Abstract
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.
Highlights
In the rolling industry, hydraulic automatic gauge control (HAGC) system is a pivotal component to guarantee the precision of strip thickness. e reliability of its work is the kernel of ensuring the rolling process with stabilization
It can be found that with the increase of rolling force, the vibration severity of the load of the HAGC system increases gradually. It indicates that the vibration strength of the HAGC system will augment with the increase of rolling force. is result reflects the effect of the operating pressure pL, which shows agreement with the influence of pL on the system stability derived from the instability condition
In order to derive the absolute stability condition and instability condition, the Popov frequency criterion was employed. e instability conditions of the HAGC system under pressure closed loop (PCL) control were obtained under two working conditions, that is, when the spool displacement of servo valve is positive and negative, respectively
Summary
Hydraulic automatic gauge control (HAGC) system is a pivotal component to guarantee the precision of strip thickness. e reliability of its work is the kernel of ensuring the rolling process with stabilization. Erefore, for the rolling production process, it is urgent to thoroughly investigate the instability mechanism of the HAGC system and take effective control measures in real time. E HAGC system is an intricate dynamic system formed by mechanical, electrical, and hydraulic elements It has the features such as nonlinear, time-varying, strong coupling, and large hysteresis. The Lyapunov method was often adopted by scholars to research the absolute stability of nonlinear closed-loop system. Liu et al [45] studied regenerative chatter mechanism in rolling through stability analysis by using integral criterion and Lyapunov method. It is a novel research way to theoretically deduct the instability mechanism of HAGC via utilizing the Popov criterion, which needs an in-depth study.
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