Design Of Master-Slave Station Based On Industrial Ethernet Protocol EtherCAT

The traditional fieldbus has been unable to meet the current requirements of industrial control because of its close structure,poor system compatibility,lacking of network communication and other defects.Real time Industrial Ethernet has overcome the disadvantages of fieldbus with high speed Ethernet Fieldbus universality and real-time characteristics.Among them,EtherCAT has become the development direction of industrial Ethernet technology because of its flexible topology,simple system configuration,high speed and high data transmission,and low cost.This paper is based on MW-class wind turbine PLC control system localization project of XEMC.Based on the TCP / IP Ethernet model,the paper can not completely avoid the uncertainties caused by commercial network interference,and the real-time performance is not high.This paper proposes a modified Ethernet data link layer model,which uses special hardware to process data to improve real-time performance.It uses special frame types to distinguish data frames from process data to improve the certainty of data read.For the design of the master station,this paper chooses the PC which contains the Intel network card as the master station,studies the open source scheme based on IgH,and builds the Linux-based development environment.With the double blessing configuration software TwinCAT to achieve the management of the slave.For the design of slave station,considering the stability and sustainable purchase,select the FPGA as a processor,ET1100/ET1200 as a protocol chip.The schematic PCB is drawn and the system board is completed.The interface circuit used in the development of the slave station is designed and analyzed.The implementation of the slave software uses a hierarchical structure including the underlying driver,the EtherCAT protocol stack,and the application.Using TwinCAT to complete the IO test with the direct input and output of the slave,through the software wireshark capturing packet analysis of real-time.SPI read and write control is realized by SPI driver,SPI timing is analyzed,and the implementation of EtherCAT protocol stack is analyzed.This topic is still in the research stage,the follow-up research work is mainly based on the development of open source master environment,how to use libethercat library and libethercat_rtdm library to write applications to interact with the station.The workload is reflected in the familiarity of the master environment with the Linux system and the implementation of the master EtherCAT protocol.This topic for the EtherCAT protocol applied to the company PLC has accumulated a lot of theoretical and practical basis.