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[Example 6] Moving and Restructuring (#238)
Co-authored-by: Dr. Denis <[email protected]>
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‎README.md

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*RRBot* - or ''Revolute-Revolute Manipulator Robot'' with multiple interfaces
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##### Example 6: "Modular Robots with separate communication to each actuator"
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The example shows how to implement robot hardware with separate communication to each actuator.
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## Quick Hints
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These are some quick hints, especially for those coming from a ROS1 control background:
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### Example 5: "Modular Robots with separate communication to each actuator"
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- Launch file: [rrbot_modular_actuators.launch.py](ros2_control_demo_bringup/launch/rrbot_modular_actuators.launch.py)
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- Controllers: [rrbot_modular_actuators.yaml](ros2_control_demo_bringup/config/rrbot_modular_actuators.yaml)
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- URDF: [rrbot_modular_actuators.urdf.xacro](ros2_control_demo_description/rrbot_description/urdf/rrbot_modular_actuators.urdf.xacro)
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- ros2_control URDF: [rrbot_modular_actuators.ros2_control.xacro](ros2_control_demo_description/rrbot_description/ros2_control/rrbot_modular_actuators.ros2_control.xacro)
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- Command interfaces:
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- joint1/position
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- joint2/position
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- State interfaces:
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- joint1/position
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- joint2/position
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Available controllers:
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- `forward_position_controller[forward_command_controller/ForwardCommandController]`
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- `joint_state_broadcaster[joint_state_broadcaster/JointStateBroadcaster]`
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Commanding the robot: see the commands below.
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### Example 6: "Industrial Robots with an exposed transmission interface"
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Files:

‎example_6/CMakeLists.txt

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cmake_minimum_required(VERSION 3.5)
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project(ros2_control_demo_example_6)
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# Default to C++14
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if(NOT CMAKE_CXX_STANDARD)
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set(CMAKE_CXX_STANDARD 14)
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endif()
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if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID MATCHES "Clang")
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add_compile_options(-Wall -Wextra)
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endif()
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# find dependencies
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set(THIS_PACKAGE_INCLUDE_DEPENDS
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hardware_interface
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pluginlib
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rclcpp
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rclcpp_lifecycle
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)
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# find dependencies
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find_package(ament_cmake REQUIRED)
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foreach(Dependency IN ITEMS ${THIS_PACKAGE_INCLUDE_DEPENDS})
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find_package(${Dependency} REQUIRED)
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endforeach()
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## COMPILE
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add_library(
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${PROJECT_NAME}
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SHARED
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hardware/rrbot_actuator.cpp
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)
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target_include_directories(
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${PROJECT_NAME}
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PRIVATE
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hardware/include
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)
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ament_target_dependencies(
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${PROJECT_NAME}
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${THIS_PACKAGE_INCLUDE_DEPENDS}
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)
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# Causes the visibility macros to use dllexport rather than dllimport,
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# which is appropriate when building the dll but not consuming it.
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target_compile_definitions(${PROJECT_NAME} PRIVATE "ROS2_CONTROL_DEMO_EXAMPLE_6_BUILDING_DLL")
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# Export hardware plugins
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pluginlib_export_plugin_description_file(hardware_interface ros2_control_demo_example_6.xml)
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# INSTALL
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install(
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TARGETS ${PROJECT_NAME}
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DESTINATION lib
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)
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install(
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DIRECTORY hardware/include/
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DESTINATION include
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)
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install(
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DIRECTORY description/launch description/ros2_control description/urdf description/rviz description/meshes
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DESTINATION share/${PROJECT_NAME}
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)
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install(
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DIRECTORY bringup/launch bringup/config
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DESTINATION share/${PROJECT_NAME}
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)
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if(BUILD_TESTING)
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find_package(ament_cmake_gtest REQUIRED)
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endif()
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## EXPORTS
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ament_export_include_directories(
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include
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)
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ament_export_libraries(
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${PROJECT_NAME}
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)
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ament_export_dependencies(
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${THIS_PACKAGE_INCLUDE_DEPENDS}
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)
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ament_package()

‎example_6/README.rst

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***********************************************************************
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Example 6: Modular Robots with separate communication to each actuator
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***********************************************************************
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The example shows how to implement robot hardware with separate communication to each actuator. This
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is implemented with a hardware interface of type ``hardware_interface::ActuatorInterface``.
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1. To check that *RRBot* descriptions are working properly use following launch commands
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.. code-block:: shell
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ros2 launch ros2_control_demo_example_6 view_robot.launch.py
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**NOTE**: Getting the following output in terminal is OK: ``Warning: Invalid frame ID "odom" passed to canTransform argument target_frame - frame does not exist``.
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This happens because ``joint_state_publisher_gui`` node need some time to start.
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The ``joint_state_publisher_gui`` provides a GUI to generate a random configuration for rrbot. It is immediately displayed in *RViz*.
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2. To start *RRBot* example open a terminal, source your ROS2-workspace and execute its launch file with
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.. code-block:: shell
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ros2 launch ros2_control_demo_example_6 rrbot.launch.py
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The launch file loads and starts the robot hardware, controllers and opens *RViz*.
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In starting terminal you will see a lot of output from the hardware implementation showing its internal states.
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This is only of exemplary purposes and should be avoided as much as possible in a hardware interface implementation.
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If you can see two orange and one yellow rectangle in in *RViz* everything has started properly.
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Still, to be sure, let's introspect the control system before moving *RRBot*.
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3. Check if the hardware interface loaded properly, by opening another terminal and executing
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.. code-block:: shell
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ros2 control list_hardware_interfaces
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.. code-block:: shell
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command interfaces
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joint1/position [available] [claimed]
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joint2/position [available] [claimed]
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state interfaces
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joint1/position
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joint2/position
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Marker ``[claimed]`` by command interfaces means that a controller has access to command *RRBot*.
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4. Check is controllers are running
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.. code-block:: shell
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ros2 control list_controllers
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.. code-block:: shell
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forward_position_controller[forward_command_controller/ForwardCommandController]
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joint_state_broadcaster[joint_state_broadcaster/JointStateBroadcaster]
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5. If you get output from above you can send commands to *Forward Command Controller*, either:
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#. Manually using ros2 cli interface.
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.. code-block:: shell
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ros2 topic pub /forward_position_controller/commands std_msgs/msg/Float64MultiArray "data:
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- 0.5
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- 0.5"
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#. Or you can start a demo node which sends two goals every 5 seconds in a loop
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.. code-block:: shell
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ros2 launch ros2_control_demo_example_6 test_forward_position_controller.launch.py
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You should now see orange and yellow blocks moving in *RViz*.
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Also, you should see changing states in the terminal where launch file is started, e.g.
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.. code-block:: shell
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[RRBotModularJoint]: Writing...please wait...
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[RRBotModularJoint]: Got command 0.50000 for joint 'joint1'!
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[RRBotModularJoint]: Joints successfully written!
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[RRBotModularJoint]: Writing...please wait...
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[RRBotModularJoint]: Got command 0.50000 for joint 'joint2'!
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[RRBotModularJoint]: Joints successfully written!
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Files used for this demos
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#########################
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- Launch file: `rrbot_modular_actuators.launch.py <https://github.com/ros-controls/ros2_control_demos/example_6/bringup/launch/rrbot_modular_actuators.launch.py>`__
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- Controllers yaml: `rrbot_modular_actuators.yaml <https://github.com/ros-controls/ros2_control_demos/example_6/bringup/config/rrbot_modular_actuators.yaml>`__
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- URDF: `rrbot_modular_actuators.urdf.xacro <https://github.com/ros-controls/ros2_control_demos/example_6/description/urdf/rrbot_modular_actuators.urdf.xacro>`__
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+ ``ros2_control`` URDF tag: `rrbot_modular_actuators.ros2_control.xacro <https://github.com/ros-controls/ros2_control_demos/example_6/description/ros2_control/rrbot_modular_actuators.ros2_control.xacro>`__
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- RViz configuration: `rrbot.rviz <https://github.com/ros-controls/ros2_control_demos/example_6/description/rviz/rrbot.rviz>`__
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- Hardware interface plugin: `rrbot_modular_actuators.cpp <https://github.com/ros-controls/ros2_control_demos/example_6/hardware/rrbot_modular_actuators.cpp>`__
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Controllers from this demo
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##########################
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- ``Joint State Broadcaster`` (`ros2_controllers repository <https://github.com/ros-controls/ros2_controllers>`__): `doc <https://control.ros.org/master/doc/ros2_controllers/joint_state_broadcaster/doc/userdoc.html>`__
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- ``Forward Command Controller`` (`ros2_controllers repository <https://github.com/ros-controls/ros2_controllers>`__): `doc <https://control.ros.org/master/doc/ros2_controllers/forward_command_controller/doc/userdoc.html>`__

‎example_6/bringup/config/rrbot_forward_position_publisher.yaml

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publisher_forward_position_controller:
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ros__parameters:
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wait_sec_between_publish: 5
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publish_topic: "/forward_position_controller/commands"
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goal_names: ["pos1", "pos2", "pos3", "pos4"]
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pos1: [0.785, 0.785]
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pos2: [0, 0]
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pos3: [-0.785, -0.785]
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pos4: [0, 0]

‎ros2_control_demo_bringup/config/rrbot_modular_actuators.yaml renamed to ‎example_6/bringup/config/rrbot_modular_actuators.yaml

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