DC servo motors are divided into brushless and brushless motors.

Brush motor has low cost, simple structure, large starting torque, wide speed range, easy control and maintenance, but it is easy to maintain (carbon brush replacement), produces electromagnetic interference, and has requirements for the use environment. It is usually used in cost-sensitive ordinary industrial and civil occasions.

Brushless motor has the advantages of small size, light weight, large output, fast response, high speed, small inertia, stable rotation and smooth torque, complex control, intellectualization, flexible electronic commutation mode, square wave or sinusoidal wave commutation, maintenance-free motor, high efficiency and energy saving, small electromagnetic radiation, low temperature rise and long life, and is suitable for various environments.

AC servo motor is also a brushless motor, which is divided into synchronous and asynchronous motors. At present, synchronous motor is commonly used in motion control. Its power range is large, its power can be large, its inertia is large, its maximum speed is low, and its speed decreases uniformly with the increase of power. It is suitable for low-speed and stable operation.

The internal rotor of the servo motor is a permanent magnet. The driver controls the U/V/W three-phase electricity to form an electromagnetic field. The rotor rotates under the action of this magnetic field.

At the same time, the encoder of the motor transmits the feedback signal to the driver, and compares the feedback value with the target value, so as to adjust the rotation angle of the rotor. The accuracy of the servo motor depends on the accuracy of the encoder (line number).