Cooperative Optimization Strategy Of Gauge-Looper Integrated Control System For Hot Strip Mills

The important production process of iron and steel industry in hot strip finishing rolling process has extremely strict requirements for geometric size,mechanical properties and surface quality.Among them,the gauge of strip is an important index to measure the quality of strip products.Although most hot strip rolling production lines use a variety of automatic control systems,because of its poor production conditions and complex rolled process,there are still all kinds of disturbances.The traditional control method takes strip thickness,loop angle and strip tension as a separate subsystem(or loop angle and strip tension as a subsystem),which can not coordinate the coupling between the three elements.,its control performance can not meet the increasingly stringent requirements of the market for hot rolled strip.In this paper,the thickness-loop integrated system of hot strip rolling is taken as the research object,and the thickness-loop integrated system of hot strip finishing mill is taken as the research object.The state space model of the thickness-loop integrated system of hot strip mill is established.The predictive control of the single stand thickness-loop integrated system and the distributed predictive control of the overall thickness-loop integrated system of the hot strip finishing mill are studied respectively.According to the basic equation and mathematical model of hot continuous rolling process,the strip thickness increment equation,the strip tension increment equation and the looper angle increment equation are established,and the state space model of the thickness-loop integrated system is established considering the adjusting actuator and process delay and thickness delay.The coefficient matrix in the state space model is determined by solving the partial differential coefficients such as partial differential coefficients and forward slip partial differential coefficients of rolling force.At present,most hot strip rolling production lines use programmable logic controller.The discrete predictive controller can meet the needs of practical application,so the MPC of hot strip thickness-loop integrated system is designed based on the state space model.On the basis of the actual production data,the on-line simulation is carried out.The simulation results show that the thickness response time,the angle response time and the tension response time of the MPC controller are 20ms,30ms and 10ms respectively.When the system is disturbed,the maximum thickness fluctuation value is 1.24μm,and the maximum angle fluctuation value is 9.27e-2rad.The maximum tension fluctuation vaiue is 1.14MPa,and has strong robustness.The MPC controller can realize the coordinated optimization of the hot continuous rolling thicknesslooper comprehensive system.there are many subsystems in hot strip finishing rolling and each subsystem is related to each other.The model is more complex and there are many constraints and control objectives,the thickness-loop integrated system of hot strip finishing rolling process not only requires its effectiveness,but also ensures the large-scale system related to each subsystem.In this paper,a distributed predictive control method based on neighborhood optimization is proposed to design a distributed MPC controller.The simulation results show that the thickness response time,angle response time and tension response time are 20ms,30ms and 10ms,respectively.When the system is disturbed,the maximum thickness fluctuation value is 7.34e-2μm,and the maximum angle fluctuation value is 1.5e-3rad.The maximum tension fluctuation vaiue is 2.18e-2MPa.The distributed MPC controller can better maintain the stability of the system,and realize the global coordinated optimization control of hot rolling.