ArduPilot Flight Controller

ArduPilot is a flexible open-source autopilot that can run with Project AirSim through Software-In-The-Loop (SITL). The repository includes quadrotor and hexarotor examples in client/python/example_user_scripts/ardupilot.

Compatibility note: this integration has not been recently validated against the latest ArduPilot release. Start with the supplied examples and their parameter files before adapting it to a different vehicle.

Supported airframes and control

Project AirSim includes these ArduPilot SITL examples:

Airframe	Scene configuration	Client script	Parameter file
Quadrotor	`sim_config/scene_ardu_quadrotor.jsonc`	`ardupilot_quadrotor.py`	`project-airsim-quad.param`
Hexarotor	`sim_config/scene_ardu_hexarotor.jsonc`	`ardupilot_hexarotor.py`	`project-airsim-hexa.param`

The examples display camera streams and load the scene; Project AirSim Client API flight commands such as arm, takeoff, and move are not supported with ardupilot-api. Control the vehicle from the ArduPilot console or through a ground control station (GCS), for example Mission Planner or QGroundControl.

ArduPilot settings

Set the robot controller type to ardupilot-api and configure ardupilot-settings:

"controller": {
  "id": "ArduPilot_Controller",
  "airframe-setup": "hexarotor-x",
  "type": "ardupilot-api",
  "ardupilot-settings": {
    "local-host-ip": "127.0.0.1",
    "ardupilot-ip": "127.0.0.1",
    "ardupilot-udp-port": 9003,
    "local-host-udp-port": 9002,
    "use-distance-sensor": true,
    "actuator-order": [
      { "id": "Prop_2_actuator" }
    ]
  }
}

Parameter	Type	Description
`local-host-ip`	string	IP address of the Project AirSim host.
`ardupilot-ip`	string	IP address of the ArduPilot host.
`ardupilot-udp-port`	integer	UDP port on the ArduPilot host. The examples use `9003`.
`local-host-udp-port`	integer	UDP port on the Project AirSim host. The examples use `9002`.
`use-distance-sensor`	boolean	Sends distance-sensor data to ArduPilot when enabled.
`actuator-order`	array	Ordered actuator identifiers connected to the ArduPilot outputs.

ArduPilot and Project AirSim exchange simulator messages, including sensor and actuator data, over UDP/IP. The Project AirSim receive port is local-host-udp-port.

Network configurations

Configuration	`ardupilot-ip`	`local-host-ip`
Same Linux computer	`127.0.0.1`	`127.0.0.1`
Separate computers	ArduPilot host IP	Project AirSim host IP
ArduPilot in WSL1	`127.0.0.1`	`127.0.0.1`
ArduPilot in WSL2	WSL virtual adapter IP	WSL virtual adapter IP

For WSL2, run ipconfig on Windows and use the IPv4 address of the WSL virtual network adapter in both settings. When using separate hosts or WSL, configure firewalls to allow the required UDP traffic. A GCS on another host also needs outgoing access from the Project AirSim host and incoming access on its configured UDP port.

Install and run ArduPilot SITL

Complete the Project AirSim installation and client setup, then prepare ArduPilot on a Linux host, VM, WSL1, or WSL2. The standard ArduPilot prerequisites may change, so consult the ArduPilot build documentation if the setup script reports an error.

git clone --recursive https://github.com/ArduPilot/ardupilot.git
cd ardupilot
Tools/environment_install/install-prereqs-ubuntu.sh -y

Copy the matching parameter file from the Project AirSim examples directory into ArduPilot’s Tools/autotest directory. For a hexarotor, copy project-airsim-hexa.param; for a quadrotor, copy project-airsim-quad.param.

Start the hexarotor SITL instance from the ArduPilot repository:

cd Tools/autotest
python sim_vehicle.py -v ArduCopter -f airsim-copter --add-param-file=project-airsim-hexa.param

When ArduPilot runs in WSL2 or on a different computer, append --sim-address=<project-airsim-host-ip> to that command.

WSL1 display setup

If you use an X Windows application in WSL1, install and start an X server such as VcXsrv. In XLaunch, select Multiple windows, then Start no client, and enable Clipboard without Native OpenGL. Set DISPLAY in WSL; the following persistent configuration uses the Windows-side nameserver address:

export DISPLAY=$(cat /etc/resolv.conf | grep nameserver | awk '{print $2}'):0

If the X client cannot connect, enable Disable access control in the X server only when appropriate for your environment.

Run an example flight session

Start ArduPilot SITL with the matching parameter file.
In a terminal with the Project AirSim Python client environment activated, change to client/python/example_user_scripts/ardupilot.
Run python ardupilot_hexarotor.py or python ardupilot_quadrotor.py.
Control the vehicle from the ArduPilot console or a GCS.

For a local Linux host or WSL1, the checked-in configurations already use loopback addresses. For WSL2 or separate machines, update local-host-ip and ardupilot-ip in the matching sim_config/robot_ardu_*.jsonc file before running the example.

Always stop Project AirSim before stopping ArduPilot. After Project AirSim stops, restart ArduPilot before beginning another session.

Useful ArduPilot console commands

Command	Notes
`arm throttle`	Arms the vehicle.
`mode guided`	Wait until the console reports that EKF3 is using GPS before switching to Guided mode.
`takeoff <alt>`	Takes off to the requested altitude in metres. Wait for completion before the next command.
`guided <lat> <lon> <alt>`	Flies to latitude/longitude in degrees and altitude in metres. Wait for the waypoint to be reached.
`mode land`	Lands the vehicle.

If AP: Arm: Main loop slow... appears, try arm throttle again. If it persists, review the simulation clock settings such as step-ns.

Autotune a different vehicle

Vehicles other than the supplied examples should be autotuned for stable flight. Autotune can take hours.

Run arm throttle.
Run rc3 1800 and wait until the vehicle is clear of obstacles.
Run rc3 1500.
Run mode autotune.

ArduPilot reports the tuned roll, pitch, and yaw values in its console. Copy them to the corresponding ATC_RAT_*, ATC_ANG_*, and ATC_ACCEL_* entries in a .param file, then start SITL with --add-param-file=<file>. The supplied project-airsim-hexa.param and project-airsim-quad.param files are reference examples.

It is safe to ignore an AP: Auto-Tune: failing to level message if it appears during the procedure.