Ardupilot Update

docs/architecture.md

@@ -62,6 +62,34 @@ Data flow:
 - DroneController receives telemetry, publishes to `/cmd_vel`
 - GazeboBridge forwards to `/drone/cmd_vel` → Gazebo moves drone
 
+### 4. ArduPilot SITL + Gazebo Mode (Three Terminals, Linux/WSL2)
+
+```
+Terminal 1           Terminal 2              Terminal 3
+┌──────────────┐    ┌─────────────────┐     ┌────────────────────────┐
+│ Gazebo +     │    │ ArduPilot SITL  │     │   run_ardupilot.py     │
+│ ArduPilot    │◄──►│ sim_vehicle.py  │     │  ┌──────────────────┐  │
+│ Plugin       │JSON│  + MAVProxy     │◄───►│  │ MAVLinkBridge    │  │
+│              │    │                 │ UDP │  │ DroneController  │  │
+│ ardupilot_   │    │ Flight Control  │     │  │ RoverController  │  │
+│ drone.sdf    │    │ + GCS           │     │  └──────────────────┘  │
+└──────────────┘    └─────────────────┘     └────────────────────────┘
+```
+
+Data flow:
+- ArduPilot SITL sends motor commands → Gazebo plugin controls drone
+- Gazebo plugin sends sensor data → ArduPilot SITL for state estimation
+- MAVProxy outputs telemetry → MAVLinkBridge converts to ROS telemetry
+- DroneController receives telemetry, publishes velocity commands
+- MAVLinkBridge sends MAVLink commands → ArduPilot SITL executes
+
+Key differences from simple Gazebo mode:
+- Full ArduPilot flight controller (EKF, stabilization, failsafes)
+- Real MAVLink protocol for commands and telemetry
+- Support for all ArduPilot flight modes (GUIDED, LAND, etc.)
+- Arming checks and safety features
+- Compatible with ground control stations (QGroundControl, Mission Planner)
+
 ## Components
 
 | File | Description |
@@ -71,12 +99,16 @@ Data flow:
 | `simulation_host.py` | PyBullet physics server (UDP) |
 | `run_bridge.py` | PyBullet bridge + controllers |
 | `run_gazebo.py` | Gazebo bridge + controllers |
+| `run_ardupilot.py` | **ArduPilot SITL** + MAVLink bridge |
+| `mavlink_bridge.py` | MAVLink ↔ ROS 2 bridge |
 | `drone_controller.py` | **Your landing algorithm** |
 | `rover_controller.py` | Moving landing pad |
 | `ros_bridge.py` | ROS-UDP bridge (used by run_bridge.py) |
 | `gazebo_bridge.py` | Gazebo-ROS bridge (used by run_gazebo.py) |
 | `gazebo/launch/drone_landing.launch.py` | ROS 2 launch file for Gazebo |
-| `gazebo/worlds/drone_landing.sdf` | Gazebo world with drone + rover |
+| `gazebo/launch/ardupilot_drone.launch.py` | ROS 2 launch file for ArduPilot |
+| `gazebo/worlds/drone_landing.sdf` | Gazebo world with simple velocity control |
+| `gazebo/worlds/ardupilot_drone.sdf` | Gazebo world with ArduPilot plugin |
 
 ## ROS 2 Topics