Basics Of The Servo Motors And Drives

Servo motors are independent electric devices that accurately rotate or push parts of a machine. Servo motors and drives can be found in a variety of applications, from kids toys to cars and airplanes. If you have a radio-controlled model helicopter or a car, there are at least several servo motors included. The servo regulates the speed by rotating the shaft connected to the engine of a car or airplane. Servo motors have been introduced many years ago and their range of applications is vast. They find use in industrial applications, robotics, manufacturing plants (conveyors), solar tracking systems, food and pharmaceutics services.


Servos appear to be included in various devices we use on a daily basis. For example, the new car models use servo motors and drives to manage the speed, as the gas pedal sends an electrical signal to tell the computer how fast should the vehicle move. The computer processes received information and information received from other sensors and then sends a signal to the servo attached on the throttle of the engine which adjusts the engine speed.

While many would say that the working principle of servo motors is difficult, it couldn’t be any simpler. And we all know that simplicity equals reliability. The main part of a servo motor is a small DC motor, running on electricity from a battery. Servo motors and drives spin at very high RTM, but provide a very low torque. A proper arrangement of gears takes the high speed of the motor and slows it down in order to increase the torque

The most recognizable characteristic of servo motors and drives is the ability to control position with rapid response to varying disturbances and commands. Although there are some servo applications that do not need quick acceleration, most applications that use servos usually cycle a motor from one to another position at high rates. For instance, web-handling applications do not require big accelerations during normal operation, as they try to hold a constant velocity regardless of the torque disturbances.

To close control loops, servo systems use feedback devices to send feedback signals. These feedback devices are usually independent components, connected mechanically to the motor (resolvers or encoders). But lack of separate feedback devices doesn’t automatically mean that a system is not servo operated. In some cases, thee feedback device may be present but not identified. One example can be the head-positioning servo motor of a HDD, which uses built-in feedback signals into the disk rather than using a separate feedback sensor.