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Chapter 3: Digital Twin & Simulation

Overview​

This chapter explores the concepts of digital twins and simulation environments, which are crucial for developing and testing robotic systems.

Objectives​

  • Understand the concept of a digital twin.
  • Learn about popular simulation environments like Gazebo and Unity.
  • Understand how to set up a basic simulation.

Core Content​

A digital twin is a virtual representation of a physical object or system. In robotics, a digital twin is a detailed simulation of a robot and its environment, which can be used for development, testing, and validation before deploying to a physical robot. Simulation environments like Gazebo and Unity are commonly used to create these digital twins.

Setting up a basic simulation with Gazebo​

Gazebo is a popular open-source robotics simulator. To set up a basic simulation, you would typically define your robot and its environment in SDF (Simulation Description Format) or URDF (Unified Robot Description Format) files.

Examples​

A simple robot in SDF​

<?xml version='1.0'?>
<sdf version='1.6'>
  <model name='simple_robot'>
    <pose>0 0 0.5 0 0 0</pose>
    <link name='chassis'>
      <collision name='collision'>
        <geometry>
          <box>
            <size>0.4 0.2 0.1</size>
          </box>
        </geometry>
      </collision>
      <visual name='visual'>
        <geometry>
          <box>
            <size>0.4 0.2 0.1</size>
          </box>
        </geometry>
      </visual>
    </link>
  </model>
</sdf>

Controlling the robot with a ROS 2 node​

You can then use a ROS 2 node to control the robot in the simulation. For example, you could publish velocity commands to a topic that the simulated robot subscribes to.

Figures​

simple robot in Gazebo

Figure 1: A simple robot model in the Gazebo simulation environment.

Summary​

This chapter introduced the concept of digital twins and showed how to set up a basic simulation using Gazebo and SDF. We also discussed how to control a simulated robot using ROS 2. In the next chapter, we will explore the more advanced capabilities of NVIDIA Isaac Sim.