Design Of The Control System Based On PLC For Shipborne Seawater Automatic Sampling And Distribution System

There is a great upsurge in the development of marine resources around the world, and the pollution of the marine environment is more serious than anytime before. As the foundation of marine environmental protection and sustainable development, marine environmental monitoring is increasingly valued by all countries. The key process of many monitoring projects is to get effective samples.In this thesis, a ship-borne seawater automatic sampling and distribution system is developed. It is an important part of"shipborne marine environment monitoring system"project that is supported by Chinese national programs for high technology research and development (863 Program).It can get quantitative seawater samples from appointed depth and transport to the analytical equipment by totally enclosed pipeline. So it can keep the physical and chemical properties of samples. It's control system has PLC as its core and HMI as user interface, with the appropriate sensors and hardware module. This system receives instructions from the control platform and report state of work to it. The main hardwares are Mitsubishi FX2N Series PLC and AD modules, RS-232 communications board and the Weinview's HMI.The major work of this thesis includes following aspects:1) Refer to a large number of relevant literature cite. Analyze the technique of water sampling, development and direction of PLC and HMI. Design the whole system framework and control plan of sampling and distribution system base on the requirements and target ship. Then choose appropriate hardware for the system.2) Design the user interface of control system which connect two HMI to one PLC and achieve automatic control. Describe PLC programming methods and software design steps.Then divide up the software into nine functional modules and develop it use the ladder language. The programming of some important modules was discussed in detail.3) Test the system in port and on the sea.We compared this system with manual and electronic control seawater sampling device. The result showed a high degree of automation, reliable, maintenance expediently, easy to use and so on.