Design of a robust thickness controller for a single-stand cold rolling mill

We derive a mathematical model of a single-stand cold rolling mill and design control systems to improve the thickness precision while maintaining prescribed tension for the strip. On the basis of a linearized model of the rolling mill system, we propose a thickness controller using an internal model control (IMC) structure which effectively rejects periodic disturbances. We also discuss how the so-called BISRA AGC method can be combined with the proposed thickness controller in the presence of modeling error. It is illustrated by simulations that the proposed thickness controller yields better performance than existing methods when a periodic thickness disturbance exists, and that it is robust to the uncertainty of the mill modulus.