Motion Control Systems Integrator
Servo Motors

Servo Motors – Overview

A servo motor is an electrical motor with precision feedback and movement that allows for very fine position and speed control. These motors can be positioned precisely by controlling how far and at what speed the shaft rotates. They are controlled with circuitry that provides negative feedback, making them self-correcting. This maintains repeatable operation, achieving the same rotational angle every time, if necessary. Such an approach makes them suitable to actuate mechanical linkages or levers to produce movement, like robot arms and flight simulator platforms.

Motion controllers send and receive signals to and from the motor drive, checking the rotation angle and speed of the output shaft, and then sending corrections back to the motor. Motion controllers are programmable devices that generate commands to the servo motor to perform a particular rotation, at a particular speed and at a particular time. These command signals are sent to a servo drive, which is a device that processes, filters and amplifies the command signals to match the input levels for the servo motor.

Some servo motors only rotate a certain amount because they do not need to rotate in a complete circle to perform their job. Others can rotate continuously, and are used for steering or drive applications that require fine control of output speed or repositioning of the shaft.

Examples of common servo motors are those seen on radio controlled models that control steering or altitude. A controller signal commands the servo motor to rotate to a particular angle. The motor rotates to that angle and stops, in the process moving an actuating lever attached to the output shaft, which will push linkage to steer the car or move the elevator surfaces on the plane.

A less commonly seen type of servo motor is the linear servo motor. These motors have the same design characteristics of the rotary servo motor, but instead of providing rotation, they provide movement in a straight line Linear servo motors allow for very precise linear positioning, since the linear movement is produced directly from the linear motor, and there is no mechanical translation from rotary to linear movement.

This type of servo motor is seen in CNC laser and EDM machining centers.