The Research Of Automatic Control System For Tea Twisting Machine Based On PLC

The subject is a part of 948 projects of Chinese ministry of agriculture named importing international advanced Science and Technology of agriculture. It is mainly research on automation transformation of tea twisting machine. The automation control of working pressure, time, rotating speed and handling of leaves of tea twisting machine is realized. The control system includes sensor data acquisition system, electrical system, control interface system and software system.First, the paper analyzes the principle of tea twisting machine to design twisting process which is suitable for automatic control .Then the whole design plan of automation control is proposed, which is divided into three subsystem: speed regulating, pressure control and the control of handling of leaves, taking PLC as the main control unit. The selection and connect of hardware are realized by calculation and analysis. Second, the software of upper computer is developed using Delphi, and the database is set up. The software development of lower computer uses STEP7-Micro/WIN32 which is special for SIMTIC S7-200 series. The application program consists of main program, interrupt service program and some function modules. At last, the communication of the whole system is analyzed to establish Modbus communication protocol.The equipment of the subject was placed into use in July, 2008. the test with autumn tea is done twice to get six groups of data. The result proves the development of tea twisting machine has primarily met design requirements.The subject is the beginning of research of a serial of tea machines, so it is creative and very significant.