Chrono Integration

This guide outlines what Chrono is, how to use it in CARLA, and the limitations involved in the integration.

Project Chrono

Project Chrono is an open-source, multi-physics simulation engine that provides highly realistic vehicle dynamics using a template-based approach. The integration in CARLA allows users to utilize Chrono templates to simulate vehicle dynamics while navigating a map.

Using Chrono with CARLA

To use the Chrono integration for vehicle Physics in CARLA, you must first build or launch the server with a build flag and then use the PythonAPI to enable Chrono for a vehicle spawned in the CARLA simulation.

Note

The CARLA-Chrono integration is compatible with Chrono version 6. Ensure that your Chrono installation is compatible before starting.

Configuring the server

Chrono will only work if the CARLA server is compiled with the Chrono tag.

In the build from source version of CARLA, run the following command to start the server:

make launch ARGS="--chrono"

The above command pulls the source code for version 6 from the Project Chrono repository. If you wish to use your own Chrono installation, use the following command to specify the path to your Chrono source code:

make launch ARGS="--chrono --chrono-path <PATH>"

Enabling Chrono physics

Chrono physics is enabled using the enable_chrono_physics method available through the Actor class. As well as values for substeps and substep delta time, it requires three template files and a base path to locate those files:

  • base_path: Path of the directory which contains the template files. This is necessary to ensure that auxiliary files referenced from the template files have a common base path from which to search.
  • vehicle_json: Path of the vehicle template file relative to the base_path.
  • tire_json: Path of the tire template file relative to the base_path.
  • powertrain_json: Path of the powertrain template file relative to the base_path.

Important

Double-check your paths. Incorrect or missing paths can cause Unreal Engine to crash.

A default implementation for a sedan is provided in Co-Simulation/Chrono/Vehicles/sedan/ but you can find a variety of example template files for different vehicles available in Build/chrono-install/share/chrono/data/vehicle. Read the Project Chrono documentation to find out more about their vehicle examples and how to create templates.

See below for an example of how to enable Chrono physics:

    # Spawn your vehicle
    vehicle = world.spawn_actor(bp, spawn_point)

    # Set the base path
    base_path = "/path/to/carla/Co-Simulation/Chrono/Vehicles/"

    # Set the template files

    vehicle_json = "sedan/vehicle/Sedan_Vehicle.json"
    powertrain_json = "sedan/powertrain/Sedan_SimpleMapPowertrain.json"
    tire_json = "sedan/tire/Sedan_TMeasyTire.json"

    # Enable Chrono physics

    vehicle.enable_chrono_physics(5000, 0.002, vehicle_json, powertrain_json, tire_json, base_path)

You can try the Chrono physics integration using the example script manual_control_chrono.py found in PythonAPI/examples. After running the script, press Ctrl + o to enable Chrono.

Limitations

This integration does not support collisions. When a collision occurs, the vehicle will revert to CARLA default physics.