Control theory is
- a theory that deals with influencing the behavior of dynamical systems
- an interdisciplinary subfield of science, which originated in engineering and mathematics, and evolved into use by the social sciences, like psychology, sociology, criminology and in the financial system.
Control systems can be thought of as having four functions; Measure, Compare, Compute, and Correct. These four functions are completed by five elements; Detector, Transducer, Transmitter, Controller, and Final Control Element. The measuring function is completed by the detector, transducer and transmitter. In practical applications these three elements are typically contained in one unit. A standard example of a measuring unit is a Resistance thermometer. The compare and compute functions are completed within the controller which may be completed electronically through a Proportional control, PI Controller, PID Controller, Bistable, Hysteretic control or Programmable logic controller. Older controller units have been mechanical, as in a Centrifugal governor or a Carburetor. The correct function is completed with a final control element. The final control element changes an input or output in the control system which affect the manipulated or controlled variable.
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