Ethernet-based Network Control System Study

Industrial network has developed from analog-signal based simple DDC (Direct Digital Control) to FCS (Field bus Control System), which is digital and intelligentized with totally distributed structure. Fieldbus indeed had brought a revolution in industrial automation. But the international standards of fieldbus could not be carried out quickly. The diversity of communication protocols of fieldbus could make it impossible to realize interconnection and interoperation between different kinds of fieldbus products. So the so-called openness of fieldbus cannot be achieved. With the rapid development of information technology, such as the Intranet/Internet, the ability of seamless integration between management layer and field control layer is required as well as an open infrastructure.According to the requirement of industrial control system, the key techniques of traditional Ethernet for industrial field control, such as real-time communications, fieldbus power supplier, and interoperability, etc. are discussed in this dissertation. The networked control system based on Ethernet is put forward; also its hardware and software for the system are designed in this paper.As far as the system's communications are concerned, the network communication model based Ethernet +Modbus TCP/IP is presented. The communication programs are explored by VB6.0. In order to integrate multiple FCS into the networked control system, two schemes are provided.Moreover, in order to solve the problems induced from the uncertain delay in networked control systems, a new control scheme that integrates control technology with communication technology is brought forward, which is composed of two parts. Firstly, originated from the idea of online delay evaluation, which is used to obtain the delays characteristics on line. Then a scheme based on DCLQG controller combined with application of priority technique is designed to achieve desired Real-time performance. The result illustrates the effectiveness of the proposed control design.