ROS bridge for CARLA simulator

This ROS package aims at providing a simple ROS bridge for CARLA simulator.

Features

• Provide Sensor Data (Lidar, Cameras (depth, segmentation, rgb), GNSS, Radar, IMU)
• Provide Object Data (Transforms (via tf), Traffic light status, Visualization markers, Collision, Lane invasion)
• Control AD Agents (Steer/Throttle/Brake)
• Control CARLA (Support synchronous mode, Play/pause simulation, Set simulation parameters)

Additional Functionality

Beside the bridging functionality, there are many more features provided in separate packages.

Name	Description
Carla Ego Vehicle	Provides a generic way to spawn an ego vehicle and attach sensors to it.
Carla Manual Control	A ROS-based visualization and control tool for an ego vehicle (similar to carla_manual_control.py provided by CARLA)
Carla Infrastructure	Provides a generic way to spawn a set of infrastructure sensors defined in a config file.
Carla Waypoint Publisher	Provide routes and access to the Carla waypoint API
Carla ROS Scenario Runner	ROS node that wraps the functionality of the CARLA scenario runner to execute scenarios.
Carla Ackermann Control	A controller to convert ackermann commands to steer/throttle/brake
Carla AD Agent	A basic AD agent, that follows a route, avoids collisions with other vehicles and stops on red traffic lights.
RVIZ Carla Plugin	A RVIZ plugin to visualize/control CARLA.
RQT Carla Plugin	A RQT plugin to control CARLA.

For a quick overview, after following the Setup section, please run the CARLA AD Demo. It provides a ready-to-use demonstrator of many of the features.

Setup

For Users

First add the apt repository:

For ROS Melodic Users

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 81061A1A042F527D &&
sudo add-apt-repository "deb [trusted=yes] http://dist.carla.org/carla-ros-bridge-melodic/ bionic main"

For ROS Kinetic Users

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 9BE2A0CDC0161D6C &&
sudo add-apt-repository "deb [trusted=yes] http://dist.carla.org/carla-ros-bridge-kinetic xenial main"

Then simply install the ROS bridge:

sudo apt update &&
sudo apt install carla-ros-bridge-<melodic or kinetic>

This will install carla-ros-bridge- in /opt/carla-ros-bridge

For Developers

Create a catkin workspace and install carla_ros_bridge package

#setup folder structure
mkdir -p ~/carla-ros-bridge/catkin_ws/src
cd ~/carla-ros-bridge
git clone https://github.com/carla-simulator/ros-bridge.git
cd ros-bridge
git submodule update --init
cd ../catkin_ws/src
ln -s ../../ros-bridge
source /opt/ros/kinetic/setup.bash
cd ..

#install required ros-dependencies
rosdep update
rosdep install --from-paths src --ignore-src -r

#build
catkin_make

For more information about configuring a ROS environment see http://wiki.ros.org/ROS/Tutorials/InstallingandConfiguringROSEnvironment

Start the ROS bridge

First run the simulator (see carla documentation: http://carla.readthedocs.io/en/latest/)

# run carla in background
SDL_VIDEODRIVER=offscreen ./CarlaUE4.sh -opengl

Wait a few seconds

export PYTHONPATH=$PYTHONPATH:<path-to-carla>/PythonAPI/carla/dist/carla-<carla_version_and_arch>.egg

For Users

source /opt/carla-ros-bridge/<melodic or kinetic>/setup.bash

For Developers

source ~/carla-ros-bridge/catkin_ws/devel/setup.bash

Start the ros bridge (choose one option):

# Option 1: start the ros bridge
roslaunch carla_ros_bridge carla_ros_bridge.launch

# Option 2: start the ros bridge together with an example ego vehicle
roslaunch carla_ros_bridge carla_ros_bridge_with_example_ego_vehicle.launch

Settings

You can setup the ros bridge configuration carla_ros_bridge/config/settings.yaml.

If the rolename is within the list specified by ROS parameter /carla/ego_vehicle/rolename, the client is interpreted as an controllable ego vehicle and all relevant ROS topics are created.

Mode

Default Mode

In default mode (synchronous_mode: false) data is published:

• on every world.on_tick() callback
• on every sensor.listen() callback

Synchronous Mode

CAUTION: In synchronous mode, only the ros-bridge is allowed to tick. Other CARLA clients must passively wait.

In synchronous mode (synchronous_mode: true), the bridge waits for all sensor data that is expected within the current frame. This might slow down the overall simulation but ensures reproducible results.

Additionally you might set synchronous_mode_wait_for_vehicle_control_command to true to wait for a vehicle control command before executing the next tick.

Control Synchronous Mode

It is possible to control the simulation execution:

• Pause/Play
• Execute single step

The following topic allows to control the stepping.

Topic	Type
/carla/control	carla_msgs.CarlaControl

A CARLA Control rqt plugin is available to publish to the topic.

Available ROS Topics

Ego Vehicle

Sensors

The ego vehicle sensors are provided via topics with prefix /carla/ego_vehicle/<sensor_topic>

Currently the following sensors are supported:

Camera

Topic	Type
/carla/<ROLE NAME>/camera/rgb/<SENSOR ROLE NAME>/image_color	sensor_msgs.Image
/carla/<ROLE NAME>/camera/rgb/<SENSOR ROLE NAME>/camera_info	sensor_msgs.CameraInfo

Lidar

Topic	Type
/carla/<ROLE NAME>/lidar/<SENSOR ROLE NAME>/point_cloud	sensor_msgs.PointCloud2

Radar

Topic	Type
/carla/<ROLE NAME>/radar/<SENSOR ROLE NAME>/radar	ainstein_radar_msgs.RadarTargetArray

Radar data can be visualized on rviz using ainstein_radar_rviz_plugins.

IMU

Topic	Type
/carla/<ROLE NAME>/imu	sensor_msgs.Imu

GNSS

Topic	Type	Description
/carla/<ROLE NAME>/gnss/<SENSOR ROLE NAME>/fix	sensor_msgs.NavSatFix	publish gnss location

Collision Sensor

Topic	Type	Description
/carla/<ROLE NAME>/collision	carla_msgs.CarlaCollisionEvent	publish collision events

Lane Invasion Sensor

Topic	Type	Description
/carla/<ROLE NAME>/lane_invasion	carla_msgs.CarlaLaneInvasionEvent	publish events on lane-invasion

Object Sensor

Topic	Type	Description
/carla/<ROLE NAME>/objects	derived_object_msgs.ObjectArray	all vehicles and walkers, except the ego vehicle

Control

Topic	Type
/carla/<ROLE NAME>/vehicle_control_cmd (subscriber)	carla_msgs.CarlaEgoVehicleControl
/carla/<ROLE NAME>/vehicle_control_cmd_manual (subscriber)	carla_msgs.CarlaEgoVehicleControl
/carla/<ROLE NAME>/vehicle_control_manual_override (subscriber)	std_msgs.Bool
/carla/<ROLE NAME>/vehicle_status	carla_msgs.CarlaEgoVehicleStatus
/carla/<ROLE NAME>/vehicle_info	carla_msgs.CarlaEgoVehicleInfo

There are two modes to control the vehicle.

1. Normal Mode (reading commands from /carla/<ROLE NAME>/vehicle_control_cmd)
2. Manual Mode (reading commands from /carla/<ROLE NAME>/vehicle_control_cmd_manual)

This allows to manually override a Vehicle Control Commands published by a software stack. You can toggle between the two modes by publishing to /carla/<ROLE NAME>/vehicle_control_manual_override.

carla_manual_control makes use of this feature.

For testing purposes, you can stear the ego vehicle from the commandline by publishing to the topic /carla/<ROLE NAME>/vehicle_control_cmd.

Examples for a ego vehicle with role_name 'ego_vehicle':

Max forward throttle:

 rostopic pub /carla/ego_vehicle/vehicle_control_cmd carla_msgs/CarlaEgoVehicleControl "{throttle: 1.0, steer: 0.0}" -r 10

Max forward throttle with max steering to the right:

 rostopic pub /carla/ego_vehicle/vehicle_control_cmd carla_msgs/CarlaEgoVehicleControl "{throttle: 1.0, steer: 1.0}" -r 10

The current status of the vehicle can be received via topic /carla/<ROLE NAME>/vehicle_status. Static information about the vehicle can be received via /carla/<ROLE NAME>/vehicle_info

Additional way of controlling

Topic	Type
/carla/<ROLE NAME>/twist_cmd (subscriber)	geometry_msgs.Twist

CAUTION: This control method does not respect the vehicle constraints. It allows movements impossible in the real world, like flying or rotating.

You can also control the vehicle via publishing linear and angular velocity within a Twist datatype.

Currently this method applies the complete linear vector, but only the yaw from angular vector.

Carla Ackermann Control

In certain cases, the Carla Control Command is not ideal to connect to an AD stack. Therefore a ROS-based node carla_ackermann_control is provided which reads AckermannDrive messages. You can find further documentation here.

Other Topics

Object information of other actors

Topic	Type	Description
/carla/objects	derived_object_msgs.ObjectArray	all vehicles and walkers
/carla/marker	visualization_msgs.Marker	visualization of vehicles and walkers
/carla/actor_list	carla_msgs.CarlaActorList	list of all carla actors
/carla/traffic_lights	carla_msgs.CarlaTrafficLightStatusList	list of all traffic lights with their status
/carla/traffic_lights_info	carla_msgs.CarlaTrafficLightInfoList	static information for all traffic lights (e.g. position)

Status of CARLA

Topic	Type	Description
/carla/status	carla_msgs.CarlaStatus
/carla/world_info	carla_msgs.CarlaWorldInfo	Info about the CARLA world/level (e.g. OPEN Drive map)

Walker

Topic	Type	Description
/carla/walker/<ID>/walker_control_cmd (subscriber)	carla_msgs.CarlaWalkerControl	Control a walker
/carla/walker/<ID>/odometry	nav_msgs.Odometry	odometry of walker

Other Vehicles

Topic	Type	Description
/carla/vehicle/<ID>/odometry	nav_msgs.Odometry	odometry of vehicle

Debug Marker

It is possible to draw markers in CARLA.

Caution: Markers might affect the data published by sensors.

The following markers are supported in 'map'-frame:

• Arrow (specified by two points)
• Points
• Cube
• Line Strip

Topic	Type	Description
/carla/debug_marker (subscriber)	visualization_msgs.MarkerArray	draw markers in CARLA world

Troubleshooting

ImportError: No module named carla

You're missing Carla Python. Please execute:

export PYTHONPATH=$PYTHONPATH:<path/to/carla/>/PythonAPI/carla/dist/<your_egg_file>

Please note that you have to put in the complete path to the egg-file including the egg-file itself. Please use the one, that is supported by your Python version. Depending on the type of CARLA (pre-build, or build from source), the egg files are typically located either directly in the PythonAPI folder or in PythonAPI/dist.

Check the installation is successfull by trying to import carla from python:

python -c 'import carla;print("Success")'

You should see the Success message without any errors.