Stability analysis of rolling mill system for flexible rolling process based on maximum Lyapunov exponent

Flexible rolling technology is the current development trend of strip production industry. However, due to the simultaneous change of mechanical, process and strip specification parameters in the flexible rolling process, the motion state of the system is difficult to analyze and stability control is hard to achieve. In this paper, the active motion characteristics of rolls in flexible rolling technology are considered, and the dynamic rolling process model is established to reflect the influence mechanism of process and specification parameters on the dynamic rolling force. The dynamic model of a 4-roll rolling mill was developed and the structure-process-specification coupling strategy was applied to couple the models. The Runge-Kutta method was applied to solve the system dynamic equation, and the maximum Lyapunov exponent was calculated under single-parameter variation and in the two-parameter plane. Then the stable region of the system was analyzed. The results suggest that the parameters influence the motion state in the form of coupling, the influence pattern of each parameter on the stability is clarified, the evolution of the stable domain under the effect of parameter coupling is revealed, and the parameter matching strategy is determined. The results of this paper will provide a solution for the system parameter setting of flexible rolling technology and a theoretical reference for enhancing the stability of the rolling mill.