Control System

Control system is that means by which any quantity of interest in a machine, mechanism or other equipment is maintained or altered in accordance with a desired manner.
Control system can also be defined as the combination of elements arranged in a planned manner wherein each element causes an effect to produce a desired output.
Figure shows the general diagrammatic representation of a typical control system. For the automobile driving system, the input (command) signal is the force on the accelerator pedal which through linkages causes the carburettor value to open (close) so as to increase or decrease fuel (liquid form) flow to the engine bring the engine-vehicle speed (controlled variable) to the desired value.

The diagrammatic representation of above figure is known as block diagram representation wherein each block represents an element, a plant, mechanism, devices etc., whose inner details are not indicated. Each block has an input and output signal which are linked by a relationship characterizing the block. It may be noted that the signal flow through the block is unidirectional.