2014 Volume 45 Issue 3 Pages 42-49
Many kinds of electro-hydraulic servo systems are applied to rolling mills such as a hot strip mill, a cold strip mill and a seamless tube mill because of quick response, high power and high positioning accuracy. However when applying an electro-hydraulic servo system to a hot strip downcoiler, it was found that the controlled object has low natural frequency and is lightly damped so that stable control is very difficult. In the former report, optimal control theory was applied in order to improve these characteristics. However, the derived control system was found to be poor in robustness. Especially, the control effectiveness was highly influenced by the response of the servo valve and the length of piping between the servo valve and the cylinder. In this report, a newly developed control system has been presented, and was found in the adjustment of the control system applied to the production machine. The new control system belongs to a kind of Posicast Control proposed by O.J.M. Smith in 1957. However the final type of this system, named new Posicast Control, has realized a robust control and a kind of Dead-Beat Control.
