TurtleBot3 Navigation: Wall Following & Bug2 Algorithm

This repository contains a ROS 2 implementation of autonomous navigation behaviors for the TurtleBot3 (Burger). It features a reactive Wall Follower and a Bug2 Algorithm that enables the robot to navigate toward a global goal while avoiding obstacles by switching between goal-seeking and boundary-following states.

Features

• Reactive Wall Following: Utilizes LiDAR data to maintain a consistent distance (0.5m - 0.7m) from walls on the right side of the robot.
• Bug2 Navigation: Implements a finite state machine to navigate to specific (x, y) coordinates.
• PID Control: Uses proportional control for smooth angular and linear velocity adjustments during goal seeking.
• M-Line Tracking: Calculates the distance to the direct path between the start and goal to determine when to exit obstacle avoidance.

Getting Started

Prerequisites

• ROS 2 (Humble or Foxy)
• TurtleBot3 Simulation Packages
• Gazebo

Installation

1. Clone this repo into your workspace src folder:

cd ~/ros2_ws/src
git clone <your-repo-link>

2. Build the package:

cd ~/ros2_ws
colcon build --packages-select turtlebot3_navigation
source install/setup.bash

🕹 Usage

Part 1: Wall Follower

To launch the robot in an environment where it will follow the right-hand wall indefinitely:

ros2 launch turtlebot3_navigation wall_follow.launch.py

Part 2: Bug2 Algorithm

To navigate to a specific goal (default defined in params.yaml):

ros2 launch turtlebot3_navigation bug2.launch.py

How it Works

Wall Follower Logic

The robot samples LiDAR ranges at specific angles:

• Front: 0° to 10° and 350° to 360° to detect obstacles ahead.
• Right: 320° to 350° to monitor the wall distance. It maintains a distance between 0.5 and 0.7 meters. If it gets too close, it steers left; if too far, it steers right.

Bug2 State Machine

1. Goal Seek: The robot calculates the heading to the goal and moves forward.
2. Wall Follow: If an obstacle is detected, the robot switches to wall following.
3. Transition: It continues following the wall until it intersects the "M-line" (the original straight line from start to goal) and is closer to the goal than when it started following the wall.

---

Customizing the Goal

You can change the navigation target by editing turtlebot3_navigation/config/params.yaml:

goal_position: [2.0, -1.2]

---

Result

Wall-follow:

BUG2:

---

Resources

• Including Launch Files
• ROS Params
• rclpy Parameters
• LaserScan Message
• Bug Algorithms