Study Of Supervisory Control And Data Acquisition System Based On Embedded Web Server

With the rapid development of embedded system and Web technology, Web servers are embedded into industrial equipments, then Web technology is extended to industry field, networked automatic control is becoming a research hot and tendency. With the help of Web servers embedded into field equipments, operators may monitor field equipments by browsers. Different from the traditional SCADA system, the human-machine interacting of the monitoring system designed in this paper is mainly executed through browser explaining dynamic webpage returned by Web server.Firstly, the advantage of monitoring system based on Web server is described, the aim and significance of the dissertation are listed, and the main work of this paper is mentioned.Mainly, hardware expanding circuits are designed and software architecture is studied in this paper. For hardware, RCM5700 is adopted as the core module of this system, which is supplied by Digi Inc. RS-485 bus, SPI bus and switching I/O parallel bus are expanded, which are going to be used for collecting field equipment information and outputting control signals. At the same time, the function modules (power module, programming module and Ethernet interfacing module) are designed in detail. TheμC/OS-Ⅱreal time kernel is chose to realize multitasking programming. For the software, Ajax and CGI are the core technology for realizing dynamic webpage and automatic refreshing. After the processing procedure of Web application based on Ajax-CGI is introduced, embedded Web server software architecture based on Ajax-CGI is put forward. Instead of CGI, script language may be applied for carrying out simple interacting tasks. In this paper, an example of dynamic webpage using ZHTML script language is given.The SCADA system designed in this paper is able to run steadily when it is connected the LAN in the lab. We may introduce the system into industrial field after testing and verifying its reliability.