Design And Implementation Of High Performance EtherCAT Network Controller

This paper presents a complete method for designing and implementing a high-performance EtherCAT network controller.The method is divided into four parts: kernel functions of master station,performance optimization,interface design and overall system design.Experiments are carried out to verify the method.Experimental results demonstrate the effectiveness and superiority of the method.The kernel functions are divided into eight parts,which are data link layer service,datagram scheduling mechanism,process image management,network state machine,mailbox state machine,So E state machine,Co E state machine and DC controller,and their functions and implementation methods are described respectively.For the performance optimization part,optimization methods for EtherCAT synchronous communication performance and isochronous synchronization performance are designed.The performance optimization of synchronous communication is achieved by reducing synchronous communication jitter.The EtherCAT communication process is analyzed in this paper.It is considered that system scheduling,program branch and network IO are the three main reasons leading to the communication jitter of EtherCAT master station.In response to these three reasons,the jitter is effectively suppressed by modifying the program scheduling mode,optimizing the program flow and improving the network card driver.The optimization of isochronous performance is achieved by optimizing the parameters of the EtherCAT clock synchronization mechanism.In this paper,the effects of the three parameters of 0x930,0x934 and 0x935 that affect the clock synchronization of EtherCAT are analyzed,and a gradient descent-based optimization method is designed to minimize the average number of 0x92 C parameters and the standard deviation,thus the isochronous performance of the EtherCAT network is indirectly improved.For the interface design this paper designs three interfaces,which are network state control,synchronous communication and asynchronous communication with the upper application,and four interfaces,such as timer,clock,file access and network adaptation,which interact with the lower hardware.For the overall implementation of EtherCAT network controller,this paper analyzes the design architecture of the current representative commercial software Twin CAT and open source software Igh EtherCAT.Based on the related research in this paper,an EtherCAT network controller architecture based on embedded system is proposed.The EtherCAT network controller is implemented on a Beaglebone Black development board based on the architecture.In order to verify the conclusion and the design is correct and advanced,the EtherCAT network controller is deployed in a four-axis motion control environment for testing.The test contents include three aspects: synchronous communication performance,isochronous synchronization performance and asynchronous communication function.In the test results,the minimum cycle period of the controller reaches 125 microseconds and the jitter boundary is 2.92 microseconds;the average value of the drift from the clock between stations is low to 10 nanoseconds and the standard deviation is low to 9.83 nanoseconds;the transmission function of the So E and the Co E protocol can be carried out normally.The test results show that the EtherCAT network controller designed in this paper has excellent performance.The design and optimization methods in this paper can be used as a reference for the research and development of the same kind of equipment.