Optimal Thread-In and Thread-Out Strategies for Heavy Plate Levelers

In this paper, a method to determine optimal adjustment trajectories for the loading and unloading phases of heavy plate levelers is proposed. Due to the high leveling forces, the elastic structure of the leveler is deformed. The available adjustment possibilities of the machine are typically used to actively compensate for the deflection of its work rolls. However, only a small subset of the available degrees of freedom of the leveler may be controlled under load. Therefore, the optimal adjustment is typically determined for the highest expected load and uniformly applied during the whole leveling process. As a consequence, the deflection is overcompensated during the loading and unloading phases of the plate and the head and tail ends of the plate might develop ski-ends. To avoid such an overcompensation, the adjustable degrees of freedom of the leveler can be used. Based on an accurate deflection model of the leveler, the loading and unloading phases of the plate are simulated and the input trajectories for the adjustable degrees of freedom of the leveler are optimized. The proposed approach is validated with simulations.