Architecture Overview

GPS-denied drone landing simulation with multiple operation modes.

Operation Modes

1. Standalone Mode (Any Platform)

Single-process simulation - no ROS 2 or networking required:

┌────────────────────────────────────────┐
│      standalone_simulation.py          │
│  ┌──────────────────────────────────┐  │
│  │  PyBullet Physics + Camera       │  │
│  │  Built-in Landing Controller     │  │
│  │  Rover Movement Patterns         │  │
│  └──────────────────────────────────┘  │
└────────────────────────────────────────┘

2. PyBullet + ROS 2 Mode (2 Terminals)

Terminal 1                    Terminal 2
┌──────────────────┐         ┌──────────────────────────┐
│ simulation_host  │◄─UDP───►│      run_bridge.py       │
│   (PyBullet)     │         │  ┌────────────────────┐  │
│   Port 5555      │         │  │ ROS2SimulatorBridge│  │
│                  │         │  │ DroneController    │  │
│                  │         │  │ RoverController    │  │
└──────────────────┘         │  └────────────────────┘  │
                             └──────────────────────────┘

3. Gazebo + ROS 2 Mode (2 Terminals, Linux Only)

Terminal 1                    Terminal 2
┌──────────────────┐         ┌──────────────────────────┐
│     Gazebo       │◄─ROS───►│      run_gazebo.py       │
│  (gz sim ...)    │         │  ┌────────────────────┐  │
│                  │         │  │ GazeboBridge       │  │
│                  │         │  │ DroneController    │  │
│                  │         │  │ RoverController    │  │
└──────────────────┘         │  └────────────────────┘  │
                             └──────────────────────────┘

Components

File	Description
`standalone_simulation.py`	All-in-one simulation
`simulation_host.py`	PyBullet physics server (UDP)
`run_bridge.py`	PyBullet bridge + controllers
`run_gazebo.py`	Gazebo bridge + controllers
`drone_controller.py`	Landing algorithm
`rover_controller.py`	Moving landing pad

ROS Topics

Topic	Type	Description
`/cmd_vel`	`Twist`	Drone velocity commands
`/drone/telemetry`	`String`	GPS-denied sensor data
`/rover/telemetry`	`String`	Rover position (internal)

Network Configuration

All components default to 0.0.0.0 for network accessibility.

Remote Setup

Machine 1 (with display):

python simulation_host.py  # Listens on 0.0.0.0:5555

Machine 2 (headless controller):

python run_bridge.py --host 192.168.1.100

UDP Ports

Port	Direction	Content
5555	Bridge → Simulator	Commands
5556	Simulator → Bridge	Telemetry

GPS-Denied Sensors

All modes provide the same sensor data:

Sensor	Data
IMU	Orientation, angular velocity
Altimeter	Altitude, vertical velocity
Velocity	Estimated from optical flow
Camera	320x240 downward JPEG
Landing Pad	Relative position (when visible)

Platform Support

Mode	Ubuntu	Arch	macOS	Windows	WSL2
Standalone	✅	✅	✅	✅	✅
PyBullet+ROS	✅	⚠️	❌	❌	✅
Gazebo+ROS	✅	⚠️	❌	❌	✅

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