The Design Of Constant Pressure Water Supply Control System Based On PLC

Traditional water supply system use the way of fixed speed pump pressurized water supply, which has a low degree of automation, as well as a waste of resources. Besides, it can not meet the user's demand for constant water pressure. The automation of the system with the Single chip microcomputer as the controller has been improved. But there are still some disadvantages:low reliability and higher requirements for the application environment. By adopting PLC to the control system, on the basis of the high automation, the operation reliability of the system can be guaranteed, which can also save the manpower.According to the control requirements of the constant pressure water supply control system, the PLC based constant pressure water supply control system was designed by the research. Meanwhile, the monitoring system was designed by the host computer which was composed by the touch screen and industrial PC. With the reliability and flexibility of the PLC, the functional requirements of the water supply system can be realized.First, the characteristics and performance of frequency conversion water supply system were introduced, and the corresponding mathematical model was established. At the same time, the overall scheme and control process as well as the method were designed in accordance with the system functional requirements.Then the control method of the system was analyzed in detail. Considering the problem of poor adjustment of conventional PID parameters and poor adaptability, the self-tuning fuzzy PID control algorithm was put forward, and the Matlab software was used to simulate the control system. Simulation results showed that, compared with the conventional PID algorithm, the fuzzy PID algorithm has the advantages of small overshoot, short rise time and good robustness, which is more suitable for the systems with the characteristics of nonlinear and great lag such as the constant pressure frequency conversion water supply control system.Finally, the design scheme of software and hardware was introduced in particular, including the hardware selection, design of control program and PC monitoring software. The selection of the main hardware such as PLC and inverter was given; the ladder diagram of the control algorithm was introduced in the control program; the remote monitoring software on the PC has many functions such as field monitoring, data logging and fault alarm, which can save the human resources and realize the real automation of control systems.The constant pressure water supply control system designed in this paper was an integration of on-site systems and monitoring systems. It can not only achieve the requirements of constant pressure, but also has high stability and automation.