With the development of technology, man has learnt to use very reliable and accurate systems that require least manpower. Automatic control systems are one such development. Control is defined as the science of regulation of a parameter by comparing it with a standard value. This is the aim of an automatic control system. They constantly monitor the output of system and if this output is found to deviate from the desired value, it produces a control signal that server to bring down the change by providing a driving energy to the component that is responsible for the deviation.

Description: typical control system

A system is said to be made of a number of components such that the behaviour of the overall combination can be predicted if

1. the behaviour of the each component can be predicted, and
2. the interaction between each component is known.

Hence, a system is obtained when a number of components are connected in a sequence to perform a specific function. Suppose in a system, the output quantity is controlled by altering the input quantity, then such a system is called control system.

The output quantity is called the controlled variable and the input quantity is called the input signal. Automatic control system have become an integral part of modern manufacturing and industrial processes.

Examples:

manufacturing industry : numerical control of machine tool.

Industrial process : control of pressure, temperature and flow.