German: Regelkreis
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Definition
Information processing structures consisting in a control process with inclosed degenerative feedback are referred to as feedback control system. Feedback control thus permits that vitally important parameters of body function like osmolality, pH and Oxygen-tension as well as plasma level of hormones and body temperature remain constant or in a compliant range.
Example
Example of a 0th order linear feedback control system with load:
e(t) = x(t) - yR(t)
yS(t) = V1 e(t) = V1 [x(t) - yR(t)]
y(t) = yS(t) + z(t) = V1 [x(t) - yR(t)] + z(t)
yR(t) = V2 y(t)
y(t) = V1 x(t) - V1 V2 y(t) + z(t)
y = [V1 x + z] / [1 + V1 V2]
x: set point, e: error, y: controlled variable, yS: manipulated variable, yR: measured variable, z: load, disturbance variable, V1: amplification factor of direct branch, V2: amplification factor of feedback path.
Physiology
Feedback control systems play essential roles in the organism. Examples are:- Osmoregulation
- corticotropic feedback control
- gonadotropic feedback controls
- homeostasis of blood glucose level
- control of blood pressure
- control of respiration
- thyrotropic feedback control
Background
Physiological systems theory, a subsection of medical cybernetics deals with mathematical description and analysis of feedback control systems and other information processing structures.
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