#include <Servo.h>  

Servo ATL1; 
Servo ATL2;
Servo ATL3;
int pos = 0;    

void setup() {
  ATL1.attach(9);  
  ATL2.attach(10);
   ATL3.attach(8); 
   
}

void loop() {
   
  for (pos = 0; pos <= 180; pos += 1) { 
                                        
    ATL1.write(pos);   
    ATL2.write(180-pos);   
    ATL3.write(pos*2);    
    delay(15);                    
  }
  for (pos = 180; pos >= 0; pos -= 1) { 
    ATL1.write(pos);   
    ATL2.write(180-pos);
    ATL3.write(2*pos);            
    delay(15);                      
  }
}