In strip rolling, hydraulic automatic gauge control (HAGC) system is the key element to guarantee the precision of strip gauge. The stability of the kernel pressure closed loop (PCL) in the HAGC system plays an essential role in guaranteeing the rolling process with high performance. Nevertheless, there is some difficulty in exploring the instability mechanism of the HAGC system due to the fact that the PCL is a representative nonlinear closed-loop control system. In this work, for each component of the HAGC system, the mathematical model was established. And on the basis of the linking relation of various elements, we derived the incremental transfer model of the PCL system. Furthermore, in accordance with the deduced information transfer relation, the transfer block diagram of disturbing variable of the PCL system was obtained. Moreover, for the purpose of deriving the instability condition of the PCL system, the Popov frequency criterion was employed. The instability conditions of the HAGC system were obtained under PCL control. Furthermore, the derived instability conditions of the HAGC system were experimentally verified under various working conditions. The research results provide a fundamental foundation for studying the instability mechanism of the HAGC system.

中文翻译：

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压力闭环控制下液压AGC系统不稳定性条件推导

在带钢轧制中，液压自动厚度控制（HAGC）系统是保证带钢厚度精度的关键因素。HAGC系统中内核压力闭环（PCL）的稳定性对于保证轧制过程的高性能起着至关重要的作用。然而，由于 PCL 是具有代表性的非线性闭环控制系统，因此在探索 HAGC 系统的不稳定机制方面存在一些困难。在这项工作中，针对HAGC系统的每个组成部分，建立了数学模型。并根据各要素之间的联系关系，推导出PCL系统的增量传递模型。进而根据推导出的信息传递关系，得到PCL系统干扰变量传递框图。而且，为了推导 PCL 系统的不稳定条件，采用了波波夫频率准则。HAGC 系统的不稳定条件是在 PCL 控制下获得的。此外，HAGC 系统的衍生不稳定性条件在各种工作条件下进行了实验验证。研究成果为研究HAGC系统的失稳机理提供了基础。