In most modern servo motor controls, what has replaced servo amplifiers as the controlling system?

• A. Servo motor controllers
• B. Inverter drives
• C. Microprocessors
• D. PLC units

Answer: (A)

A servo motor controller is what now handles the closed‑loop control and sends precise drive commands to the motor. Modern servo systems place the control logic—processing encoder feedback, running the position and velocity loops, applying feedforward or trajectory commands—inside the controller (often integrated with the drive). That controller does the thinking and the command generation, while the power stage supplies the actual current to the motor. This replaces the older setup where a separate servo amplifier was the primary controlling device.

Inverter drives are geared more toward general speed control of motors without the tight, encoder-based position control that servos require. Microprocessors are the brains inside the controller or drive, not the standalone controlling system themselves. PLCs handle higher‑level sequencing and coordination, not the direct servo loop. So the device that replaces the servo amplifier as the controlling element is the servo motor controller.