Launching rviz with mavic drone

[MatWaze]

I wanted to be able to launch rviz in addition to the webots simulation to interact with the model there. So I changed the robot_launch.py as follows:

import os
import launch
from launch.substitutions import LaunchConfiguration, Command
from launch.actions import DeclareLaunchArgument
from launch.substitutions.path_join_substitution import PathJoinSubstitution
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_controller import WebotsController
import launch_ros

def generate_launch_description():
    package_dir = get_package_share_directory('webots_ros2_mavic')
    world = LaunchConfiguration('world')

    webots = WebotsLauncher(
        world=PathJoinSubstitution([package_dir, 'worlds', world]),
        ros2_supervisor=True
    )

    robot_description_path = os.path.join(package_dir, 'resource', 'mavic_webots.urdf')
   # I added rviz config inside the rviz folder
    default_rviz_config_path = os.path.join(package_dir, 'rviz/urdf_config.rviz')

    robot_state_publisher_node = launch_ros.actions.Node(
        package='robot_state_publisher',
        executable='robot_state_publisher',
        parameters=[{'robot_description': Command(['xacro ', LaunchConfiguration('model')])}]
    )

    joint_state_publisher_node = launch_ros.actions.Node(
        package='joint_state_publisher',
        executable='joint_state_publisher',
        name='joint_state_publisher',
        condition=launch.conditions.UnlessCondition(LaunchConfiguration('gui'))
    )

    joint_state_publisher_gui_node = launch_ros.actions.Node(
        package='joint_state_publisher_gui',
        executable='joint_state_publisher_gui',
        name='joint_state_publisher_gui',
        condition=launch.conditions.IfCondition(LaunchConfiguration('gui'))
    )
    rviz_node = launch_ros.actions.Node(
        package='rviz2',
        executable='rviz2',
        name='rviz2',
        output='screen',
        arguments=['-d', LaunchConfiguration('rvizconfig')],
    )
    mavic_driver = WebotsController(
        robot_name='Mavic_2_PRO',
        parameters=[
            {'robot_description': robot_description_path},
        ],
        respawn=True
    )

    return LaunchDescription([
        DeclareLaunchArgument(name='world', default_value='mavic_world.wbt',
                                              description='Choose one of the world files from `/webots_ros2_mavic/worlds` directory'),
       
        DeclareLaunchArgument(name='gui', default_value='True',
                                            description='Flag to enable joint_state_publisher_gui'),
       
        DeclareLaunchArgument(name='model', default_value=robot_description_path,
                                            description='Absolute path to robot urdf file'),
        
        DeclareLaunchArgument(name='rvizconfig', default_value=default_rviz_config_path,
                                            description='Absolute path to rviz config file'),
        joint_state_publisher_node,
        joint_state_publisher_gui_node,
        robot_state_publisher_node,
        rviz_node,
        webots,
        webots._supervisor,
        mavic_driver,
        launch.actions.RegisterEventHandler(
            event_handler=launch.event_handlers.OnProcessExit(
                target_action=webots,
                on_exit=[
                    launch.actions.EmitEvent(event=launch.events.Shutdown())
                ],
            )
        )
    ])

When I colcon built the workspace containing webots_ros2_mavic and ran ros2 launch webots_ros2_mavic robot_launch.py, I got this error:
[robot_state_publisher-2] Error: No link elements found in urdf file
[robot_state_publisher-2] at line 206 in ./urdf_parser/src/model.cpp
[robot_state_publisher-2] Failed to parse robot description using: urdf_xml_parser/URDFXMLParser
[robot_state_publisher-2] terminate called after throwing an instance of 'std::runtime_error'
[robot_state_publisher-2] what(): Unable to initialize urdf::model from robot description

As I understand it, the error is related with the way urdf file is written: there are no links in there only some device references. What should I do?

[ygoumaz]

The robot_state_publisher needs the URDF of the robot as parameter to publish links over topics. Here you give the Command(['xacro ', LaunchConfiguration('model')]) xacro file, which doesn't seem to work.
What you can do is tell Webots to publish the URDF of the robot (with links and joints) in the background. You can inspire yourself from other examples like the tiago one for example. Here is the configuration you should use:

robot_state_publisher_node = launch_ros.actions.Node(
  package='robot_state_publisher',
  executable='robot_state_publisher',
  parameters=[{'robot_description': '<robot name=""><link name=""/></robot>'}]
)

mavic_driver = WebotsController(
  robot_name='Mavic_2_PRO',
  parameters=[
    {'robot_description': robot_description_path,
     'set_robot_state_publisher': True},
  ],
  respawn=True
)

[MatWaze]

Thanks it worked! But I noticed that when I run teleop_twist_keyboard and move the drone around in webots simulation, the model in rviz remains static. Can I actually make it move in rviz?