Merge pull request #4 from cyberbotics/fix-start-ros2supervisor-node

Fix missing supervisor node creation and explanation

Author: ygoumaz

source/Tutorials/Advanced/Simulators/Code/robot_launch.py

@@ -4,7 +4,7 @@
 from launch_ros.actions import Node
 from launch import LaunchDescription
 from ament_index_python.packages import get_package_share_directory
-from webots_ros2_driver.webots_launcher import WebotsLauncher
+from webots_ros2_driver.webots_launcher import WebotsLauncher, Ros2SupervisorLauncher
 
 
 def generate_launch_description():
@@ -15,10 +15,13 @@ def generate_launch_description():
         world=os.path.join(package_dir, 'worlds', 'my_world.wbt')
     )
 
+    ros2_supervisor = Ros2SupervisorLauncher()
+
     my_robot_driver = Node(
         package='webots_ros2_driver',
         executable='driver',
         output='screen',
+        additional_env={'WEBOTS_CONTROLLER_URL': 'my_robot'},
         parameters=[
             {'robot_description': robot_description},
         ]
@@ -27,6 +30,7 @@ def generate_launch_description():
     return LaunchDescription([
         webots,
         my_robot_driver,
+        ros2_supervisor,
         launch.actions.RegisterEventHandler(
             event_handler=launch.event_handlers.OnProcessExit(
                 target_action=webots,

source/Tutorials/Advanced/Simulators/Code/robot_launch_sensor.py

@@ -4,7 +4,7 @@
 from launch_ros.actions import Node
 from launch import LaunchDescription
 from ament_index_python.packages import get_package_share_directory
-from webots_ros2_driver.webots_launcher import WebotsLauncher
+from webots_ros2_driver.webots_launcher import WebotsLauncher, Ros2SupervisorLauncher
 
 
 def generate_launch_description():
@@ -15,10 +15,13 @@ def generate_launch_description():
         world=os.path.join(package_dir, 'worlds', 'my_world.wbt')
     )
 
+    ros2_supervisor = Ros2SupervisorLauncher()
+
     my_robot_driver = Node(
         package='webots_ros2_driver',
         executable='driver',
         output='screen',
+        additional_env={'WEBOTS_CONTROLLER_URL': 'my_robot'},
         parameters=[
             {'robot_description': robot_description},
         ]
@@ -32,6 +35,7 @@ def generate_launch_description():
     return LaunchDescription([
         webots,
         my_robot_driver,
+        ros2_supervisor,
         obstacle_avoider,
         launch.actions.RegisterEventHandler(
             event_handler=launch.event_handlers.OnProcessExit(

source/Tutorials/Advanced/Simulators/Webots.rst

@@ -204,31 +204,41 @@ You have to specify in the constructor which world file the simulator will open.
     :dedent: 4
     :lines: 14-16
 
+A supervisor Robot is always automatically added to the world file by ``WebotsLauncher``.
+This robot is controlled by the custom node ``Ros2Supervisor``, which must also be started using the ``Ros2SupervisorLauncher``.
+This node allows to spawn URDF robots directly into the world, and it also publishes useful topics like ``/clock``.
+
+.. literalinclude:: Code/robot_launch.py
+    :language: python
+    :dedent: 4
+    :lines: 18
+
 Then, the ROS node interacting with the simulated robot is created.
 This node, named ``driver``, is located in the ``webots_ros2_driver`` package.
 The node will be able to communicate with the simulated robot by using a custom protocol based on IPC and shared memory.
 In your case, you need to run a single instance of this node, because you have a single robot in the simulation.
 But if you had more robots in the simulation, you would have to run one instance of this node per robot.
+``WEBOTS_CONTROLLER_URL`` is used to define the name of the robot the driver should connect to.
 The ``robot_description`` parameter holds the contents of the URDF file which refers to the ``my_robot_driver.py`` Python plugin.
 
 .. literalinclude:: Code/robot_launch.py
     :language: python
     :dedent: 4
-    :lines: 18-25
+    :lines: 20-28
 
-After that, the two nodes are set to be launched in the ``LaunchDescription`` constructor:
+After that, the three nodes are set to be launched in the ``LaunchDescription`` constructor:
 
 .. literalinclude:: Code/robot_launch.py
     :language: python
     :dedent: 4
-    :lines: 27-29
+    :lines: 30-33
 
 Finally, an optional part is added in order to shutdown all the nodes once Webots terminates (e.g., when it gets closed from the graphical user interface).
 
 .. literalinclude:: Code/robot_launch.py
     :language: python
     :dedent: 8
-    :lines: 30-35
+    :lines: 34-39
 
 6 Modify the setup.py file
 ^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -351,7 +361,7 @@ Go to the file ``robot_launch.py`` and replace ``def generate_launch_description
 
 .. literalinclude:: Code/robot_launch_sensor.py
     :language: python
-    :lines: 10-42
+    :lines: 10-46
 
 This will create an ``obstacle_avoider`` node that will be included in the ``LaunchDescription``.