Robot-Operating-System

ROS2 Hands-on Practice for Robotics

This repository contains 10 practical ROS2 projects designed to help understand and master the core concepts of ROS2.
The tasks gradually cover topics, services, actions, parameters, lifecycle management, TF2, plugin architecture, and a simplified Navigation (Nav2) flow.
Completing these exercises will prepare you for working with ROS2 core libraries like rclcpp, and complex frameworks like Navigation2 (Nav2).

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Repository Structure

. ├── Task01_PubSub ├── Task02_CustomMsg ├── Task03_Service ├── Task04_Action ├── Task05_Parameters ├── Task06_LifecycleNode ├── Task07_Pluginlib ├── Task08_TF2 ├── Task09_Composition └── Task10_MiniNavDemo

Each folder contains:

• src/ → ROS2 node source files
• msg/, srv/, or action/ → Custom interfaces (when applicable)
• CMakeLists.txt & package.xml → ROS2 package configuration
• README.md → Task-specific details and run instructions

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Tasks Overview

Task 1: Minimal Publisher & Subscriber

• Goal: Implement a basic publisher and subscriber node.
• Key Concepts: rclcpp::Node, create_publisher, create_subscription.
• Deliverable: Publishes random integers, subscriber prints them.

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Task 2: Custom Message & Interface

• Goal: Learn how to create and use custom message types.
• Key Concepts: rosidl, custom .msg files, message generation.
• Deliverable: Publishes custom SensorReading messages and subscribes to them.

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Task 3: ROS2 Service

• Goal: Implement request-response communication.
• Key Concepts: create_service, create_client, synchronous and asynchronous calls.
• Deliverable: Simple AddTwoInts service and client.

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Task 4: ROS2 Action

• Goal: Handle long-running tasks with progress feedback.
• Key Concepts: Action servers, action clients, feedback and result handling.
• Deliverable: MoveRobot.action with progress updates.

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Task 5: Parameters & Dynamic Reconfigure

• Goal: Tune node parameters at runtime.
• Key Concepts: declare_parameter, get_parameter, parameter callbacks.
• Deliverable: Node with dynamically adjustable speed and name parameters.

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Task 6: Lifecycle Node

• Goal: Understand deterministic node state transitions (important for Nav2).
• Key Concepts: Managed nodes, transition services.
• Deliverable: Lifecycle node with configure(), activate(), deactivate().

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Task 7: Pluginlib

• Goal: Implement a runtime plugin architecture.
• Key Concepts: Abstract base classes, pluginlib registration, dynamic loading.
• Deliverable: Two controller plugins (SimpleController, AdvancedController) loaded dynamically.

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Task 8: TF2 & Robot State Broadcasting

• Goal: Work with robot frames and coordinate transforms.
• Key Concepts: tf2_ros::TransformBroadcaster, tf2_ros::Buffer, lookupTransform.
• Deliverable: Broadcast a moving transform (odom → base_link) and query it from another node.

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Task 9: Composition (Nodelets Style)

• Goal: Launch multiple nodes within one process.
• Key Concepts: rclcpp_components, intra-process communication.
• Deliverable: Publisher & Subscriber as composable nodes loaded in a component_container.

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Task 10: Mini Navigation Demo (Custom Simplified Nav2 Flow)

• Goal: Implement a simplified navigation pipeline.
• Key Concepts: Multi-node system (Goal node → Planner → Controller → TF → Velocity command).
• Deliverable:
  • Goal node sends target position
  • Simple planner calculates path
  • Controller publishes velocity commands
  • TF updates robot movement

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How to Build

Prerequisites

• Ubuntu 22.04 or similar
• ROS2 Humble or newer
• Colcon build system

Build Steps

# Source ROS2 environment
source /opt/ros/humble/setup.bash

# Clone repository
git clone https://github.com/<your-username>/ros2-hands-on-tasks.git
cd ros2-hands-on-tasks

# Build all packages
colcon build --symlink-install

# Source workspace
source install/setup.bash

# Run an example (Task 1)
ros2 run task01_pubsub publisher
ros2 run task01_pubsub subscriber