Rolling Characteristics Analysis And Multi-variable Optimization Strategy For Tandem Cold Rolling Process

As the highly efficient cold rolling mill,the tandem cold rolling mill has large amounts of equipment and complex control procedure.The technology of automatic gauge control and automatic tension control is extremely comprehensive,highly difficult and requires high precision.Based on the research and development project of a pickling and tandem cold mill,the cold rolling characteristics and the multi-variable optimization strategyof automatic gauge control and andautomatic tension control were studied in this paper.The main work is as follows:(1)The main parameters and calculation method of deformation zone in tandem cold rolling process were analyzed.In order to analyze cold rolling characteristics and deduce incremental equations,the rolling force model,deformation resistance model,friction coefficient model and forward slip model were given.Meanwhile,the basic equations for strip rolling process were studied,including mass flow equation,mill spring equation,tension equation and power equation.(2)According to the basic equations of rolling process,the incremental models for tandem cold rolling characteristics analysis were established one by one,such as rolling force incremental model,thickness incremental model,forward slip incremental model and interstand tension increment incremental model.Meanwhile,the expression of incremental equations of entry thickness change was put forword,which using several inertia links instead of time delay.What’s more,the actuators were modeled as inertia links.Based on the deduced incremental equations,the state space expression was established,which lay the foundation for tandem cold rolling characteristics analysis.(3)Combined with mechanical equipment parameters and the related partial differential coefficients,cold rolling characteristics were analyzed using the established state space expression.In order to obtain the influence rule of disturbances and adjustment on the each exit thickness and interstand tension,a series of simulation was performedby given step signal on annealed thickness;roll gap and work roll speed respectively.(4)Based on the linear quadratic optimal control theory,the multi-variable optimization strategy for automatic gauge control and tension control was developed,and the value principles of weight matrix were also developed.After establishing the simulation platform by MATLAB,through giving the annealed thickness,hardness and intermediate disturbance as interference value respectively,the control effects of the traditional control strategy and multi-variable optimal control strategies were compared,the results show that the optimization control strategy has the advantages of high control precision and strong robustness.The research of this study is practical for thickness control and tension control in tandem cold rolling.The thickness control precision and tension control precision of the optimal control system were turn out to be satisfactory.