RT limit of ROS
Dear all,
As we know ROS is not a RT system (due to its use of TCP/IP, memory allocations in messages...). Hence I was wondering whether you could build systems such as the one in this Maxon Epos 3 EtherCAT demo with ROS.
I guess that a typical ROS architecture will have the high level planification computed onto the ROS PC (i.e. the desired joints position and velocity will be computed within ROS). Now what I understand is that if the low level controllers do not receive these instructions at the same time (due to non-RT transport) then the instructions will not be executed simultaneously by the motors. This would result in the 2 wheels shown in the video not aligned well enough for the pins of one wheel to match the holes of the other wheel.
Am I right? If I am wrong, does this mean the +-1 ms error typically found in ROS transport is negligible for such mouvements coordination ? I fear you'll tell me it depends on the speed and the configuration of the system and task and there is no other way but trying... ;)
Thanks,
Antoine.