Looper and tension control in hot rolling mills: A survey ☆

H-infinity (H/sub /spl infin//) control theory has been applied to some engineering fields including the steel making process. The H/sub /spl infin// control theory makes it possible to apply multivariable control with frequency domain design method and to get robust stable control systems. A looper H/sub /spl infin// multivariable control system for hot-strip finishing mills is developed and achieves better results than conventional control methods. Looper control is one of the most important control items in hot-strip mills. A looper is placed between rolling stands and is used for controlling the interstand strip tension. It is very important to control stably both a looper and strip tension at their target values. Especially, we intended to reduce strip tension fluctuation more than looper angle fluctuation, because strip tension severely affects thickness and width gage. This paper presents the design method of the looper H/sub /spl infin// control system. Also showing some actual control data, we compare the performance of conventional PI control, noninteractive control (NIC), and H/sub /spl infin// control.

Looper H-infinity control for hot strip mills

Hot strip mill tension–looper control based on decentralization and coordination

Optimal Control System for Hot Strip Finishing Mill

A gauge control system for a hot strip finishing mill based on optimal regulator theory has been developed. The control objective is to minimize finisher exit strip thickness deviation resulting from temperature disturbance and other factors. A linearized mathematical model, valid for the fluctuations about the steady-state operating point, was derived. Then, the stability condition of the conventional gauge control system was derived. As a result, a novel system with greater response for interstand strip tension control was required. In order to improve the strip gauge accuracy, a multivariable compensator based on optimal regulator theory was introduced. Simulation studies and experimental results show that this gauge control system with the multivariable compensator is superior to the conventional gauge control system in terms of strip gauge control accuracy. >

F. Watanabe

Papers

Multivariable Control of Hot Strip Mill Looper