Tutorial for Localization

In this tutorial we will localize the robot in a map using “AMCL” (Adaptive Monte Carlo Localization) algorithm. It uses a particle filter to estimate the pose of a robot in a known map

Running Map-server

If using real-robot, launch the robot (after ssh-ing to the robot)

ros2 launch robile_bringup robot.launch

Check which map will be loaded by the navigation stack

echo $ROBOT_ENV

If you need to change it, set the environment variable ROBOT_ENV to the map name you want to use

export ROBOT_ENV=map_name

If ROBOT_NAME environment variable is not set, set it to the robot name you want to use. For example,

export ROBOT_NAME=robile1               [when using Robile1 real-robot]
export ROBOT_NAME=robile_gazebo         [when using Robile in simulation]

Before running map_server node, build the robile_navigation package from the source directory of the workspace and source the setup.bash file. When built, the map will be stored in the share folder in the install directoy of the workspace. This makes the map to be accessible to the map_server node

cd ~/ros2_ws
colcon build --packages-select robile_navigation
source install/setup.bash

Run map_server node in new terminal of your PC. If you are using real-robot, make sure to set the environment variable ROS_DOMAIN_ID to respective robot id while using your terminal. Eg: while using Robile1, export ROS_DOMAIN_ID=1

ros2 launch robile_navigation robile_nav2_bringup.launch.py

If your application requires to subscribe to the map topic, then the qos profile has to be set to qos_profile_sensor_data. An example of creating a subscriber is as follows:

self.map_subscriber = self.create_subscription(OccupancyGrid, "/map", self.map_callback, qos_profile=rclpy.qos.qos_profile_sensor_data);

Running AMCL

Launch AMCL node

ros2 launch robile_navigation localization.launch.py

Localize the robot

  1. Run rviz2 in new terminal and select this config file: robile_navigation/config/robile_ros2_nav.rviz

  2. Select “2D Pose Estimate” placed in the top bar of rviz visulizer and click drag the arrow on the map where the robot is actually located

  3. Use joystick o teleop_twist_keyboard to rotate and translate such that the PoseArray arrows align

  4. The particles will converge to the actual location of the robot and the robot will be localized

  5. Keeping the terminal where localization node is running open, use a new terminal to run the navigation node, which is discussed in the next section