Joint trajectory controller detailed parameters don't exist on param server

[livanov93]

As stated here and here parameters for checking the error through trajectory and on the goal position are not propagated on the parameter server. We also had problems with checking the errors on the last trajectory point - the problem occurs here

[destogl]

@livanov93 Can you explain a bit more about your test-setup and what is expected behavior and what is the issue?

[livanov93]

While testing joint_trajectory_controller on the real hardware I was getting the Aborted due to goal tolerance violation error. Afterwards, decided to add parameter per joint to increase goal tolerance:

The paramaters were defined in the following manner:

controller_manager:
  ros__parameters:
    update_rate: 600  # Hz

    forward_command_controller_position:
      type: forward_command_controller/ForwardCommandController

    joint_state_controller:
      type: joint_state_controller/JointStateController

    ur_joint_trajectory_controller:
      type: joint_trajectory_controller/JointTrajectoryController

ur_joint_trajectory_controller:
  ros__parameters:
    joints:
      - shoulder_pan_joint
      - shoulder_lift_joint
      - elbow_joint
      - wrist_1_joint
      - wrist_2_joint
      - wrist_3_joint
    state_publish_rate: 100.0
    action_monitor_rate: 20.0
    allow_partial_joints_goal: false
    constraints:
      stopped_velocity_tolerance: 0.01
      goal_time: 0.0
      shoulder_pan_joint:
        trajectory: 0.05
        goal:       0.03
      shoulder_lift_joint:
        trajectory: 0.05
        goal:       0.03
      elbow_joint:
        trajectory: 0.05
        goal:       0.03
      wrist_1_joint:
        trajectory: 0.05
        goal:       0.03
      wrist_2_joint:
        trajectory: 0.05
        goal:       0.03
      wrist_3_joint:
        trajectory: 0.05
        goal:       0.03

forward_command_controller_position:
  ros__parameters:
    joints:
      - shoulder_pan_joint
      - shoulder_lift_joint
      - elbow_joint
      - wrist_1_joint
      - wrist_2_joint
      - wrist_3_joint
    interface_name: position

This did not help at all but the worse thing is that parameter were not on the parameter server: There were only the following parameters:

/ur_joint_trajectory_controller:
  action_monitor_rate
  allow_partial_joints_goal
  constraints.goal_time
  constraints.stopped_velocity_tolerance
  joints
  state_publish_rate
  use_sim_time

[MGBla]

As it seems in ros2 contrary to ros1 parameters are only available if they were declared within a node https://github.com/ros-controls/ros2_controllers/blob/a80ce8d2b9a22fa83978976bc4257ede70dbc810/joint_trajectory_controller/src/joint_trajectory_controller.cpp#L65-L71 So the mechanic described here https://github.com/ros-controls/ros2_controllers/blob/a80ce8d2b9a22fa83978976bc4257ede70dbc810/joint_trajectory_controller/include/joint_trajectory_controller/tolerances.hpp#L78-L96 does not really work. I think two possible ways to deal with this are:

• Declare the constraints parameter for each element of the joints parameter or
• Properly use the interface of the FollowJointTrajectory action (https://github.com/ros-controls/control_msgs/blob/foxy-devel/control_msgs/action/FollowJointTrajectory.action) where a JointTolerance is already defined (https://github.com/ros-controls/control_msgs/blob/foxy-devel/control_msgs/msg/JointTolerance.msg)

Personally I would prefer the second approach since this would enable us to dynamically adjust the tolerances for different trajectories without always adjusting the parameter server.