Module 2: The Digital Twin (Gazebo & Unity)
Welcome to Module 2 of the Physical AI & Humanoid Robotics textbook. In this module, you will learn to build digital twins—virtual replicas of physical robots—using industry-standard simulation tools.
What You Will Learn
This module covers three essential aspects of robot simulation:
- Physics Simulation in Gazebo - Create realistic virtual environments with accurate physics
- Unity for Human-Robot Interaction - Build photorealistic scenes for perception and HRI testing
- Sensor Simulation - Emulate LiDAR, depth cameras, and IMUs for perception development
Prerequisites
Before starting this module, you should have completed:
- Module 1: ROS 2 Fundamentals - Understanding of nodes, topics, services, and launch files
- Basic familiarity with 3D coordinate systems (X, Y, Z axes)
- Python programming experience
Module Overview
| Chapter | Topic | Estimated Time |
|---|---|---|
| 1 | Physics Simulation in Gazebo | 45-60 minutes |
| 2 | Unity for Human-Robot Interaction | 50-65 minutes |
| 3 | Sensor Simulation: LiDAR, Depth Cameras, IMUs | 60-75 minutes |
Why Digital Twins?
Digital twins enable robotics developers to:
- Test safely - Validate robot behaviors without risking hardware damage
- Iterate quickly - Make changes and see results in seconds, not hours
- Generate data - Create synthetic training data for perception algorithms
- Scale testing - Run thousands of simulations in parallel
Tools Covered
Gazebo Harmonic
The latest generation of the Gazebo simulator, featuring:
- High-fidelity physics engines (ODE, DART, Bullet)
- SDF 1.10 world description format
- Native ROS 2 integration via ros_gz packages
Unity with Robotics Hub
Unity's official robotics packages provide:
- URDF model importing with automatic coordinate transforms
- ROS 2 communication via ROS-TCP-Connector
- Photorealistic rendering for vision-based AI
Getting Started
Start with Chapter 1: Physics Simulation in Gazebo to learn the fundamentals of simulation world creation.
Before You Begin
Make sure you have Gazebo Harmonic and Unity 2022 LTS installed. See the Quickstart Guide for installation instructions.