Time Synchronization Between EtherCAT Network and External Processor

We employ an external processor to distribute the master computing load in the EtherCAT networked control system and develop a method for time synchronization between the Linux on the external processor and EtherCAT network. The synchronization between the Linux on the external processor and EtherCAT master is performed by using general-purpose input/output and shared memory, and the synchronization accuracy is significantly improved by compensating for the system time setting latency and general-purpose input detection latency in the EtherCAT master. The developed method is implemented as part of the master application without modifying the EtherCAT protocol or requiring an excessive computational load. By performing extensive experiments and analyzing the results, we demonstrate that the developed method achieves the synchronization error means less than 1 $\mathrm {~ \mu s}$ with standard deviations less than 5 $\mathrm {~ \mu s}$ between the external processor and EtherCAT network. This synchronization accuracy can be acceptable for various networked control applications based on Linux.