[Iron] - Robot description is empty if ros2control is configured to load it from topic

[firesurfer]

Hi @stefanscherzinger,

ros2control deprecated loading the robot_description from the parameter file and wants us to load it from the corresponding topic. I just adapted to this change and realized I can not load the cartesian controllers anymore.

For example for the cartesian_motion_controller

[ros2_control_node-12] [INFO] [1710834336.674188673] [controller_manager]: Loading controller 'cartesian_motion_controller_top'
[ros2_control_node-12] [INFO] [1710834336.701249189] [controller_manager]: Configuring controller 'cartesian_motion_controller_top'
[ros2_control_node-12] [ERROR] [1710834336.703519230] [cartesian_motion_controller_top]: robot_description is empty
[ros2_control_node-12] [WARN] [1710834336.703674259] [cartesian_motion_controller_top]: Error occurred while doing error handling.
[ros2_control_node-12] [ERROR] [1710834336.703766080] [controller_manager]: After configuring, controller 'cartesian_motion_controller_top' is in state 'unconfigured' , expected inactive.

Not sure if this is a bug in ros2control (that is should properly pass this parameter to the controller nodes) or if a controller is supposed to obtain the robot_description from the corresponding topic itself. I will also open an issue in the ros2control repository asking how this should be handled.

[firesurfer]

@stefanscherzinger A follow up for you -> In the current rolling branch of ros2control they introduced the URDF as member of the controller base class. This change will not be backported to iron/humble.

[tonynajjar]

So what's the latest state? How do we actually load a controller from this repo if the robot_description is read from the topic?

[firesurfer]

You simply don't at the moment. I think @stefanscherzinger doesn't find any time to work on these controllers at the moment.

[stefanscherzinger]

@firesurfer @tonynajjar

This should now be solved with a mixed approach (see #198 ):

• Jazzy: Load from topic as recommended. See e.g. here. The cartesian controllers will fetch the robot_description directly from the controllers' base class.
• Iron, Humble: Additionally pass the robot_description to the controller_manager. See e.g. here. The cartesian controllers will get the robot_description from the controller_manager as parameter (depricated but working)

[stefanscherzinger]

Please re-open if still unclear.