Feedforward "control"?

[From Rick Marken (931108.1500)]

Hans Blom (931108)--

Me:

The conditions under which feedforward
works are VERY RARE in real behavior.

Hans:

That you perceive this may be due to your never having looked for the
phenomenon.

Have YOU ever looked for this phenomenon (feedforward based behavior)?
If so, tell me how you found examples of it -- and how you knew that
feedforward was involved in this behavior.

Me

"Feedforward" (open loop) elements are already recognized
implicitly in PCT; they are just UNCONTROLLED variables.

Hans:

Funny terminology: feedforward control results in uncontrolled variables?

The problem is the use of the oxymoron "feedforward control"; a
feedforward system does NOT control (produce consistent results
in the face of disturbance). Feedforward processes cause results;
they don't control them.

Me:

                                A variable that is under
feedforward "control" is easily detected using "the test";
disturbances to such a variable will simply not be resisted.

Hans:

You might be surprised. If feedforward control operates within feedback
control, feedforward might eventually become optimally tuned. It WOULD be
possible to play football on the moon -- although it would soon be a very
different game.

If a variable is controlled, then it CANNOT POSSIBLY be the result of
a feedforward process even if that feedforward process is "optimally
tuned" so that it produces results (in a disturbance free environment)
that precisely mimic the behavior of the controlled variable . I think
what you need to do, Hans, is point to ONE (count them, ONE) example of
a human behavior that you consider to be the result of feedforward
"control". It should be a common everyday behavior and you should be
able to explain how you KNOW that it is a result of feedforward
"control". Then we could go out and test it -- and demonstrate
the phenomenon of feedforward based behavior to ouselves.

The "feedforward controllers" with which I am familair operate in
environments that are MADE to be predictable by the existance of
OTHER CONTROL SYSTEMS (including the control engineer). This is not
the kind of world people live in (as Tom Bourbon pointed out); it is
not how people are designed (as Bill Powers pointed out). Feedforward is
something that can be USED by a control system (living or artifactual)
but a feedforward system does NOT control (as I pointed out).

I have no idea why you think that feedforward is an important
priciple of biological design. How could it be? Feedforward systems
don't CONTROL . If feedforward systems DO control, then please show
me the equations so I can test it out as a spreadsheet model. If
feedforward systems don't control, then WHO CARES about them (other
than the people building machines that produce programmed outputs
in controlled environments).

I can't understand why you seem to WANT to conceive of living systems
as being organized around the production of output (feedforward) rather
than around the control of input (negative feedback). What is it that
drives you to this perspective? What tests convince you of the
feedforward nature of living systems? What in the world leads you to
think that a great deal of human behavior is like the behavior of a
wind up doll? I was in Germany in 1964 and people seemed pretty much
like they are everywhere else. Has something changed?

Best

Rick