The document discusses AC servomotors. It defines a servomotor as a rotary actuator that allows precise control of position, velocity, and acceleration using a motor, position sensor, and controller. Servomotors are used in closed-loop control systems. The document describes the key components of a typical servo system and explains how the motor works with a controller and amplifier to receive position commands from a PLC. It provides details on the construction and speed-torque characteristics of AC servomotors that make them suitable for servo applications.