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Gazebo Simulation

Learning Objectives:

  • Set up Gazebo Harmonic for robot simulation
  • Build custom simulation worlds with SDF
  • Add sensors (camera, LIDAR, IMU) to simulated robots
  • Understand physics engines and simulation fidelity

Prerequisites: Module 1: ROS 2 Foundations

Estimated Reading Time: 45 minutes

Why Simulate?​

Building and testing robot software on physical hardware is:

  • Expensive: hardware breaks, components cost money
  • Slow: charging, resetting, physical setup time
  • Dangerous: a bug in navigation code can damage the robot or its environment

Simulation lets you test robot behavior in a safe, fast, and reproducible virtual environment. A simulated robot can crash 1,000 times with zero real-world consequences.

Gazebo Harmonic​

Gazebo (formerly Ignition Gazebo) is the standard open-source robot simulator for ROS 2. It provides:

  • Accurate physics simulation (DART, Bullet)
  • Sensor simulation (camera, LIDAR, depth, IMU)
  • ROS 2 integration via ros_gz bridge
  • Scalable for multi-robot scenarios

Installation​

# Install Gazebo Harmonic on Ubuntu 22.04
sudo apt install ros-humble-ros-gz

Launching Your First Simulation​

# Launch an empty world
gz sim empty.sdf

# Launch with a robot
gz sim -r shapes.sdf

Building Worlds with SDF​

Worlds are described in SDF (Simulation Description Format) — an XML-based format:

<?xml version="1.0" ?>
<sdf version="1.9">
  <world name="warehouse">
    <physics type="dart">
      <max_step_size>0.001</max_step_size>
      <real_time_factor>1.0</real_time_factor>
    </physics>

    <light type="directional" name="sun">
      <direction>-0.5 0.1 -0.9</direction>
    </light>

    <include>
      <uri>https://fuel.gazebosim.org/1.0/OpenRobotics/models/Ground Plane</uri>
    </include>

    <model name="box_obstacle">
      <static>true</static>
      <pose>2 0 0.5 0 0 0</pose>
      <link name="link">
        <collision name="collision">
          <geometry><box><size>1 1 1</size></box></geometry>
        </collision>
        <visual name="visual">
          <geometry><box><size>1 1 1</size></box></geometry>
        </visual>
      </link>
    </model>
  </world>
</sdf>

Simulating Sensors​

Camera​

<sensor name="camera" type="camera">
  <camera>
    <horizontal_fov>1.047</horizontal_fov>
    <image>
      <width>640</width>
      <height>480</height>
    </image>
    <clip>
      <near>0.1</near>
      <far>100</far>
    </clip>
  </camera>
  <update_rate>30</update_rate>
</sensor>

LIDAR​

<sensor name="lidar" type="gpu_lidar">
  <lidar>
    <scan>
      <horizontal>
        <samples>360</samples>
        <resolution>1</resolution>
        <min_angle>-3.14159</min_angle>
        <max_angle>3.14159</max_angle>
      </horizontal>
    </scan>
    <range>
      <min>0.1</min>
      <max>10.0</max>
    </range>
  </lidar>
  <update_rate>10</update_rate>
</sensor>

ROS 2–Gazebo Bridge​

The ros_gz_bridge package translates between Gazebo and ROS 2 topics:

# Bridge camera images from Gazebo to ROS 2
ros2 run ros_gz_bridge parameter_bridge \
    /camera@sensor_msgs/msg/Image@gz.msgs.Image

# Bridge LIDAR scans
ros2 run ros_gz_bridge parameter_bridge \
    /lidar@sensor_msgs/msg/LaserScan@gz.msgs.LaserScan

Exercise: Warehouse Navigation World​

Build a Gazebo world that represents a simple warehouse:

  1. A ground plane
  2. Four shelf obstacles (static boxes)
  3. A TurtleBot 4 robot with camera and LIDAR
  4. Bridge sensor topics to ROS 2

Then use ros2 topic echo to verify sensor data is flowing.

Summary​

  • Gazebo provides physics-accurate robot simulation with ROS 2 integration
  • Worlds are described in SDF format with models, lights, and physics
  • Sensors (camera, LIDAR, IMU) can be attached to simulated robots
  • The ros_gz_bridge translates between Gazebo and ROS 2 messages

Next: Chapter 2: Unity Digital Twin — build photorealistic simulations.