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A hybrid system approach to tension control in hot strip mills

This talk presents a new control design method for the strip tension between adjacent stands in hot strip mills. The focus is placed on the start-up phase of each rolling, where the looper is raised above the pass line just after the leading end of the strip passes through the downstream stand so that the looper comes into contact with the strip and forms a loop of the stored strip between the stands. Both tension and looper angle control in this phase is normally performed in an ad-hoc manner; a constant value is given as the looper motor torque reference and the feedback control does not start until the looper comes into contact with the strip. In the proposed method, strip tension and looper trajectories are simultaneously optimized all the way through the start-up phase which consists of the non-contact and contact modes. First, a discrete-time piecewise affine model is derived to describe the discontinuous dynamics of this system. Next, the optimal manipulated variables are calculated within a model predictive control framework. An approximate solution method is also presented for the ease of online optimization. Furthermore, the proposed method is applied to generate the optimal feedforward control input which can be used as a good alternative of the conventional constant torque reference. This is very practical because the optimization can be done offline in advance of rolling operations. Simulation results are shown with respect to the offline optimization.

Type of Seminar:
Public Seminar
Dr.Eng. Kasuya Asano
Instrument and Control Engineering Department, JFE R&D Corporation, Kawasaki, Japan
Sep 07, 2004   10:00

ETH-Zentrum, ETZ E6, Gloriastrasse 35, 8006 Zurich
Contact Person:

Prof. M. Morari
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Biographical Sketch:
1983 Received Master's degree from the University of Tokyo Joined Kawasaki Steel Corp. 2003 Joined JFE R&D Corp., which is established by the consolidation of Kawasaki Steel and NKK. 1993~1994 Visiting associate at Caltech 1994-1995 Academic guest at ETH 2001 Received Doctor of Engineering from the University of Tokyo