Unit 3 - Simulation Robot took a lot of time (significantly) to load

The robot took a lot of time to load.
I try to switch back to Unit 1 and the robot loaded fine for that unit.
I don’t know why it took significantly more time to load for Unit 3.
Because of that, I cannot do anything else since it will always return errors. For ex.:

user:~$ ros2 control list_controller_types
Could not contact service /controller_manager/list_controller_types

Do we have any mitigations for this?
I even try to clear my cache and reload but the result is still the same

So far, I have waited more than 30 minutes and the simulation still displayed blank.
This is a very unsatisfaction experience with the unit since nothing can be done.

I don’t know if any Robot is required to load for Unit 4 but its simulation’s window suffer the same thing as the Unit 3.


I think you have to spawn the robot with these commands:

source /home/simulations/ros2_sims_ws/install/setup.bash
ros2 launch unit2_simulation spawn_rrbot.launch.py

The unit only starts a basic empty world in gazebo.

The robot appeared now.

However, the guidance of Unit 3 doesn’t work at all.
From the beginning, the commands already failed.

Do I have to do this for other Units for robots to show up as well? I don’t know which to wait and which to do this by myself.

Are you sure you didn’t skip some commands at the beginning?

No, you don’t have to. Where you need to spawn the robot yourself, it should be mentioned in the notebook. If this is not the case, please let us know.

Yes I use the first two commands as shown in Unit 3 (you can check it for yourself)
I have taken the screenshot with the first two commands as followed in the above reply:

ros2 control list_controller_types
ros2 control list_controllers

These commands are executed right after the spawning robot commands:

source /home/simulations/ros2_sims_ws/install/setup.bash
ros2 launch unit2_simulation spawn_rrbot.launch.py

Also, I see nothing said about spawning the robot on our own

Hello @PhongNguyen,

this units assumes that you have completed the previous unit and requires you to spawn the robot using the files that you created in the previous unit. If you did so, you should be able to run the commands and see the expected results.

I have added new additional instructions to spawn the robot from the previous unit to make it clear.

Please confirm if you are seeing the expected results now.



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Nicely done @rzegers
It works for me now.
Thank you so much for your detailed update on the web shell numbers as well.

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