Line Follower

Overview

This project implements an advanced autonomous line-following robot using ESP32, an 8-channel sensor array, Bluetooth communication, and a PID control algorithm.

The robot continuously reads line sensor values, calculates the line position, determines the error from the center, and dynamically adjusts motor speeds using PID control for smooth and accurate navigation.

A Bluetooth interface allows real-time tuning of PID parameters without reprogramming the microcontroller, making it ideal for robotics competitions and research applications.

Features

Autonomous Line Following

• Real-time line detection
• 8-channel sensor array
• Weighted position calculation
• Dynamic steering correction

PID Control System

• Proportional Control (Kp)
• Integral Control (Ki)
• Derivative Control (Kd)

Provides:

• Smooth turns
• Reduced oscillations
• Faster line recovery
• Stable navigation

Bluetooth Tuning

• Wireless parameter adjustment
• Real-time PID tuning
• Remote start and stop control

Motor Driver Control

• Independent left and right motor control
• PWM speed regulation
• Direction control support

Hardware Components

Component

Quantity

ESP32 Development Board

1

TB6612FNG Motor Driver

1

IR Sensor Array (8 Channel)

1

DC Gear Motors

2

Li-ion Battery Pack

1

Chassis

1

System Architecture

IR Sensor Array ↓ ESP32 ↓ Position Detection ↓ PID Controller ↓ Motor Driver ↓ DC Motors ↓ Robot Navigation

Bluetooth App ↓ ESP32 ↓ PID Parameter Update

Sensor Configuration

Sensor

GPIO

Sensor 1

GPIO32

Sensor 2

GPIO33

Sensor 3

GPIO34

Sensor 4

GPIO35

Sensor 5

GPIO25

Sensor 6

GPIO26

Sensor 7

GPIO27

Sensor 8

GPIO23

Motor Driver Connections

Left Motor

AIN1 → GPIO2

AIN2 → GPIO4

PWMA → GPIO13

Right Motor

BIN1 → GPIO18

BIN2 → GPIO19

PWMB → GPIO14

Standby

STBY → GPIO5

Bluetooth Configuration

Device Name:

LineFollower

Connect using any Bluetooth terminal or custom Android application.

Working Principle

Sensor Calibration

At startup:

• Reads all sensor values
• Calculates minimum values
• Calculates maximum values
• Generates calibration reference

This improves performance under different lighting conditions.

Position Detection

Each sensor contributes to a weighted average calculation:

Position = Weighted Sum / Total Sensor Value

Center Position = 3500

Error = Position − Center

PID Controller

Error is processed using:

P = Current Error

I = Accumulated Error

D = Change in Error

PID Output:

PID = Kp × P + Ki × I + Kd × D

Motor speeds are adjusted accordingly.

Bluetooth Commands

Set Kp

Command ID = 1

Set Ki

Command ID = 3

Set Kd

Command ID = 5

Start/Stop Robot

Command ID = 7

Software Libraries

Required Libraries:

• BluetoothSerial
• ESP32 Arduino Core

Installation

Step 1

Install ESP32 Board Package.

Step 2

Upload firmware.

Step 3

Power the robot.

Step 4

Allow sensor calibration to complete.

Step 5

Connect to Bluetooth device:

LineFollower

Step 6

Tune PID values.

Step 7

Start autonomous navigation.

Applications

• Line Following Competitions
• Autonomous Navigation
• Industrial AGV Research
• Warehouse Robots
• Educational Robotics
• Embedded Control Systems
• PID Control Experiments

Advantages

✔ Real-Time PID Tuning

✔ Bluetooth Controlled

✔ High Accuracy Tracking

✔ Sensor Auto Calibration

✔ Smooth Navigation

✔ Embedded Intelligence

✔ Competition Ready

Future Improvements

• OLED Status Display
• Mobile PID Dashboard
• Data Logging
• AI-Based Path Prediction
• Maze Solving Algorithm
• Obstacle Avoidance
• WiFi Monitoring
• ROS Integration

Project Highlights

✔ ESP32 Based

✔ Bluetooth Communication

✔ PID Controlled Navigation

✔ 8 Sensor Array

✔ Autonomous Robotics

✔ Embedded Systems

✔ Real-Time Control

✔ Competition Grade Design

Author

Hariharan Balakrishnan

B.E Electronics and Communication Engineering

Embedded Systems | Robotics | IoT | Edge AI | ESP32 | Zephyr RTOS