Mini AGV as a Gas Decomposer using Fan with PID Control

#define MQ2pin (0)

int kanan1 = 4;
int kanan2 = 6;
int kiri1 = 7;
int kiri2 = 8;
int enA= 11;
int enB= 3;
int setpoint = 300;
int INA = 5;
int INB = 12;
float kp = 0.2;
float error, p, pid;
int sensorValue;

int IR1=9;   //kanan
int IR2=10;   //kiri

int speed = 70;
int speed2 = 150;

void setup(){
  Serial.begin(9600);
  pinMode(kanan1,OUTPUT);
  pinMode(kanan2,OUTPUT);
  pinMode(kiri1,OUTPUT);
  pinMode(kiri2,OUTPUT);
  pinMode(enA,OUTPUT);
  pinMode(enB,OUTPUT);
  pinMode(IR1,INPUT);
  pinMode(IR2,INPUT);
  pinMode(INA, OUTPUT);
  pinMode(INB, OUTPUT);
  Serial.begin(9600);
}

void loop(){
  int s1=digitalRead(9);
  int s2=digitalRead(10);
  sensorValue = analogRead(MQ2pin);
  Serial.print("GAS : ");
  Serial.print(sensorValue);
  Serial.println(" ppm");
  delay(10);
  error = setpoint - sensorValue ;
  p = error * kp;
//  pid = setpoint - p;
  if(p<=0){
    p = 0;
  }

  if (sensorValue > 300) {
    berhenti();
    for(int p = 0; p < 255; p++){
      analogWrite(INA, p);
      digitalWrite(INB, LOW);
      delay(10);
    }
  } else if (sensorValue < 300) {
    for(int p = 255; p > 0; p--){
      digitalWrite(INA, LOW);
      digitalWrite(INB, LOW);
    }
    //LURUS
    if(s1==LOW && s2==LOW)
    {
      maju();
    }
    //KANAN
    else if(s1==LOW&&s2==HIGH)
    {
      kanan();
    }
    //KIRI
    else if(s1==HIGH&&s2==LOW)
    {
      kiri();
    }
    //BERHENTI
    else
    {
      berhenti();
    }
  }
}

void maju() {
  Serial.println("maju");
  digitalWrite(kanan1, HIGH);
  digitalWrite(kanan2, LOW);
  analogWrite (enA, speed);
  digitalWrite(kiri1, HIGH);
  digitalWrite(kiri2, LOW);
  analogWrite (enB, speed);
  digitalWrite(INA, LOW);
  digitalWrite(INB, LOW);
}

void kanan() {
  digitalWrite(kanan1, HIGH);
  digitalWrite(kanan2, LOW);
  analogWrite (enA, speed2);
  digitalWrite(kiri1, LOW);
  digitalWrite(kiri2, LOW);
}

void kiri() {
  digitalWrite(kanan1, LOW);
  digitalWrite(kanan2, LOW);
  digitalWrite(kiri1, HIGH);
  digitalWrite(kiri2, LOW);
  analogWrite (enB, speed2);
}


void berhenti() {
  digitalWrite(kanan1, LOW);
  digitalWrite(kanan2, LOW);
  digitalWrite(kiri1, LOW);
  digitalWrite(kiri2, LOW);
}