Design And Implementation Of The Supervisory Control And Data Acquisition System Of Automatic Production Line For Roasted Green Tea

Abstrat:Tea manufaturing is undergoing a transformation from a trational processing way to a modern processing approach as tea industry status raised in agriculture economy. In this thesis, we treated the automatic production line for roasted green tea as a research object, according to the characteristics of tea processing technologies, in closed connection with the requirements of this object, and drawing lessons from domestic and foreign advanced control technologies and successful cases, we finally designed a new SCADA (supervisory control and data acquistion) system based on PLC (programmable logic controller)which is suitable for small or medium-sized control requirements.In this thesis we divide the SCADA system of tea production line into three layers according to control requirements:field controlling layer, process centralized monitoring layer and management&service layer; while these three layers were realized by two structure levels of lower computer and host computer at the same time. And field controlling layer constitutes the whole lower computer system of the SCADA, processing centralized monitoring layer and management&service layer consititute the host computer system of SCADA. In the lower computer system, we use PLC and automatic mesuring instruments (such as temperatre sensor, pressure sensor and inverter) to realize data acquisition and devices controlling, and at the same time we exploit site operator terminal to achieve human-machine interaction. And in the host computer system, we write supervisory programs through configuration software to complete the process centralized monitoring of production, while we take advantage of data processing program compiled by Web components and Visual Basic to meet the need of management&service requirements.Temperature is the most critical process parameters that can affect the quality of tea, and the traditional temperature control methods based on experience is difficult to get a stable controlling of temperature. So in this paper we used fuzzy control technology which was a mature method in industry control area to achieve a stable temperarture controlling, in order to reduce the host and lower computer traffic, taking PLC as the fuzzy controller.According to the overall designing of this system, in lower computer simens S7-200PLC was selected as the key controlling unit, for supervisory of host computer we taken Simatic WinCC as monitoring software, and we take Visual Basic+SQL(Struct Query Language)+OPC(Process Control for Object Link Embed)+IIS(Internet Information Service) based on data processing and Web service of WinCC to complete management&service task.