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Chapter 1: What is ROS 2?

Introduction​

ROS 2 (Robot Operating System 2) is the next generation of the world's most popular robot middleware framework. Despite its name, ROS is not an operating system but rather a flexible framework for writing robot software - a collection of tools, libraries, and conventions that aim to simplify the task of creating complex and robust robot behavior across a wide variety of robotic platforms.

What Makes ROS 2 Different?​

Evolution from ROS 1​

ROS 2 is a complete redesign of ROS 1, addressing critical limitations:

FeatureROS 1ROS 2
CommunicationCustom TCPROSDDS (Data Distribution Service)
Real-time SupportLimitedNative support
Multi-robotDifficultBuilt-in
SecurityBasicEncrypted, authenticated
Platform SupportLinux onlyLinux, Windows, macOS
Production ReadyResearch-focusedProduction-grade

Key Improvements​

  1. Real-time Performance: Built-in support for real-time systems
  2. Security: Encryption and authentication at the transport layer
  3. Cross-platform: Native support for Linux, Windows, and macOS
  4. Multi-robot: First-class support for multi-robot systems
  5. Commercial Quality: Production-ready with quality-of-service (QoS) policies

Core Concepts​

1. Nodes​

A node is a process that performs computation. Nodes communicate with each other using:

2. Topics (Publish/Subscribe)​

Topics enable asynchronous, many-to-many communication:

# Publisher example
import rclpy
from rclpy.node import Node
from std_msgs.msg import String

class MinimalPublisher(Node):
    def __init__(self):
        super().__init__('minimal_publisher')
        self.publisher_ = self.create_publisher(String, 'topic', 10)
        timer_period = 0.5  # seconds
        self.timer = self.create_timer(timer_period, self.timer_callback)

    def timer_callback(self):
        msg = String()
        msg.data = 'Hello ROS 2!'
        self.publisher_.publish(msg)
        self.get_logger().info(f'Publishing: "{msg.data}"')

3. Services (Request/Response)​

Services provide synchronous request/response communication:

# Service server example
from example_interfaces.srv import AddTwoInts

class MinimalService(Node):
    def __init__(self):
        super().__init__('minimal_service')
        self.srv = self.create_service(
            AddTwoInts,
            'add_two_ints',
            self.add_two_ints_callback
        )

    def add_two_ints_callback(self, request, response):
        response.sum = request.a + request.b
        self.get_logger().info(f'{request.a} + {request.b} = {response.sum}')
        return response

4. Actions (Goal-oriented Tasks)​

Actions enable long-running tasks with feedback:

DDS: The Communication Backbone​

ROS 2 uses DDS (Data Distribution Service) for communication:

Benefits of DDS:​

  • Quality of Service (QoS): Configure reliability, durability, latency
  • Discovery: Automatic node discovery without master
  • Scalability: Efficient for large-scale systems
  • Interoperability: Standard protocol (OMG DDS)

QoS Policies Example:​

from rclpy.qos import QoSProfile, ReliabilityPolicy, DurabilityPolicy

# Sensor data: best effort, volatile
sensor_qos = QoSProfile(
    reliability=ReliabilityPolicy.BEST_EFFORT,
    durability=DurabilityPolicy.VOLATILE,
    depth=10
)

# Commands: reliable, transient local
command_qos = QoSProfile(
    reliability=ReliabilityPolicy.RELIABLE,
    durability=DurabilityPolicy.TRANSIENT_LOCAL,
    depth=10
)

ROS 2 Architecture​

When to Use ROS 2​

Perfect For:​

  • ✅ Research robots
  • ✅ Commercial products (manufacturing, logistics, agriculture)
  • ✅ Autonomous vehicles
  • ✅ Drones and UAVs
  • ✅ Humanoid robots
  • ✅ Service robots

Not Ideal For:​

  • ❌ Bare-metal microcontrollers (use micro-ROS instead)
  • ❌ Hard real-time less than 1ms requirements
  • ❌ Simple single-board projects (might be overkill)

Supported Platforms​

PlatformTier 1 SupportTier 2 Support
Ubuntu 22.04✅-
Ubuntu 24.04✅-
Windows 10/11-✅
macOS-✅
RHEL-✅

ROS 2 Distributions​

ROS 2 follows a release cycle with LTS (Long-Term Support) versions:

DistributionRelease DateEOLType
Humble HawksbillMay 2022May 2027LTS ✅
Iron IrwiniMay 2023Nov 2024Standard
Jazzy JaliscoMay 2024May 2029LTS ✅

Recommendation: Use Humble (stable, well-tested) or Jazzy (latest features).

Real-World Applications​

1. Autonomous Vehicles​

  • Waymo, Cruise, Zoox use ROS-based stacks
  • Sensor fusion, perception, planning, control

2. Industrial Robots​

  • BMW uses ROS 2 for production lines
  • Collaborative robots (cobots)

3. Service Robots​

  • Hospital delivery robots
  • Cleaning robots
  • Warehouse automation

4. Research​

  • Universities worldwide
  • Benchmark platform for robotics research

Summary​

ROS 2 is the industry-standard framework for modern robotics:

  • 🚀 Production-ready with real-time support
  • 🔒 Secure with built-in encryption
  • 🌍 Cross-platform (Linux, Windows, macOS)
  • 🤖 Multi-robot systems out of the box
  • 📦 Ecosystem of 3000+ packages

Exercise​

  1. Research: Find 3 companies using ROS 2 in production
  2. Comparison: List 5 differences between ROS 1 and ROS 2
  3. Use Case: Identify a robot application where ROS 2 would be beneficial

Next Chapter​

In Chapter 2, we'll set up your ROS 2 development environment and create your first node!

Additional Resources​