servomechanism

A servomechanism: sometimes shortened to servo , is an automatic device that uses error- sensing negative feedback to correct the performance of a mechanism. The term correctly applies only to systems where the feedback or error- correction signals help control mechanical position, speed or other parameters. For example, an automotive power window control is not a servomechanism, as there is no automatic feedback that controls position—the operator does this by observation. By contrast the car's cruise control uses closed loop feedback, which classifies it as a servomechanism.

Uses:> Position control
>Speed control