cubeBot: ROS 2 + Gazebo Classic

A tiny cubeBot built for ROS 2 (Humble / Jazzy) with a differential-drive base and a 2D LiDAR - hoping to make this work well for reinforcement-learning experiments and robotics demos. If there's anything wonky please let me know ...it took me a long time to learn all this & getting the basic to work properly - ROS is no joke ya'll lol

It includes:

• Gazebo Classic world & spawn launch
• /cmd_vel -> differential-drive control plugin
• /scan from simulated LiDAR (sensor_msgs/LaserScan)
• Basic obstacle-avoidance node
• Random-policy node + scan logger for quick RL prototyping

---

Quick Start

# 1️ Create a workspace and clone the repo
mkdir -p ~/ros2_ws/src
cd ~/ros2_ws/src
git clone https://github.com/YOUR_USERNAME/cubebot.git
cd ~/ros2_ws

# 2️Install dependencies (Ubuntu 22.04 + ROS 2 Humble)
sudo apt update
sudo apt install -y   ros-humble-gazebo-ros-pkgs   ros-humble-xacro   ros-humble-robot-state-publisher   ros-humble-joint-state-publisher-gui

# 3️Build & source
colcon build --symlink-install
source install/setup.bash

# 4️ Run the simulation 
ros2 launch cubebot cubebot_sim.launch.py

Tips

# If Gazebo says "Address already in use", free the port:
pkill -9 gazebo gzserver gzclient 2>/dev/null

# Switch to a random driving policy instead of obstacle avoidance:
ros2 run cubebot random_policy

---

Topics

Topic	Type	Description
/cmd_vel	geometry_msgs/Twist	velocity command
/odom	nav_msgs/Odometry	published by diff-drive plugin
/scan	sensor_msgs/LaserScan	LiDAR range data

---

TF Frames

odom → base_link - >lidar_link

---

Reinforcement Learning Notes

• Observation (example): downsampled LiDAR scan (≈ 36 beams) + linear/angular speeds + previous action
• Action: [linear_x, angular_z]
• Reward suggestion:
  +v_forward * dt − turn_penalty * |ω| − collision_penalty (if min range < threshold)
• For Gymnasium integration: wrap the environment to publish on /cmd_vel and read /scan + /odom or TF for pose.

---

Parameters (obstacle_avoider)

Parameter	Default	Description
linear_speed	0.4	forward velocity
turn_speed	0.8	angular speed when turning
min_range	0.6	minimum LiDAR range before turning
fov_deg	60.0	field of view used for obstacle check

---

Test Controls

# Move forward
ros2 topic pub -r 10 /cmd_vel geometry_msgs/Twist "{linear: {x: 0.5}, angular: {z: 0.0}}"

# Turn in place
ros2 topic pub -r 10 /cmd_vel geometry_msgs/Twist "{linear: {x: 0.0}, angular: {z: 1.0}}"

---

Notes

• Requires Gazebo Classic, not Ignition Gazebo / Fortress.
• Works with both ROS 2 Humble and ROS 2 Jazzy (update the ros-* package names accordingly).
• For tele-operation:

  sudo apt install ros-humble-teleop-twist-keyboard
  ros2 run teleop_twist_keyboard teleop_twist-keyboard

---

❤️ Acknowledgments