Synonyms: control circuit, control loop, closed-loop control, feedback interaction
Information processing structures consisting of a control process with degenerative feedback are referred to as feedback control systems. In living systems, feedback control systems permit that vitally important parameters of body function like body core temperature, pH and Oxygen-tension as well as plasma level of hormones and osmolality remain constant or in a compliant range. Today, feedback control systems find wide application in technology, e.g. in power plants, automotive systems, space flight, air conditioning or chemical industry.
Example of a 0th order linear feedback control system with load:
e(t) = x(t) - yR(t)
yS(t) = G1 e(t) = G1 [x(t) - yR(t)]
y(t) = yS(t) + z(t) = G1 [x(t) - yR(t)] + z(t)
yR(t) = G2 y(t)
y(t) = G1 x(t) - G1 G2 y(t) + z(t)
y = [G1 x + z] / [1 + G1 G2]
x: set point, e: error, y: controlled variable, yS: manipulated variable, yR: measured variable, z: load, disturbance variable, G1: amplification factor of direct branch, G2: amplification factor of feedback path.