servomechanism, automatic device for the control of a large power output by means of a small power input or for maintaining correct operating conditions in a mechanism. It is a type of feedback control system. The constant speed control system of a DC motor is a servomechanism that monitors any variations in the motor's speed so that it can quickly and automatically return the speed to its correct value. Servomechanisms are also used for the control systems of guided missiles, aircraft, and manufacturing machinery.

Device used to correct the performance of a mechanism automatically, by means of error-sensing feedback. The term properly applies only to systems in which the feedback and error-correction signals control mechanical position or velocity. Servomechanisms were first used in military and marine navigation equipment. Today they are used in automatic machine tools, satellite-tracking antennas, celestial-tracking systems on telescopes, automatic navigation systems, and antiaircraft-gun control systems. The design of servomechanisms is considered to be a branch of both robotics and cybernetics.

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