RDC_Simulation/docs/gazebo.md

Gazebo Simulation

Running the GPS-denied drone simulation with Gazebo (Linux only).

Quick Start (2 Terminals)

Terminal 1 - Start Gazebo:

source activate.sh
gz sim gazebo/worlds/drone_landing.sdf

Terminal 2 - Run Controllers:

source activate.sh
python run_gazebo.py --pattern circular --speed 0.3

Options

python run_gazebo.py --help

Options:
  --pattern       stationary, linear, circular, square, random
  --speed, -s     Rover speed in m/s (default: 0.5)
  --amplitude, -a Movement amplitude (default: 2.0)
  --no-rover      Disable rover controller

Spawning the Drone

If the drone isn't in the world, spawn it:

gz service -s /world/drone_landing_world/create \
  --reqtype gz.msgs.EntityFactory \
  --reptype gz.msgs.Boolean \
  --req 'sdf_filename: "gazebo/models/drone/model.sdf", name: "drone"'

GPS-Denied Sensors

The run_gazebo.py script provides the same sensor interface as PyBullet:

Sensor	Source
IMU	Gazebo odometry
Altimeter	Gazebo Z position
Velocity	Gazebo twist
Camera	Gazebo camera sensor
Landing Pad	Computed from relative position

Gazebo Topics

Topic	Type	Description
/drone/cmd_vel	Twist	Velocity commands
/model/drone/odometry	Odometry	Drone state
/drone/camera	Image	Camera images

Headless Mode

Run without GUI:

gz sim -s gazebo/worlds/drone_landing.sdf

---

ROS 2 Launch File (Advanced)

Location: gazebo/launch/drone_landing.launch.py

This launch file automates Gazebo startup for ROS 2 integration:

1. Starts Gazebo with the world
2. Spawns the drone automatically
3. Starts ros_gz_bridge to connect topics

Option 1: Direct Launch (Recommended)

Run the launch file directly with ros2 launch:

source activate.sh
ros2 launch gazebo/launch/drone_landing.launch.py

Then in another terminal, run just the controllers:

source activate.sh
python controllers.py --pattern circular

Option 2: Include in Your ROS 2 Package

If you have a ROS 2 package, copy the launch file and use:

ros2 launch my_drone_package drone_landing.launch.py

Launch Arguments

Argument	Default	Description
use_sim_time	true	Use Gazebo clock
headless	false	Run without GUI

ros2 launch gazebo/launch/drone_landing.launch.py headless:=true

Topics Bridged by Launch File

ROS 2 Topic	Description
/drone/cmd_vel	Velocity commands
/model/drone/odometry	Drone state
/drone/imu	IMU sensor
/clock	Simulation time

---

Troubleshooting

Model not found

Set the model path:

export GZ_SIM_RESOURCE_PATH=$PWD/gazebo/models:$GZ_SIM_RESOURCE_PATH

Drone falls immediately

Enable the velocity controller:

gz topic -t /drone/enable -m gz.msgs.Boolean -p 'data: true'

"Cannot connect to display"

Use headless mode or WSLg:

# Headless
gz sim -s gazebo/worlds/drone_landing.sdf

# Or ensure DISPLAY is set
export DISPLAY=:0