one huge misunderstanding?

[HANS_BLOM1]

[Hans Blom, 932211]

(Bill Powers (931119.1315 MST))

Have we just had one huge misunderstanding all that time? In your comments
below, you give a beautiful description of the type of feedforward that I
have been harping about: navigation in the dark, i.e. control with blanked
out sensors.

                 The reality of what my perceptions are telling
me is irrelevant to solving my control problem of not barking my
shins. The only way I can solve this problem is to construct a
map inside my head, in which I place things (and myself)
according to my perceptual experiences. Even when I can see, many
of the objects on this map have locations without being seen,
such as the doorway I just came through, and the bottoms of my
feet and my hip pocket. All that changes when the lights go out
is that I have to maintain the map without as many updates. This
map is what I call the "real bedroom."

What I called "feedforward" is exactly what you describe: control based on
the "map" (an internal model), rather than on real-time observations. You
do not call that "control", whereas I do. But it seems that we are really
talking about the same thing.

All branches of adaptive control theory are concerned with how to initial-
ly build up such a map from scratch ("systems identification"), how to
maintain the map as best conforming with what we perceive as "reality"
("adaptation", "tuning"), and how to use that map in the endeavor to
fulfill our goals (which I call "feedforward").

You can still control your relationship to your perception of the
bed with the lights out, can't you? You can look at your map, and
say "Here's the bed, and here I am, so if I move THAT way I will
make the distance between the me-object and the bed-object
smaller." You can place the me-object using kinesthetic
information as you walk. The bed-object stays where it was the
last time the map was updated.

Right! The control of the relationship of my perception of the bed with
the lights out through consultation of my inner map is what I have been
talking about all the time! Do you know a better term than "feedforward"
to describe this process?

So the control process can occur in the usual way. It doesn't
require any change of organization when the lights go out. It
doesn't suddenly need a "feedforward" connection that it didn't
have before. Just acting as an ordinary control system, it's
doing as well as can be done.

Right! There is no break in control (nor in control mode) when the lights
go out because of that inner map. I have called that going from "feedback"
into "feedforward" mode, and I have tried to emphasize that there is no
break because that map is there always. Whenever the lights are on, it is
recalibrated all the time; therefore it is the best possible at the time
the lights go off.

Why "feedforward" (or whatever you call it)? Why the map? Because the
lights go (partially) off so often!

Greetings,

Hans

[Tom_BOURBON3]

From Tom Bourbon [931122.1201]

[Hans Blom, 932211]

(Bill Powers (931119.1315 MST))

Hans:

Have we just had one huge misunderstanding all that time? In your comments
below, you give a beautiful description of the type of feedforward that I
have been harping about: navigation in the dark, i.e. control with blanked
out sensors.

. . .

Bill:

You can still control your relationship to your perception of the
bed with the lights out, can't you? You can look at your map, and
say "Here's the bed, and here I am, so if I move THAT way I will
make the distance between the me-object and the bed-object
smaller." You can place the me-object using kinesthetic
information as you walk. The bed-object stays where it was the
last time the map was updated.

Hans:

Right! The control of the relationship of my perception of the bed with
the lights out through consultation of my inner map is what I have been
talking about all the time! Do you know a better term than "feedforward"
to describe this process?

Me:

Yes: feedback. Hans, after reading this post of yours, and before composing
my reply, I discovered that Rick Marken (931122.0800) sent a similar
one-word reply. But as the author of the post to which you replied when you
introduced the scenraio of walking in the dark, I want to add my comment
that this is, indeed, what we were talking about all along. Rick, Bill and
I have been putting forth the idea that controlling present perceptions
against a present-time map (controlling in "imagination mode") is still
feedback control. To us, as non-real control theorists, the fact that a map
is involved does not require that a new name (feedforward, feed-through,
feed-whatever) be used to identify the situation. We simply call it
another instance of negative feedback control.

The big problam we were having with your interpretation of the scenario came
from statements like the following:

Hans:

Right! There is no break in control (nor in control mode) when the lights
go out because of that inner map. I have called that going from "feedback"
into "feedforward" mode, and I have tried to emphasize that there is no
break because that map is there always. Whenever the lights are on, it is
recalibrated all the time; therefore it is the best possible at the time
the lights go off.

Why "feedforward" (or whatever you call it)? Why the map? Because the
lights go (partially) off so often!

You seemed to be saying there is no feedback when the lights go out. We
were saying that feedback control continues after the lights go out. What
you called feedforward, we saw (and still see) as a contiuation of feedback
control.

···

==========================================
On the same thread:

[Martin Taylor 931122 11:50]
(Tom Bourbon 931119.1046)

Tom:

To make the example more specific, point P is in a
room down the hall from the bedroom and around a corner to the left. With
the lights on, when the person walks from P to B and climbs into the bed, at
which point(s), if any, is the person's relation control system operating
"open-loop?"

At all points where the person cannot see the bed. When all required elements
of the relation perception can be derived from current sensory data,
real-world perceptual control is possible. If they can't, then the effect
of output on the real CEV cannot be perceived. What can't be perceived
can't be controlled. Outputs that have effects that can't be perceived
are open-loop, in my understanding of the term.

Martin, had you seen Bill's post [Bill Powers (931119.1315 MST), Re:
Martin Taylor (931118.1440)] when you sent this reply to me? In his post,
Bill said, with far greater clarity and eloquence, what I was trying to say
to you and Hans. We don't perceive "the real CEV;" from inside, there
is only the real perception. Relationships are on the output side of a
relationship perceptual function, not on the input side -- relationships are
created out of an array of lower level perceptions, some of which might be
available in imagination. When the lights go out, or when we are down the
hall and around the corner with the lights on, we can intend a perceived
relationship that does not exist, then act to create it. Pehaps it would
be more accurate to say that we can intend a particular value or state of
the relationship, then act to create it. As Bill said in his post,
ordinarily we don't control the self-bed relationship by moving the bed
(although there are exceptions), but by moving ourselves relative to the
perceived bed (whether it is present in "reality" or in "imagination").

As an aside, I can think of several ways a person might control the
magnitude or state of the self-bed relationship while in the dark. One way
would be for the person to imagine the space as though walking trough it --
controlling for perceptions of walking through the space. The another way
would be to imagine a view from overhead, or some vantage point other than
being in the space itself. The first implementation of control in
imagination would be like running a flight simulator in the mode where you
have the pilot's view; the second would be like flying the plane from the
vantage point of an air-traffic controller or a satellite image superimposed
on a map. In the first case, the person is "looking out the windshield;"
in the second, the person "manipulates" an icon on a "playing surface" or on
a map. I wonder how many people following this topic use one or the other of
those two strategies.

Until later,

Tom