Research On Decoupling Control Method Of Thickness And Tension In Reversing Mill

In the process of reversible mill rolling the strip entry speed would vary consequently when changing the roll position to adjust the strip thickness, thereby the entrance strip tension would be influenced through the change of the strip entry speed. When the tension is changed, the strip thickness would be influenced through the change of rolling force. Therefore, in order to improve the system control precision and control performance, it is very necessary to make research on the decoupling control method of the thickness and tension system.Firstly, the feedforward AGC module, the mass flow AGC module, thickness measurement AGC module and the acceleration and deceleration compensation function of the reversing mill automatic gauge control system are analyzed in this thesis. Then the control principles of direct tension control, indirect tension control and compound tension control are introduced. After that the coupling relationship between the thickness and the tension control system in the rolling process is deeply studied.Secondly, based on the mathematical model research of the thickness and tension and the coupling relationship between variables, this thesis has set up thickness -tension multivariate model taking the roll reference position and the uncoiler drive motor torque as manipulated variables and the strip exit thickness and the strip entry tension as controlled variables.Thirdly, the diagonal matrix decoupling method and the decoupling method based on invariance principle which are commonly used in engineering are studied in order to reduce the interaction between the strip thickness and tension and further improve the strip thickness and tension control precision. After that the decoupling compensator applying the invariance principle is designed for the thickness-tension coupled model and then the decoupling effects of the thickness -tension coupling system are simulated.Finally, the robust controllers are designed based on the mixed sensitivity control method since there exists the uncertainty of the model parameters perturbation and all kinds of interference in the decoupled thickness and tension system. The parameters selection of weighting function has randomness in the process of robust controllers designing. Therefore, the genetic algorithm is applied in this thesis to optimize the weighting function parameters. Finally, the simulation experiments of the thickness and tension control system with robust controllers and PID controllers have been made using MATLAB and the corresponding control performances are compared. The research results show that the decoupled thickness and tension control systems with the robust controllers could get better control effect.