Universal Robots+

Lag between pogram start and execution after installation of External Control URCap for ROS control


we have an issue with our new UR10e robot. We would like to use ROS for the control of our robot and installed the recommended ROS driver (https://github.com/UniversalRobots/Universal_Robots_ROS_Driver). We have the following system setup:

  • Robot: UR10e
  • URSoftware 5.5.1 / 5.6.0
  • Ubuntu 18.04
  • ROS Melodic
  • externalcontrol-1.0.1.urcap

I installed the External Control URCap and created a new program ‘extCtrlROS’ as explained in the setup guide. After starting the robot driver on my ROS PC, I also started the robot program using the play button. However, it takes around two minutes before the program actually executes and shows that the connection to the remote PC could not be established (IP and URCap settings should be fine because on the day before it was already working).

If I start a different program (not ROS related), then the program start takes around two minutes as well but the execution works normally, i.e. the robot moves its desired path. If I uninstall the External Control URCap, then the lag is reduced to just a few seconds but this is still slightly slower than prior the first URCap installation. A reinstall of the URCap leads again to the same behaviour (lag of two minutes). Sometimes not just the program but also the whole software seems to lag like it was explained in another forum (https://dof.robotiq.com/discussion/726/lag-time-between-pressing-play-on-ur-and-program-start-with-ucg-1-1-1)…

After the upgrade to UR Software 5.6.0 I still have the same problem. Any help would be appreciated and log files can be provided.

Thanks and best regards,

I just wanted to let you know that I solved my problem with the support of a GitHub Universal Robots collaborator. It turned out that the firewall UFW (Uncomplicated Firewall) was installed and active on my Ubuntu PC. I just needed to disable the firewall to get it working ( sudo ufw disable ).

Now I can start my external control program and the connection to my ROS PC is established instantly. I can also start a ROS independent program without any lag. That`s great but it is also very strange that my firewall had such a big effect on the UR!

For more details, please see:

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