Audibot

A ROS 2 / Gazebo simulation of an Audi R8-based autonomous vehicle. The package provides a realistic vehicle dynamics model with steering geometry, speed control, and a full sensor suite.

Packages

Package	Description
audibot	Metapackage
audibot_description	Meshes and SDF robot descriptions
audibot_gazebo	Gazebo plugin, launch files, and world files

---

Launching the Simulator

Two ready-to-use launch files are provided, one for each vehicle color variant.

Blue Audibot:

ros2 launch audibot_gazebo blue_audibot.launch.xml

Orange Audibot:

ros2 launch audibot_gazebo orange_audibot.launch.xml

Both launch files start:

• Gazebo with an empty world
• The ROS ↔ Gazebo topic bridge
• robot_state_publisher for TF transforms
• rqt_publisher for manually sending control commands
• RViz2 with a pre-configured display

Launch Arguments

The underlying gazebo_bringup.launch.py accepts the following arguments:

Argument	Default	Description
robot_sdf_file	(required)	Full path to the robot SDF file
world_sdf_file	(required)	Full path to the world SDF file
gz_bridge_file	(required)	Full path to the ROS/GZ bridge YAML config
verbose	false	Enable verbose Gazebo output
start_paused	false	Start simulation paused
headless	false	Run server only (no GUI)

---

Including Audibot in Your Own Launch File

XML launch file

<?xml version="1.0"?>
<launch>

    <!-- Include the blue audibot simulator -->
    <include file="$(find-pkg-share audibot_gazebo)/launch/blue_audibot.launch.xml" />

    <!-- Your nodes here -->
    <node pkg="my_package" exec="my_node" name="my_node">
        <param name="use_sim_time" value="true" />
    </node>

</launch>

Python launch file

from ament_index_python.packages import get_package_share_directory
from launch import LaunchDescription
from launch.actions import IncludeLaunchDescription
from launch.launch_description_sources import AnyLaunchDescriptionSource
from launch_ros.actions import Node
import os

def generate_launch_description():
    audibot_launch = IncludeLaunchDescription(
        AnyLaunchDescriptionSource(
            os.path.join(
                get_package_share_directory('audibot_gazebo'),
                'launch', 'blue_audibot.launch.xml'
            )
        )
    )

    my_node = Node(
        package='my_package',
        executable='my_node',
        parameters=[{'use_sim_time': True}]
    )

    return LaunchDescription([audibot_launch, my_node])

Note: Always set use_sim_time: true on your nodes so they use the /clock topic from Gazebo instead of wall-clock time.

---

ROS Topics

Control Inputs (subscribe to these to drive the robot)

Topic	Type	Description
/audibot/steering_cmd	std_msgs/msg/Float64	Steering wheel angle in radians. Range: approximately ±8.8 rad (±3.2 turns lock-to-lock). Internally maps to a front wheel angle of ±0.375 rad.
/audibot/throttle_cmd	std_msgs/msg/Float64	Throttle percentage. Range: 0.0 (no throttle) to 1.0 (full throttle).
/audibot/brake_cmd	std_msgs/msg/Float64	Brake torque in N·m. Range: 0.0 (no braking) to 5000.0 (full braking). Brakes take priority over throttle.
/audibot/speed_cmd	std_msgs/msg/Float64	Target speed in m/s. Range: 0.0 to ~36.1 m/s (130 km/h). When published, this overrides throttle_cmd and brake_cmd and uses an internal PI controller to reach the target speed.
/audibot/gear_cmd	std_msgs/msg/UInt32	Gear selection. 0 = Drive (forward), 1 = Reverse.

Tip: Use either throttle_cmd + brake_cmd for low-level control, or speed_cmd for higher-level speed tracking. Do not mix them — speed_cmd overrides throttle and brake when active.

Command timeouts: All control commands time out after 0.1 seconds. Commands must be published continuously (e.g., at 10 Hz or faster) to keep the vehicle moving.

Sensor Outputs (subscribe to these to perceive the environment)

Topic	Type	Rate	Description
/audibot/imu	sensor_msgs/msg/Imu	100 Hz	IMU data: linear acceleration, angular velocity, and orientation. Frame: chassis.
/audibot/twist	geometry_msgs/msg/TwistStamped	100 Hz	Vehicle velocity: linear (m/s) and angular (rad/s) in the body frame.
/audibot/fix	sensor_msgs/msg/NavSatFix	1 Hz	GPS position fix. Default origin: 45.0° N, 81.0° W.
/audibot/gnss_heading	std_msgs/msg/Float64	50 Hz	Vehicle heading derived from GNSS, in radians.
/audibot/camera/image_raw	sensor_msgs/msg/Image	30 Hz	Forward-facing camera image. Resolution: 640×480 RGB. Mounted 2.0 m forward and 1.5 m above ground, pitched down 0.25 rad.
/audibot/camera/camera_info	sensor_msgs/msg/CameraInfo	30 Hz	Camera intrinsic parameters for /audibot/camera/image_raw.
/joint_states	sensor_msgs/msg/JointState	100 Hz	Positions and velocities of all wheel and steering joints.
/tf	tf2_msgs/msg/TFMessage	100 Hz	Transform tree: world → base_footprint → chassis → wheels and steering links.
/clock	rosgraph_msgs/msg/Clock	—	Simulation time. Subscribe via use_sim_time: true rather than directly.

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Vehicle Parameters

Parameter	Value
Wheelbase	2.67 m
Track width	1.638 m
Max front wheel steer angle	±0.375 rad (±21.5°)
Steering ratio	17.3
Max speed	130 km/h (≈36.1 m/s)
Max brake torque	5000 N·m
Vehicle mass	1700 kg
Wheel radius	0.36 m