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:

/** * @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; } 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 /** * @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 ; }

And this is how the robot navigates autonomously in my kitchen:

