[David Goldstein (2014.01.19.14:020]
I am re-posting this.
Quotes,
and Comments about Living Control Systems III: The Fact of Control
David
M. Goldstein, Ph.D.
About the Author: iv to v. Isnât the quote âIâve
always been pretty much a blue-collar type, by training and by preferenceâ?
interesting. I wouldnât have expected this from a theoretician.
Forward: xi to xiii: â
that negative feedback
control is the ingredient that has been mmissing from the life sciences for as
long as they have existed
/span>
â
They control. They never produce any behavior
exceptt for the purpose of making what they are experiencing become more like
what they intend or want to experience, and then keeping it that way even in a
changing world.â?
âIf they plan, they plan perceptions, not actions.
If they respond to stimuli, they do so in order to prevent those stimuli from
affecting variables they have under control.â?
âTo me, this theory is beautiful, not because it is mine
but because it is true.â?
Chapter 1: Concepts of Control
Page 1: âTo control something is to act to bring it
to a specified condition, and then maintain it close to that condition even if
unpredictable external forces and changes in environmental properties tend to
alter it.â?
MCT:
ANALYZE-COMPUTE-ACT CONTROL
Input
leads to actions which leads to the desired result.
The engineers in the Apollo 13 mission had to figure out how to reduce the CO2
level with something that the astronauts could build; they came up with a
system that worked.
Page 3 ââ¦get the flavor of all the little problems
that arise in trying to build a system that, all by itself, can analyze the
environment, compute how to achieve a prescribed result, and then act on the
environment in exactly the calculated way.â?
Problem: controlling the speed of a car. Bill goes
through all the forces acting on the car. The problem is that the net force
acting on the car changes as the car moves over the terrain.
PERCEIVE-COMPARE-ACT
CONTROL
Page 7: âNegative feedback control as used in PCT
can be summed up very quickly. It involves continuously perceiving the current
state of whatever is to be controlled, continuously comparing that perception
with the intended state, and continuously acting to reduce the difference
between perceived and intended states , keeping the difference as close to zero
as possible.â?
Page 9: âA negative feedback controller, or
perceive-compare-act controller, or PCT controller doesnât have to know what is
causing the speed to change.â?
âMost of what has been said in the literature of the
life sciences about limitations of negative feedback control is simple false.â?
SIMULATION
AND MODELING
The two ways of calculating the time to fill a
bucket is discussed.
Simulation is advocated over analytical solutions.
Readers may want to download a free version of
VenSim:
http://www.shodor.org/tutorials/vensim/pre.php
and follow a simulation of how a temperature control system works
in Vensim:
http://plaidcircuitry.com/computational_thinking/vensim/index.html
SOME
PHILOSOPHY OF SCIENCE
Page 17: â
the way that collections of materials
behave depends as much on how they are organized as on what the materials are.â?
âYou canât cause a mouse to jump in the air by
itself if it doesnât want to.â?