[Example 12] Controller chaining example (#318)

Co-authored-by: Christoph Froehlich <christoph.froehlich@ait.ac.at>

README.md

@@ -56,7 +56,9 @@ The following examples are part of this demo repository:
 
 * Example 11: "Car-like robot using steering controller library (tba.)"
 
-* Example 12: "Controller chaining example (tba.)"
+* Example 12: ["Controller chaining"](example_12)
+
+   The example shows a simple chainable controller and its integration to form a controller chain to control the joints of *RRBot*.
 
 * Example 13: "Multi-robot example (tba.)"
 

doc/index.rst

@@ -67,6 +67,8 @@ Example 8: "Using transmissions"
 Example 9: "Gazebo Classic"
    Demonstrates how to switch between simulation and hardware.
 
+Example 12: "Controller chaining"
+   The example shows a simple chainable controller and its integration to form a controller chain to control the joints of *RRBot*.
 
 .. _ros2_control_demos_install:
 
@@ -254,3 +256,4 @@ Examples
    Example 7: Full tutorial with a 6DOF robot <../example_7/doc/userdoc.rst>
    Example 8: Using transmissions <../example_8/doc/userdoc.rst>
    Example 9: Gazebo classic <../example_9/doc/userdoc.rst>
+   Example 12: Controller chaining <../example_12/doc/userdoc.rst>

example_12/CMakeLists.txt

@@ -0,0 +1,115 @@
+cmake_minimum_required(VERSION 3.16)
+project(ros2_control_demo_example_12 LANGUAGES CXX)
+
+if(CMAKE_CXX_COMPILER_ID MATCHES "(GNU|Clang)")
+  add_compile_options(-Wall -Wextra)
+endif()
+
+# find dependencies
+set(THIS_PACKAGE_INCLUDE_DEPENDS
+  hardware_interface
+  pluginlib
+  rclcpp
+  rclcpp_lifecycle
+  control_msgs
+  generate_parameter_library
+  controller_interface
+  parameter_traits
+  realtime_tools
+  std_msgs
+)
+
+# find dependencies
+find_package(ament_cmake REQUIRED)
+foreach(Dependency IN ITEMS ${THIS_PACKAGE_INCLUDE_DEPENDS})
+  find_package(${Dependency} REQUIRED)
+endforeach()
+
+## COMPILE
+add_library(
+  ros2_control_demo_example_12
+  SHARED
+  hardware/rrbot.cpp
+)
+target_compile_features(ros2_control_demo_example_12 PUBLIC cxx_std_17)
+target_include_directories(ros2_control_demo_example_12 PUBLIC
+$<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/hardware/include>
+$<INSTALL_INTERFACE:include/ros2_control_demo_example_12>
+)
+ament_target_dependencies(
+  ros2_control_demo_example_12 PUBLIC
+  ${THIS_PACKAGE_INCLUDE_DEPENDS}
+)
+
+# Causes the visibility macros to use dllexport rather than dllimport,
+# which is appropriate when building the dll but not consuming it.
+target_compile_definitions(${PROJECT_NAME} PRIVATE "ROS2_CONTROL_DEMO_EXAMPLE_9_BUILDING_DLL")
+
+# Export hardware plugins
+pluginlib_export_plugin_description_file(hardware_interface ros2_control_demo_example_12.xml)
+
+# Add library of the controller and export it
+generate_parameter_library(passthrough_controller_parameters
+  controllers/src/passthrough_controller_parameters.yaml
+)
+
+add_library(passthrough_controller SHARED
+  controllers/src/passthrough_controller.cpp
+)
+target_include_directories(passthrough_controller PUBLIC
+$<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/controllers/include>
+$<INSTALL_INTERFACE:include/passthrough_controller>
+)
+target_link_libraries(passthrough_controller PUBLIC passthrough_controller_parameters)
+ament_target_dependencies(passthrough_controller PUBLIC ${THIS_PACKAGE_INCLUDE_DEPENDS})
+
+# Causes the visibility macros to use dllexport rather than dllimport,
+# which is appropriate when building the dll but not consuming it.
+target_compile_definitions(passthrough_controller PRIVATE "passthrough_controller_BUILDING_DLL")
+
+pluginlib_export_plugin_description_file(controller_interface passthrough_controller.xml)
+
+
+# INSTALL
+install(
+  DIRECTORY hardware/include/
+  DESTINATION include/ros2_control_demo_example_12
+)
+install(
+  DIRECTORY description/launch description/ros2_control description/urdf description/gazebo description/rviz
+  DESTINATION share/ros2_control_demo_example_12
+)
+install(
+  DIRECTORY bringup/launch bringup/config
+  DESTINATION share/ros2_control_demo_example_12
+)
+install(TARGETS ros2_control_demo_example_12
+  EXPORT export_ros2_control_demo_example_12
+  ARCHIVE DESTINATION lib
+  LIBRARY DESTINATION lib
+  RUNTIME DESTINATION bin
+)
+
+install(
+  DIRECTORY controllers/include/
+  DESTINATION include/passthrough_controller
+)
+
+install(TARGETS
+    passthrough_controller
+    passthrough_controller_parameters
+  EXPORT export_passthrough_controller
+  RUNTIME DESTINATION bin
+  ARCHIVE DESTINATION lib
+  LIBRARY DESTINATION lib
+)
+
+if(BUILD_TESTING)
+  find_package(ament_cmake_gtest REQUIRED)
+endif()
+
+## EXPORTS
+ament_export_targets(export_passthrough_controller HAS_LIBRARY_TARGET)
+ament_export_targets(export_ros2_control_demo_example_12 HAS_LIBRARY_TARGET)
+ament_export_dependencies(${THIS_PACKAGE_INCLUDE_DEPENDS})
+ament_package()

example_12/README.md

@@ -0,0 +1,5 @@
+# ros2_control_demo_example_12
+
+   This example demonstrates the switching between simulation and real hardware by means of the *RRBot* - or ''Revolute-Revolute Manipulator Robot''.
+
+Find the documentation in [doc/userdoc.rst](doc/userdoc.rst) or on [control.ros.org](https://control.ros.org/master/doc/ros2_control_demos/example_12/doc/userdoc.html).

example_12/bringup/config/rrbot_chained_controllers.yaml

@@ -0,0 +1,44 @@
+controller_manager:
+  ros__parameters:
+    update_rate: 10  # Hz
+
+    joint_state_broadcaster:
+      type: joint_state_broadcaster/JointStateBroadcaster
+
+    joint1_position_controller:
+      type: passthrough_controller/PassthroughController
+
+    joint2_position_controller:
+      type: passthrough_controller/PassthroughController
+
+    position_controller:
+      type: passthrough_controller/PassthroughController
+
+    forward_position_controller:
+      type: forward_command_controller/ForwardCommandController
+
+# First-level controllers
+joint1_position_controller:
+  ros__parameters:
+    interfaces: ["joint1/position"]
+
+
+joint2_position_controller:
+  ros__parameters:
+    interfaces: ["joint2/position"]
+
+
+# Second-level controller
+position_controller:
+  ros__parameters:
+    interfaces:
+      - joint1_position_controller/joint1/position
+      - joint2_position_controller/joint2/position
+
+# Third-level controllers
+forward_position_controller:
+  ros__parameters:
+    joints:
+      - position_controller/joint1_position_controller/joint1
+      - position_controller/joint2_position_controller/joint2
+    interface_name: position

example_12/bringup/launch/launch_chained_controllers.launch.py

@@ -0,0 +1,51 @@
+# Copyright 2021 Stogl Robotics Consulting UG (haftungsbeschränkt)
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+from launch import LaunchDescription
+from launch.actions import RegisterEventHandler
+from launch.event_handlers import OnProcessExit
+from launch_ros.actions import Node
+
+
+def generate_launch_description():
+
+    position_controller_spawner = Node(
+        package="controller_manager",
+        executable="spawner",
+        arguments=["position_controller", "--controller-manager", "/controller_manager"],
+    )
+
+    forward_position_controller_spawner = Node(
+        package="controller_manager",
+        executable="spawner",
+        arguments=["forward_position_controller", "--controller-manager", "/controller_manager"],
+    )
+
+    # Delay start of forward_position_controller_spawner after `position_controller_spawner`
+    delay_forward_position_controller_spawner_after_position_controller_spawner = (
+        RegisterEventHandler(
+            event_handler=OnProcessExit(
+                target_action=position_controller_spawner,
+                on_exit=[forward_position_controller_spawner],
+            )
+        )
+    )
+
+    nodes = [
+        position_controller_spawner,
+        delay_forward_position_controller_spawner_after_position_controller_spawner,
+    ]
+
+    return LaunchDescription(nodes)

example_12/bringup/launch/rrbot.launch.py

@@ -0,0 +1,115 @@
+# Copyright 2021 Stogl Robotics Consulting UG (haftungsbeschränkt)
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+from launch import LaunchDescription
+from launch.actions import RegisterEventHandler
+from launch.event_handlers import OnProcessExit
+from launch.substitutions import Command, FindExecutable, PathJoinSubstitution
+
+from launch_ros.actions import Node
+from launch_ros.substitutions import FindPackageShare
+
+
+def generate_launch_description():
+    # Get URDF via xacro
+    robot_description_content = Command(
+        [
+            PathJoinSubstitution([FindExecutable(name="xacro")]),
+            " ",
+            PathJoinSubstitution(
+                [
+                    FindPackageShare("ros2_control_demo_example_12"),
+                    "urdf",
+                    "rrbot.urdf.xacro",
+                ]
+            ),
+        ]
+    )
+    robot_description = {"robot_description": robot_description_content}
+
+    robot_controllers = PathJoinSubstitution(
+        [
+            FindPackageShare("ros2_control_demo_example_12"),
+            "config",
+            "rrbot_chained_controllers.yaml",
+        ]
+    )
+    rviz_config_file = PathJoinSubstitution(
+        [FindPackageShare("ros2_control_demo_example_12"), "rviz", "rrbot.rviz"]
+    )
+
+    control_node = Node(
+        package="controller_manager",
+        executable="ros2_control_node",
+        parameters=[robot_description, robot_controllers],
+        output="both",
+    )
+    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"],
+    )
+
+    j1_controller_spawner = Node(
+        package="controller_manager",
+        executable="spawner",
+        arguments=["joint1_position_controller", "--controller-manager", "/controller_manager"],
+    )
+
+    j2_controller_spawner = Node(
+        package="controller_manager",
+        executable="spawner",
+        arguments=["joint2_position_controller", "--controller-manager", "/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=[j1_controller_spawner, j2_controller_spawner],
+        )
+    )
+
+    nodes = [
+        control_node,
+        robot_state_pub_node,
+        joint_state_broadcaster_spawner,
+        delay_rviz_after_joint_state_broadcaster_spawner,
+        delay_robot_controller_spawner_after_joint_state_broadcaster_spawner,
+    ]
+
+    return LaunchDescription(nodes)