High Precision Thickness Control in a Cold Rolling Mill using a Non-Linear Roll Stand Deflection Model

European Control Conference (ECC), pp. 1907–1912

Abstract

Re-rolling is considered the last processing step in the cold rolling process, which has a substantial influence on the surface quality and the associated properties of the surface. In the case of steel materials, a height reduction of less than 5% is selected to avoid unnecessarily restricting the formability for subsequent forming operations. For this reason, low forces act in this stage of the process, which is non-linearly related to the deflection of the roll stand. In this paper, a nonlinear roll stand deflection model is identified by combining the Iteratively Reweighted Least Squares algorithm (IRLS) and the Gaussian Process Regression (GPR). This approach is designed to achieve a self-calibration of the roll gap, reduce the sensitivity to measurement errors and enable a highly accurate estimation of the stand deflection. This model is then used in a model-based control of the strip thickness that adjusts the roll gap and is evaluated in an experiment by providing a trajectory of the desired strip thickness. The experimental results show a high-precision tracking performance with a tolerance of 4 µm.

Authors 4

1. Christopher Schulte Aachen Institute of Automatic Control (IRT)

   RWTH Aachen University

   Affiliation as printed

   Institute of Automatic Control, RWTH Aachen University, Aachen, Germany

2. Xinyang Li Aachen Institute of Metal Forming

   RWTH Aachen University

   Affiliation as printed

   Institute of Metal Forming, RWTH Aachen University, Aachen, Germany

3. Dirk Abel Aachen Institute of Automatic Control (IRT)

   RWTH Aachen University

   Affiliation as printed

   Institute of Automatic Control, RWTH Aachen University, Aachen, Germany

4. Gerhard Hirt Aachen Institute of Metal Forming

   RWTH Aachen University

   Affiliation as printed

   Institute of Metal Forming, RWTH Aachen University, Aachen, Germany