Description
Any means, natural or artificial, by which a variable quantity or set of quantities is caused to conform, more or less accurately, to some prescribed norm which may either be a constant value or values which vary in prescribed ways. Control systems may be considered as a mix of two extreme types, namely intrinsic, in which the controls are part of the system under control, and extrinsic, in which the controls are external to the system under control or only loosely linked to it.