Performance evaluation of industrial Ethernet and its modeling

The real-time industrial network, often referred to as fieldbus, is an important approach for building automated manufacturing system. However, the application of fieldbus has been limited due to the high cost of hardware, moreover, a number of different fieldbus standards and each of them providing specific features, and the difficulty in interfacing with multivendor products. So it is difficult in integrating various fieldbus on the manufacturing floor. In order to solve these problems, the networked control system based on Ethernet is presented, in other words, the industrial automation field adopts Ethernet (IEEE802.3). The key technical obstacle for Ethernet for industrial application is that its nondeterministic behavior makes it inadequate for real-time application where the frames containing real-time information such as control command and alarm signal have to be delivered within a certain time limit. This paper first presents a comprehensive analysis of the temporal characteristics of traditional Ethernet and a new model of the Ethernet application in industry process is introduced. Two methods for performance improvement are presented in this dissertation. The first method tunes the network system parameters such as the prioritization of different subsystems or nodes and the choice of different types of network protocols. The second method is to design an optimal (LQG) controller on the premise of both theorems are derived based on Lyapunov´s second method aimed the stability of the NCS based on Ethernet. At last, a scheme based on LQG controller is designed to achieve desired real-time performance. The result illustrate that the effectiveness of the proposed control design and the satisfactory performance of the system.