(un)known physical mechanisms

[Martin Taylor 960215 19:15]

Rick Marken (960215.1400)

I really have a problem interpreting your answer to my question:

Me:

I would like to be given a clear discussion of how an observer can discover
which phenomenon [control or equilibrium] is occurring, if the mechanisms
for causing the observed effect are not physically clear or accurately
described.

Rick:

You know that the
phenomenon of control is occurring when one variable (the disturbance) has
far less of an effect on another variable (the controlled variable) than is
expected based on a physical analysis of the situation;

If the mechanism is not physically clear, how do you know what is expected
based on a physical analysis of the situation?

What could be clearer?

Oh, a summer's day, perhaps? Or a Los Angeles smog?

ยทยทยท

----------------
Rick:

I think you will see that continuous temporal variations in the applied
force/ disturbance will be completely effective, resulting in proportional
continuous temporal variations in partical position that are highly
correlated with variations in the disturbance.

Martin Taylor (960215 13:30) --

Then so will any true control system, for which:

p = d/(1+G) + rG/(1+G)

Yes, but note that variations in p (the controlled variable) will be 1/(1+G)
of the variations in d.

Yes, but as Bill P was at pains to point out, "d" is not the disturbing
variable here. It is the effect that the disturbing variable would have
if there were no control, and the presumption is that we can't know that.
If you know d you can find G, and vice-versa, but you have to know one of
them to determine that k<1 in p = k*d. We go back to:

if the mechanisms
for causing the observed effect are not physically clear or accurately
described.

Now, how about the 5 questions?

Martin