A Flatness Based Approach for the Thickness Control in Rolling Mills

A mulit-stand rolling mill is a highly complex coupled nonlinear system. If the operating point is changing in a wider range the non-linearities can no longer be neglected in the controller design. For a control concept to be feasible in the rough industrial environment, it is absolutely necessary to consider the fact that not all quantities are directly measurable and that they are significantly corrupted by noise. The proposed control approach consists of a non-linear servo compensation in the inner loop and a flatness based thickness and interstand tension controller in the outer loop.