This document contains code for calibrating and controlling the motors of a line-following robot using an array of 8 infrared sensors. It defines constants for PID control parameters and motor pin assignments. The main loop uses PID control to adjust the left and right motor speeds based on the robot's position relative to the center of the line to follow the line smoothly.

1. #include <QTRSensors.h>
#define Kp 0.2 // experiment to determine this, start by something small that
just makes your bot follow the line at a slow speed
#define Kd 4 // experiment to determine this, slowly increase the speeds and
adjust this value. ( Note: Kp < Kd)
#define MaxSpeed 255// max speed of the robot
#define BaseSpeed 100 // this is the speed at which the motors should spin when
the robot is perfectly on the line
#define NUM_SENSORS 8 // number of sensors used
#define speedturn 255
#define rightMotor1 4
#define rightMotor2 5
#define rightMotorPWM 6
#define leftMotor1 8
#define leftMotor2 9
#define leftMotorPWM 3
#define motorPower 8
QTRSensorsAnalog qtra((unsigned char[]) {0,1,2,3,4,5,6,7} ,
NUM_SENSORS, 4, QTR_NO_EMITTER_PIN);
unsigned int sensorValues[NUM_SENSORS];
void setup()
{
pinMode(rightMotor1, OUTPUT);
pinMode(rightMotor2, OUTPUT);
pinMode(rightMotorPWM, OUTPUT);
pinMode(leftMotor1, OUTPUT);
pinMode(leftMotor2, OUTPUT);
pinMode(leftMotorPWM, OUTPUT);
pinMode(motorPower, OUTPUT);
delay(3000);
int i;
for (int i = 0; i < 100; i++) // calibrate for sometime by sliding the sensors
across the line, or you may use auto-calibration instead
{
//comment this part out for automatic calibration

2. if ( i < 25 || i >= 75 ) // turn to the left and right to expose the sensors to
the brightest and darkest readings that may be encountered
{
move(1, 70, 1);//motor derecho hacia adelante
move(0, 70, 0);//motor izquierdo hacia atras
}
else
{
move(1, 70, 0);//motor derecho hacia atras
move(0, 70, 1);//motor izquierdo hacia adelante
}
qtra.calibrate();
delay(20);
}
wait();
delay(3000); // wait for 2s to position the bot before entering the main loop
}
int lastError = 0;
unsigned int sensors[8];
int position = qtra.readLine(sensors);
void loop()
{
position = qtra.readLine(sensors); // get calibrated readings along with the
line position, refer to the QTR Sensors Arduino Library for more details on line
position.
if(position>6700){
move(1, speedturn, 1);//motor derecho hacia adelante
move(0, speedturn, 0);//motor izquierdo hacia adelante
return;
}
if(position<300){
move(1, speedturn, 0);//motor derecho hacia adelante
move(0, speedturn, 1);//motor izquierdo hacia adelante
return;

3. }
int error = position - 3500;
int motorSpeed = Kp * error + Kd * (error - lastError);
lastError = error;
int rightMotorSpeed = BaseSpeed + motorSpeed;
int leftMotorSpeed = BaseSpeed - motorSpeed;
if (rightMotorSpeed > MaxSpeed ) rightMotorSpeed = MaxSpeed; // prevent the
motor from going beyond max speed
if (leftMotorSpeed > MaxSpeed ) leftMotorSpeed = MaxSpeed; // prevent the motor
from going beyond max speed
if (rightMotorSpeed < 0)rightMotorSpeed = 0;
if (leftMotorSpeed < 0)leftMotorSpeed = 0;
move(1, rightMotorSpeed, 1);//motor derecho hacia adelante
move(0, leftMotorSpeed, 1);//motor izquierdo hacia adelante
}
void wait(){
digitalWrite(motorPower, LOW);
}
void move(int motor, int speed, int direction){
digitalWrite(motorPower, HIGH); //disable standby
boolean inPin1=HIGH;
boolean inPin2=LOW;
if(direction == 1){
inPin1 = HIGH;
inPin2 = LOW;
}
if(direction == 0){
inPin1 = LOW;
inPin2 = HIGH;
}
if(motor == 0){

4. digitalWrite(leftMotor1, inPin1);
digitalWrite(leftMotor2, inPin2);
analogWrite(leftMotorPWM, speed);
}
if(motor == 1){
digitalWrite(rightMotor1, inPin1);
digitalWrite(rightMotor2, inPin2);
analogWrite(rightMotorPWM, speed);
}
}