feedback to slow

[Avery Andrews 930112.1133]
Bill Powers (930112.0900)

>>Where can I read about why this claim [feedback too slow] is false or
>>irrelevant (e.g., true only for certain kinds of highly skilled movements
>>that people practice enough to make it plausible that they have
>>elaborate feedforward schemes for).
>
>Look up analogue computer methods for solving second-order
>differential equations. Korn and Korn is the only reference in my
>head, and it's probably way out of date (Greg?). See also my arm
>model, which controls a dynamical system without solving the
>inverse kinematic or dynamic equations.

This sort of reading isn't enough to make an impression on the
establishment. Academics are usually too busy, & maybe in some
cases, too stupid, to actively extract the relevant implications
from the stuff they read--everything has to be spelled out in
ghastly, explicit detail, not left to lie in math books, or buried
in CSG-L archives or C code. Students have more time, but they also
can't expected to have very broad backgrounds, so again, the needed
bits and pieces have to be laid out and put together slowly and
carefully.

It needs to be documented in full

  a) who first made the too slow claim, and what they were talking about
      when and why.

  b) wherein what was said is factually wrong.

  c) wherein it is irrelevant to the general case.

Could something like this be published in Biological Cybernetics?

Remember that one the most important aspects of academic streetfighting
is to make the opposition look stupid (as Chomsky did to Skinner with
his review of Verbal Behavior), but to do this effectively you have to lay
out the details in a way to be clearly accessible to prospective
students, and practioners of neighboring disciplines.

Avery.Andrews@anu.edu.au

[Martin Taylor 930114 12:00]
(Avery Andrews 930112.1133)

It needs to be documented in full

a) who first made the too slow claim, and what they were talking about
     when and why.

b) wherein what was said is factually wrong.

c) wherein it is irrelevant to the general case.

Could something like this be published in Biological Cybernetics?

I doubt it could be published. Who made the claim was presumably not
an electronics person. Early in EE you get taught (or did a few decades
ago) about a concept called Gain-Bandwidth Product. With positive feedback
the apparent gain goes up and the bandwidth (and normally the delay) goes
down. With negative feedback the reverse should be expected to happen.
At least that's my very vague and distant memory, and what feeds my
intuition about this issue.

Maybe my memory os all screwed up, but if not, there's nothing to publish
except a reference to standard textbooks.

Martin