QTR sensor array follow black line on not perfectly white surface

Projects Programming
1

Hello!

I'm making line follower, it has to follow black line on grey wooden background:

line
line1920×2557 425 KB

problem is, that it follows wooden lines instead of tape

I've seen line follower, that follows tape on brown wooden background.

Here's my code:

#include <QTRSensors.h>
#include <Arduino.h>
#include <SoftwareSerial.h>




//Defning pins for motors
#define left_mtr_frwrd 7
#define left_mtr_bkwrd 6
#define right_mtr_frwrd 4
#define right_mtr_bkwrd 5

#define left_mtr_sped 9
#define right_mtr_sped 10

//define variables for qtr sensor array

QTRSensors qtr;

const uint8_t SensorCount = 6;
uint16_t sensorValues[SensorCount];


//define constants for PID

const double KP = 0.04;
const double KD = 0;

double lastError = 0;
int GOAL = 2500;
const unsigned char max_speed = 100;

void setup() {
  //Starting serial to exchange status with our PC
  Serial.begin(9600);

  qtr.setTypeAnalog();
  qtr.setSensorPins((const uint8_t[]){ A0, A1, A2, A3, A4, A5 }, SensorCount);
  qtr.setEmitterPin(2);

  delay(500);
  pinMode(LED_BUILTIN, OUTPUT);
  digitalWrite(LED_BUILTIN, HIGH);  // turn on Arduino's LED to indicate we are in calibration mode

  //turn motors on, so it can turn himself around to calibrate

  // analogRead() takes about 0.1 ms on an AVR.
  // 0.1 ms per sensor * 4 samples per sensor read (default) * 8 sensors
  // * 10 reads per calibrate() call = ~24 ms per calibrate() call.
  // Call calibrate() 400 times to make calibration take about 9.8 seconds.
  for (uint16_t i = 0; i < 400; i++) {
    qtr.calibrate();
  }
  digitalWrite(LED_BUILTIN, LOW);  // turn off Arduino's LED to indicate we are through with calibration


  for (uint8_t i = 0; i < SensorCount; i++) {
    Serial.print(qtr.calibrationOn.minimum[i]);
    Serial.print(' ');
  }
  Serial.println();

  // print the calibration maximum values measured when emitters were on
  for (uint8_t i = 0; i < SensorCount; i++) {
    Serial.print(qtr.calibrationOn.maximum[i]);
    Serial.print(' ');
  }
  Serial.println();
  Serial.println();
  delay(1000);

  motor(1, 0, 1, 0);
}

void loop() {
  // read calibrated sensor values and obtain a measure of the line position
  // from 0 to 5000 (for a white line, use readLineWhite() instead)
  uint16_t position = qtr.readLineBlack(sensorValues);

  //compute eerror
  int error = GOAL - position;

  //Compute motor adjustment
  int adjustment = (KP) * (error) + KD * (error - lastError);

  //Store error for next iteration

  lastError = error;

  //Adjust motors
  motor_speed(constrain((max_speed - adjustment), 0, max_speed), constrain((max_speed + adjustment), 0, max_speed));
}

And my functions:


// function to easily control motors; e.g. motor(1, 0, 1, 0); - forward

void motor( int left_frwrd, int left_bkwrd, int right_frwrd, int right_bkwrd) {
  digitalWrite(left_mtr_frwrd, left_frwrd);
  digitalWrite(left_mtr_bkwrd, left_bkwrd);
  digitalWrite(right_mtr_frwrd, right_frwrd);
  digitalWrite(right_mtr_bkwrd, left_bkwrd);
}

//function to easily control speed of motor

void motor_speed(int left_sped, int right_sped) {
  analogWrite(left_mtr_sped, left_sped);
  analogWrite(right_mtr_sped, right_sped);
}




void ir_status() {

  // print the sensor values as numbers from 0 to 1000, where 0 means maximum
  // reflectance and 1000 means minimum reflectance, followed by the line
  // position
  for (uint8_t i = 0; i < SensorCount; i++)
  {
    Serial.print(sensorValues[i]);
    Serial.print('\t');
  }
//  Serial.println(position);
}

thanks for your time

2

Not enough information.

To debug this problem, first you need to understand how the QTR sensor works, and why it is being deceived.

Start by collecting and analyzing the printout of sensor values for several cases where the black line is present, or not, and the corresponding value returned as "position" from the readLineBlack function.

3

ok, then I'll collect data. Keep you up to date.

@jremington thanks for respond

4
  1. I've noticed my last pin IR wasn't working, do PWM pins anyhow interfere with analog pins on UNO R3 (ch340 chipset), if yes I've connected one of my motor pins to PWM on 5th pin. Whatever, I just removed it from code.
  2. IR input on more greyer background 240, less greyer background 100 and tape is 900
  3. Should I create my own algorithm to calculate position with threshold for "more greyer" background?
5

Still not enough information.

Please post a complete schematic diagram of the wiring, with all pins, parts and connections clearly labeled. Hand drawn is preferred.

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