Research Switch Ethernet Network Control System Delay And Scheduling Algorithm

With the continuous development of Control science, Computer and Network technology, the alternating between the three disciplines is more and more frequently, and the technology of these three disciplines becomes maturity. The comprehensive application of the theory and technology of the three subjects in the field of industrial control formed a Network Control System (NCS). NCS breaks the bottleneck of the traditional control systems and uses the network technology to achieve resource sharing and co-operating. Its distributed, networked, intelligent with flexible and efficient characteristics are the important direction of the development of modern control systems.However, the time-delay of network-induced, packet segmentation, multipath transmission, network congestion, data-packet dropout in the inherent communication network stands out due to the introduction of the network. Different network technologies, such as Ethernet, Controller Area Network (CAN), Switch Ethernet and wireless network seriously affected the quality of the NCS’s performance. CSMA/CD, the inherent traditional communication mechanism of Ethernet, is a non-deterministic communication scheduling mechanism, which will cause unpredictable delay in the communication network control system, thus affecting the overall system performance. The invention of switch technology is the major achievements of the development of Ethernet. It not only improves the speed and bandwidth of the network which offers network delay "certainty" to a certain extent, but also makes up the defects of CAN and Switch Ethernet in the control systems, which played a huge role in promoting the development and application of Business Ethernet in the control system.This thesis first analyses the problem of Network-induced delays and real-time scheduling in the NCS about Switched Ethernet network, introduces the commonly used real-time scheduling algorithm and the TrueTime of Simulink toolbox. Then the paper makes a detailed analysis of the composition and. the model of the network delay. Besides, this paper researches different delay characteristics based on Ethernet, CAN and Switch Ethernet of NCS through simulation experiments。The results show that the time-delay distribution of Switch Ethernet is smooth. With a considerable advantage in the same transmission rate, delay statistical characteristics of Switched Ethernet has considerable advantages, and is better to maintain the stability of the system. Finally, this thesis offers a secondary scheduling algorithm based on the Switch Ethernet of network control system. The first level of priority based on the data constructed three kinds of output buffer queue, the second level scheduling based on Genetic algorithm for real-time data generated offline static scheduling. Then, the paper designs an instance to show that the algorithm is better than the RM which could get optimal scheduling sequence, also it won’t increase such as EDF dynamic scheduling system overhead, but calculating costs will increase as the task of data increased significantly.