Looper Control System Modeling And Its Predictive Control In Hot Strip Mill

The looper control system includes looper height control and strip tension control,and the coupling relationship makes it more complicated.By taking the looper system in hot strip mill as the research object,the working principle and control strategy were analyzed in the looper control system,also the looper height control and strip tension control coupling models of state space were established.Based on the comprehensive looper control system with model predictive control,the control effects were analyzed finally.The main research contents are as follows:(1)The looper control process in hot strip mill was discussed,in which the looper rising control,constant tension rolling control and looper lowering control were studied.The control strategies of looper rising and looper lowering were given.Focusing on the constant tension rolling stage,the control principle of looper height and strip tension were deep researched.(2)The mechanism of tension was detailed elaborated,and the strip tension model in hot rolling process was established,also the industrial looper length model was build.And the looper force condition in constant tension rolling process was analyzed,in which the torque of strip tension,gravity torque,and the accelerating torque were calculated,finally the looper mechanical model was build.According to the features of actuators,the dynamic models were represented as inertia link.Finally,comprehensive consideration with the coupling relationship between looper height and strip tension,the dynamic state-space model of looper system was received.(3)The looper height and tension control system was a typical double-input and double-output multivariable control system,in which the dynamic coupling process and rolling condition disturbance were existed in the rolling process.Based on the loop state space model,the comprehensive looper control strategy of predictive control was given.Combined with the control process of looper height and strip tension,the control algorithms of model prediction,rolling optimization,and on-line model correction in predictive control are deep researched.(4)The simulation platforms of traditional control and predictive control for looper control system were built by MATLAB.By giving the step signal and sine signal to the strip tension and looper angle,the control accuracy and tracking performance of the two control methods were compared.Also the anti-interference ability and robustness of the two controllers were compared and analyzed by the simulation process of rolling gap adjustment and rolling parameters changed.The simulation results showed that,the predictive control model had better control performance and higher system stability.The research results in the paper are effective and practical to the looper control system in hot tandem mill,and it has popularization value.Additional,the model predictive control method has extensive application prospect for other control systems in rolling process.