Defining control

[From Bill Powers (950529.1410 MDT)]

It seems that all we have to do to distinguish the PCT meaning of
control from other meanings is to call it "negative feedback control."
My reference texts aren't very up-to-date, but this is what I found in
two of them:

Phillips, C. L. and Harbor, R. D. (1988). _Feedback control systems_.

     To control any physical variable, which we usually call a
     _signal_, we must know the value of this variable, that is, we
     must measure this variable. We call the system for the
     measurement of this variable a _sensor_... We define the _plant_
     of a control system as that part of the environment to be
     controlled. (p. 1)

Ogata, K. (1970) _Modern Control Engineering_.

     FEEDBACK CONTROL. Feedback control is an operation which, in the
     presence of disturbances, tends to reduce the difference between
     the output of a system and the reference input (or an arbitrarily
     varied, desired state) and which does so on the basis of this
     difference. Here, only unpredictable disturbances (i.e., those
     unknown beforehand) are designated for as such, since with
     predictable or known disturbances, it is always possible to
     include compensation within the system so that measurements are
     unnecessary.

Maybe some others can look up more definitions.

···

----------------------------------------------------------------------
-
Best,

Bill P.

<[Bill Leach 950530.02:03 U.S. Eastern Time Zone]

[From Bill Powers (950529.1410 MDT)]

To my shock and surprise, I only found one reference that properly
defined the term "control". The McGraw-Hill Electronics Engineers
Handbook does have a section entitled "Control Theory" and presents the
basic control loop in diagramatical form with which we are all so
familiar (including proper labeling).

All of the electronic "dictionaries" were abysmal in their treatment of
the term "control" or "control system".

The physics books and Dictionary for Science Writers that I have were
equally abysmal.

Unfortunately, even the term "negative feedback" is treated poorly for
our purposes. The problem of course is that for an amplifier that is
"stabilzed" with negative feedback IT IS the actual value of the output
signal itself that is "desired" to match the input times some transform
and it is the feedback (with appropriate inverse function) and almost
unlimited "open loop" gain that produces this result.

Additionally, negative feedback in amplifiers is not nearly as straight
forward in principle as what we are trying to deal with. That is, we
don't concern ourselves with feedback within a single stage or between a
few stages as do the electronics folks. Also we are not dealing with
"cathode" feedback and the like where the feedback signal has a
significantly different affect upon the circuit as the reference on the
grid. If the "electronics" definition of feedback dealt only with
Operational Amplifiers then their definition would look much more like
ours.

-bill

[from Bruce Buchanan 950603:1540 EDT]

As an occasional lurker I have noted Bill Powers promotion of discussion
inter alia of terminology related to Control and Negative Feedback...

A number of definitions have been cited. The problem with many of them is
that they are of a technical nature and derivation, not at a level of
general principle which carries well to other fields or has potentially
larger implications...

So here are some thoughts - in the spirit of Bill Leach [950601.14:34 EDT] -
(per the Sorcerer to the Apprentice?)

   >I believe someone once said something along the lines of "Be careful of
   >what you ask for... you just might get it!"

An article in the June/95 Scientific American (3From Complexity to
Perplexity2) suggests that the current approaches to questions of
complexity, which include systems of dynamic control, are far from
successful. So a discussion of some fundamentals may not be out of place.

I take it that a principle objective of science is the creation of
abstract models valid for classes of systems. For example, physics, at
its highest level, deals with matter as energy, manifested fundamentally
in heat and played out through variously organized structures in the
photosynthetic, oxidative and metabolic processes which support life. One
does not require mathematical precision to understand this much.

In describing these things, we of course discuss conceptual models of
reality, not Boss reality itself. Nevertheless, such processes must
involve organization in space and time - presumably in the world and
certainly in the concepts. And any models or patterns of which we can
speak must also reflect information and some selectivity or choice. So
what are the irreducible fundamentals of our information about things?

The thesis I have in mind (not as original, but for emphasis and
discussion) is that the most basic and primary level is the cybernetic
model of negative feedback. Below this level of organization events do not
exist for us (unknowable because unrepeated), there are no identifiable
elements, no possibility of patterned relationships to be conceived.
Events and elements become identifiable insofar as they participate and
can be accessed repeatedly and via feedback processes, which are essential
to any structure of relationships involving time, hence any perceivable
or knowable data. (I am probably repeating thing Bill Powers has written
somewhere.)

Considerations:

An essential primary process/condition for any existant or existence
itself is some persistence through time. It has been believed, and still
is believed by many, that the external world consisted of objects, e.g.
rocks and people and 3facts2, and certainly we can perceive the world in
this way. More discriminating or selective perception reveals, however,
that underlying and within primary experience are dynamic processes,
including perceptual processes, in constant renewal and interaction, both
in the world and within the organism. Persistence and renewal through
time requires the action of circular causal processes through which the
enduring world and the repeatablity and consistent identification of
perceptions become possible.

In relation to the external world we speak of causal processes, which are
selections we make both among (1) interactive relations among events as
these play out in time (which in engineering may include Feedforward), and
(2) retroactive or circular causal loops which link elements and events to
repeat patterns in time, dampened depending upon Negative Feedback, but
always with some delay (e.g. hysteresis) which is required and provides
the existential condition for possibilities for adaptive change. The
relation with time is crucial. Disturbance must actually occur, then be
organized via negative feedback, for random contingencies to be overcome,
and for life to arise and endure.

Examples of relatively stable cyclic processes in the inorganic world,
which also impact upon other events and life in changing ways, are the
hydrologic cycle, the magnetosphere, jet stream, etc. etc. For negative
feedback also underlies the stability of universal processes.

In relation to man9s thought and the conceptual world e.g. science, it may
be recognized that sensation and perception occur over many levels which
are all, in principle, subject to control by feedback in terms of various
criteria.

Perhaps the most accurate overall view of this process is that which
recognizes thatit is the activity or behavior of the organism which
controls perception (cf. B:CP). (I am just trying to paint the picture as
I see it, in order to clarify ideas, not preach to the converted!)

External stimuli may be perceived, but they do not control, since they are
not as such properties of the system. Subsequent events and memory may
change this, and the picture may be confused if the chronology is not
recognized.

So there are other views ( e.g. S-R) which see behavior as determined
simply by What is perceived. Such views are employed because they appear
to the proponents be useful for special purposes, and may be validated by
repetition within tightly constrained conditions. However, they do not
take into account the actual nature of the fundamental dynamic processes
at work, and do not meet criteria for science that reach for valid
formulations which are the most comprehensive.

Terminology:

Standard definitions of negative feedback appear mostly to be based upon
experience derived from specialized and applied fields of engineering and
control systems. A more comprehensive theoretical view of the principles
of feedback and control may also require more adequate nomenclature and
less restrictive definitions.

Being very tentative, and harking back to an earlier thread in
bit.sci-purposive-behavior, and as an alternative to the term Control
(which tends to suggest control in isolation, by some agency of something
else, I offer for discussion the (made-up) term COMCONACTION, to connote
e.g.:
   COM - communication, common/together, selectively guided
   CON - control, connect, con/with, consciousness (knowing together)
   ACT and ACTION - actual event, selectively directed.
Comconaction is intended to suggest some independent action by some
entity, as well as by groups of entities coordinated and guided by common
purposes, i.e. activity of system-based vector(s). The word is a little
complicated, as is appropriate to what it expresses.

Since a scientific term should be primarily denotative I suggest (again
for purposes of discussion): COMCONACTION is the integration of action in
space and time, through negative feedback, of dynamic processes within
systems at any level of organization or complexity, which enable
relatively stable and persisting output or behavior despite the effects of
unpredicted contingencies.

Other implications:

Since selectivity based upon criteria for error correction is inherent in
the irreducible primary conception and model for anything that can exist,
structures required for evaluation and feedback must be present in any
systems which continue to live and function.

While the values may be unspecified, the structural conditions exist, and
there may also be functional requirements for appropriate specific
values. Indeed, many problems may ensue if the criteria utilized are
inappropriate, e.g. at too low and restricted a level of the organization,
rather than criteria devised to reflect strategies which can benefit the
whole. Indeed the highest value may attach to the processes by which
such strategies may be developed - e.g. those required for a sustainable
civilization on earth.

It is said by some that the highest values attach to the long term
evolution of life and intelligence. However, in general, ideals which are
too abstract to be applied operationally do not provide useful criteria
for the guidance of current decisions, i.e. they may not provide an
ethical basis in practice for existential judgements. The contention that
such unapproachable values provide useful guidance has been historically
fraught with disaster, so that the onus is on the proponents to prove
their case.

I would of course be interested in comments and any discussion. My whole
purpose is to try to suggest alternative appoaches for consideration while
the discussion thread is still alive. However, I will be out of the
country until June 24, and may miss Newsgroup postings, so I would
appreciate email copies of anything for which follow up or response from
me is requested.

In any case, cheers and best wishes.

Bruce B.
Bruce Buchanan
*We are all in this together!*

<[Bill Leach 950604.00:31 U.S. Eastern Time Zone]

[from Bruce Buchanan 950603:1540 EDT]

A number of definitions have been cited. The problem with many of them
is that they are of a technical nature and derivation, not at a level of
general principle which carries well to other fields or has potentially
larger implications...

This is absolutely meanless to me. Addition of real numbers is a very
precisely defined term. It is technical in the extreme and combined with
the rest of the similarly strictly defined terms of mathematics provides
us with the most precise language that we have. Is it useful? I think
that a reasonable case can be made that it is useful.

This almost sounds like "Terms" must be ambigious enough in meaning to
allow one to make 'profound' statements without having to work very
hard."

The term "control" itself is "context sensitive" even here on CSG-L where
there really is an effort to maintain a precise meaning. For example
mine own recent use of the term without my having made a careful effort
to explain that my use was not quite in the "classic" (to PCT) meaning is
likely the major reason that Martin replied to my "control of a
perception not currently perceived" discussion.

The thesis I have in mind (not as original, but for emphasis and
discussion) is that the most basic and primary level is the cybernetic
model of negative feedback. Below this level of organization events do
not exist for us (unknowable because unrepeated), there are no
identifiable elements, no possibility of patterned relationships to be
conceived. Events and elements become identifiable insofar as they
participate and can be accessed repeatedly and via feedback processes,
which are essential to any structure of relationships involving time,
hence any perceivable or knowable data. (I am probably repeating thing
Bill Powers has written somewhere.)

If Bill Powers wrote this somewhere then I certainly missed it. Indeed,
if I had read this in one of his works over a year ago I would still be
asking him what he meant!

... More discriminating or selective perception reveals, however, that
underlying and within primary experience are dynamic processes,
including perceptual processes, in constant renewal and interaction,
both in the world and within the organism. Persistence and renewal
through time requires the action of circular causal processes through
which the enduring world and the repeatablity and consistent
identification of perceptions become possible.

That causal processes must exist to be able to develop a model of the
world I accept. That all processes must be circular causal processes for
such to occur I do not accept.

... (2) retroactive or circular causal loops which link elements and
events to repeat patterns in time, dampened depending upon Negative
Feedback, but always with some delay (e.g. hysteresis) which is
required and provides the existential condition for possibilities for
adaptive change. The relation with time is crucial. Disturbance must
actually occur, then be organized via negative feedback, for random
contingencies to be overcome, and for life to arise and endure.

Arg! Bruce, you are in an entirely different world from PCT here.

Patterns that repeat in time may not be retroactive causal loops with
respect to the observed pattern. The actual circular causality may not
be observed at all but rather only causal results (several times removed
from the "ultimate" initiating cause).

In addition, generalizing "negative feedback" to exist in all processes
is unreasonable for several reasons. In the first place while the
limiting caused by system nonlinearities in oscillating system can be
refered to as negative feedback, doing so without mentioning the nature
of the system and the presence of positive feedback in a significant
portion of the operating cycle is highly misleading.

Using the term "negative feedback" in reference to systems with an open
loop gain of less than one is also not generally productive. Systems
without a continuous energy input are not well described in feedback
terms.

Are you saying that "Delay" is hysteresis for negative feedback? Or that
there is a hysteresis in loop transit time values? Your statement
appears meaningless to me.

Disturbances to CEVs are resisted not organized by control systems.

The inorganic _exampleS_ that you give are arbitrary classifications by
humans. It is highly likely that these examples are interacting systems
that defy analysis in isolation.

So there are other views ( e.g. S-R) which see behavior as determined
simply by What is perceived. Such views are employed because they
appear to the proponents be useful for special purposes, and may be
validated by repetition within tightly constrained conditions. ...

The "special purpose" that you are referring to is, to the proponents,
the same one as for PCT -- create a general theory of behaviour.

Terminology:

Feedback

The precise mathematical definition for feedback in a closed loop control
system is THE ONLY proper definition for purposes related to PCT. That
even we often error in our verbal communications with respect to the
meaning of the term do not invalidate the correct meaning.

For some reason, there seems to be a general "movement" toward what I
call relaxing the definitions of terms. It seems that a significant
number of people want to be able to "say things" and "use terms" that
will "make them sound impressive and knowledgeable" without also being
subject to critical scrutiny. That is they specifically do not want
terms to have precise enough definitions so that someone else could
possibly make a valid challenge to what they say (ie: No one could claim
that they might be in error).

While it might possibly be true that demands for strict use of terms
might be a source for conflict between people, I personally view this
situation as vastly superiour to the situation where no one can hope to
achieve even a modest understanding of the ideas of another because "it
is pretty much OK for 'you' to mean whatever you want to mean by what you
say"!

Even though it is true "that it's ALL perception" and that I, for
example, can not know with certainty that I really understand what
someone else is expressing (at best), it is also equally true that it is
the serious attempts by one person to understand another that is the
source of all of the knowledge that is worth considering.

I personally now recognize that in practice, engineering use of the term
control is also sloppy. Even work in Control Theory tends to possibly
improperly use the term. However, the meaning with respect to the
fundamental closed loop control system is exacting.

Thus, I still believe that we are better off, to stick with this existing
definition and point people to the source when needed rather than trying
to invent a new symbol.

In addition, I see your proposal as one that would create a significantly
diluted replacement.

The statement "which tends to suggest control in isolation, by some
agency of something else" IS A CORRECT DESCRIPTION OF THE PHENOMENON OF
CONTROL from the viewpoint of an observer. "Some agency of a system is
forcing some other external 'thing' to maintain some constant condition,
that is isolating this 'thing' from the affects of other forces." Such
is (correctly) the external observers view of what happens when a control
system is functioning upon a CEV.

Comconaction is intended to suggest some independent action by some
entity, as well as by groups of entities coordinated and guided by
common purposes, i.e. activity of system-based vector(s). The word is
a little complicated, as is appropriate to what it expresses.

And by meeting this requirement set is useless for purposes of saying
anything "concrete", in my opinion.

Since a scientific term should be primarily denotative I suggest (again
for purposes of discussion): COMCONACTION is the integration of action
in space and time, through negative feedback, of dynamic processes
within systems at any level of organization or complexity, which enable
relatively stable and persisting output or behavior despite the effects
of unpredicted contingencies.

Control systems most explicitely DO NOT "enable relatively stable and
persisting output or behavior despite the effects of unpredicted
contingencies"!! It IS BEHAVIOUR that is changed by control action to
maintain the desired perception!! Perception is what is constant in the
presence of "unpredicted contingencies" or disturbances.

Arg!!

Since selectivity based upon criteria for error correction is inherent
in the irreducible primary conception and model for anything that can
exist, structures required for evaluation and feedback must be present
in any systems which continue to live and function.

And just where does this "axiom" come from?

Double Arg!!

While the values may be unspecified, the structural conditions exist,
and there may also be functional requirements for appropriate specific
values.

for what?

Indeed, many problems may ensue if the criteria utilized are
inappropriate, e.g. at too low and restricted a level of the
organization, rather than criteria devised to reflect strategies which
can benefit the whole.

Are you saying that a living control system that is "intended by design"
to live by foreaging for berries in the forest that is equiped with only
a "gil type breathing system" is inappropriate? Also "whole" what?

Indeed the highest value may attach to the processes by which such
strategies may be developed - e.g. those required for a sustainable
civilization on earth.

By whom and to what purpose? What is "sustainable civilization"? (give
three examples) :slight_smile:

However, I will be out of the country until June 24, and may miss
Newsgroup postings, so I would appreciate email copies of anything for
which follow up or response from me is requested.

I'm not sure that you would appreciate an email copy of this posting
(just be thankful that I too "ran out of time").

-bill