Modeling And Simulation Of Thickness Control In The Hot Rolling Process

With the development of the science and technology,the automation level of rolling mill increases gradually,and thus the requirement for the strip production quality are growing higher and higher.As an important quality performance,a high precision and in-depth study of automatic gauge control is very necessary.By virtue of its high control accuracy,fast response speed and simple and reliable overload protection characteristics,hydraulic AGC(Automatic Gauge Control)is widely used in modern rolling production.In this thesis,based on the mill deformation curve and the strip plastic deformation curve,some factors' influences on the strip exit gauge are analyzed.Through the mathematical model of HGC(Hydraulic Gap Control)system is built according to the basic equation of servo valve,the continuity equation of hydraulic cylinder and the equation of force equilibrium with load and hydraulic cylinder.In the same time,the model of speed and rolled piece are also built,and all of this is the basic of multi-rolling mill continuously working.Because Smith predictive monitoring AGC is sensitive to the model change,generalized predictive control is applied to monitoring AGC,and the two algorithms are simulated and compared.Later,this thesis basing on Advantech Industrial Personal Computer and using Visual Studio C#language completed the virtual mill system software.The basic working process of the rolling mill can be simulated in virtual mill system software,including the generating of rolling mill's model,the process monitoring,the calculation during the mill's working process and the export of working data.And this software also has many other functions.Relied on the Siemens SIMATIC TDC control platform,we have gotten the difference equation of HGC system through its discrete mathematical model,and then used the CFC(Continuous the Function Chart)language in STEP7 to build the HGC computer control system.With high-speed processing capability of the TDC and on the basis of AGC theory,we have designed Gaugemeter AGC,the Feedforward AGC and Monitor AGC control algorithm and given its control block diagram and programming flow chart.The rolling force limiting control and roll gap leveling function are also designed to protect the mill.Finally,based on the Siemens TDC platform,we design and compile a controller to control virtual mill system.Then using the AGC control algorithm,simulate single stand in simulation experiment.After achieving good control effect in single stand mode,we simulate the five stands all together,to test the function of five-stand tandem rolling.At last,we introduce the random disturbance into virtual mill system.And all of the results show us that the virtual mill system simulates real rolling mill system well.