Research On Data Acquisition System Based On EtherCAT

Conventional fieldbus system have many weaknesses. First they lack of the ability of network communications. Second they have a poor realtime performance and they are not compatible with each other. With the rise of Industry 4.0, the concept of smart factory comes up. Industrial Ethernet are applied to industry controlling network more widely. Compared with conventional fieldbus, the Industrial Ethernet based data transmission mode have long transmit distance, high speed, good realtime performance and large capacity.. It has been a trend to use Industrial Ethernet in data acquisition system. So, after the analysis of a variety of Industrial Ethernets, The paper researched on the data acquisition system based on Ether CAT.First, the PC machine with standard network card was selected as the master station, and chose the Twin CAT as the upper computer software to manage the slave devices. Through the analysis of transmission characteristics of Ethernet packets in the Ether CAT slave controller and the automatic loopback function of the ESC, the data acquisition system designed a kind of ring topology structure which is a redundant structure.Then according to the hardware structure and function of the ET1100 chips, the subject designed a set of slave station devices independently, include interface card of Ether CAT based on ET1100 chip, control circuits based on STM32 MCU and signal conditioning circuits based on amplifier chips. In order to improve the electromagnetic compatibility of the circuit board, the design of PCB adopted multilayer board and the reasonable PCB layout and wiring.The software of the system was designed. For the master software, Twin CAT ADS communication protocol was studied, and ADS interface software was programmed in Visual Studio. Then according to the the structure of the slave configuration file, using the XML language to design the configuration document. As to the slave software, in order to facilitate the expansion of the slave station function, the paper analysed the Ether CAT protocol stack and CANopen protocol, and the object dictionary of CANopen DS401 was programmed and implemented in the Ether CAT protocol stack. In view of the shortcomings of the common digital filtering algorithms, an improved digital filtering algorithm was proposed.Finally, the experimental platform of the data acquisition system based on Ether CAT was built based on the software and hardware above. The real-time performance, synchronization and accuracy of the system were tested, and the the system’s remote access ability and reliability of the redundant topology structure were verified.