Update cartesian_space_example.launch.py

launch/cartesian_space_example.launch.py

@@ -9,9 +9,13 @@
 import os
 
 def generate_launch_description():
+ # Load the controller confguration file for the Cartesian space example. This contains the parameters for all ros2 controllers. 
  iiwa_controllers = PathJoinSubstitution([FindPackageShare('wbc_ros'), 'config', 'cartesian_space_example', 'iiwa_controllers.yaml'])
+ # Load the trajectory configuration file
  trajectory_publisher_config = os.path.join(get_package_share_directory('wbc_ros'),'config','cartesian_space_example','trajectory_publisher.yml')
 
+ # Create the robot description parameter (URDF) from the iiwa.config.xacro file. Use the "fake" flag, which means that the input command is mirrored to the
+ # robot state, producing a simple mini simulation
  robot_description = Command([
  PathJoinSubstitution([FindExecutable(name='xacro')]),' ',
  PathJoinSubstitution([FindPackageShare('wbc_ros'), 'models', 'urdf', 'iiwa.config.xacro']),' ',
@@ -23,19 +27,24 @@ def generate_launch_description():
  'namespace:=', '/'])
  robot_description = {'robot_description': robot_description}
 
+ # Load the controller manager (ros2_control_node). This is resposible for loading, configuring, activating and deactivating the controllers
  controller_manager = Node(
  package='controller_manager',
  executable='ros2_control_node',
  parameters=[robot_description, iiwa_controllers],
  output='both',
  namespace='/'
  )
+
+ # Spawn the whole-body controller (WBC). The WBC receive the control output from all controllers in task space (in this case only the Cartesian position controller)
+ # and integrates into a coherent control signal in joint space (in this case joint position commands), which are written to hardware interface directly
  whole_body_controller_spawner = Node(
  package='controller_manager',
  executable='spawner',
  arguments=['whole_body_controller', '--controller-manager', ['/', 'controller_manager']],
  namespace='/')
 
+ # Spawn the Cartesian position controller. This controller stabilizes the desired end effector trajectory in cartesian space
  cartesian_position_controller_spawner = Node(
  package='controller_manager',
  executable='spawner',
@@ -49,18 +58,21 @@ def generate_launch_description():
  target_action=whole_body_controller_spawner,
  on_exit=[cartesian_position_controller_spawner])))
 
+ # The joint state broadcaster is actually not really a controller, it simply collects the joint states and publishes them
  joint_state_broadcaster = Node(
  package='controller_manager',
  executable='spawner',
  arguments=['joint_state_broadcaster', '--controller-manager', ['/', 'controller_manager']])
 
+ # This node publishes a circular trajectory and sends it to the Cartesian position controller
  cartesian_trajectory_publisher = Node(
  package='wbc_ros',
  executable='cartesian_trajectory_publisher',
  name='trajectory',
  namespace='/cartesian_position_controller',
  parameters=[trajectory_publisher_config])
 
+ # The robot state publisher computes the transform between all robot links given the joint_status topic to visualize the robot in rviz
  robot_state_publisher = Node(
  package='robot_state_publisher',
  executable='robot_state_publisher',