# Control Theory

Control theory is an interdisciplinary branch of engineering and mathematics that deals with the behavior of dynamical systems with inputs. The external input of a system is called the reference. When one or more output variables of a system need to follow a certain reference over time, a controller manipulates the inputs to a system to obtain the desired effect on the output of the system.

The usual objective of a control theory is to calculate solutions for the proper corrective action from the controller that result in system stability, that is, the system will hold the set point and not oscillate around it.

The inputs and outputs of a continuous control system are generally related by differential equations. If these are linear with constant coefficients, a transfer function relating the input and output can be obtained by taking their Laplace transform. If the differential equations are nonlinear and have a known solution, it may be possible to linearize the nonlinear differential equations at that solution. If the resulting linear differential equations have constant coefficients one can take their Laplace transform to obtain a transfer function.

The transfer function is also known as the system function or network function. The transfer function is a mathematical representation, in terms of spatial or temporal frequency, of the relation between the input and output of a linear time-invariant solution of the nonlinear differential equations describing the system.

Extensive use is usually made of a diagrammatic style known as the block diagram.

### Other articles related to "control theory, theory, control":

Lennart Ljung - Background, Present Appointments and Scientific Contributions
... and a position as an Associate Professor (Docent) in Control Theory at Lund University in 1975-1976, Lennart Ljung was elected as a Professor in the Chair ... He has made extensive contributions to control theory, particularly in the area of system identification ...
Systems Science - Fields
... Systems sciences cover formal sciences like dynamical systems theory and applications in the natural and social sciences and engineering, such as social systems ... Chaos theory Complex systems Complex system Cybernetics Biocybernetics Engineering cybernetics Management cybernetics Medical cybernetics New Cybernetics Second-order cybernetics Control theory Affect ...
Control Theory - Main Control Strategies
... Every control system must guarantee first the stability of the closed-loop behavior ... Non-linear control systems use specific theories (normally based on Aleksandr Lyapunov's Theory) to ensure stability without regard to the inner dynamics of the system ... fulfill different specifications varies from the model considered and the control strategy chosen ...
Affect Control Theory - Emotions
... According to affect control theory, an event generates emotions for the individuals involved in the event by changing impressions of the individuals ... emotions have been derived in empirical studies Affect control theory's computer simulation program uses these equations to predict emotions that arise in social interaction, and displays the predictions via facial ... Based on cybernetic studies by Pavloski and Goldstein, that utilise Perceptual Control Theory, Heise hypothesizes that emotion is distinct from stress ...
Affect Control Theory
... In control theory (sociology) affect control theory proposes that individuals maintain affective meanings through their actions and interpretations of events ...

### Famous quotes containing the words theory and/or control:

The things that will destroy America are prosperity-at-any- price, peace-at-any-price, safety-first instead of duty-first, the love of soft living, and the get-rich-quick theory of life.
Theodore Roosevelt (1858–1919)

Knowledge in the form of an informational commodity indispensable to productive power is already, and will continue to be, a major—perhaps the major—stake in the worldwide competition for power. It is conceivable that the nation-states will one day fight for control of information, just as they battled in the past for control over territory, and afterwards for control over access to and exploitation of raw materials and cheap labor.
Jean François Lyotard (b. 1924)