rqt_joint_controller fix for getting feedback

[tstoyanov]

At some point there has been a change in the feedback that joint_trajectory_controllers publish and that has not propagated tot the rqt plugin. I've deduced the correct place to get the joint state values would be from /controller_name/state.actual instead of /controller_name/controller_state.feedback. Tested change with current humble release and gazebo plugin, seems to work fine for me.

[christophfroehlich]

Hi @tstoyanov!
It is the other way round, ~/controller_state is the new topic :) see

ros2_controllers/joint_trajectory_controller/src/joint_trajectory_controller.cpp

Lines 811 to 812 in 960e073

	publisher_ = get_node()->create_publisher<ControllerStateMsg>(
	"~/controller_state", rclcpp::SystemDefaultsQoS());

We made the change somewhen on rolling, and fixted rqt_jtc with #643
Humble should have worked always, because we only deprecated the "old" topic and message type. But soon we will backport this also to humble to use the new one (to avoid deprecation warnings), see #659

Or have you encountered a problem recently? We fixed some issues with #890. I'll close this PR now, if you still have problems feel free to open an issue describing it.

You are cordially invited to contribute to this repo, e.g., I just created an issue with some ideas for refurbishing rqt_jtc: #894

[tstoyanov]

Right, sorry about that, should have checked more carefully. I am running the most recent humble release, that has joint_trajectory_controller at version 2.26 (current in humble branch is 2.29) and probably that change has not propagated there yet, since I don't see the controller_state topic at all when I get a controller up and running. Thanks for checking, will either build from source or wait for the next releases.

[christophfroehlich]

That is strange, controller_state is there even for an earlier version of 2.26. Can you verify with ros2 node info that there aren't two publishers? E.g.

$ ros2 node info /trajectory_controllers
/trajectory_controllers
  Subscribers:
    /clock: rosgraph_msgs/msg/Clock
    /parameter_events: rcl_interfaces/msg/ParameterEvent
    /trajectory_controllers/joint_trajectory: trajectory_msgs/msg/JointTrajectory
  Publishers:
    /parameter_events: rcl_interfaces/msg/ParameterEvent
    /rosout: rcl_interfaces/msg/Log
    /trajectory_controllers/controller_state: control_msgs/msg/JointTrajectoryControllerState
    /trajectory_controllers/state: control_msgs/msg/JointTrajectoryControllerState
    /trajectory_controllers/transition_event: lifecycle_msgs/msg/TransitionEvent

[tstoyanov]

Yes, here is the output:

ros2 node info /joint_trajectory_position_controller
/joint_trajectory_position_controller
  Subscribers:
    /joint_trajectory_position_controller/joint_trajectory: trajectory_msgs/msg/JointTrajectory
    /parameter_events: rcl_interfaces/msg/ParameterEvent
  Publishers:
    /joint_trajectory_position_controller/state: control_msgs/msg/JointTrajectoryControllerState
    /joint_trajectory_position_controller/transition_event: lifecycle_msgs/msg/TransitionEvent
    /parameter_events: rcl_interfaces/msg/ParameterEvent
    /rosout: rcl_interfaces/msg/Log
  Service Servers:
    /joint_trajectory_position_controller/describe_parameters: rcl_interfaces/srv/DescribeParameters
    /joint_trajectory_position_controller/get_parameter_types: rcl_interfaces/srv/GetParameterTypes
    /joint_trajectory_position_controller/get_parameters: rcl_interfaces/srv/GetParameters
    /joint_trajectory_position_controller/list_parameters: rcl_interfaces/srv/ListParameters
    /joint_trajectory_position_controller/set_parameters: rcl_interfaces/srv/SetParameters
    /joint_trajectory_position_controller/set_parameters_atomically: rcl_interfaces/srv/SetParametersAtomically
  Service Clients:

  Action Servers:
    /joint_trajectory_position_controller/follow_joint_trajectory: control_msgs/action/FollowJointTrajectory
  Action Clients:

Only one publisher pops up. This is when running example_1 from https://github.com/ros-controls/ros2_control_demos

[christophfroehlich]

Are you sure you have 2.26 installed? See

$ ros2 pkg xml joint_trajectory_controller
<package format="3">
  <name>joint_trajectory_controller</name>
  <version>2.29.0</version>
  <description>Controller for executing joint-space trajectories on a group of joints</description>
  ...

[tstoyanov]

Right, this was unexpected :) I had an overlay from franka which was running a joint trajectory controller at version 3.3. I did a clean workspace and with 2.26 I get both state and controller_state, as expected. The release version of rqt_joint_trajectory_cntroller still does not work out of the box with that particular example, but I think that's because the joints are continuous (no limits) and the plugin doesn't know what to do when initializing the sliders. Mystery solved, thanks for the help!

[christophfroehlich]

You're welcome :)

See
ros-controls/ros2_control_demos#387
and
#897

-> if you build both from source it should work now (maybe you need to copy the changes from the demos to the humble branch unless the backport was merged there).