Width control system of the hot strip mill using learning control technique

Learning and repetitive control techniques are applied to the width control system of a newly built hot strip mill in order to improve product width quality. The width control system in this paper consists of four functions: (1) edger gap preset; (2) learning control of width deformation model in rough rolling; (3) learning control of width change in finish rolling; and (4) repetitive control of rougher delivery width. The edger gap preset calculates the preset gap of edger work rolls by solving a width deformation model whose error is compensated by the learning control of the width deformation model in rough rolling. Since the strip width changes in finish rolling, the learning control of the width change in finish rolling learns the width change in finish rolling and adjusts the target width of the rougher delivery of the coming bar. Repetitive control of the rougher delivery width compares the actual width and target width of rougher delivery and controls the edger roll gap so as to decrease the deviation between actual and target. The width control system was installed in China Steel Corporation's No. 2 hot strip mill, which began rolling at the end of 1996 and was able to achieve an excellent width performance.