What is the use of servo motor encoder?！

Why is servo motor as a power source used with an encoder?

Servo motor without encoder can not  be used?
Yes, but the effect of control will certainly not be good.

1. Can remember the pole position of the motor, the servo drive according to the pole position to the best control of the servo motor.
2. Speed closed loop and position closed loop to achieve precise speed control and precise position control.

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