Abstract
The authors have developed a new looper control system for hot strip mill finisher using H∞ control method, and have obtained good results. Looper control is one of the most important control items in hot strip mills. Loopers are placed between each rolling stands. Strip tension is controlled by raising and lowering the looper, and by changing rolling speed. The tension severely affects the quality of steel products such as thickness and width, so it is very important to control stably both looper angle and strip tension as their target values.
This paper presents the design way of the looper H∞ controller, and shows some on-line results. Two types of H∞ controller, i.e. output feedback type and state feedback type, are discussed. And a new way of reducing strip tension fluctuation using looper angle is proposed. Also performances of previous looper control such as conventional PI control and non-interactive control, and that of the looper H∞ control are compared. Actually controlled data show that the performance of H∞ control is better than the others.
