Re: [asa] Guided evolution mechanism?

Christine Smith wrote:
> Can someone provide some more background on "control theory"?
>
>
Christine:

Look at
http://en.wikipedia.org/wiki/Control_theory
for a good description of Control theory is.

 From wiki, a typical control application looks like:
<http://en.wikipedia.org/wiki/Image:Feedback_loop_with_descriptions.svg>
<http://en.wikipedia.org/wiki/Image:Feedback_loop_with_descriptions.svg>
The concept of the feedback loop to control the dynamic behaviour of the
system: this is negative feedback, because the sensed value is
subtracted from the desired value to create the error signal which is
amplified by the controller.
...

Take the case of a car cruise control. The Reference is the desired
speed. The controller interacts with the car system by changing the
position of the throtle. The speedometer (logically) is the sensor and
feeds the actual speed back to the Measured error point where it is
subtracted from the desired speed and feed into the controller.

Of course the actual system is likely to be more complex than I have
described in that the difference between the reference speed and the
actual speed is likely allowed to reach some small difference prior to
actually increasing/decreasing the throttle. Otherwise one would likely
get surging where the fuel going to the engine was constantly being
changed.

The study of the behaviors of such systems is called control theory and
is quite complex in many cases as instabilities can tend towards
oscillations or vary large values.

Feedback is a very powerful mechanism and I tend to think of the
Variation/Natural Selection mechanism in those terms.
  
Dave W

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Received on Wed Nov 12 13:39:48 2008