| Based on the750mm hot strip mill project, with the purpose of practicality, the ultra fast cooling control system which include feedback and feedforward control, closed-loop control of water pressure,optimum control of the temperature in ultra fast cooling area is developed..The main work and results are as follows:(1) The controlled cooling technologies and equipments at home and abroad are analyzed,The advantages and disadvantages of several cooling manner are comparing. Expound the principle of ultra fast cooling and it’s core status in newTMCP.(2) The whole system which include feedback and feedforward control, closed-loop control of water pressure, track of head and tail of strip, opening-closing sequence and some other functions is designed according to process equipment requirements of ultra fast cooling.(3) In the ultra fast cooling area, the speed variation of the strip tail at the moment the strip leaves the last fine stand makes temperature control more difficult. Now the dynamic feedforward control strategy is designed, which will improve control accuracy of the strip tail temperature.(4) Under the circumstances of pure lag in feedback control system and the imprecision of the controlled object model, the fuzzy logic and pure lag compensation theory is used to design a Fuzzy PI-Smith control system. By the Simulink toolbox and Fuzzy logic toolbox of MATLAB, the system has been simulated. The simulation results show that the Fuzzy PI-Smith system has faster response speed and smaller overshoot than the traditional PI-Smith system.The explicit formulation of Fuzzy PI-Smith system is derived, and it lay the basis for the practical application of control algorithms.(5) HMI (Human Machine Interface) of ultra fast cooling area is developed by WinCC of SIEMENS. It communicate with PLC, and complete the supervisor control tasks of ultra fast cooling area. And the actual data record can be exported by calling WinCC SQL Database.This control system has been successfully applied in some750mm hot strip mill. The actual record curves indicate that the dynamic feedforward strategy can do well in controlling the tail temperature. And the FuzzyPI-Smith system can get better dynamic characteristic and effectively overcome the problems by pure lag with the traditional PI-Smith method. The accuracy of the ultra fast cooling temperature can be controlled in±20℃. This system can not only complete all functions and satisfy the needs of the mill, but also has good quality in temperature control. So it can be widely used in cooling systems of hot strip mill. |
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