RDC_Simulation/docs/ardupilot.md

ArduPilot + Gazebo Guide

Overview

This project uses:

• ArduPilot SITL: Software-in-the-loop flight controller
• Gazebo: 3D physics simulation
• MAVLink: Communication protocol

Architecture

┌─────────────┐     JSON (UDP 9002)    ┌─────────────┐    MAVLink (TCP 5760)    ┌─────────────┐
│   Gazebo    │◄──────────────────────►│ ArduPilot   │◄────────────────────────►│   Your      │
│  (Physics)  │     sensor data        │    SITL     │     commands/telemetry   │ Controller  │
└─────────────┘                        └─────────────┘                          └─────────────┘

Quick Start

Step 1: Start Gazebo

cd ~/RDC_Simulation
./scripts/run_ardupilot_sim.sh runway

Wait until the drone appears in the 3D view.

Step 2: Start SITL

source ~/venv-ardupilot/bin/activate
sim_vehicle.py -v ArduCopter -f gazebo-iris --model JSON --console

You should see telemetry scrolling (NOT "No JSON sensor message").

Step 3: Run Controller

source ~/venv-ardupilot/bin/activate
cd ~/RDC_Simulation
python scripts/run_ardupilot.py --pattern square

Flight Patterns

# Square pattern (5m sides, 5m altitude)
python scripts/run_ardupilot.py --pattern square --size 5 --altitude 5

# Circle pattern (5m radius)
python scripts/run_ardupilot.py --pattern circle --size 5

# Hover in place for testing
python scripts/run_ardupilot.py --pattern hover

# Larger pattern at higher altitude
python scripts/run_ardupilot.py --pattern square --size 10 --altitude 15

Controller Code

The flight controller is in src/drone_controller.py:

from src.drone_controller import DroneController

drone = DroneController()
drone.connect()
drone.set_mode("GUIDED")
drone.arm()
drone.takeoff(5.0)
drone.fly_square(size=5, altitude=5)
drone.land()

Key Methods

Method	Description
connect()	Connect to SITL via MAVLink
set_mode(mode)	Set flight mode (GUIDED, LAND, etc.)
arm()	Arm motors (force arm)
takeoff(alt)	Take off to altitude
goto(x, y, z)	Go to position (NED frame)
fly_to_and_wait(x, y, alt)	Go to position and wait
fly_square(size, alt)	Fly square pattern
fly_circle(radius, alt)	Fly circle pattern
land()	Land the drone

Available Worlds

# Outdoor runway (default)
./scripts/run_ardupilot_sim.sh runway

# Indoor warehouse
./scripts/run_ardupilot_sim.sh warehouse

MAVLink Connection

The controller connects via TCP port 5760:

# config.py
MAVLINK = {
    "connection_string": "tcp:127.0.0.1:5760",
}

Troubleshooting

"No JSON sensor message received"

SITL isn't receiving data from Gazebo.

Fix:

1. Make sure Gazebo is running FIRST
2. Wait for the world to fully load
3. Then start SITL

Drone won't arm

Fix:

# Check pre-arm status in MAVProxy
arm status

# Force arm
arm throttle force

Wrong Python environment

Fix:

source ~/venv-ardupilot/bin/activate
which python3  # Should be ~/venv-ardupilot/bin/python3

Gazebo plugin not loading

Fix:

# Check plugin exists
ls ~/ardupilot_gazebo/build/libArduPilotPlugin.so

# Check paths
echo $GZ_SIM_SYSTEM_PLUGIN_PATH
# Should include: ~/ardupilot_gazebo/build

Manual SITL Control

Use MAVProxy commands:

# In SITL console
mode GUIDED
arm throttle force
takeoff 5

# Move to position
guided 10 0 -5

# Land
mode LAND

Useful Commands

# List Gazebo topics
gz topic -l

# Check SITL status
sim_vehicle.py -v ArduCopter -f gazebo-iris --model JSON --console --map

# View camera (if available)
gz topic -e -t /camera