Servomechanism, << `sur` voh MEHK uh nihz uhm, >> is a type of control system that automatically corrects errors in the position, velocity, or acceleration of an object. Industry uses servomechanisms to control automatic machines such as robots.
In a servomechanism, a sensing device measures the characteristic to be controlled—the position, velocity, or acceleration of an object. This device then sends a signal representing this characteristic to another device, called a controller. The controller produces a signal that represents the desired position, velocity, or acceleration and compares this signal with the signal from the sensing device. The difference between the signals, known as the error signal, is used to control the object until the error signal approaches zero. For example, the automatic flight control system used in airplanes has a servomechanism that compares the desired course of the airplane with the actual course. The error signal represents any difference between the two, and is used to operate the controls of the airplane until it is back on course. When the airplane is on course, the error signal is zero. See Automatic flight control system (AFCS) .
Much early development of servomechanisms occurred during World War II (1939-1945). Servomechanisms on warships, for example, used signals from radar antennas to aim antiaircraft guns.
See also Automation .
