Servo motor is mainly used for precise positioning and servo control, which is actually the position control of servo motor. In fact, the servo motor also uses two other working modes, namely speed control and torque control.

Speed control is generally realized by frequency converter. Servo motor is used for speed control, which is generally used for fast acceleration and deceleration or speed precise control occasions. Because relative to frequency converter, servo motor can achieve several thousand revolutions within a few millimeters. Because servo is closed-loop, the speed is very stable. Torque control is mainly to control the output torque of servo motor, also because of the fast response of servo motor.

The most important application of servo motor is positioning control. Position control is speed and position. Specifically, it is to control how fast the servo motor reaches where and exactly stops.

PLC controls the servo motor by controlling the transmitted pulse. It is the most commonly used way to send the pulse by physical means, that is to say, using the transistor output of PLC, which is generally adopted by low-end PLC. The medium and high-end PLC transmits the number and frequency of pulses to the servo driver through communication.
These two ways are just different channels of realization, but the essence is the same.