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I am trying to run the ros2_control_demo_example_7 package of ros2_control_demos with some modifications to spawn r6bot robot inside gazebo. I am not using gazebo_ros2_control plugin since on using it I am getting error as pointed out here. As suggested there, I am using ros2_control_node in place of gazebo_ros2_control plugin.

I have also included the physical properties of each joint in the urdf:

<dynamics damping="0.15" friction="0"/>

Also, defined the material properties of each link in the gazebo description as below:

    <gazebo reference="${prefix}base_link">
        <selfCollide>true</selfCollide>
        <mu1 value="0.0"/>
        <mu2 value="0.0"/>
        <kp value="10000000.0"/>
        <kd value="1.0"/>
        <turnGravityOff>false</turnGravityOff>
    </gazebo>

Everything seems to be working in the terminal but I am getting below output in the gazebo:

enter image description here

r6bot_controller.launch.py

def generate_launch_description():
    gaz_pkg_share = FindPackageShare(package='ros2_control_demo_example_7').find('ros2_control_demo_example_7')

    world_file_name = 'empty.world'
    world_path = os.path.join(gaz_pkg_share, 'worlds', world_file_name)

    # Set the path to the SDF model files.
    gazebo_models_path = os.path.join(gaz_pkg_share, 'models')
    
    if 'GAZEBO_MODEL_PATH' in os.environ:
        os.environ['GAZEBO_MODEL_PATH'] =  os.environ['GAZEBO_MODEL_PATH'] + ':' + gazebo_models_path
    else:
        os.environ['GAZEBO_MODEL_PATH'] =  gazebo_models_path

    # Get URDF via xacro
    robot_description_content = Command(
        [
            PathJoinSubstitution([FindExecutable(name="xacro")]),
            " ",
            PathJoinSubstitution(
                [
                    FindPackageShare("ros2_control_demo_example_7"),
                    "urdf",
                    "r6bot.urdf.xacro",
                ]
            ),
        ]
    )
    robot_description = {"robot_description": robot_description_content}

    robot_controllers = PathJoinSubstitution(
        [
            FindPackageShare("ros2_control_demo_example_7"),
            "config",
            "r6bot_controller.yaml",
        ]
    )
    rviz_config_file = PathJoinSubstitution(
        [FindPackageShare("ros2_control_demo_description"), "r6bot/rviz", "view_robot.rviz"]
    )

    gazebo = IncludeLaunchDescription(
        PythonLaunchDescriptionSource(
            [PathJoinSubstitution([FindPackageShare("gazebo_ros"), "launch", "gazebo.launch.py"])]
        ),
        launch_arguments={"verbose": "true",
                          "paused":"false",
                          "gui":"true",
                          "world":world_path,
                          "headless":"false",
                          "use_sim_time":"true"}.items(),
    )

    spawn_entity = Node(
        package="gazebo_ros",
        executable="spawn_entity.py",
        arguments=["-topic", "robot_description", "-entity", "r6bot"],
        output="screen",
    )

    control_node = Node(
        package="controller_manager",
        executable="ros2_control_node",
        parameters=[robot_description, robot_controllers],
        remappings=[
            (
                "/forward_position_controller/commands",
                "/position_commands",
            ),
        ],
        output="both",
    )
    
    joint_state_publisher_node = Node(
        package="joint_state_publisher_gui",
        executable="joint_state_publisher_gui",
        condition=IfCondition("true"),
    )

    robot_state_pub_node = Node(
        package="robot_state_publisher",
        executable="robot_state_publisher",
        output="both",
        parameters=[robot_description],
    )
    rviz_node = Node(
        package="rviz2",
        executable="rviz2",
        name="rviz2",
        output="log",
        arguments=["-d", rviz_config_file],
    )

    joint_state_broadcaster_spawner = Node(
        package="controller_manager",
        executable="spawner",
        arguments=["joint_state_broadcaster", "--controller-manager", "/controller_manager"],
    )

    robot_controller_spawner = Node(
        package="controller_manager",
        executable="spawner",
        arguments=["r6bot_controller", "-c", "/controller_manager"],
    )

    # Delay rviz start after `joint_state_broadcaster`
    delay_rviz_after_joint_state_broadcaster_spawner = RegisterEventHandler(
        event_handler=OnProcessExit(
            target_action=joint_state_broadcaster_spawner,
            on_exit=[rviz_node],
        )
    )

    # Delay start of robot_controller after `joint_state_broadcaster`
    delay_robot_controller_spawner_after_joint_state_broadcaster_spawner = RegisterEventHandler(
        event_handler=OnProcessExit(
            target_action=joint_state_broadcaster_spawner,
            on_exit=[robot_controller_spawner],
        )
    )

    nodes = [
        joint_state_publisher_node,
        control_node,
        robot_state_pub_node,
        gazebo,
        spawn_entity,
        joint_state_broadcaster_spawner,
        delay_rviz_after_joint_state_broadcaster_spawner,
        delay_robot_controller_spawner_after_joint_state_broadcaster_spawner,
    ]

    return LaunchDescription(nodes)

r6bot_controller.yaml

controller_manager:
  ros__parameters:
    update_rate: 10  # Hz

    joint_state_broadcaster:
      type: joint_state_broadcaster/JointStateBroadcaster

    r6bot_controller:
      type: ros2_control_demo_example_7/RobotController

    forward_position_controller:
      type: forward_command_controller/ForwardCommandController


forward_position_controller:
  ros__parameters:
    joints:
      - joint_1
      - joint_2
      - joint_3
      - joint_4
      - joint_5
      - joint_6

    interface_name: position

r6bot_controller:
  ros__parameters:
    joints:
      - joint_1
      - joint_2
      - joint_3
      - joint_4
      - joint_5
      - joint_6

    command_interfaces:
      - position

    state_interfaces:
      - position

ros2 control

(Here I am using ros2_control_demo_example_8/RRBotTransmissionsSystemPositionOnlyHardware plugin, defined in the ros2_control_demo_example_8 package)

<ros2_control name="${name}" type="system">

  <hardware>
    <plugin>ros2_control_demo_example_8/RRBotTransmissionsSystemPositionOnlyHardware</plugin>
    <param name="actuator_slowdown">100.0</param>
  </hardware>
  
  <joint name="joint_1">
    <command_interface name="position">
      <param name="min">{-2*pi}</param>
      <param name="max">{2*pi}</param>
    </command_interface>
    <state_interface name="position">
      <param name="initial_value">0.0</param>
    </state_interface>
  </joint>

  <joint name="joint_2">
    <command_interface name="position">
      <param name="min">{-2*pi}</param>
      <param name="max">{2*pi}</param>
    </command_interface>
    <state_interface name="position">
      <param name="initial_value">0.0</param>
    </state_interface>
  </joint>

  <joint name="joint_3">
    <command_interface name="position">
      <param name="min">{-pi}</param>
      <param name="max">{pi}</param>
    </command_interface>
    <state_interface name="position">
      <param name="initial_value">0.0</param>
    </state_interface>
  </joint>

  <joint name="joint_4">
    <command_interface name="position">
      <param name="min">{-2*pi}</param>
      <param name="max">{2*pi}</param>
    </command_interface>
    <state_interface name="position">
      <param name="initial_value">0.0</param>
    </state_interface>
  </joint>

  <joint name="joint_5">
    <command_interface name="position">
      <param name="min">{-2*pi}</param>
      <param name="max">{2*pi}</param>
    </command_interface>
    <state_interface name="position">
      <param name="initial_value">0.0</param>
    </state_interface>
  </joint>

  <joint name="joint_6">
    <command_interface name="position">
      <param name="min">{-2*pi}</param>
      <param name="max">{2*pi}</param>
    </command_interface>
    <state_interface name="position">
      <param name="initial_value">0.0</param>
    </state_interface>
  </joint>

  <transmission name="transmission1">
    <plugin>transmission_interface/SimpleTransmission</plugin>
    <actuator name="actuator1" role="actuator1"/>
    <joint name="joint_1" role="joint_1">
      <mechanical_reduction>4.0</mechanical_reduction>
      <offset>0.0</offset>
    </joint>
  </transmission>

  <transmission name="transmission2">
    <plugin>transmission_interface/SimpleTransmission</plugin>
    <actuator name="actuator2" role="actuator2"/>
    <joint name="joint_2" role="joint_2">
      <mechanical_reduction>4.0</mechanical_reduction>
      <offset>0.0</offset>
    </joint>
  </transmission>

  <transmission name="transmission3">
    <plugin>transmission_interface/SimpleTransmission</plugin>
    <actuator name="actuator3" role="actuator3"/>
    <joint name="joint_3" role="joint_3">
      <mechanical_reduction>4.0</mechanical_reduction>
      <offset>0.0</offset>
    </joint>
  </transmission>

  <transmission name="transmission4">
    <plugin>transmission_interface/SimpleTransmission</plugin>
    <actuator name="actuator4" role="actuator4"/>
    <joint name="joint_4" role="joint_4">
      <mechanical_reduction>4.0</mechanical_reduction>
      <offset>0.0</offset>
    </joint>
  </transmission>

  <transmission name="transmission5">
    <plugin>transmission_interface/SimpleTransmission</plugin>
    <actuator name="actuator5" role="actuator5"/>
    <joint name="joint_5" role="joint_5">
      <mechanical_reduction>4.0</mechanical_reduction>
      <offset>0.0</offset>
    </joint>
  </transmission>

  <transmission name="transmission6">
    <plugin>transmission_interface/SimpleTransmission</plugin>
    <actuator name="actuator6" role="actuator6"/>
    <joint name="joint_6" role="joint_6">
      <mechanical_reduction>4.0</mechanical_reduction>
      <offset>0.0</offset>
    </joint>
  </transmission>

</ros2_control>

I am expecting robotic arm to spawn inside gazebo with below configuration: enter image description here

Am I missing something or doing something wrong? Is this happening because of PID or other parameters? I would really appreciate some advice on this.

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2 Answers 2

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Why you want to use gazebo if you take the hardware component from example_8? How do you interface gazebo at all if you use the hardware component?

Use gazebo_ros2_control, because this loads the controller_manager and all your controller plugins. There is no need for ros2_control_node then.

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  • 1
    $\begingroup$ You are right that either hardware component from example_8 or gazebo_ros2_control should be used. Not both. Initially, gazebo_ros2_control plugin wasn't working. Was getting errors like no controller_manager available. Now everything is fixed. Thanks1 $\endgroup$
    – Anubhav Singh
    Commented Jan 31 at 12:53
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Include gazebo_ros2_control plugin as

<gazebo>
   <plugin filename="libgazebo_ros2_control.so" name="gazebo_ros2_control">
      <parameters>$(find ros2_control_demo_example_7)/config/r6bot_controller.yaml</parameters>
   </plugin>
</gazebo>

Remove the control_node from r6bot_controller.launch.py.

Also, Include gazebo_ros2_control/GazeboSystem hardware plugin as

<plugin>gazebo_ros2_control/GazeboSystem</plugin>
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  • $\begingroup$ This is done in my case, but i get a [Err] [Model.cc:1160] Exception occured in the Load function of plugin with name[gazebo_ros2_control] and filename[libgazebo_ros2_control.so]. This plugin will not run. . Apart from installing with apt or source, did you do anything else like sourcing gazebo somehow to update the plugins path? $\endgroup$
    – M.K
    Commented Apr 11 at 7:21

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