ROS 2 Line-Follower Robot

This repository contains the source code and configuration for a high-performance ROS 2 (Jazzy) line-follower robot. It supports both IR-based and Computer Vision-based line following.

Installation & Building

Prerequisites

ROS 2 Jazzy Jalisco
Gazebo Sim (for simulation)
OpenCV (for CV mode)

Build the Workspace

# Clone the repository (if not already done)
git clone https://github.com/MehrzadGolabi/ROS2_linefollower.git
cd linebot_ws

# Install dependencies
rosdep update
rosdep install --from-paths src --ignore-src -r -y

# Build
colcon build --symlink-install

# Source the workspace
source install/setup.bash

Quick Start / Cheat Sheet

Task	Command
Bringup (Physical Robot)	`ros2 launch linebot robot.launch.py`
Bringup (Simulation)	`ros2 launch linebot sim.launch.py`
Manual Control (Keyboard)	`ros2 run teleop_twist_keyboard teleop_twist_keyboard`
View Camera Stream	`ros2 run rqt_image_view rqt_image_view`
IR Line Following	`ros2 launch linefollower_ir linefollower_ir_launch.py`
CV Line Following	`ros2 launch linefollower_cv linefollower_cv_launch.py`
Visualize System (RViz)	`rviz2`

Workspace Packages

linebot (Core Bringup)

The primary package for system orchestration and hardware/simulation bringup.

Robot Bringup

Starts the physical robot, including motor drivers, encoders, and selected sensors. - Command: ros2 launch linebot robot.launch.py - Arguments: | Argument | Default | Description | | --- | --- | --- | | mode | camera | Sensor mode: camera, ir, or hybrid | | camera_topic | /camera/image_raw | Topic to subscribe for images | | use_ros2_control | true | Use ros2_control framework | | rviz | false | Launch RViz for debugging | - Key Nodes: ros2_control_node, robot_state_publisher, twist_mux, twist_stamper

Simulation

Launches the robot in the Gazebo Sim environment. - Command: ros2 launch linebot sim.launch.py - Arguments: | Argument | Default | Description | | --- | --- | --- | | world | linefollow.sdf | SDF world file to load | | use_sim_time | true | Sync with simulator clock | - Key Nodes: gz_sim, ros_gz_bridge, robot_state_publisher

linefollower_cv (Computer Vision)

Handles high-speed line detection and navigation using OpenCV.

Launch CV Node

Command: ros2 launch linefollower_cv linefollower_cv_launch.py
Arguments: | Argument | Default | Description | | --- | --- | --- | | camera_topic | /camera/image_raw | Topic to subscribe for images |
Key Nodes: linefollower_cv_node

linefollower_ir (IR Sensors)

State-machine based line following using the 5-array IR sensor.

Launch IR Node

Command: ros2 launch linefollower_ir linefollower_ir_launch.py
Key Nodes: linefollower_ir_node

External ROS 2 Tools

teleop_twist_keyboard

Standard tool for manual control of the robot using the keyboard. - Command: ros2 run teleop_twist_keyboard teleop_twist_keyboard - Usage: Follow the on-screen instructions to use keys like i, j, l, k for movement.

rqt_image_view

A GUI tool to view camera streams and processed images. - Command: ros2 run rqt_image_view rqt_image_view - Usage: Select the desired image topic (e.g., /camera/image_raw or /line_image) from the dropdown menu.

RViz2

The primary visualization tool for ROS 2. - Command: rviz2 - Usage: Used to monitor robot state, sensor data (Lidar, Odometry), and coordinate frames.

Scenario-Based Tutorials

1. Running in IR Line-Following Mode

Use this mode for high-reliability line following using the infrared sensor array. 1. Bringup the robot in IR mode: bash ros2 launch linebot robot.launch.py mode:=ir 2. Start the IR line-follower logic: bash ros2 launch linefollower_ir linefollower_ir_launch.py

2. Running in Computer Vision Mode

Use this mode for advanced navigation using the camera. 1. Bringup the robot in camera mode: bash ros2 launch linebot robot.launch.py mode:=camera 2. Start the CV line-follower logic: bash ros2 launch linefollower_cv linefollower_cv_launch.py 3. Optional: View processed image: bash ros2 run rqt_image_view rqt_image_view (Select /line_image to see the detection result)

3. Running in Simulation

Test your algorithms in a virtual environment. 1. Launch the simulator: bash ros2 launch linebot sim.launch.py 2. Optional: Control manually to test bridges: bash ros2 run teleop_twist_keyboard teleop_twist_keyboard

ros2 launch linefollower_cv linefollower_cv_launch.py use_sim_time:=true camera_topic:=/camera/depth/image_raw/image