbance attenuation and the stability of the closed loop. To address these problems, we apply μ synthesis to compensate such a fluctuation and to stabilize the closed loop. Finally, we validate the effectiveness of the proposed method by a numerical simulation.