How to Autonomously Navigate while avoiding obstacles#

By the end of this tutorial, you will know how to make the robot autonomously navigate in the environment while avoiding static and dynamic obstacles.

Pre-requisites#

You should be able to remotely connect to your robot Set up ROS 2 communication with the robot.

You should be familiar with ROS’s RViz

You should first have completed the How to Localize in a known map of the environment

Send a Goal using RViz#

The easiest way to send a goal to the robot is by using the RViz GUI. This requires that you first establish the communication with the robot as explained in Set up ROS 2 communication with the robot.

Then, in the same terminal that is connected to the robot, you can start RViz with the command:

rviz2 -d /opt/pal/$PAL_DISTRO/share/<ROBOT>_2dnav/config/rviz/navigation.rviz

Attention

Make sure to replace the <ROBOT> placeholder with the name of your robot (e.g. tiago, omni_base, tiago_pro, etc.).

Then, using the 2D Nav Goal tool, you can set the desired goal position by clicking on the map. This will send a new Action Goal to the /navigate_to_pose Server, which will trigger the Navigation system that will make the robot reach the desired position.

To monitor the status of the Navigation system and obtain information about ETA, distance to the goal, etc., you can use the Navigation 2 RViz panel.

Send a Goal using ROS 2 Action#

Alternatively, to trigger the Goal Navigation, one can use the /navigate_to_pose Action. By sending an Action Goal to this Server it will make the robot reach the desired position. Thus, in this Action Goal, you need to specify the desired Goal Pose and the Behavior Tree to be used.

Send an action goal to the NavigateToPose action server#

ros2 action send_goal /navigate_to_pose nav2_msgs/action/NavigateToPose "pose:
  header:
    stamp:
      sec: 0
      nanosec: 0
    frame_id: 'map' # The frame in which the pose is expressed
  pose:
    position:
      x: 0.0
      y: 0.0
      z: 0.0
    orientation:
      x: 0.0
      y: 0.0
      z: 0.0
      w: 1.0
behavior_tree: ''"  # Optional: full/path/to/the/desired/Behavior/Tree

Note

Change the values of the position and orientation fields to the desired Goal Pose you want to reach. To use a custom Behavior Tree, specify the full path to the desired Behavior Tree file in the behavior_tree field. By default, if the behavior_tree field is empty, the navigate_to_pose_w_replanning_and_recovery.xml is used.

Send a Goal using ROS 2 Topic#

Alternatively, to trigger the Goal Navigation, one can simply publish a Goal Pose to the /goal_pose.

Publish a Goal Pose on the goal_pose topic#

ros2 topic pub /goal_pose geometry_msgs/msg/PoseStamped "header:
  stamp:
    sec: 0
    nanosec: 0
  frame_id: 'map' # The frame in which the pose is expressed
pose:
  position:
    x: 0.0
    y: 0.0
    z: 0.0
  orientation:
    x: 0.0
    y: 0.0
    z: 0.0
    w: 1.0"

Note

Change the values of the position and orientation fields to the desired Goal Pose you want to reach.

Next steps#

If you want to know more about Goal Navigation and how to use it in your code, you can refer to the 🔌 Goal Navigation API chapter.

If you want to know more about how to create custom Behavior Trees for the Navigation system, you can refer to the 🌳 Goal Navigation BT chapter.