Control process for a roll stand for rolling a strip

A method of controlling a roll stand for rolling a strip, wherein the roll stand has at least one pair of work rolls and one pair of back up rolls, and optionally one pair of intermediate rolls, each of the rolls mounted on bearings, wherein the method comprises the steps of:

• a) using controls for controlling a rolling force, a deflecting force, and optionally a roll shift in the roll stand;
• b) using a roll stand model and a deflection model to generate values for controlling the rolling force, deflecting force, and optionally the roll shift;
• c) assigning a specified roll gap variation to the roll stand model and using the roll stand model to calculate from the specified roll gap variation on-line set points for the rolling force, the deflecting force, and optionally the roll shift;
• d) wherein the on-line set points for the rolling force, the deflecting force and optionally the roll shift are calculated by calculating relationships between on the one hand rolling force, deflecting force, and optionally roll shift and on the other hand a corresponding roll gap variation, on-line at a plurality of interpolation points, the relationships being determined by the steps of:
• e) establishing along an axis of each roll a number of interpolation points, wherein corresponding interpolation points are arranged at the same axial position on each roll;
• f) obtaining a local force at each interpolation point of each roll, wherein the sum of the local forces of each roll is equal to the outside force acting on the bearings of that roll;
• g) calculating at each interpolation point of each roll a deflection based on the local force corresponding to each interpolation point of each roll;
• and
• h) calculating a correction value for each of the local forces of neighboring rolls at each interpolation point from the deflections on neighboring rolls at each interpolation point.