Summary

Introduction to the issue

When executing multiple trajectories sequentially using remote control, some trajectory may fail silently due to "Sending data through socket failed.". For example, when executing A->B->C. If B failed, then C will directly be executed after A which out any error throwing.

Versions

ROS Driver version: ROS Noetic
Affected Robot Software Version(s): 5.11.1
Affected Robot Hardware Version(s): UR3e

Impact

If a trajectory is skipped, then it might cause the robot to blindly move from the end of the previous trajectory to the beginning of the next trajectory which my cause a big hazard.

Project status at point of discovered

When did you first observe the issue?
This happens by chance with relatively low probability.

Workaround Suggestion

By searching in this repo, the cause to this failure of "Sending data through socket failed." might be due to that we are not using a real time kernal. We will be testing it following https://github.com/UniversalRobots/Universal_Robots_ROS_Driver/blob/master/ur_robot_driver/doc/real_time.md. However, if this case happens, the driver should either retry, or throw an error instead of fail silently.