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ROS 2 Fundamentals

What is ROS 2?​

ROS 2 (Robot Operating System 2) is the next generation of ROS, designed to address the limitations of ROS 1 while maintaining its core philosophy of code reuse and modularity.

Key Concepts​

Nodes​

A node is a process that performs computation. Nodes are combined into a graph and communicate with one another using topics, services, or actions.

import rclpy
from rclpy.node import Node

class MyNode(Node):
    def __init__(self):
        super().__init__('my_node')
        self.get_logger().info('Node started!')

def main():
    rclpy.init()
    node = MyNode()
    rclpy.spin(node)
    rclpy.shutdown()

if __name__ == '__main__':
    main()

Topics​

Topics are named buses over which nodes exchange messages. Topics have one or more publishers and one or more subscribers.

Services​

Services are another method of communication for nodes in the ROS graph. Services are based on a call-and-response model, unlike topics.

ROS 2 Architecture​

ROS 2 uses a distributed architecture where:

  • Nodes communicate through a DDS (Data Distribution Service) middleware
  • Topics enable publish-subscribe communication
  • Services enable request-response communication
  • Actions enable long-running tasks with feedback

Installation​

Ubuntu 22.04​

sudo apt update
sudo apt install ros-humble-desktop
source /opt/ros/humble/setup.bash

Verify Installation​

ros2 --help

Next Steps​

In the next chapter, we'll dive deeper into creating nodes, topics, and services.