Do servo motors need to be controlled by PLC?

Early PLCs (Programmable Logic Controllers) did not have motion control functions and were only used as logic controllers, as can be seen from their name. Even now, servo motors do not necessarily require the use of PLC for control.
In some simple scenarios, servo motors can independently control the mechanism without the need for PLC pulses. The internal position mode of some servo drives can be controlled through the touch screen, and there is no need for PLC to send pulses. For example, our PLS (Programmable Logic Servo) actually integrates the PLC interpreter into the servo system.
In addition, servo can also be controlled through motion controllers, boards, CNC, and PCs. However, in most cases, servo motors still need to be used in conjunction with PLCs to achieve precise motion control. When controlling servo motors, PLC needs to perform initialization settings, motion control, feedback monitoring, and fault handling. Through these operations, PLC can ensure that the servo motor moves according to the predetermined trajectory and speed, while monitoring the status of the motor and taking corresponding measures in case of faults.

Not necessarily. In fact, PLC has never been the direct controller of servo motors. A servo motor is driven by a servo driver, also known as a servo amplifier. PLC controls the servo driver through PTO (pulse train) or communication (bus, serial port, etc.), and the servo driver then controls the servo motor to move.
In industry, large companies such as Siemens, Mitsubishi, SEW, and Lenz all have their own servo drive products. Servo drives and servo motors are used in conjunction, and generally, motor and encoder cables are ready-made products that can be purchased according to demand. In some low demand situations, microcontrollers can also be used to send signals to servo drives, and in this case, PTO signals are generally used. There are many stepper motor drivers on the market that are used to control stepper motors, which are different from servo motors.