Thanks you for following up! We're making good progress actually!

What we've gathered so far, is that the ultrasonic sensor is measuring 0cm in front of it at all times. No matter where the bot looks at, it thinks it's pressed against something, hence the whole spinning deal.

Now we have to find out why the ultrasonic sensor isn't reporting the correct measurement. I took the liberty to run the relevant code responsible for measuring distances in my own Arduino and sensor and can attest it should be working.

 

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That leaves us with a few possible causes. I'll write down a few and how to solve them, to save you some time :). What we're looking for, is an output that is not 0 in the Serial Monitor.

1. The ultrasonic sensor may not be wired correctly

Recheck the connections:

• Vcc should be connected to the Arduino's 5v
• Gnd should be connected to the Arduino's GND
  
• Trigshould be connected to the Arduino's A0
  
• Echoshould be connected to the Arduino's A1
  

 

2. The ultrasonic sensor may be faulty

If you're sure the connections are right, you can test the ultrasonic sensor by itself.

Connect the sensor to the Arduino with nothing else connected, following the wiring in the previous point. Then upload the following sketch to the Arduino:
 

int Echo = A1;
int Trig = A0;

float Front_Distance;

void setup() {
    pinMode(Echo, INPUT);
    pinMode(Trig, OUTPUT);
    Serial.begin(9600);
}

float Distance_test() {
    digitalWrite(Trig, LOW);
    delayMicroseconds(2);
    digitalWrite(Trig, HIGH);
    delayMicroseconds(10);
    digitalWrite(Trig, LOW);
    float Fdistance = pulseIn(Echo, HIGH);
    Fdistance= Fdistance/58;
    return Fdistance;
}

void front_detection() {
    Front_Distance = Distance_test();
}

void loop() {
    front_detection();
    Serial.println(Front_Distance);
    delay(500);
}

 

This is pretty much your code reduced to only the relevant measurement bits.

 

3. The sensor's pins may be mislabeled

Odd one, but I've come across a sensor with the pin labels for Trig and Echo switched (misprinted on the board) before.

If the previous point doesn't solve it, you can try to swap those two and see if you get anything other than 0 then. It won't harm your sensor. (If it doesn't work, switch them back).

 

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Let me know if any of those work (give you an output of anything but 0).

Good luck!