RDC_Simulation/docs/pybullet.md

PyBullet Simulation Guide

Running the GPS-denied drone simulation with PyBullet physics engine.

Standalone Mode (Single Terminal - Any Platform)

No ROS 2 required! Works on Windows, macOS, and Linux:

source activate.sh  # Linux/macOS
. .\activate.ps1    # Windows

python standalone_simulation.py --pattern circular --speed 0.3

Options

python standalone_simulation.py --help

Options:
  --pattern, -p   stationary, linear, circular, square
  --speed, -s     Rover speed in m/s (default: 0.5)
  --amplitude, -a Movement amplitude in meters (default: 2.0)

---

ROS 2 Mode (Two Terminals)

For distributed or remote simulation with ROS 2:

Terminal 1 - Simulator:

source activate.sh
python simulation_host.py

Terminal 2 - Controllers:

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

How It Works

1. simulation_host.py runs PyBullet physics and listens on UDP port 5555
2. run_bridge.py starts:
   • ROS2SimulatorBridge - connects ROS topics to UDP
   • DroneController - your landing algorithm
   • RoverController - moves the landing pad

The rover position is sent to the simulator, so both drone AND rover move!

Remote Setup

Run simulator on one machine, controllers on another:

Machine 1 (with display):

python simulation_host.py  # Listens on 0.0.0.0:5555

Machine 2 (headless):

python run_bridge.py --host 192.168.1.100 --pattern circular

---

Configuration

All parameters are configurable in config.py:

DRONE = {
    "mass": 1.0,
    "start_position": (0.0, 0.0, 5.0),
    "thrust_scale": 15.0,
    ...
}

ROVER = {
    "start_position": (0.0, 0.0, 0.15),
    "default_pattern": "circular",
    "default_speed": 0.5,
    ...
}

CONTROLLER = {
    "Kp_z": 0.5,
    "Kd_z": 0.3,
    ...
}

---

Simulation Parameters

Parameter	Value
Physics Rate	240 Hz
Telemetry Rate	24 Hz
Drone Mass	1.0 kg (configurable)
Rover Mass	Static (kinematic)
UDP Port	5555 (commands), 5556 (telemetry)

GPS-Denied Sensors

Sensor	Description
IMU	Orientation (roll, pitch, yaw), angular velocity
Altimeter	Altitude above ground, vertical velocity
Velocity	Estimated horizontal velocity (x, y, z)
Camera	320x240 downward-facing JPEG image
Landing Pad	Vision-based relative position when in camera FOV

Troubleshooting

"Cannot connect to X server"

PyBullet GUI requires a display:

# Use virtual display
xvfb-run python standalone_simulation.py

# Or use X11 forwarding
ssh -X user@host

Drone flies erratically

Reduce control gains in config.py:

CONTROLLER = {
    "Kp_z": 0.3,
    "Kd_z": 0.2,
    "Kp_xy": 0.2,
    "Kd_xy": 0.1,
}

Camera image not appearing

Install Pillow:

pip install pillow numpy

Rover not moving (ROS 2 mode)

Ensure run_bridge.py is used (not ros_bridge.py directly). The rover controller must be running to send position updates.

WSL2 GUI issues

Set display scaling:

export GDK_DPI_SCALE=1.0
export QT_SCALE_FACTOR=1.0
python standalone_simulation.py