Synchronous Multi-axis Motion Control Based on Modified EtherCAT Distributed Clock

EtherCAT is one of the most popular industrial Ethernet protocols used in multi-axis motion control. Its unique Distributed Clocks mechanism can ensure high-precision clock synchronization among multiple devices. In the study, we first improve the clock drift compensation algorithm used in Distributed Clocks. This algorithm not only shows excellent compatibility with existing standard protocol but also tracks the reference clock faster and more accurately. Similarly, we also propose a method for synchronization between the network clock and the local motor control task. The modified timing after synchronization eliminates the time uncertainty that up to one PWM period and reduces the necessary interrupts for network control. The proposed methods pave the way for better motion control performance and are verified by both simulations and experiments.