The so-called servo, in fact, is the most common servo motor system, so the English name is Servo, which is short for Servomotor. It compares the PWM signal with the voltage of the sliding rheostat and implements a position control of the fixed control gain through the hardware circuit. That is, it contains the motor, sensor, and controller and is a complete servo motor (system). The price is low and the structure is compact, but the accuracy is very low, and the position is poor in the ability to calm and can meet many low-end requirements.