Robust Control of Strip Thickness for Cold Rolling Mill

In this paper, we derive a mathematical model for the final stand of the tandem cold rolling mill and design control systems to improve the thickness precision for the strip. On the basis of a linearized model which discussed the uncertainty of stand module, strip stiffness and the time delay of gauge measurement of the rolling mill system, we propose a thickness controller using robust control which effectively rejects the uncertainties and disturbances. The comparison of suboptimal H∞ control and μ Control for strip thickness control is given. It is illustrated by simulations that the robust μ thickness controller yields better performance than H∞ methods when the system uncertainties and a periodic thickness disturbance exist.