Research And Design Of Distributed Data Acquisition System Based On EtherCAT

With the increase of the amount of data in the industrial field and the improvement of real-time requirements,the future industrial manufacturing will be more digitized,networked and intelligent.The EtherCAT(Ethernet for Control Automation Technology)which was emerged in recent years has greater bandwidth capacity than the traditional industrial field bus and has higher transmission efficiency than the commercial Ethernet.Its internal clock synchronization mechanism greatly improves the real-time performance of communication.Based on the comparison of mainstream industrial Ethernet,this essay studies and designs a distributed data acquisition system based on EtherCAT.Firstly,this essay describes the basic principle,system structure and clock synchronization mechanism of EtherCAT communication protocol.Through the Wireshark packet capture experiment at the back of this essay,the data packets of the communication process are analyzed.It is clearly demonstrated that a single data frame of EtherCAT contains input and output data of multiple slaves at the same time,which effectively improves the bandwidth utilization of the Ethernet.Secondly,this essay designs the slave equipment of the EtherCAT data acquisition system.The slave station uses the Infineon XMC4800 as the communication controller and application processor.Compared with the traditional ASIC solution,this single-chip solution has higher integration and lower power consumption.The slave station uses the SSC(Slave Stack Code)protocol stack of the ETG Alliance to ensure the compatibility and stability of the software.The experimental results in the TwinCAT3 master station environment show that the slave station can be correctly identified and accessed by the master station,also it supports the function of a distributed clock.Finally,this essay designs the master station equipment of the EtherCAT data acquisition system.We choose the Allwinner V3s SoC as the master 's processor.The software environment consists of U-Boot,Linux kernel and Debian root file system.The master station transplantes the IgH protocol stack to realize the application layer communication function,and designs a graphical user interface based on LittlevGL.In order to comply with the development trend of "Internet Plus" and "Industry 4.0",the embedded Web application service was created using the Flask framework on the EtherCAT master station.The master station can read the sensor data of the slave stations in real time and display the operating status and process data of the slave stations through the LCD screen and the webpage.Through experimental verification,the EtherCAT-based distributed data acquisition system designed in this essay has high real-time response capability,and the synchronization cycle of the entire system has reached 4ms,which greatly improves the real-time and synchronization of the traditional data acquisition system.