This is a simple autonomous robot able to detect and avoid obstacles. I use a cheap 4WD robot platform (You can use any of these platforms), an Arduino UNO($18.59 on Amazon), and a cheap HC-SR04 sensor (2 pieces at $2.83 on Amazon).
The robot is programmed to drive forward till an obstacle is detected. Then it turns the sensor left and right. Compare the values returned by the ultrasonic sensor and take a decision.
This is the Arduino code:
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/**
* @file Arduino UNO Autonomous Robot
* @author Calin Dragos for intorobotics.com
* @version V1.0
* @date 13.10.2016
* @description This is an Arduino sketch for an autonomous robot able to detect and avoid obstacles
*/
#include <AFMotor.h>
#include <Servo.h>
#include <NewPing.h>
Servo myservo;
int ENABLE_A = 6;
int PIN_A1 = 3;
int PIN_A2 = 2;
int ENABLE_B = 11;
int PIN_B1 = 5;
int PIN_B2 = 4;
int SENSOR_DISTANCE;
int LEFT_SENSOR_DISTANCE;
int RIGHT_SENSOR_DISTANCE;
int SNZ_DISTANCE_L;
int SNZ_DISTANCE_R;
int LFT_SNZ_DIS;
int RGT_SNZ_DIS;
#define TRIG_PIN 7
#define ECHO_PIN 8
#define MIN_DISTANCE 40
#define MAX_DISTANCE 200
#define INTERVAL 200
NewPing sonar(TRIG_PIN, ECHO_PIN, MAX_DISTANCE);
void setup() {
Serial.begin(9600);
//pin mode for the DC motors
pinMode (ENABLE_A, OUTPUT);
pinMode (PIN_A1, OUTPUT);
pinMode (PIN_A2, OUTPUT);
pinMode (ENABLE_B, OUTPUT);
pinMode (PIN_B1, OUTPUT);
pinMode (PIN_B2, OUTPUT);
//pin mode for the ultrasonic sensor
pinMode(TRIG_PIN, OUTPUT);
pinMode(ECHO_PIN, INPUT);
//for servo motor
myservo.attach(9);
//set the ultrasonic sensor to center
sensorCenter();
//stop the motors
stopMotors();
}
void loop() {
SENSOR_DISTANCE=sensorDistance();
Serial.print(“Front sensor distance is: “);
Serial.println(SENSOR_DISTANCE);
if(SENSOR_DISTANCE >= MIN_DISTANCE || SENSOR_DISTANCE==0)
{
goForward();
Serial.println(“Go forward”);
}
else {
//stop the motors
stopMotors();
LFT_SNZ_DIS=toTheLeft();
RGT_SNZ_DIS=toTheRight();
if(LFT_SNZ_DIS >= MIN_DISTANCE && LFT_SNZ_DIS >= RGT_SNZ_DIS)
{
int NEW_SNZ_DIS_LFT;
//try three times to escape
for(int i=1;i<=3;i++){
goLeft();
Serial.println(“Go left”);
delay(300);
//stop the motors
stopMotors();
NEW_SNZ_DIS_LFT=sensorDistance();
if(NEW_SNZ_DIS_LFT >=MIN_DISTANCE)
{
break;
}
}
sensorCenter();
}
else if(RGT_SNZ_DIS >= MIN_DISTANCE && RGT_SNZ_DIS >= LFT_SNZ_DIS)
{
int NEW_SNZ_DIS_RGT;
//try three times to escape
for(int j=1;j<=3;j++){
goRight();
Serial.println(“Go right”);
delay(300);
//stop the motors
stopMotors();
NEW_SNZ_DIS_RGT=sensorDistance();
if(NEW_SNZ_DIS_RGT >=MIN_DISTANCE)
{
break;
}
}
sensorCenter();
}
else
{
goBackward();
Serial.println(“Go backward”);
delay(500);
//stop the motors
stopMotors();
sensorCenter();
}
}
}
void stopMotors(){
analogWrite (ENABLE_A, 0);
analogWrite (ENABLE_B, 0);
digitalWrite (PIN_A1, LOW);
digitalWrite (PIN_A2, LOW);
digitalWrite (PIN_B1, LOW);
digitalWrite (PIN_B2, LOW);
}
int sensorDistance(){
int distance;
int uS = sonar.ping();
distance = uS / US_ROUNDTRIP_CM;
if(distance !=0){
return distance;
delay(300);
}
}
void goForward(){
analogWrite (ENABLE_A, 255);
digitalWrite (PIN_A1, HIGH);
digitalWrite (PIN_A2, LOW);
analogWrite (ENABLE_B, 255);
digitalWrite (PIN_B1, HIGH);
digitalWrite (PIN_B2, LOW);
}
void goBackward(){
analogWrite (ENABLE_A, 180);
digitalWrite (PIN_A1, LOW);
digitalWrite (PIN_A2, HIGH);
analogWrite (ENABLE_B, 180);
digitalWrite (PIN_B1, LOW);
digitalWrite (PIN_B2, HIGH);
}
void goLeft(){
analogWrite (ENABLE_A, 180);
digitalWrite (PIN_A1, HIGH);
digitalWrite (PIN_A2, LOW);
analogWrite (ENABLE_B, 180);
digitalWrite (PIN_B1, LOW);
digitalWrite (PIN_B2, HIGH);
}
void goRight(){
analogWrite (ENABLE_A, 180);
digitalWrite (PIN_A1, LOW);
digitalWrite (PIN_A2, HIGH);
analogWrite (ENABLE_B, 180);
digitalWrite (PIN_B1, HIGH);
digitalWrite (PIN_B2, LOW);
}
void sensorCenter(){
myservo.write(90);
delay(500);
}
void turnSensorLeft(){
myservo.write(120);
delay(500);
}
void turnSensorRight(){
myservo.write(60);
delay(500);
}
int leftSensorDistance(){
int LEFT_SENSOR_DISTANCE;
LEFT_SENSOR_DISTANCE=sensorDistance();
return LEFT_SENSOR_DISTANCE;
}
int rightSensorDistance(){
int RIGHT_SENSOR_DISTANCE;
RIGHT_SENSOR_DISTANCE=sensorDistance();
return RIGHT_SENSOR_DISTANCE;
}
int toTheLeft(){
int LEFT_SENSOR_DISTANCE;
turnSensorLeft();
LEFT_SENSOR_DISTANCE=leftSensorDistance();
Serial.print(“Left sensor distance is: “);
Serial.println(LEFT_SENSOR_DISTANCE);
return LEFT_SENSOR_DISTANCE;
}
int toTheRight(){
int RIGHT_SENSOR_DISTANCE;
turnSensorRight();
RIGHT_SENSOR_DISTANCE=rightSensorDistance();
Serial.print(“Right sensor distance is: “);
Serial.println(RIGHT_SENSOR_DISTANCE);
return RIGHT_SENSOR_DISTANCE;
}
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And this is how the robot navigates autonomously in my kitchen: