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Chapter 4: ROS 2 Architecture and Core Concepts

Learning Objectives​

By the end of this section, you will be able to:

  • Explain the ROS 2 architecture and its layers
  • Understand DDS (Data Distribution Service) middleware
  • Describe Quality of Service (QoS) policies and when to use them
  • Define and navigate the computational graph (nodes, topics, services, actions)
  • Compare ROS 1 and ROS 2 design philosophies
  • Recognize why ROS 2 is the standard for modern robotics

Status: In Progress​

This section is being created by the technical writing sub-agent. Expected delivery: December 7, 2025.

Research Phase: Input from robotics_researcher - Task 1.1 Details

Coming Soon​

This section will cover:

  • ROS 2 Ecosystem Overview: History, motivation, and modern robotics needs
  • DDS Middleware: What it is, why it matters, how it enables distributed computing
  • Quality of Service (QoS): Reliability policies, deadlines, liveliness, and when each matters
  • Computational Graph: Nodes, topics, services, actions, and their relationships
  • ROS 1 vs ROS 2: Key differences and why the redesign was necessary
  • Real-World Impact: How ROS 2 enables physical AI and humanoid robotics

Code Examples Included:

  • Your first ROS 2 node
  • Visualization of a computational graph
  • QoS configuration examples

Placeholder: Content Structure​

## Introduction
Why ROS 2 matters for Physical AI

## What is ROS 2?
ROS 2 ecosystem and its role

## ROS 2 Architecture
Layer by layer explanation

## DDS Middleware
The communication backbone

## Quality of Service
Configuring reliability and performance

## The Computational Graph
Nodes and their relationships

## Key Takeaways
Summary and reflection

## Further Reading
Resources and links

Previous: Chapter 2 Overview
Next: 2.2 Nodes and Communication Patterns