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What is a servomechanism? How Servo works?

Updated on December 15, 2012

Servomechanisms and servo motors have got wide rage of applications. A Servo mechanism is a closed loop electro mechanic system. This mechanism will the control action or output automatically depending upon the desired result.The performance of a mechanism will be corrected and controlled by error sensing negative feedback signals used in the servomechanism.

Types of servomechanism

There are many types of servomechanisms available for different applications. They are classified based on its functions or based to the type of drive motor which is used in it. Under functional classification there are two types of servomechanisms viz. Positioning servos & velocity servos. In response to input command signal the positioning servos will produces required output positions of shaft. Whereas in case of velocity type of servos, input signal will produce required output velocity of shaft.

AC & DC servo motors

Servomechanisms are also classified based on their input power as AC and DC servos. The DC servo motor is a variable speed motor. Output speed and armature current of a DC motor is linear i.e. the output speed increases when the armature current increases and output speed decreases when the armature current decreases. Speed of the motor can be changed smoothly by changing the armature current. We can also change the rotation from clockwise to anticlockwise or vice versa by changing reversing the direction of current in the armature. We can get higher torque in DC motors compared to AC servo motors.

AC servomotors are used where constant speed is desired. AC motors has got some advantages over DC motors. AC motors doesn’t require brushes and commutators which are used in DC motors. This reduces the maintenance and other problems at a large extent.Servo amplifiers used in AC motors usually have less drift compared to amplifiers used in DC servo motors. The selection of servomotor and servomechanism is completely based on the applications.


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