A flexible mechanism for efficient transmission of aperiodic real-time messages over EtherCAT networks

EtherCAT is a real-time Ethernet protocol mainly designed for periodic real-time transmission in factory automation. As EtherCAT does not provide efficient mechanisms to transmit aperiodic real-time messages, recently a solution to this problem, called an EDF-based Swapping approach, was proposed. Such an approach implements a swapping policy based on the Earliest Deadline First algorithm. The approach proposed in this paper, called a Flexible EDFS, introduces two novel features. First, it reduces the overhead introduced when multiple aperiodic messages have to be transmitted. Second, it provides for variable cycle times according to the aperiodic real-time workload. The paper describes the proposed approach and presents comparative assessments, obtained through OMNeT++ simulations, with the EtherCAT standard and the original EDF-based Swapping.