Motor/ Robot, Sensor

ESP32 PD Line Following Robot with Maker Line

by Idris
August 21, 2019

ESP32, IR Line Sensor, Line Following Robot, Maker Line

Let's try to build line following robot using ESP32.

Introduction

Last week I have shared Raspberry Pi Line Following Robot with Maker Line tutorial. This time I would like to try another 3.3V controller which is ESP32. Plus, instead of using digital pins, I will use analog signal from Maker Line and implement simple PD (proportional and derivative) technique to control mobile robot. Before we start, I recommend you to understand the basic of line following robot. You can refer to this tutorial:

Building a Low-Cost Line Following Robot

Video

This video is about ESP32 PD line following robot with Maker Line sensor.

Hardware Preparation

This is the list of items used in the video.

Node32 Lite

Maker Drive

3.7V 2000mAh Li-Ion Battery

40 Ways Male to Female Jumper Wire

Maker Line

2WD Smart Robot Car Chassis

1×18650 Battery Holder

Breadboard 8.5×5.5cm

Wiring connection table.

18650 BATTERY	CHARGER MODULE	MAKER DRIVE	DC MOTOR	NODE32 LITE	MAKER LINE
Positive	B+
Negative	B-
	OUT+	VB+
	OUT-	VB-
		M1A Terminal	Left Motor
		M1B Terminal	Left Motor
		M2A Terminal	Right Motor
		M2B Terminal	Right Motor
		5V		RAW
		GND		GND	GND
		M1A Pin		GPIO33
		M1B Pin		GPIO25
		M2A Pin		GPIO26
		M2B Pin		GPIO27
				3.3V	VCC
				GPIO36	AN

Sample Program

This is Arduino sample code for ESP32 PD line following robot with Maker Line. Please install ESP32 package in order to upload this code into your board. You may need to tune the gain (try and error) based on your hardware.


	#define MAKERLINE_AN A0

	#define M1A 33
	#define M1B 25
	#define M2A 26
	#define M2B 27

	#define PWM_FREQUENCY 1000
	#define PWM_RESOLUTION 8
	#define M1A_PWM_CHANNEL 0
	#define M1B_PWM_CHANNEL 1
	#define M2A_PWM_CHANNEL 2
	#define M2B_PWM_CHANNEL 3

	#define MAX_SPEED 255

	int adcMakerLine = 0;
	int adcSetPoint = 0;
	int proportional = 0;
	int lastProportional = 0;
	int derivative = 0;
	int powerDifference = 0;
	int motorLeft = 0;
	int motorRight = 0;
	unsigned long currentMillis = 0;
	unsigned long previousMillis = 0;
	const int interval = 10;

	void setup()
	{
	pinMode(MAKERLINE_AN, INPUT);
	analogReadResolution(10);

	ledcSetup(M1A_PWM_CHANNEL, PWM_FREQUENCY, PWM_RESOLUTION);
	ledcSetup(M1B_PWM_CHANNEL, PWM_FREQUENCY, PWM_RESOLUTION);
	ledcSetup(M2A_PWM_CHANNEL, PWM_FREQUENCY, PWM_RESOLUTION);
	ledcSetup(M2B_PWM_CHANNEL, PWM_FREQUENCY, PWM_RESOLUTION);

	ledcAttachPin(M1A, M1A_PWM_CHANNEL);
	ledcAttachPin(M1B, M1B_PWM_CHANNEL);
	ledcAttachPin(M2A, M2A_PWM_CHANNEL);
	ledcAttachPin(M2B, M2B_PWM_CHANNEL);

	Serial.begin(115200);
	Serial.println("ESP32 PD Line Following Robot with Maker Line");

	// Place robot at the center of line
	adcSetPoint = analogRead(MAKERLINE_AN);
	delay(2000);
	}

	void loop()
	{
	currentMillis = millis();
	if (currentMillis – previousMillis > interval) {
	previousMillis = currentMillis;

	adcMakerLine = analogRead(MAKERLINE_AN);

	if (adcMakerLine < 51) { // Out of line
	robotMove(0, 0);
	}
	else if (adcMakerLine > 972) { // Detects cross line
	robotMove(MAX_SPEED-25, MAX_SPEED-25);
	}
	else {
	proportional = adcMakerLine – adcSetPoint;
	derivative = proportional – lastProportional;
	lastProportional = proportional;

	powerDifference = (proportional * 1.5) + (derivative * 5);

	if (powerDifference > MAX_SPEED) {
	powerDifference = MAX_SPEED;
	}
	if (powerDifference < -MAX_SPEED) {
	powerDifference = -MAX_SPEED;
	}

	if (powerDifference < 0) {
	motorLeft = MAX_SPEED + powerDifference;
	motorRight = MAX_SPEED;
	}
	else {
	motorLeft = MAX_SPEED;
	motorRight = MAX_SPEED – powerDifference;
	}

	robotMove(motorLeft, motorRight);

	Serial.print("ADC:\t");
	Serial.print(adcMakerLine);
	Serial.print("\tMotor Left:\t");
	Serial.print(motorLeft);
	Serial.print("\tMotor Right:\t");
	Serial.println(motorRight);
	}
	}
	}

	void robotMove(int speedLeft, int speedRight)
	{
	speedLeft = constrain(speedLeft, –255, 255);
	speedRight = constrain(speedRight, –255, 255);

	if (speedLeft > 0) {
	int speedL = map(speedLeft, 0, 255, 255, 0);
	ledcWrite(M1A_PWM_CHANNEL, speedL);
	ledcWrite(M1B_PWM_CHANNEL, 255);
	}
	else {
	int speedL = map(speedLeft, –255, 0, 0, 255);
	ledcWrite(M1A_PWM_CHANNEL, 255);
	ledcWrite(M1B_PWM_CHANNEL, speedL);
	}

	if (speedRight > 0) {
	int speedR = map(speedRight, 0, 255, 255, 0);
	ledcWrite(M2A_PWM_CHANNEL, speedR);
	ledcWrite(M2B_PWM_CHANNEL, 255);
	}
	else {
	int speedR = map(speedRight, –255, 0, 0, 255);
	ledcWrite(M2A_PWM_CHANNEL, 255);
	ledcWrite(M2B_PWM_CHANNEL, speedR);
	}
	}