from machine import Pin, PWM
from utime import sleep, sleep_ms

servo=PWM (Pin (21), freq=50)
servo1=PWM (Pin (19), freq=50)
servo2=PWM (Pin (18), freq=50)

while True:
      for i in range(1800, 8800):
        servo.duty_u16(i)
        sleep_ms(1)
        servo1.duty_u16(i)
        sleep_ms(1)
        servo2.duty_u16(i)
        sleep_ms(1)