LineBot

Line follower is an autonomous robot, that tracks the black line. Robot works thanks to the line sensor (qtr8 from pololu). The sensors detects difference between colors. This projects consists of automatics, micrcontroller programming and 3d printing.

Table of contents

• Introduction
• PD Algorithm
• Installation
• Assembly
• Contribution
• License

Introduction

Stable and fast line follower is a great robot that helps us understand the role of the contorl theory in modern autonomous vehicles. The same algorithm can be implemented in camera based line follower or cars that drive between the lines. Knowledge gained by completing this project will help to create more advanced driving systems in the future.

Note:
An example of this robot in use can be found in the assets folder as video.mp4 (/assets/video.mp4).
The calibration process should take about two seconds — follow the same procedure as shown in the video.

PD Algorithm

This project implements PD regulator in velocity form, it is widely used in mobile robots. We have implemented the discrete form of the PD reulator's equation.

• P - the propotional term, it produces a correction propotional to how big error is. This term pushes robot toward the line and acts as the main steering force. Strongly reacts to bigger errors, sometimes the result is overshooting.

• D - the derivative term, it tells how quickly the error is changing. It reacts to the speed of movement away from or toward the line. Tuning this parameter helps us to reduce oscillation and smooths turns. Overally slows down the robot to avoid overshooting.

The general equation form:

$$u(t) = K_P e(t) + K_D\frac{d e(t)}{dt}$$

The discrete equation form:

$$u(t) = K_P e(t) + K_D(e(t) - e(t-1))$$

• $u(t)$ - current velocity, in other words duty cycle of the motors.
• $K_P$ - propotional term, tells how strong react to turns.
• $K_D$ - derivative term, reduces overshooting.
• $e(t)$ - error at the time t, the difference between robot and line positions.

Installation

1. Download Arduino IDE and install QTRSensors library.
2. Clone github repository to your computer:

https://github.com/SKN-SEP/LineBot.git

3. Connect your arduino to computer and upload the program.

Assembly

In order to build this robot, you need all the parts listed in the table below. The corresponding STL models are in the models folder. The skills required to assemble this robot include 3D printing, soldering, and cable management.

Name	Description	Image
Arduino Uno	Microcontroller board for controlling sensors and motors
Cables 15 cm	Short cables for connecting sensors, motors, power, and controller
QTR‑8 Pololu	IR reflectance sensor array (for line tracking / floor detection)
DC Motor 1	One of the two DC motors — drives wheel / movement
DC Motor 2	Second DC motor — drives wheel / movement
Chassis (AliExpress)	The base frame / body of the robot where motors, electronics, and wheels mount
Li‑ion Batteries ×3	Three Li‑ion batteries — main power supply for motors / controller
Battery Slot (for 3)	Battery holder/slot for the 3 Li‑ion batteries
DC Switch	Power switch controlling overall power on/off for the robot
L298N Motor Driver	Dual H‑bridge driver to control the two DC motors (direction & speed)
Filament (for 3D printing)	Thermoplastic filament used if you 3D‑print custom parts (e.g. mounts, holders, covers)

Contribution

Student Information

Image

Michał Zientek is the primary author and creator of the LineBot project. He was responsible for all stages of development, including: - Designing the robot architecture and system concept - Implementing the full control logic and line-following algorithm - Creating the calibration procedure (approx. 2 seconds) - Building and testing the hardware - Writing all software components - Producing documentation and demonstration materials (including the example video)

License

This project is licensed under the MIT License. See the LICENSE file for details.