Using SITL with Webots Python

ArduPilot’s python-based Webots implementation is a cross-platform simulation tool that allows running ArduPilot without risking real-life crashes. This page goes over how to set up and use Webots with ArduPilot’s SITL as well as touching on how to create new vehicles and worlds.


Installation

Webots itself can be downloaded from www.cyberbotics.com. If there is any trouble with installation see Webots’ install guide for further guidance.

Note

The Webots python implementation was built for Webots 2023a and is not backward compatible. Newer versions should also work, however.

Running the Iris Example

The following assumes you have already successfully set up your ArduPilot dev environment (see Building the code).

  1. Run Webots and open /path/to/ardupilot/libraries/SITL/examples/Webots_Python/worlds/iris.wbt (File > Open World). If everything is working you should see the simulation time advancing and no errors in the console (red warnings are fine).

  2. Run the SITL with the following command, replacing /path/to/ with your local absolute path to ardupilot:

    /path/to/ardupilot/Tools/autotest/sim_vehicle.py -v ArduCopter -w --model webots-python --add-param-file=/path/to/ardupilot/libraries/SITL/examples/Webots_Python/params/iris.parm

Warning

When running SITL in WSL2 and Webots in Windows you will have to provide the SITL with Windows’ IP by adding something like --sim-address=172.x.x.1 to the command above. Your exact IP can be found by running ipconfig in cmd and looking for the IP under the WSL adapter. You may also need to add WSL’s IP found with hostname -I to iris.wbt so it looks something like this:

Iris {
   controller "ardupilot_vehicle_controller"
   controllerArgs [
      "--motors"
      "m1_motor, m2_motor, m3_motor, m4_motor"
      "--sitl-address"
      "172.x.x.x"
   ]
}

If all goes well you should see Connected to ardupilot SITL in the Webots console. At this point, you should be able to use MAVProxy (in the SITL terminal window) or a GCS to fly the drone around.

Other Example Worlds

  • iris.wbt implements a basic quadcopter.

  • iris_camera.wbt implements a camera on a quadcopter. See example_camera_receive.py in the scripts folder for one way to get access to the camera.

  • iris_depth_camera.wbt implements a camera that sees depth rather than color. The example camera script can also receive these images.

  • pioneer3at.wbt implements a pioneer3at rover. For the SITL command, run it with Rover instead of ArduCopter and pioneer3at.parm instead of iris.parm.

  • crazyflie.wbt implements a crazyflie quadcopter. Run the SITL command with crazyflie.parm instead of iris.parm.

  • crazyflie_double.wbt implements two crazyflie drones in a swarm. For the SITL command, run it with crazyflie.parm instead of iris.parm and additionally add -n 2 --auto-sysid.

Creating a New World

Creating a new world can be done by copying an example world (such as iris.wbt) and making desired changes. Prebuilt models (called PROTOs) can be added directly through Webots by pressing CTRL+SHIFT+A, or by adding them directly into the world file (see options in documentation).

If you want to go a bit further, check out Webots’ tutorials.

Note

An important parameter to set in every new world is the basicTimeStep parameter in the WorldInfo object. This parameter should be set to 1 or 2, as it represents how many milliseconds the simulation should delay between physics timesteps. Setting this value any higher causes ArduPilot’s main loop to run too slow.

Creating a New Vehicle

An ArduPilot vehicle in Webots is a Robot object that uses the ardupilot_vehicle_controller.py controller (found in the controllers directory). This controller is run when the simulation is started and is responsible for connecting to the SITL and passing it Webots sensor information. Note that to do this it assumes that the Robot object has an Accelerometer, Gyro, InertialUnit, and GPS.

To create a new vehicle that can be used in multiple worlds, like the Iris model, we can create a PROTO file which will describe the vehicle (a Robot object) and be importable into any world. The simplest way to do this is to copy the iris.proto file in the protos folder and edit or remove components (such as propellers, mesh, and the extension slot). If you want to start from scratch, you can look at the documentation for creating a PROTO file.

Of particular note, the Robot object has a property called controllerArgs which are passed to the controller when the simulation is run, allowing us to specify traits of the vehicle such as motor names, count, and directions. The full list of available arguments are documented in ardupilot_vehicle_controller.py.