The Research Of Network Control System Based On EtherCAT Protocol

Network control system is a real-time feedback control system in which distributed and network-based is realized by using communication network. With the increase requirements of control system to network performance, automation vendors made dozens of different industrial Ethernet protocols, which have been widely used in network control systems. Industrial Ethernet technology carried on the advantages of compatibility, low cost, high speed communications from traditional Ethernet, and also have features of real-time and deterministic required in industrial control.By comparing the performances of existing industrial Ethernet protocols, EtherCAT protocol is the most prominent industrial Ethernet protocol and sets new performance standards. Because of its low cost, high transmission efficiency and real-time characteristics, EtherCAT is ideal for high speed data acquisition and servo motion control. In the application of wave maker, a transmission network which has the feature of flexible topology and high real-time characteristic is urgently needed to meet the requirements of high accuracy and synchronization movement.This paper introduces the principle of major existing industrial network protocols, and gives a brief comparative analysis of their main properties. Then this paper introduces the main principles of EtherCAT network protocols, and details of the physical layer and data link layer's unique composed structure. On this basis, the paper proposed a network-based high-speed EtherCAT real-time data acquisition system and network motion control system by using high-performance 16-bit microcontroller/DSP as application controller. System is built on the background of marine engineering, and realized high-speed real time data acquisition from a large number of sensors distributed in the experimental wave pool. At the same time, build a servo network motion control system based on position control mode. This paper gives an analysis of system structure, principles in detail separately from the main station and slave station. For the requirements proposed by control system, designed complete hardware of two types of system, and wrote application procedures and network communication protocol procedures between master and slave, realized the application requirements proposed by network control.Finally, under laboratory conditions, did experimental test on these two types of network control system including several salve controllers, results show that the system has high real-time characteristics, high communication efficiency, well satisfied the high-speed data acquisition and real-time motion control requirements.