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Control System Theory Explained

written by: Swagatam • edited by: Rebecca Scudder • updated: 3/23/2011

The objective of a control system is to control the output of some process in the prescribed manner by sending the input through the elements of the control system. These elements will perform the control action on the input signal to keep the output signal at the desired level.

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    Origin Of Control Systems

    Early people relied upon their muscle power or used animals for doing work, which took a lot of energy. Simple mechanical devices such as wheels and levers were later used to ease their workload.

    Power from natural resources was utilized to drive ships, windmills, and water wheels to supplement the human energy. Since then, slow and steady progress was made in the design and development of devices to allow people to utilize power in a convenient way. These early devices predominantly had manual controls. Soon, it was felt that manual control of machines and equipment was very monotonous.

    Further, control of some machines was beyond the physical ability of human beings. Thus the theory of control systems for controlling machines and equipment by themselves was thought of. The first significant work came in the form of automatic control of a centrifugal governor for the speed control of steam ships.

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    Need for Control Systems

    An average human being is capable of performing a wide range of tasks, including decision making. Some of these tasks, such as picking up objects or walking from one point to another, are normally carried out in a routine fashion.

    Under certain conditions, some of these tasks need to be performed in the best possible way. For instance, an athlete running a 100 yard dash has the objective of running that distance in the shortest possible time. A marathon runner, on the other hand, not only must run the distance as quickly as possible, but in doing so he or she must control the consumption of energy so that the best result can be achieved.

    Therefore, we can state in general that in life there are numerous “objectives" that need to be accomplished, and the means of achieving the objective usually involve the need for a control system.

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    Uses Of Control Systems

    Business control systemBoiler control System using PLCBoiler Local Control PannelEngine Control Room in shipsShips Bridge Control for  steering
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    Modern Control System:

    Precision Irrigation Control SystemControl system used in engine assembly
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    Control System Theory

    The theory of control systems has assumed an increasingly important role in the development and advancement of modern civilization and technology. Practically every aspect of our day-to-day activities is affected by some type of control system.

    For example:

    In the domestic realm, automatic controls in heating and air-conditioning systems regulate the temperature and humidity of homes and buildings for comfortable living.

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    Embedded Control Systems

    To achieve maximum efficiency in energy consumption, many modern heating and air-conditioning systems in large offices and factory buildings are computer controlled by embedded, or built-in, control systems called Programmable Logic Control or PLC.

    Control systems are found in abundance in all sectors of industries: such as the quality control of manufactured products; automatic assembly lines; machine-tool controls; space technology; as well as weapon systems; computer control; transportation systems; power systems; robotics; and many other fields. Even such problems as inventory control and economic systems control may be approached from the theory of automation controls.

    In recent years automatic control systems have become an increasingly important part of modern technology. It is a very strong problem solving discipline. There are a variety of computer systems that require sophisticated control strategies to achieve acceptable performance with in an uncertain environment.

    Automatic control systems find increasing application in manufacturing, process industries, aircraft control, space research, navigation, biomedical engineering, etc. In a sense the advent of automatic control represents a second industrial revolution. Automatic control systems are physical systems which have dynamic behavior.

    The study of control is not only concerned with engineering applications, but also extends to other areas like economics, business, and other political systems.

    Image Credit:

    US-CONTROL: Control Systems

    Industrial Boiler Control Package

    Real Control Systems

    MV Arcadia

    SCADA Irrigation Management Systems

    Total Quality Management

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    References

    Book: Modern Control System Theory and Design, By Stanley M. Shinners, Control Systems Theory and Applications, By Eric Rogers, Krzysztof Galkowski, David H. Owens

    Modern Control System Theory, By M. Gopal,

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