Model-Based Optimization of Short Stroke Control in Roughing Mills

Automatic width control is one key issue in hot strip rolling and the main actuator for width control is the vertical draft (edging) applied to slabs in the roughing sequence. In order to compensate for the occurring strip necking, a variable edger gap is applied in the edging process. This paper introduces a comprehensive mathematical optimization approach for the fully automatic generation of the associated edger roll trajectories, which is based on a nonlinear dynamic simulation model for the material flow in the roughing mill. Due to the complexity of this simulation model, gradient-based methods are applied to solve the resulting optimization problem in reasonable time. Hence, derivatives of cost functional and constraints must be provided, which entails computing sensitivity information from the underlying simulation model. Finally, numerical results for real-world examples are discussed to illustrate the capability of the presented approach. In particular, this paper examines the influence of characteristic parameters such as the slab width or the maximum edger screw in velocity onto the optimization results.