ROS, the Robot Operating System, is the platform of choice for robot development. However, the breadth and depth of existing documentation can be daunting for the ROS beginner.
This tutorial will introduce you to the basic concepts of ROS robots using simulated robots. The concepts introduced here give you the necessary foundation to use ROS products and begin developing your own robots.
Sample commands are based on the ROS 2 Humble distribution. Although the basic concepts do not change between ROS 1 and ROS 2, many of the commands differ and the underlying architecture is quite different.
No programming experience is required to complete this tutorial! To follow along with the examples, you should either have a ROS 2 Humble installation of either turtlesim or the Robotis TurtleBot3.
If you plan to follow along with the turtlesim simulator, start it with the command:
ros2 run turtlesim turtlesim_node
Similarly if you’re using the TurtleBot WafflePi simulator, use the command:
ros2 launch turtlebot3_gazebo empty_world.launch.py
Keep the simulator running throughout the tutorial.
The software of a ROS-based robot conceptually builds up a graph of connected endpoints. The endpoints within ROS are called Nodes. They’re the primary software building block, the process that anchors all parts of the robot software design.
A node will control hardware like wheel motors, or a node may gather sensor data from a laser range finder. Use the command ros2 node list to show which nodes are running in your simulator. For turtlesim you should see the following:
/turtlesim
The turtlebot publishes multiple nodes to handle the different functions available on the robot:
/camera_driver
/gazebo
/robot_state_publisher
/turtlebot3_diff_drive
/turtlebot3_imu
/turtlebot3_joint_state
/turtlebot3_laserscan
(Optionally) Nodes can dynamically be added to a ROS robot as additional programs are launched. While turtlesim continues to run, launch a keyboard controller for it with the following command:
ros2 run turtlesim turtle_teleop_key