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Multiple Robot ROS 2 Navigation#

Support Limitations

  • Multiple Robot ROS 2 Navigation with Isaac Sim is fully supported on Linux. On Windows, Multiple Robot ROS 2 Navigation with Isaac Sim could potentially produce errors.

Learning Objectives#

In this ROS 2 sample, we are demonstrating NVIDIA Isaac Sim integrated with the ROS 2 Nav2 stack to perform simultaneous multiple robot navigation.

Getting Started#

Prerequisite

  • Completed ROS 2 Navigation for ROS 2 Nav2 with a single robot. So that

    • ROS 2 and Nav2 are installed.

    • ROS 2 bridge is enabled.

    • ros2_ws is built and sourced (see Setup ROS 2 Workspaces) so that carter_navigation and isaac_ros_navigation_goal are inside your workspace.

Note

In Windows 11, depending on your machine’s configuration, RViz2 might not open properly.

Occupancy Map#

We generate the map of both the Hospital and Office environments using the Occupancy Map Generator extension within NVIDIA Isaac Sim.

Follow the steps depending on what environment you would like to use.

  1. Go to the Isaac Sim Content browser and click Isaac Sim>Environments>Hospital. Search for hospital and drag and drop the hospital.usd asset into the scene. Ensure that it is placed at the origin by zero’ing out all the Translate components in the Transform Property.

  2. At the upper left corner of the viewport, click on Perspective. Select Top from the dropdown menu. Select the /Hospital prim and press F to zoom to selection. Adjust the camera view as needed.

  3. Go to Tools > Robotics > Occupancy Map.

  4. In the Occupancy Map extension, ensure the Origin is set to X: 0.0, Y: 0.0, Z: 0.0. For the lower bound, set Z: 0.1. For the Upper Bound, set Z: 0.62. Keep in mind, the upper bound Z distance has been set to 0.62 meters to match the vertical distance of the Lidar onboard Carter with respect to the ground.

  5. Select the Hospital prim in the stage. In the Occupancy Map extension, click on BOUND SELECTION. The bounds of the occupancy map should be updated to incorporate the selected Hospital prim.

    The map parameters should now look similar to the following image:

    Occupancy Map Properties UI Window for the Hospital Environment

    A perimeter will be generated and it should resemble this image (Top View):

    Top View of Hospital with Occupancy Map

  1. Go to the Isaac Sim Content browser Isaac Sim>Environments>Office. Search for office and drag and drop the office.usd asset into the scene. Ensure that it is placed at the origin by zero’ing out all the Translate components in the Transform Property.

  2. At the upper left corner of the viewport, click on Perspective. Select Top from the dropdown menu. Select the /Office prim and press F to zoom to selection. Adjust the camera view as needed.

  3. Go to Tools > Robotics > Occupancy Map. In the Occupancy Map extension, set the map parameters to be similar to the following image:

    Occupancy Map Properties UI Window for Office Environment

    Keep in mind, the upper bound Z distance has been set to 0.62 meters to match the vertical distance of the Lidar onboard Nova Carter with respect to the ground.

    A perimeter will be generated, verify that it resembles this image (Top View):

    Top View of Office with Occupancy Map

  1. After the setup for either environment is complete, click on CALCULATE followed by VISUALIZE IMAGE. A Visualization popup will appear.

  2. For Rotate Image, select 180 degrees and for Coordinate Type select ROS Occupancy Map Parameters File (YAML). Click RE-GENERATE IMAGE. Occupancy map parameters formatted to YAML will appear in the field below. Change the image name to your preference. Copy the full text.

  3. Click Save YAML and save the YAML file to the maps directory, which is located in the sample carter_navigation ROS 2 package (carter_navigation/maps/carter_hospital_navigation.yaml).

  4. Back in the visualization tab in NVIDIA Isaac Sim, click Save Image. Set the same image name as in the map parameters and choose to save in the same directory as the map parameters file.

    • The final saved image of the Hospital environment will look like the following:

    Sample Occupancy Map generated from hospital stage

    • The final saved image of the Office environment will look like the following:

    Sample Occupancy Map generated from office stage

An occupancy map is now ready to be used with Multiple Robot ROS 2 Navigation.

Multiple Robot ROS 2 Navigation Setup#

Open hospital scene by going to Window > Examples > Robotics Examples, and then click on the Robotics Examples tab and expand the sections on the left hand side and open the example: ROS2 > Navigation > Multiple Robots > Hospital Scene.

For details on the ROS 2 Navigation setup refer to the ROS 2 Navigation Sample.

For operating multiple robots in the same environment, namespaces are utilized. This modifies the rostopic and rosnode names for different ROS 2 packages, allowing for multiple instances of the same ROS 2 node to run simultaneously.

To publish and receive ROS 2 messages under namespaces, the node_namespace OmniGraph node found in each of the action graphs under Nova_Carter_ROS_X has been set to the corresponding robot names. The multiple_robot_carter_navigation_hospital.launch.xml and multiple_robot_carter_navigation_office.launch.xml launch files found in the sample carter_navigation ROS 2 package are also configured with the same robot namespaces.

Running Multiple Robot ROS 2 Navigation#

  1. Load scenario:

    • For the hospital environment, go to Window > Examples > Robotics Examples, and then click on the Robotics Examples tab and expand the sections on the left hand side and open the example: ROS2 > Navigation > Multiple Robots > Hospital Scene.

    • For the Office scenario, go to Window > Examples > Robotics Examples, and then click on the Robotics Examples tab and expand the sections on the left hand side and open the example: ROS2 > Navigation > Multiple Robots > Office Scene.

  2. Click on Play to begin simulation.

  3. In a new terminal, run the specific ROS 2 launch file to begin Multiple Robot Navigation with the desired environment.

    ros2 launch carter_navigation multiple_robot_carter_navigation_hospital.launch.xml

    ros2 launch carter_navigation multiple_robot_carter_navigation_office.launch.xml

    Three RViz2 windows will be launched. This process can take a few moments to startup.

  4. In each RViz2 window, click on the Map located in the Displays panel to observe the Topic name and take note of the robot namespace corresponding to the RViz2 window.

  5. Since the positions of each robot are defined in parameter files in carter_navigation/params/hospital/ or carter_navigation/params/office/, the robots should already be properly localized.

  6. In the /carter1 namespaced RViz2 window, click on the 2D Nav Goal button and then click and drag at the desired location point in the map. The ROS 2 Navigation stack will now generate a trajectory and the /carter1 robot will start moving towards its destination!

  7. Repeat the previous step for the /carter2 and /carter3 robots.

Note

The ROS 2 Image publisher pipelines are disabled by default to improve performance. To start publishing images, open the _hawk action graphs found under each of the Nova_Carter_ROS prims and enable the _camera_render_product nodes. The ROS Camera publisher nodes, which are downstream of the render product nodes, must be enabled by default and will only start publishing when the render product node is enabled. All sensors and images in Nova Carter are being published with Sensor Data QoS. If you wish to visualize the images in RViz2, expand the image tab, navigate to Topic > Reliability Policy and change the policy to Best Effort.

Troubleshooting#

This tutorial exhibits high CPU usage. If you observe instances of robots colliding or experiencing localization issues, it’s likely because the Nav2 stack is unable to properly synchronize with sensor data, resulting in missed controller commands. To improve Nav2 performance:

  1. Try enabling the Publish Full Scan checkbox accessible through the publish_front_3d_lidar_scan OmniGraph node found in the ros_lidars action graph found under each Nova_Carter_ROS_X robot.

  2. If the previous step still results in issues, also try running Isaac Sim from the terminal using the following command:

    ./isaac-sim.fabric.sh --reset-user

    Important

    The above command is experimental and not all functionality of Isaac Sim is supported there. However you might observe better overall performance.

Running in Python Directly#

Alternatively, to load this sample environment from Python directly, follow the steps outlined here.

Sending Goals Programmatically for Multiple Robots#

Note

The isaac_ros_navigation_goal package is fully supported on Linux. On Windows, running this package could potentially produce errors.

The isaac_ros_navigation_goal ROS 2 package can be used to set goal poses for multiple robots simultaneously. Refer to Sending Goals Programmatically to learn about the configurations and parameters of this package.

To send navigation goals to multiple robots simultaneously, include isaac_ros_navigation_goal.launch.xml once for each robot in a new XML launch file. Set a unique namespace and initial_pose for every include. For example:

<launch>
  <include file="$(find-pkg-share isaac_ros_navigation_goal)/launch/isaac_ros_navigation_goal.launch.xml">
    <arg name="namespace" value="carter1"/>
    <arg name="map_yaml_path" value="/path/to/map.yaml"/>
    <arg name="initial_pose" value="[0.0,0.0,0.0,0.0,0.0,1.0,0.0]"/>
  </include>
  <include file="$(find-pkg-share isaac_ros_navigation_goal)/launch/isaac_ros_navigation_goal.launch.xml">
    <arg name="namespace" value="carter2"/>
    <arg name="map_yaml_path" value="/path/to/map.yaml"/>
    <arg name="initial_pose" value="[0.0,2.0,0.0,0.0,0.0,1.0,0.0]"/>
  </include>
  <include file="$(find-pkg-share isaac_ros_navigation_goal)/launch/isaac_ros_navigation_goal.launch.xml">
    <arg name="namespace" value="carter3"/>
    <arg name="map_yaml_path" value="/path/to/map.yaml"/>
    <arg name="initial_pose" value="[0.0,-2.0,0.0,0.0,0.0,1.0,0.0]"/>
  </include>
</launch>

Update the map path and initial poses for the hospital or office scenario. The action name and initialpose topic are relative, so each include communicates with the Nav2 stack in its own namespace.

Note

If goal_generator_type is RandomGoalGenerator, a goal text file is not used. If it is GoalReader, set a separate goal_text_file_path for each robot.

  1. Save the new launch file in the isaac_ros_navigation_goal/launch directory.

  2. From the ROS workspace root, rebuild the package and source the updated workspace so ROS 2 can discover the new launch file:

    colcon build --packages-select isaac_ros_navigation_goal
source install/setup.bash

  3. Run the launch file using the filename you selected. For example:

    Important

    Before running the following command, ensure you have run steps 1 to 4 from Multiple Robot ROS 2 Navigation Setup.

    ros2 launch isaac_ros_navigation_goal multiple_robot_navigation_goal.launch.xml

Summary#

In this tutorial, we covered running multiple robots with ROS 2 navigation stack.

Next Steps#

Continue on to the next tutorial in our ROS 2 Tutorials series, ROS 2 Navigation with Heightmap Importer.

Further Learning#

  • To learn more about Nav2 refer to the website: https://nav2.org/

  • Standalone Python scripting version: Multiple Robot ROS 2 Navigation. With this approach you have the ability to manually control the timestep and rate at which ROS components are published.