7. ROS Navigation

7.1. Learning Objectives

In this ROS example, We will

  • Demonstrate Omniverse Isaac Sim integrated with the ROS Navigation stack.

  • Use the Occupancy Map Generator.

7.2. Getting Started

Prerequisite

  • The ROS Navigation stack is required to run this sample. Install the ROS Navigation stack:

    sudo apt-get install ros-$ROS_DISTRO-navigation
    
  • This tutorial requires carter_2dnav, carter_description, and isaac_ros_navigation_goal ROS packages which are provided as part of your Omniverse Isaac Sim download. The packages are located under the directory ros_workspace/src/navigation/. They contain the required launch file, navigation parameters, and robot model. Complete ROS & ROS 2 Installation, make sure ROS environment is setup correctly and those packages are inside your ROS_PACKAGE_PATH.

  • roscore is running before running Omniverse Isaac Sim.

7.3. The ROS Navigation Setup

This block diagram shows the ROS messages required for the ROS Navigation stack.

ROS Navigation Overview Block Diagram

As described above, the following topics and message types being published to the ROS Navigation stack in this scenario are:

ROS Topic

ROS Message Type

/tf

tf2_msgs/TFMessage

/odom

nav_msgs/Odometry

/map

nav_msgs/OccupancyGrid

/scan

sensor_msgs/LaserScan

7.3.1. Carter_ROS OmniGraph Nodes

Go to Isaac Examples -> ROS -> Navigation to load the warehouse scenario.

  1. Open the main ActionGraph by expanding Carter_ROS. Right click on ActionGraph and press Open Graph. The following ROS OmniGraph nodes are setup to do the following:

    Ominigraph Node

    Function

    ros1_subscribe_twist

    Subscribes to the /cmd_vel topic and triggers the differential and articulation controllers to the move the robot

    ros1_publish_odometry

    Publishes odometry received from the isaac_compute_odometry_node

    ros1_publish_raw_transform_tree

    Publishes the transform between the odom frame and base_link frame

    ros1_publish_transform_tree

    Publishes the static transform between the base_link frame and chassis_link frame. Keep in mind that since the target prim is set as Carter_ROS, the entire transform tree of the Carter robot (with chassis_link as root) will be published as children of the base_link frame

    ros1_publish_transform_tree_01

    Publishes the static transform between the chassis_link frame and carter_lidar frame

    ros1_publish_laser_scan

    Publishes the 2D LaserScan received from the isaac_read_lidar_beams_node

  2. Open the ROS_Cameras graph by expanding Carter_ROS. Right click on ROS_Cameras and press Open Graph. The following ROS Camera OmniGraph nodes are setup to do the following:

    Ominigraph Node

    Function

    ros1_create_camera_left_info

    Auto-generates the CameraInfo publisher for the /camera_info_left topic. It automatically publishes since the enable_camera_left branch node is enabled by default

    ros1_create_camera_left_rgb

    Auto-generates the RGB Image publisher for the /rgb_left topic. It automatically publishes since the enable_camera_left and enable_camera_left_rgb branch nodes are enabled by default

    ros1_create_camera_left_depth

    Auto-generates the Depth (32FC1) Image publisher for the /depth_left topic. To start publishing, ensure enable_camera_left and enable_camera_left_depth branch nodes are enabled

    ros1_create_camera_right_info

    Auto-generates the CameraInfo publisher for the /camera_info_right topic. To start publishing, ensure the enable_camera_right branch node is enabled

    ros1_create_camera_right_rgb

    Auto-generates the RGB Image publisher for the /rgb_right topic. To start publishing, ensure enable_camera_right is enabled. The enable_camera_right_rgb branch node is already enabled by default

    ros1_create_camera_right_depth

    Auto-generates the Depth (32FC1) Image publisher for the /depth_right topic. To start publishing, ensure enable_camera_right and enable_camera_right_depth branch nodes are enabled

  3. Finally, to ensure all external ROS nodes reference simulation time, a ROS_Clock graph is added which contains a ros1_publish_clock node responsible for publishing the simulation time to the /clock topic.

7.3.2. Generate Occupancy Map

In this scenario we will use an occupancy map. To generate a map there are 2 options:

  1. Using the Occupancy Map Generator extension within Omniverse Isaac Sim (Recommended)

  2. Using the slam_gmapping ROS package

7.3.2.2. Using the slam_gmapping ROS package:

  • Install the slam_gmapping ROS package, run the command below:

    sudo apt-get install ros-$ROS_DISTRO-slam-gmapping
    
  • Install the teleop_twist_keyboard ROS package:

    sudo apt-get install ros-$ROS_DISTRO-teleop-twist-keyboard
    
  1. Go to Isaac Examples -> ROS -> Navigation to load the warehouse scenario. Press Play to begin simulation.

  2. Follow the tutorial: http://wiki.ros.org/slam_gmapping/Tutorials/MappingFromLoggedData

    Note

    Since a rosbag is not available, substitute the rosbag command in the tutorial with the following command: rosrun teleop_twist_keyboard teleop_twist_keyboard.py. This will start the teleop_twist_keyboard ROS node and enable you to use your keyboard to manually drive the robot around the warehouse to simultaneously generate a map.

  3. Press Stop to terminate the simulation.

7.4. Running ROS Navigation

  1. Go to Isaac Examples -> ROS -> Navigation to load the warehouse scenario.

  2. Click on Play to begin simulation.

  3. In a new terminal, run the ROS launch file to begin ROS Navigation.

    roslaunch carter_2dnav carter_navigation.launch
    

    RViz will open and begin loading the urdf model of the robot, the global occupancy map, as well as the local costmap which will be overlaid on top.

  4. To verify that all of the transforms are broadcasting, run the following command in a new terminal to visualize the ROS TF frame tree:

    rosrun rqt_tf_tree rqt_tf_tree
    

    The generated graph should look similar to the one shown below.

    ROS TF frame tree
  5. Since the position of the robot is defined in carter_navigation.launch, the robot should already be properly localized. If required, the 2D Pose Estimate button can be used to re-set the position of the robot.

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

7.5. Sending Goals Programmatically

The isaac_ros_navigation_goal ROS package can be used to set goal poses for the robot using a python node. It is able to randomly generate and send goal poses to the navigation stack. It is also able to send user-defined goal poses if needed.

  1. Make any changes to the parameters defined in the launch file found under isaac_ros_navigation_goal/launch as required. The parameters are described below:

    • goal_generator_type: Type of the goal generator. Use RandomGoalGenerator to randomly generate goals or use GoalReader for sending user-defined goals in a specific order.

    • map_yaml_path: The path to the occupancy map parameters yaml file. Example file is present at isaac_ros_navigation_goal/assets/carter_warehouse_navigation.yaml. The map image is being used to identify the obstacles in the vicinity of a generated pose. Required if goal generator type is set as RandomGoalGenerator.

    • iteration_count: Number of times goal is to be set.

    • action_server_name: Name of the action server.

    • obstacle_search_distance_in_meters: Distance in meters in which there should not be any obstacle of a generated pose.

    • goal_text_file_path: The path to the text file which contains user-defined static goals. Each line in the file has a single goal pose in the following format: pose.x pose.y orientation.x orientation.y orientation.z orientation.w. Sample file is present at: isaac_ros_navigation_goal/assets/goals.txt. Required if goal generator type is set as GoalReader.

    • initial_pose: If initial_pose is set, it will be published to /initialpose topic and goal poses will be sent to action server after that. Format is [pose.x, pose.y, pose.z, orientation.x, orientation.y, orientation.z, orientation.w].

  2. To run the launch file, use the following command:

    roslaunch isaac_ros_navigation_goal isaac_ros_navigation_goal.launch
    

Note

The package will stop processing (setting goals) once any of the below conditions are met:

  1. Number of goals published till now >= iteration_count.

  2. If GoalReader is being used then if all the goals from file are published, or if condition (1) is true.

  3. A goal is rejected by the action server.

  4. In case of RandomGoalGenerator, if a goal was not generated even after running the maximum number of iterations, which is rare but could happen in very dense maps.

To learn more about programmatically sending navigation goals to multiple robots simultaneously see Sending Goals Programmatically for Multiple Robots.

7.6. Troubleshooting

If you are noticing performance related issues with the ROS Navigation stack or errors such as:

Could not transform the global plan to the frame of the control
  • Consider increasing the transform_tolerance parameter for the local and global occupancy maps found in local_costmap_params.yaml and global_costmap_params.yaml.

7.7. Summary

In this tutorial, we covered

  1. Occupancy map

  2. Running Isaac Sim with ROS navigation stack.

  3. Running the Isaac ROS Navigation Goal package to send nav goals programmatically.

7.7.1. Next Steps

Continue on to the next tutorial in our ROS Tutorials series, Multiple Robot ROS Navigation to move multiple navigating robots.

7.7.2. Further Learning