Multivariable control for the AGC and looper control system at a hot strip mill

It is necessary to make the most of AGC while keeping the interstand tension stable in order to reduce the thickness deviation in hot strip coils. As the conventional control does not take into account the strong dynamic interaction between the AGC and the looper control system, it is difficult to obtain both stability and quick response of the system at the same time. In order to obtain both stability and quick response of the AGC and looper control system, multivariable compensation control, which is based on optimal control theory, was developed and introduced. This new system was designed using linearized state equations which describe the AGC, looper control system and rolling process for the F4, F5 and F6 mills. Simulation tests and experimental tests using an actual hot strip mill at the Wakayama Steel Works showed that this new control system is effective in obtaining both stability and quick response at the same time and in reducing thickness deviation in hot strip coils.