Both drives have an internal FIFO buffer for SM commands and in this case buffers are filled by position setpoint commands. Drives are set to excecute commands from the buffer at 250 Hz rate and command execution clock between the drives is being sychronized over the bus.

Most of the tracking error comes simply from servo overshooting as we’re asking too high accelerations at sharp corners. We didn’t calculate trajectories for all speeds separately so acceleration scales up same amount with speed (and that’s why it starts overshooting). Trajectory is simply a large table of axis coordinates generated by gcodecompiler (EMC2/LinuxCNC based app).

Happy holidays and a smooth start in 2014!!!