RDC_Simulation/docs/ardupilot.md

ArduPilot + Gazebo Guide

Architecture

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

Quick Start (3 Terminals)

Terminal 1: Start Gazebo FIRST

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

Wait until the drone appears in the 3D view!

Terminal 2: Start ArduCopter SITL

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

You should see:

• "JSON received: timestamp, imu, position..." ✅
• NOT "No JSON sensor message received" ❌

Terminal 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
python scripts/run_ardupilot.py --pattern hover

# GPS mode (instead of GPS-denied)
python scripts/run_ardupilot.py --pattern square --gps

Controller Code

from src.drone_controller import DroneController

drone = DroneController()
drone.connect()

# GPS-denied setup
drone.setup_gps_denied()
drone.set_mode("GUIDED_NOGPS")

# Or GPS mode
# drone.set_mode("GUIDED")

drone.arm()
drone.takeoff(5.0)
drone.fly_square(size=5, altitude=5)
drone.land()

ArduCopter Flight Modes

Mode	ID	Description
STABILIZE	0	Manual, self-leveling
ALT_HOLD	2	Hold altitude
GUIDED	4	Waypoint commands (GPS required)
LOITER	5	Hold position (GPS required)
RTL	6	Return to launch
LAND	9	Automatic landing
GUIDED_NOGPS	20	Commands without GPS

MAVProxy Commands

In the SITL console, you can type:

# Check status
status

# Change mode
mode GUIDED
mode GUIDED_NOGPS

# Arm
arm throttle force

# Takeoff (in GUIDED mode)
takeoff 5

# Land
mode LAND

# Set parameter
param set ARMING_CHECK 0

Gazebo Worlds

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

# Indoor warehouse
./scripts/run_ardupilot_sim.sh warehouse

MAVLink Connection

Default: tcp:127.0.0.1:5760

Port map:

• 5760: Primary MAVLink (SERIAL0)
• 5762: Secondary (SERIAL1)
• 5763: Tertiary (SERIAL2)
• 14550: MAVProxy GCS output (UDP)

Troubleshooting

"No JSON sensor message received"

Gazebo isn't sending data.

Fix:

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

Drone won't arm

Fix:

# In MAVProxy console
arm throttle force

# Or set in your code
drone.set_param("ARMING_CHECK", 0)

Wrong vehicle type (ArduPlane)

Mode list shows FBWA, FBWB, QSTABILIZE instead of GUIDED_NOGPS, ALT_HOLD.

Fix:

pkill -9 -f sim_vehicle
sim_vehicle.py -v ArduCopter -f gazebo-iris --model JSON --console --wipe-eeprom

Mode not changing

The controller hardcodes mode IDs for ArduCopter. If using ArduPlane, modes will differ.

Gazebo plugin not loading

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

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

Useful Debug Commands

# List Gazebo topics
gz topic -l

# Echo a topic
gz topic -e -t /model/iris_with_gimbal/pose

# Check SITL processes
ps aux | grep ardupilot

# Check port usage
lsof -i :5760