Line-Following Robot with PID Control

This project implements a line-following robot using PID (Proportional–Integral–Derivative) control on an Arduino-based system. The robot reads analog values from infrared (IR) sensors to detect the line and adjusts the speed of its motors to stay centered.

Demo: https://youtu.be/5oXEWmr-w1s

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Features

• PID control loop to correct deviation from the line.
• Three IR sensors (left, center, right) for line detection.
• PWM motor control for smooth movement.
• Configurable parameters for base speed, minimum speed, and maximum speed.
• Tunable PID constants for fine adjustments.

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How It Works

1. The IR sensors measure reflectivity:

   • Black line = lower value
   • White surface = higher value

2. The error is calculated as the difference between the left and right sensors.

3. PID control is applied:

   • P → proportional correction based on error.
   • I → accumulates past error.
   • D → predicts future error by measuring rate of change.

4. The robot adjusts left and right motor speeds accordingly.

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Pinout

Motors

• AIA = 3
• AIB = 11
• BIA = 10
• BIB = 6

Sensors

• IR sensors (digital control):

  • Left: 9
  • Center: 7
  • Right: 8

• Analog inputs (reading sensor values):

  • Right: A0
  • Center: A1
  • Left: A2

LED

• ledTest = 13 (status indicator)

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PID Tuning Parameters

You can adjust the following constants to fine-tune performance:

float Kp2 = 0.0008;   // Proportional gain factor
float Kd2 = 0.1;      // Derivative gain factor
float Ki2 = 0.0001;   // Integral gain factor

They are dynamically scaled depending on the sensor readings.

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Adjustable Speed Settings

int baseSpeed = 200;   // Default motor speed
int maxSpeed  = 255;   // Maximum PWM speed
int minSpeed  = 75;    // Minimum PWM speed

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Installation

1. Connect your Arduino and motors according to the pinout above.
2. Upload the code using the Arduino IDE.
3. Place the robot on a track with a black line on a white surface.
4. Adjust PID constants if needed for stability.

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Usage

• When the center sensor detects the line (> 450), PID control is activated.
• The robot continuously reads sensors and applies corrections to follow the line.
• The built-in LED blinks at startup for a quick test.

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Future Improvements

• Implement automatic calibration for sensor thresholds.
• Add serial output logging for PID values and error debugging.
• Support for different track shapes and speeds.

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Would you like me to also create a schematic diagram (in Markdown with ASCII or using Fritzing-style description) to visually show the wiring in the README?