| The research subject involved in this thesis comes from the capital Jingtang iron&steel company's 300t converter water treatment project. This paper mainly discusses the hardware configuration and software development of the water treatment control system and focuses on solving the key problem of the supply water under constant pressure by using variable frequency speed regulation.Firstly, the paper introduces the technology characteristic and control requirement of the water treatment system. Treating gas cooler water supply pumps, evaporative cooling water pumps and medium-speed filter as the main research objects, using the programmable controller Siemens S7-400 PLC as hardware platform and using Siemens software STEP7 and Wince as software development platform, the paper discusses the selection of hardware, PLC program and monitoring software development of water treatment control system. Moreover, the paper also introduces the situation of PROFIBUS field bus's application in the engineering.The paper pay great emphasise on the constant pressure PID control and achieve the objective of constant pressure water supply by using PLC and frequency conversion technology. The utilization in the real production shows that when the requirement on overshoot and response time are not very tight, the digital PID can get well control effect and meet the requirement of production using after the tuning of parameters.To obtain better control performance and meet higher control requirement, the paper has implement a research on fuzzy PID control method. The simulation shows that fuzzy PID control method has better control effect than conventional PID control method.Finally, the paper does a summary about the industrial debugging process. Actual operation proves that the system meets the control requirements and runs in good condition. |
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