Abstract Hot-dip galvanizing is a standard technology to produce coated steel strips. The primary objective of the galvanizing process is to establish a homogeneous zinc layer with a defined thickness. One condition to achieve this objective is a uniform transverse distance between the strip and the gas wiping dies, which blow off excessive liquid zinc. Therefore, a flat strip profile at the gas wiping dies is required. However, strips processed in such plants often exhibit residual curvatures which entail unknown flatness defects of the strip. Such flatness defects cause non-uniform air gaps and hence an inhomogeneous zinc coating thickness. Modern hot-dip galvanizing lines often use electromagnets to control the transverse strip profile near the gas wiping dies. Typically, the control algorithms ensure a flat strip profile at the electromagnets because the sensors for the transverse strip displacement are also located at this position and it is unfeasible to mount displacement sensors directly at the gas wiping dies. This brings along that in general a flatness defect remains at the gas wiping dies, which in turn entails a suboptimal coating. In this paper, a model-based method for a feedforward control of the strip profile at the position of the gas wiping dies is developed. This method is based on a plate model of the axially moving strip that takes into account the flatness defects in the strip. First, an estimator of the flatness defects is developed and validated for various test strips and settings of the plant. Using the validated mathematical model, a simulation study is performed to compare the state-of-the-art control approach (flat strip profile at the electromagnets) with the optimization-based feedforward controller (flat strip profile at the gas wiping dies) proposed in this paper. Moreover, the influence of the distance between the gas wiping dies and the electromagnets is investigated in detail.

中文翻译：

---

热镀锌线横向带钢轮廓的前馈控制

摘要 热镀锌是生产镀层钢带的标准技术。镀锌过程的主要目标是建立具有规定厚度的均匀锌层。实现这一目标的一个条件是带钢和气体擦拭模具之间的横向距离均匀，这会吹走过多的液态锌。因此，在气体擦拭模具处需要平坦的带材轮廓。然而，在此类设备中加工的带材通常会出现残留曲率，这会导致带材出现未知的平整度缺陷。这种平整度缺陷会导致气隙不均匀，从而导致锌涂层厚度不均匀。现代热镀锌生产线通常使用电磁铁来控制气体擦拭模具附近的横向带材轮廓。通常，控制算法可确保电磁铁上的带钢轮廓平坦，因为横向带钢位移传感器也位于该位置，将位移传感器直接安装在气体擦拭模具上是不可行的。这导致通常在气体擦拭模具处保留平整度缺陷，这反过来又导致次优涂层。在本文中，开发了一种基于模型的方法，用于在气体擦拭模具位置对带钢轮廓进行前馈控制。该方法基于轴向移动带钢的板模型，该模型考虑了带钢的平整度缺陷。首先，针对各种测试条和工厂设置开发和验证平整度缺陷的估计器。使用经过验证的数学模型，进行了一项模拟研究，将最先进的控制方法（电磁铁上的扁平带材轮廓）与本文提出的基于优化的前馈控制器（气体擦拭模具上的扁平带材轮廓）进行比较。此外，详细研究了气体擦拭模具与电磁体之间距离的影响。