🐢 ROS2 Multi-Node Control and Coordination

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📌 Overview

This project demonstrates a multi-node ROS2 application built using the Turtlesim simulator. A primary turtle (turtle1) autonomously chases dynamically spawned turtles using ROS2 nodes, topics, services, timers, and custom interfaces. The project focuses on ROS2 fundamentals and runtime introspection, not advanced robotics algorithms.

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🧠 System Architecture

Nodes

• /turtlesim (ROS2 provided) ROS2-provided simulation node. Publishes turtle pose and exposes /spawn and /kill services.

• /turtle_spawner Spawns turtles periodically and publishes the list of active turtles.

• /turtle_controller Subscribes to turtle pose and active turtle list, and publishes velocity commands to move turtle1.

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🔄 Communication

Topics

• /turtle1/pose
• /turtle1/cmd_vel
• /alive_turtles

Services

• /spawn
• /kill

Custom Interfaces

Turtle.msg

string name
float32 x
float32 y
float32 theta

TurtleArray.msg

Turtle[] turtles

CatchTurtle.srv

string name
---
bool success

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📂 Repository Structure

ros2-turtlesim-catch-them-all/
├── README.md
├── screenshots/
│   ├── launch_and_simulation.png
│   ├── node_list.png
│   ├── topic_list.png
│   ├── alive_turtles_info.png
│   └── rqt_graph.png
├── videos/
│   └── turtlesim_demo.gif
├── src/
│   ├── my_robot_bringup/
│   │   ├── launch/
│   │   │   └── turtlesim_catch_them_all.launch.xml
│   │   ├── config/
│   │   │   └── catch_them_all_config.yaml
│   │   └── package.xml
│   ├── my_robot_interfaces/
│   │   ├── msg/
│   │   │   ├── Turtle.msg
│   │   │   ├── TurtleArray.msg
│   │   ├── srv/
│   │   │   └── CatchTurtle.srv
│   │   └── package.xml
│   └── turtlesim_catch_them_all/
│       ├── turtlesim_catch_them_all/
│       │   ├── turtle_controller.py
│       │   └── turtle_spawner.py
│       └── package.xml

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🛠 Prerequisites

• Ubuntu 24.04 LTS
• ROS2 Jazzy
• Python 3.12

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⚙️ Build Instructions

Update dependencies

  rosdep update
  rosdep install --from-paths src --ignore-src -y

Build workspace

  colcon build --symlink-install

Source environment

  source install/setup.bash

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▶️ Run the Project

ros2 launch my_robot_bringup turtlesim_catch_them_all.launch.xml

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🔍 Runtime Introspection

Node List

ros2 node list

Topic List

ros2 topic list

Topic Info

ros2 topic info /alive_turtles

Node & Topic Graph

rqt_graph

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🎥 Demo

A short demo video showing:

• Launch execution
• Turtle spawning
• Autonomous chasing behavior
• ROS2 introspection

📽 Demo Video:

🧪 Expected Behavior

• New turtles spawn periodically
• Main turtle (turtle1) chases active turtles
• System continues autonomously

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🧠 ROS2 Concepts Demonstrated

• ROS2 Nodes & packages
• Publishers & subscribers
• Services
• Timers
• Custom interfaces
• Launch files
• Runtime introspection (ros2 node, ros2 topic, rqt_graph)

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🚀 Possible Improvements

• Smarter target selection
• Multi-hunter turtles
• Event-based architecture
• Dockerized deployment

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📜 Credits

Based on the ROS2 for Beginners curriculum by Edouard Renard (Udemy), adapted and documented here as a reproducible hands-on ROS2 systems exercise.

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👤 Author

GitHub: https://github.com/Preetbandgar