Feedback control

Synonyms: control circuit, control loop, closed-loop control, feedback interaction
German: Regelkreis

1 Definition [edit]

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.

2 Example [edit]

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.

3 Physiology [edit]

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

4 Background [edit]

Physiological systems theory, a subsection of medical cybernetics deals with mathematical description and analysis of feedback control systems and other information processing structures.

5 External Link [edit]

• Information processing structures at medical-cybernetics.de