Gazebo sim

Gazebo Simulation & ROS 2 Integration Instructions (Ubuntu 24.04 LTS)

1. Architecture Rule

Jazzy pairs with Gazebo Harmonic. Use modern Gazebo Sim (gz, formerly Ignition) and ros_gz only — never mix legacy Gazebo Classic (gazebo_ros_pkgs / gazebo_ros), whose tags and plugin names look similar and do not work here.

2. Documentation Entry Points

For	Entry point
Gazebo Harmonic (the Jazzy pairing)	https://gazebosim.org/docs/harmonic/
SDF tag reference	https://sdformat.org/
ros_gz bridge + sim launch/spawn	https://github.com/gazebosim/ros_gz
Nav2's Gazebo bringup walkthrough (URDF, SDF world, odom, sensors)	https://docs.nav2.org/setup_guides/gazebo.html

Bridge syntax (direction char is the thing people get wrong — see the symptom table):

ros2 run ros_gz_bridge parameter_bridge /scan@sensor_msgs/msg/LaserScan[gz.msgs.LaserScan

Spawning: ros_gz_sim create -topic robot_description, or gz_sim.launch.py. YAML bridge config files are supported for anything non-trivial.

3. Sensor & Motion Plugins Reference (SDF)

A. Differential Drive Motion Plugin

<plugin filename="gz-sim-diff-drive-system" name="gz::sim::systems::DiffDrive">
  <left_joint>left_wheel_joint</left_joint>
  <right_joint>right_wheel_joint</right_joint>
  <wheel_separation>0.3</wheel_separation>
  <wheel_radius>0.05</wheel_radius>
  <odom_publish_frequency>50</odom_publish_frequency>
  <topic>/cmd_vel</topic>
  <odom_topic>/odom</odom_topic>
  <frame_id>odom</frame_id>
  <child_frame_id>base_link</child_frame_id>
</plugin>

B. GPU LiDAR Sensor Plugin

<sensor name="gpu_lidar" type="gpu_lidar">
  <update_rate>10</update_rate>
  <topic>/scan</topic>
  <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>0.15</min>
      <max>12.0</max>
    </range>
  </lidar>
  <plugin filename="gz-sim-sensors-system" name="gz::sim::systems::Sensors">
    <render_engine>ogre2</render_engine>
  </plugin>
</sensor>

4. Symptom -> Root Cause -> Action

Symptom	Likely root cause	Action
Robot spawns then falls through the ground	Missing <collision> on links, or zero/invalid <inertial>	Add collision geometry; give every non-fixed link real mass and inertia
/cmd_vel published but robot doesn't move in sim	Bridge direction wrong ([ is GZ->ROS, ] is ROS->GZ, @ bidirectional) or plugin <topic> mismatch	Check bridge arg direction char; gz topic -l to see what the plugin actually subscribes to
LiDAR/camera topic exists but publishes nothing	gz-sim-sensors-system plugin missing from the world SDF (rendering sensors need it)	Add <plugin filename="gz-sim-sensors-system"> with render_engine to the world
IMU topic silent in sim	gz-sim-imu-system world plugin missing	Add the IMU system plugin to the world SDF
TF extrapolation errors as soon as sim starts	/clock not bridged, or nodes missing use_sim_time: true	Bridge /clock@rosgraph_msgs/msg/Clock[gz.msgs.Clock; set use_sim_time on every node
Sensor data arrives in an unknown/prefixed frame	Gazebo composes frame as <model>/<link>/<sensor> while URDF expects the bare link name	Set explicit <gz_frame_id>/frame remapping, or align frame_id with the URDF link
Sim odometry perfect but Nav2 behaves differently on the real robot	Sim plugin uses ideal kinematics; real wheel_radius/friction differ	Never tune Nav2 solely in sim; re-verify on hardware with check_odom_direction.py (bundled in ros2-troubleshooting)

5. Local System Verification

Check installed Gazebo & ROS 2 bridge packages locally:

• Run ros2 pkg prefix ros_gz_bridge to inspect bridge dependencies.
• Run gz sim --version in terminal to confirm active Gazebo Harmonic or Fortress version.