Nav2

The Nav2 package provides open source navigation controllers, planners, and utilities. Regardless of whether you are using SLAM or Localization, you must launch Nav2.

note

When using the simulation, it is important to add use_sim_time:=true to the Nav2, SLAM, and Localization launch files. When using a physical robot, either omit use_sim_time or set it to false.

Launching the simulation and Nav2

1. Move the robot.yaml file to your setup folder ($HOME/clearpath by default for the simulation or /etc/clearpath/robot.yaml on a physical robot).

2. Open a terminal and launch the simulation:

ros2 launch clearpath_gz simulation.launch.py

If the simulation does not start automatically, press the large orange "play" button in the bottom left corner.

3. Open a second terminal and launch nav2:

ros2 launch clearpath_nav2_demos nav2.launch.py use_sim_time:=true

4. Open a third terminal and start either SLAM or Localization, depdending on whether or not you want to create a new map or use a pre-existing map.

5. Open a fourth terminal and start Rviz. If you are using a physical robot or running the simulation on an external server, this step must be should on your workstation, not on the robot or simulation server itself.

ros2 launch clearpath_viz view_navigation.launch.py namespace:=a300_0000

6. Set the initial pose of the robot using the 2D Pose Estimate tool in RViz.

7. Give the robot a navigation goal using the Nav2 Goal tool in RViz.

Nav2 Tools in Rviz

The Rviz configuration used by the clearpath_viz view_navigation.launch.py file includes several tools for interacting with Nav2. These tools require Rviz's Fixed Frame to be set to map. To set the fixed frame, use the toolbar on the left and open Displays > Global Options > Fixed Frame.

Initially the map frame may not be connected to the rest of the TF Tree. This is normal, and will be fixed when we use the 2D Pose Estimate tool. If map does not appear in the frame drop-down simply type the word map into the box and press ENTER.

To select a Nav2 tool, simply click on the button on the toolbar at the top of Rviz's main window

Rviz's toolbar with Nav2 tools

2D Pose Estimate

The 2D Pose Estimate tool allows you to provide Nav2 with the robot's approximate initial position on the map. This is a necessary step before you can navigate with the robot. This step connects the map frame to the rest of the robot's TF tree.

To set the robot's initial position, click and hold the mouse button on the map in the robot's approximate location. While holding the left mouse button, drag the green arrow to set the robot's orientation. Releasing the left mouse button will set the robot's position and orientation relative to the map frame.

If you are using SLAM and there is no map yet, simply click on the centre of the screen and drag up.

Once you have set the robot's initial pose you should see red markers representing the lidar data as well as coloured gradients indicating collision zones around walls and obstacles.

Setting the initial pose estimate

Publish Point

The Publish Point tool allows you to click on the map and publish the XYZ coordinates of that point to the clicked_point topic. In a terminal run the command

ros2 topic echo /a300_0000/clicked_point

Then select the Publish Point tool and click somewhere on the map. In the terminal you will see the location you clicked as a geometry_msgs/msg/PointStamped message:

header:
  stamp:
    sec: 1747855824
    nanosec: 867726206
  frame_id: map
point:
  x: -0.12474524974822998
  y: 0.002330044750124216
  z: -0.001434326171875

Publishing a point

Nav2 Goal

The Nav2 Goal tool allows you to set a goal pose for the robot. The Nav2 stack will then plan a path to the goal pose and attempt to drive the robot there.

You will see a red path line appear, indicating the robot's planned path, and the robot will start to drive along this path.

Navigation in simulation