Research And Development On Real-time Master System Based On EtherCAT Protocol

Due to so many classification standards that cannot be unified and the small amount of data transmission,traditional fieldbus is more and more difficult to meet the needs of evolving industrial control.Industrial fieldbus based on Ethernet technology has gradually become an important development direction.EtherCAT is a real-time and reliable industrial fieldbus technology with the advantages of simple system structure,fast transmission speed and high efficiency.This thesis designs a complete scheme of EtherCAT master protocol stack.It uses RTX and Xenomai real-time extension kernel to improve the real-time performance of the master system under Windows and Linux platforms.As well,a clock drift compensation calculation method has been proposed to improve the synchronization accuracy between the master and slave systems.This paper first studies the EtherCAT fieldbus protocol and deeply analyzes several protocol points of the physical layer,data link layer and application layer,including physical transmission standard,data frame structure,addressing mode,communication service command,distributed clock,state machine,synchronization manager and CoE protocol.Through the in-depth analysis of the EtherCAT protocol and the communication requirements of the master and slaves,the EtherCAT master system consisting of the master protocol stack and network communication hardware is realized.According to functions,the master protocol stack is divided into four modules: protocol configuration module,communication operation module,network driver module and application layer interface module.Each module cooperates with each other according to the design requirements,which realizes the function of configuring the protocol channel in each state of the slave station,controlling the state transition of the slave station,transmitting and receiving the process data frame to control slaves during the slaves' operation state.This paper in-depth research on the key technologies of real-time performance and synchronization of EtherCAT master system.In order to make up for the lack of the real-time performance of Windows and Linux system,this text introduces Windows real-time extension subsystem RTX and Linux real-time extension Xenomai,which completes the configuration of real-time protocol stack and real-time network communication.At the same time,In order to meet the requirements of industrial control for synchronous motion of master and slave devices,several critical times are measured to configure the slaves' distributed clock and a synchronous method for real-time compensation of master-slave clock drift is proposed to optimize synchronization performance between EtherCAT master and slave devices.Finally,the paper designs and verifies the master system in terms of functionality,real-time performance,synchronized performance and stability.Connect the Gaocco servo driver slave devices to build a master-slave communication test platform and conduct multi-faceted testing and analysis on the real-time master system.