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topic_based_hardware_interfaces

cm_topic_hardware_component

The controller_manager topic System implements a ros2_control hardware_interface::SystemInterface that subscribes to topics of type pal_statistics_msgs::msg::StatisticsNames and pal_statistics_msgs::msg::StatisticsValues, and sets its state interface to the received values (if present).

Per default, the ros2_control controller manager publishes these topics to /controller_manager/introspection_data/names and /controller_manager/introspection_data/values.

This component serves as a possibility to replay ROS bags and inject the states from a hardware component into the ros2_control stack. For example, use ros2bag CLI to extract these two topics via

ros2 bag play <bag_file> \
  --topics /controller_manager/introspection_data/names /controller_manager/introspection_data/values \
  --remap /controller_manager/introspection_data/names:=/<hardware_component_name>/names\
          /controller_manager/introspection_data/values:=/<hardware_component_name>/values

Note that with this setup the current time of your OS is used and not published from the ROS bag. If you want to control the speed of playback, run

  • your ros2_control_node with --ros-args -p --use_sim_time:=true

  • and the --rate and --clock options, for example

    ros2 bag play <bag_file> --rate 2.0 --clock 100 \
  --topics /controller_manager/introspection_data/names /controller_manager/introspection_data/values \
  --remap /controller_manager/introspection_data/names:=/<hardware_component_name>/names\
          /controller_manager/introspection_data/values:=/<hardware_component_name>/values

ROS subscribers

  • /<hardware_component_name>/names: pal_statistics_msgs::msg::StatisticsNames
  • /<hardware_component_name>/values: pal_statistics_msgs::msg::StatisticsValues

ros2_control section in URDF

<ros2_control name="hardware_component_name" type="system">
  <hardware>
    <plugin>cm_topic_hardware_component/CMTopicSystem</plugin>
  </hardware>
  <joint name="joint_1">
    <command_interface name="position"/>
    <state_interface name="position">
      <param name="initial_value">0.2</param>
    </state_interface>
    <state_interface name="velocity"/>
  </joint>
  <joint name="joint_2">
    <command_interface name="position"/>
    <state_interface name="position">
      <param name="initial_value">0.3</param>
    </state_interface>
    <state_interface name="velocity"/>
  </joint>
  <joint name="joint_3">
    <command_interface name="position"/>
    <state_interface name="position">
      <param name="initial_value">0.1</param>
    </state_interface>
    <state_interface name="velocity"/>
  </joint>
</ros2_control>