| On the field of the metallurgy of iron and steel, the pickling is a pivotal working procedure before cold-rolling. The aim of the pickling process is the removal of the scale off the surface of hot rolled strips to get cleanliess strips using the chemical reaction between the scale and a pickling fluid. When pickling the strips , the solubility of ferrous ion and the pickling speed are influenced by the pickling fluid. Exorbitant high or low of the fluid temperature would be over-pickling or under-pickling. For the control of the fluid temperature can directly influence the quality of the pickling strips, the pickling fluid temperature is often controlled from 75℃to 85℃.The shallow slot hydrochloric turbulence pickling technics was choosed on the Continuous Pickling Product Line, which was adopted by the cold-rolling mill that built in 2006 in JiNan Iron & Steel Group Co.,Ltd. The acid temperature is controlled by numeric PID control mode. It is achieved by adjusting the steam flux of graphite heat exchanger. The effect is always unstable after in use. According to this state, the paper seeks a suitable control method to solve the practical problem with theory of the fuzzy control.In this paper, the production technics flow of the Continuous Pickling Line is introduced briefly. By analyzing the control process of acid temperature and characteristics of the heat system, it is said that the heat system of the Pickling Line is a multivariable parameters and great lag system. It's control request can not achieved applying with the conventional single-loop PID control. On the contorling arithmetic, by studying and researching the basic theory and method of fuzzy control and PID control in both home and abroad, the writer analyzes the advantage and disadvantage in temperature control of numeric PID control system and Fuzzy control system, and the writer designs a Fuzzy- PID composite control system on the method of combining the theory of the fuzzy and PID control, which synthesizes the advantage of PID control system in simple arithmetic, high credibility and steady state, and the advantage of the fuzzy control system in agility and moronity.Based on these methods, fuzzy PID control technique is applied to solve the pickling fluid temperature control problem. The writer obtains the simulation graphs by simulating the design of fuzzy PID control on Matlab, the output respond graphs of the fuzzy PID control and PID control are compared and analysed. The results show that the fuzzy PID control has more fine effect, such as no supercontrol, quickly response, moronity of parameter variation and highly control precision.Under the Siemens S7-400 system, the control arithmetic of the quondam system is improved on applying with the technology of the Fuzzy-PID control, and the Fuzzy PID aptitude acid temperature control system is designed, so the unstability problem of the pickling fluid temperature control effect is solved on the Pickling Line. The actual running show that this system is stable and reliable with high intelligentizing degree and can satisfy the need of production with a control precision of±2℃on the need of 80℃. Not only the Pickling quality of strip is enhanced greatly, but volatilization of the pickling fluid is controlled. The new system has nicer societal and economical benefit for the reduced acid pollution. |
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