Closed-loop transfer function
The scheme is a process in systems where interaction takes place ( in nature, control technology and society), and in which a principle variable (dynamic ) size usually is automatically kept constant or nearly constant. The term used in the science of this process is cybernetics, an interdisciplinary branch which established itself in the 40s of the 20th century. Founder of cybernetics was Norbert Wiener.
An important property of the spread encountered process scheme is that the value of the constant -held size is determined as the actual value ( measurement) and changed in case of deviation from the desired setpoint so that it approaches this again. Because the drift is counteracted by the setpoint, the feedback is negative feedback ( sign reversal ).
Examples of rules
- Nature: regulation of the body temperature of an animal
- Technology: control the speed of a machine
- Society: maintaining the value of a currency
Control of a size does not mean that the influence of disturbances are generally eliminated completely and quickly. Especially with larger disorder often occurs initially a noticeable change of the variable to be controlled, which decays only gradually and sometimes with reciprocating value (example: increased body temperature during illness). Often a small perturbation remains.
DIN - definition (technology)
The standard DIN IEC 60050-351:2009-06 defines the concept of control as follows:
" The rules that control is a process in which a continuously variable size, the control variable, recorded with another variable quantity, the reference variable, and is affected compared to the reference variable in the sense of approximation.
Related terms (technology)
Control is often confused with the control or considered identical. In the control but no feedback, and consequently no closed action flow is present.
In the English language the word control is used both for control and for control. To differentiate is to control closed-loop control and for control of open- loop control to use.