Real-time Characteristics Study Of Data Transmission On Multi-level Control Network

Various industrial control networks have successfully emerged along with the development of computer network. Meanwhile, with the widespread application of networks, heterogeneous networks connection is an irreversible trend. Due to strict transporting time requirement of industrial control networks, it is very significant to research the real-time feature of heterogeneous network communication.With its advantages such as high-performance, high-reliability and quick-instantaneity, CAN BUS has become one of commonly-used Fieldbuses. Compared to CAN BUS, Switched Ethernet with its openness, low costs and under extensive supports of soft hardware has been widely used. Therefore the connection of CAN BUS and Switched Ethernet is a general trend. The research of this dissertation is based on application background of Underground Locomotive Haulage Supervisory System. The dissertation focuses on the real-time of heterogeneous networks which composed of CAN BUS and Switched Ethernet, and mainly analyzes a more reasonable scheduling algorithm from CAN BUS, CAN-SE gateway and SE switch to meet the real-time requirement of network data transmission.This dissertation fully and systematic introduces the development of Field bus, and then deeply analyzes the current real-time problems of CAN BUS and Switched Ethernet.It also analyzes the average delay of message communication in the standard CAN Protocol, summarizes several scheduling algorithms of the current real-time system. A modified EDF algorithm, which is based on exponential division, is proposed to solve the problems that messages transmission using the method of average division of deadline is terrible when the relative deadline of each node is too large and the network load is too high. Also, we design a computing method, which could reduce system costs substantially, when we realize the algorithm concretely. Finally, we use the Canoe Simulator to verify the effectiveness of algorithm.In this dissertation, we analyze the method of calculating transmission delay of end-to-end in Switched Ethernet. Several solutions of improving real-time performance are concluded concerned with new technologies and theories in recent years. A hybrid scheduling algorithm is proposed to improve the transportation performance of soft real-time information while the transportation requirements of hard real-time could be met.we design an embedded CAN-Ethernet gateway which is use to shield the differences of application layer protocols, converse information between CAN BUS and Ethernet, and realize the transparent data transmission in heterogeneous networks.