Biology Reference
In-Depth Information
Fig. 5.12 A diagrammatic representation of a system with feedback control (Reproduced from
Control System
Controller
Goal
information
Representation
Agent
Perception
Action
Controlled
Observed
Variable
Affected
Variable
Dynamics
Disturbance
Fig. 5.13 The structure and function of a control system (Adapted from
http://pespmc1.vub.ac.be/
the new input either negatively (leading to negative feedback) or positively (leading
to
positive feedback
). In other words, feedback control is achieved when a portion of
the output signal is operated on and fed back to the input in order to obtain a desired
effect. A controller monitors its effect on the system and modifies its output
accordingly. As an example, consider a thermostat. It has two inputs: the desired
temperature or the reference and the current temperature (the latter is the feedback).
The output of the thermostat changes in order to equalize the two inputs.
A more detailed diagram of the
control system
is given in Fig.
5.13
. It consists of
two subsystems -
the controller
or
controlling system
(denoted as C) and
the
controlled
or
controlled system
(S). The interaction between C and S is asymmetric
in that C has a complete control over S, to the extent of destroying the controlled.
