Sketch 2

// Defining Pins on the Ardunio to the respective Ultrasonic sensors
#define FRONT_TRIG 13 // Front Sensor Trig to Pin 13
#define FRONT_ECHO 12 // Front Sensor Echo to Pin 12, VCC 5V and GND are connected on the Ardunio Uno board
#define RIGHT_TRIG 11
#define RIGHT_ECHO 10
#define LEFT_TRIG 9   
#define LEFT_ECHO 8
#define TOP_TRIG 7
#define TOP_ECHO 6

// Global variables
char old_command; 	       // Old command generated based on ultrasonic distances
  
// Setting up input and outputs for the pinModes for the each sensor respectively
void setup() {                 // initializes serial communication
  Serial.begin (9600);         // Open serial monitor at 9600 baud to see ping results.
  pinMode(FRONT_TRIG, OUTPUT); // Output = sonar burst from the ultrasonic sensor to an object
  pinMode(FRONT_ECHO, INPUT);  // Input  = received sound wave reflected from the obstacle
  pinMode(RIGHT_TRIG, OUTPUT);
  pinMode(RIGHT_ECHO, INPUT);
  pinMode(LEFT_TRIG, OUTPUT);
  pinMode(LEFT_ECHO, INPUT);
  pinMode(TOP_TRIG, OUTPUT);
  pinMode(TOP_ECHO, INPUT);
}
// Serial prints command if it differs from previous command, this is done to reduce buffer on the serial port
void PrintCommand(char old_c, char new_c){
	if (new_c != old_c) {
        Serial.println(new_c);
        Serial.println("\n");
    }
}
void loop() {
  long duration, FRONT, RIGHT, LEFT, TOP; // Duration used to calculate distance of an object from each sensor
 
  digitalWrite(TOP_TRIG, LOW);            // LOW triggered to ensure no interference from incoming signals, before triggering HIGH
  delayMicroseconds(2);
  digitalWrite(TOP_TRIG, HIGH);           // Send outs ultrasonic wave
  delayMicroseconds(10);                  // Delay as speicifed by datasheet
  digitalWrite(TOP_TRIG, LOW);            
  duration = pulseIn(TOP_ECHO, HIGH);     // Calculates time taken to receive signal from reflected signal, pulse is LOW when signal is received
  TOP = (duration/2) / 29.1;              // Calculates distances using the time calculated above and the speed of sound (300m/s)
  digitalWrite(FRONT_TRIG, LOW);
  delayMicroseconds(2);
  digitalWrite(FRONT_TRIG, HIGH);
  delayMicroseconds(10);
  digitalWrite(FRONT_TRIG, LOW);
  duration = pulseIn(FRONT_ECHO, HIGH);
  FRONT = (duration/2) / 29.1;  
  digitalWrite(RIGHT_TRIG, LOW);
  delayMicroseconds(2);
  digitalWrite(RIGHT_TRIG, HIGH);
  delayMicroseconds(10);
  digitalWrite(RIGHT_TRIG, LOW);
  duration = pulseIn(RIGHT_ECHO, HIGH);  
  RIGHT = (duration/2) / 29.1;
  digitalWrite(LEFT_TRIG, LOW);
  delayMicroseconds(2);
  digitalWrite(LEFT_TRIG, HIGH);
  delayMicroseconds(10);
  digitalWrite(LEFT_TRIG, LOW);
  duration = pulseIn(LEFT_ECHO, HIGH);
  LEFT = (duration/2) / 29.1;
  
// The following lines are the conditions that print the flight directions for the drone based on spatial data
    if (TOP < 50) {   
     PrintCommand(old_command, 'T');                      // If the TOP sensor detects an object less than 50cm from it
     old_command = 'T';  
     Serial.println('T');
     Serial.println("\n");     		  // It will print the character T on a new line on the serial monitor if it is different from the previous command
     }    
     else{                                                // If the TOP sensor does not detect an obstacle it will continue to the following      
       if ((RIGHT < 70) && (FRONT > 90)) {                // If the RIGHT sensor detects an object less than 90cm and FRONT sensor is greater than 90cm then to print L
        PrintCommand(old_command, 'L');			  // It will print the character L on a new line on the serial monitor if it is different from the previous command
        old_command = 'L';					  
       }
       if ((LEFT < 70) && (FRONT > 90)) {
	PrintCommand(old_command, 'R');
        old_command = 'R';	
       }                                                  // If the FRONT sensor detects an object less than 70cm it will print either of the following
       if (FRONT > 90 ) {
       PrintCommand(old_command, 'F');
       old_command = 'F';
       }   
       if (FRONT >= 7 && FRONT <= 40) {
	PrintCommand(old_command, 'S');
        old_command = 'S';
        Serial.println('S');
        Serial.println("\n");
       }    
       else {
       if ((LEFT < RIGHT) && (FRONT >=10 && FRONT <=79)) {
       PrintCommand(old_command, 'P');
       old_command = 'P';
        }
       if ((LEFT > RIGHT) && (FRONT >=10 && FRONT <=79)) {
       PrintCommand(old_command, 'Q');
       old_command = 'Q';                	                 	            			           
         } 
      }
   }
}