2

Hello to everyone,

I am struggling a bit with my gazebo project. Please any kind of help would be welcomed.

What I am trying to do:

I want to have multiple robot_descriptions as publisher for multiple robots of the same type. My goal is to visualize every robot and their scan data to rviz2.

What I have so far:

I have multiple robots in my gazebo simulation. I am using launch file to launch spawners to spawn the entities. I have sdf file xml of my model.
This is include description of the robot in my launcher:

spawn_entity1 = Node(package='robot_spawner_pkg', executable='spawn_demo',
                        arguments=['WarehouseBot1', 'robot1', '-4', '-3', '0.0'],
                        output='screen')
spawn_entity2 = Node(package='robot_spawner_pkg', executable='spawn_demo',
                        arguments=['WarehouseBot2', 'robot2', '-4', '-2', '0.0'],
                        output='screen')

return LaunchDescription([
        gazebo,
        spawn_entity1,
        spawn_entity2,
        IncludeLaunchDescription(
            PythonLaunchDescriptionSource([launch_file_dir, '/robot_state_publisher.launch.py']),
            launch_arguments={'use_sim_time': use_sim_time}.items(),
        ),
])

This is my robot_state_publisher:

def generate_launch_description():

    use_sim_time = LaunchConfiguration('use_sim_time', default='false')
    urdf_file_name = 'turtlebot3_burger.urdf'

    print('urdf_file_name : {}'.format(urdf_file_name))

    urdf = os.path.join(
        get_package_share_directory('turtlebot3_description'),
        'urdf',
        urdf_file_name)

    return LaunchDescription([
        DeclareLaunchArgument(
            'use_sim_time',
            default_value='false',
            description='Use simulation (Gazebo) clock if true'),

        Node(
            package='robot_state_publisher',
            executable='robot_state_publisher',
            name='robot_state_publisher',
            output='screen',
            parameters=[{'use_sim_time': use_sim_time}],
            arguments=[urdf]),
    ])

One thing poped up in my mind. It is to make separate sdf file for every robot with specific namespace and then publish separate robot_descriptions for every one. I am not sure if it would be working.
Al so I am kind of beginner in the terms of ros programming so I apologize for wrong formulations.

My setup:

ROS2 foxy

Python

Gazebo 11.9

Edit:
Eventually, in rviz I can specify tf prefix (I suppose frame_prefix now) for every robot_description to visualize the model. However, I would like to have something like "/robot1/tf" "robot2/tf". Is it even possible in ROS2?
According to this it is not very possible: https://answers.ros.org/question/388550/a-definitive-guide-to-launching-multi-robot-operations-in-ros2/?sort=latest

Question: "When should you use frame_prefix? When should you add a prefix directly in your URDF/Xacro files? Where do you need to apply a frame_prefix or namespace? (Gazebo plugins, ros2_control config files, robot_state_publisher)? When should you use fully qualified vs relative names? Are there any common cases other than /tf where you would not want to use relative topic names? When should you use a single tf tree for all robots, and when should you use a different tf tree for each robot?"

Answer: "Can't answer that one articulately at the moment. The prevailing standard set up by OSRF is that they've removed "prefix" in TF2, which I disagree with for exactly these multirobot situations. So there's conflict there that needs more explicit discussion. I would want to bin my TF messages either by having different /<my_robot>/tf topics or having sub-namespaces to the frames in the TF topic to be easily able to distinguish one robot from another's updates. I would prefer different topics for obvious bandwidth reasons, but I think those were implicitly removed from ROS 2 as a parameter. "

anton mlynar
  • 23
  • 3

0 Answers0