LOOPER H-INFINITY CONTROL FOR HOT-STRIP MILLS

Recently, H-infinity (H-infinity) control theory has been applied to s ome engineering fields including steel making process, The H-infinity control theory [1], [2] makes it possible to apply multivariable contr ol with frequency domain design method and to get robust stable contro l systems, Looper H-infinity multivariable control system for hot-stri p finishing mills is developed and got better results than conventiona l control methods, Looper control is one of the most important control items in hot-strip mills, A looper is placed between rolling stands a nd is used for controlling the interstand strip tension, It is very im portant to control stably both a looper and strip tension at their eac h target values, Especially, we intended to reduce strip tension fluct uation more than looper angle fluctuation, because strip tension sever ely affects thickness and width gage, This paper presents the design m ethod of the looper H-infinity control system, Also showing some actua l control data, we compare the performance of conventional PI control, noninteractive control (NIC), and H-infinity control.