Modern controller for improving product quality during threading of the tandem hot strip rolling mill

The tandem rolling of hot metal strip is a highly complex and nonlinear process which presents a difficult control challenge. The control of the threading phase of this process is especially difficult as the model of the process changes significantly and rapidly as the head of the strip is sequenced from stand to stand during threading. Moreover, to improve the quality of the final product during threading it is necessary to reduce excursions in the strip tension, looper position, as well as strip thickness. In this paper we present a comprehensive model of the threading process plus the results of our initial work to develop a suitable controller which handles the rapid changes in the model during threading. The success of our initial work is demonstrated by a simulation.