Study On Networked Control Systems Based On Ethernet

ABSTRACT With the unceasingly expanding of the scale of industrial control system,central control strategy has been unable to meet the relative control demand.Networked control system has been widely applied in industrial control. Field bus is atechnology to meet this demand. It solves this problem in a certain sense. But fieldbus is not thoroughly open. When the development of field bus runs into impediment,Ethernet develops rapidly. If Ethernet can be implied in factory floor networksuccessfully, we can break the traditional structure of control system and realize theseamless integration of office automation and industrial automation. The application of Ethernet in network control system (NCS) has manyadvantages, but it also bring some problems, including the transmission indeterminacy,the reliability of Ethernet and the lack of unified application layer protocol. The paper researches network control system based on Ethernet from twoaspects. First, the paper studies and implements the Modbus/TCP application layerprotocol, which is widely used in Industrial Ethernet. In addition a network testprogram named CIP Alyze3.0 is used to analyze the accomplished communicationprogram. Secondly, with regards to the characteristics of uncertain delay of networkedcontrol system, this paper puts forward an idea of using Generalized PredictiveControl (GPC) in the networked control system. To overcome the influence ofmodeling error and uncertainty of a system, we compensate error of the system byadopting BP neural network. The paper last designs an NCS based on Ethernet and embeds Modbus/TCPprotocol in client program and server program. In the experimental research, theresponse curves of the traditional GPC controller and the improved GPC controllerare compared. The result shows the effectiveness of the scheme.