Strip Flatness Control Based On Intelligent PID In Single Stand

With the development of national economy and the progress of science and technology,people’s requirement for the quality of steel products is more and more higher. Board strip asthe main steel products, its quality index are also increasingly becoming people’s attention. Inrecent years, the wide application of Automatic Gauge Control system makes longitudinalthickness accuracy of strip steel problem resolved, while flatness accuracy problem is still ahot topic in the field of strip rolling. How to effectively control the strip flatness is one of thedifficulties in the field of strip rolling. The strip shape control technology has both advantageand shortage, which made a larger innovation space for the strip shape control technology.Hydraulic bending roll system is one of the important means of shape control, it is themost basic links of the strip shape control system, and it usually combined with CVC, PC orHC technology. The dynamic performance and steady-state performance of the system had agreat influence on the performance of the whole control system, and with the nonlinear,time-varying, lagging and complex features, so it is difficult to establish accuratemathematical model. Traditional PID control has higher accuracy requirement to thecontrolled object‘s mathematical model, and dealing with complex nonlinear system cannotachieve the ideal effect in the actual production process. As a new research field of intelligentcontrol, classical fuzzy control does not need accurate mathematical model of the controlledsystem, and it is suitable for nonlinear complex system.In this article we treat the hydraulic bending roll system of the end strip finishing millgroup frame as the object of control. First we introduce the basic knowledge of strip shape,including the shape of crown and flatness, the factors affecting the quality of strip shape andthe classification of strip shape defect. Then deduced the dynamic components’ mathematicalmodel of the hydraulic bending roll system, and established the equivalent mathematicalmodel of hydraulic bending roll system. On the basis of the control object and controlobjectives, the controller of hydraulic bending roll flatness control system was designed.Combining the advantages of conventional PID controller and fuzzy control, putting themtogether, we design an adaptive PID controller，which is suitable for hydraulic bending rollflatness control system. The controller uses two input three output modes, with the flatness error and error change rate as two inputs, three parameters’ variation of PID control as theoutput. It realizes self-tuning of PID parameters through fuzzy reasoning, so as to meet thecontrol requirements and improve the control precision. Using MATLAB software to simulinkthe fuzzy adaptive PID controller, and comparing the simulation results with the traditionalPID controller’, the results show that the control effect of fuzzy adaptive PID controller suchas the dynamic, steady state and robustness is better.On this basis, this paper designed the hydraulic bending roll flatness control based onsingle chip microcomputer technology system, including the function modules’ software designand using single chip realizing the fuzzy adaptive PID control algorithm. Considering themicrocontroller’ resources and real-time performance of the system, the fuzzy reasoningalgorithm is used in direct look-up table method. This paper introduces the overall design ofhydraulic bending roll flatness control system based on single chip microcomputer, thesoftware system designation uses modular structure method, so that is conducive to theexpansion of the function and is convenient debugging, transplantation and modification.