Research On Circulating Water Of Steel Tube Plant Monitoring System Based On S7-300PLC

Steel pipe production process must have the supply of circulating cooling water ?Circulating water is mainly used for cooling steel products,equipment and quenching.Duying the process of cooling the equipment or product,the water pressure must be stabilized to avoid equipment to be burned or waste to be generated.In order to ensure the quality of water supply,the variable frequency constant pressure water supply mode is adopted.According to the requirements of the water supply system,the maximum frequency of the frequency converter is set to prevent long-term overload of the pump work and the minimum frequency is also set in order to meet the needs of static lift.The water pumps group are adopted the mode with the combination of power frequency pump and variable frequency pump.With the change of the working condition,the frequency converter adjusts the speed of the pump to achieve the purpose of saving energy.Because the water supply system has the characteristics of time-varying,hysteresis and uncertainty,it is difficult to establish accurate mathematical model.Conventional PID controller is difficult to obtain satisfactory dynamic and static characteristics.Specially,fuzzy control is suitable for complex control systems that are difficult to model.Particularly,The self-tuning fuzzy-PD controller has the advantages of fuzzy algorithm and PID algorithm.So this paper designs water supply mode with the self-tuning fuzzy PID controller+PLC+frequency converter based on OPC interface technology.This paper also designs the water supply mode of variable frequency constant pressure based on conventional PID.The calculation result of FB41 in PLC program is transmitted to the converter through the form of PROFIBUS bus or analog quantity.It is used as the control value the frequency converter,adjusting the pump speed and maintaining water pressure stability of the circulating water supply system.This paper also designs hardware part of the circulating water supply system.Control program is written about the frequency conversion constant pressure and other pump valve.pictures of upper computer is designed on the circulating water supply system.The pictures of upper computer not only monitors the normal operation but also improves the stability of the water supply control system.