Abstract
In the metallurgical industry, hydraulic automatic gauge control (HAGC) is a core mechanism for thickness control of plates used in the rolling process. The stability of the HAGC system’s kernel position closed-loop is key to ensuring a process with high precision, speed and reliability. However, the closed-loop position control system is typically nonlinear, and its stability is affected by several factors, making it difficult to analyze instability in the system. This paper describes in detail the functioning of the position closed-loop system. A mathematical model of each component was established using theoretical analysis. An incremental transfer model of the position closed-loop system was also derived by studying the connections between each component. In addition, based on the derived information transfer relationship, a transfer block diagram of disturbance quantity of the system was established. Furthermore, the Popov frequency criterion method was introduced to ascertain its absolute stability. The results indicate that the absolute stability conditions of the position closed-loop system are derived in two situations: when spool displacement is positive or negative. This study lays a theoretical foundation for research on the instability mechanism of an HAGC system.
Highlights
The development of “intelligent” and “green” manufacturing equipment has propelled the metallurgical industry to pursue intelligence in their rolling equipment, and to ensure high quality of plates and strips used in the industry [1]
The hydraulic automatic gauge control (HAGC) system is a core mechanism for thickness control of plates used in the rolling process
Where m1 is the equivalent mass of moving parts of the upper roll system (URS); m2 is the equivalent mass of the moving parts of the lower roll system (LRS); c1 is the linear damping coefficient of moving parts of URS (N·s/m); c2 is the linear damping coefficient of moving parts of LRS (N·s/m); k1 is the linear stiffness coefficient between the upper frame beam and the moving where m1 is the equivalent mass of moving parts of the upper roll system (URS); m2 is the equivalent mass of the moving parts of the lower roll system (LRS); c1 is the linear damping coefficient of moving parts of URS (N·s/m); c2 is the linear damping coefficient of moving parts of LRS
Summary
The development of “intelligent” and “green” manufacturing equipment has propelled the metallurgical industry to pursue intelligence in their rolling equipment, and to ensure high quality of plates and strips used in the industry [1]. Sun et al [7] proposed a dynamic model of a cold rolling mill based on strip flatness and thickness integrated control. Scholars have previously applied the Lyapunov method to study the absolute stability of a nonlinear closed-loop control system [33,34]. Popov created a frequency criterion method to determine absolute stability of a nonlinear closed-loop control system It relied on a classical transfer function and eliminated the dilemma of reconstructing a decision function. Conducting the theoretical derivation and in-depth study of the instability mechanism of the HAGC system by using Popov frequency criterion method, is a new technique which needs to be further explored. The Popov frequency criterion method is introduced to theoretically deduce the absolute stability condition for key position closed-loop system in HAGC.
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