servomechanism

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.

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servomechanism

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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servomechanism

a mechanical or electromechanical system for control of the position or speed of an output transducer. Negative feedback is incorporated to minimize discrepancies between the output state and the input control setting

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Servomechanism

A system for the automatic control of motion by means of feedback. The term servomechanism, or servo for short, is sometimes used interchangeably with feedback control system (servosystem). In a narrower sense, servomechanism refers to the feedback control of a single variable (feedback loop or servo loop). In the strictest sense, the term servomechanism is restricted to a feedback loop in which the controlled quantity or output is mechanical position or one of its derivatives (velocity and acceleration). See Control systems

The purpose of a servomechanism is to provide one or more of the following objectives: (1) ac­curate control of motion without the need for human attendants (automatic control); (2) maintenance of accuracy with mechanical load variations, changes in the environment, power supply fluctuations, and aging and deterioration of components (regulation and self-calibration); (3) control of a high-power load from a low-power command signal (power amplification); (4) control of an output from a remotely located input, without the use of mechanical linkages (remote control, shaft repeater).

The illustration shows the basic elements of a servomechanism and their interconnections; in this type of block diagram the connection between elements is such that only a unidirectional cause-and-effect action takes place in the direction shown by the arrows. The arrows form a closed path or loop; hence this is a single-loop servomechanism or, simply, a servo loop. More complex servomechanisms may have two or more loops (multiloop servo), and a complete control system may contain many servomechanisms. See Block diagram

Servomechanisms were first used in speed governing of engines, automatic steering of ships, automatic control of guns, and electromechanical analog computers. Today, servomechanisms are employed in almost every industrial field. Among the applications are cutting tools for discrete parts manufacturing, rollers in sheet and web processes, elevators, automobile and aircraft engines, robots, remote manipulators and teleoperators, telescopes, antennas, space vehicles, mechanical knee and arm prostheses, and tape, disk, and film drives. See Computer storage technology, Flight controls, Remote manipulators, Robotics