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I want to use ROS2 control PID controller plugin with my external sensor. The documentations mention how to configure the yaml file and I did mine as follows:

controller_manager:
  ros__parameters:
    update_rate: 100 # Hz

    joint_state_broadcaster:
      type: joint_state_broadcaster/JointStateBroadcaster

    test_pid_controller:
        type: pid_controller/PidController


test_pid_controller:
  ros__parameters:
    dof_names:
      - joint0
      - joint1
    command_interface: effort

    reference_and_state_interfaces: ["/test_pid_controller/measured_state"]
    use_external_measured_states: true

    gains:
      joint0: {p: 1.0, i: 1.0, d: 0.0, i_clamp_max: 5.0, i_clamp_min: -5.0}
      joint1: {p: 1.0, i: 0.0, d: 0.0, i_clamp_max: 0.1, i_clamp_min: 0.1}

Below is what I'm facing now.

  • First thing I noticed is that now there is a new topic that is available and has one subscriber which is test_pid_controller/measured_state as expected, however the test_pid_controller/reference is also being available and has one subscriber.
  • Second, when I publish to the test_pid_controller/measured_state my robot doesn't respond, yet it responds when I publish to test_pid_controller/reference.
  • Third, the test_pid_controller/controller_state has always some zero values like error and output. (probably because there is no feedback yet)
  • Finally, I want to know if I configured my yaml file correctly or not, and how should I integrate my sensor's feedback so the controller actually work? what topic should I publish to and what is the message I should I use?
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1 Answer 1

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Reference and state seem to be fine as input to the PID? State should be the feedback of the control loop, and you obviously need also a reference signal.

You already have linked to the documentation, where the expected message type on both topics is given (see also ros2 topic list -t)

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  • $\begingroup$ So if I understand correctly I should publish my sensor's feedback to the test_pid_controller/measured_state topic and and set my reference point using the test_pid_controller/reference? I will test that $\endgroup$ Commented Jul 2 at 13:15

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