PSN-L Email List Message
Subject: Re: fine structure nonlinearity vs dithering
From: ChrisAtUpw@.......
Date: Fri, 8 Feb 2008 23:29:24 EST
In a message dated 09/02/2008, Brett3mr@............. writes:
Charles,
I'm very glad to hear that you're interested in following the discussion.
My only concern had been that we were taking up bandwidth on stuff that might
not have been of interest to all that many folks. In reply to your comments,
I don't yet understand how the nonlinearity acts and how it should
mathematically be treated.
Hi Brett,
I would be quite happy to 'go public' if no one else objects?
I'm uncomfortable with taking the approach that because there exist some
fairly small (I think) nonlinear effects, then no quantitative analysis can be
valid at all. Although it's somewhat beyond
my experience, I believe that feedback designers today routinely deal with
highly nonlinear, time-varying, and stochastic system variables and still are
able to obtain quite useful results. If they couldn't there would be a lot
fewer airplanes out there and our cars wouldn't handle as well.
Read through the papers on Randall's Website?
Your car analogy misses the point. We are concerned mostly with
microscopic as opposed to macroscopic variations.
The mechanical properties of springs have a 'fine structure' of
discontinuous steps, a bit like ferro magnetic domains. This gives small 'step
function' variations and limits the ultimate performance of seismometers, clocks,
MEMS devices, etc. The macroscopic properties are also not quiite linear and
are time dependant. Hooke's Law is only an approximation.
How would you suggest incorporating step functions which are random in
time, sense and amplitude into the calculations / properties of a feedback
loop? The stochastic processes you mentioned?
Regards,
Chris Chapman
In a message dated 09/02/2008, Brett3mr@............. writes:
<=
FONT=20
style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000=20
size=3D2>Charles,
I'm very glad to hear that you're interested in follo=
wing=20
the discussion. My only concern had been that we were taking up=20
bandwidth on stuff that might not have been of interest to all that many=20
folks. In reply to your comments, I don't yet understand how the=20
nonlinearity acts and how it should mathematically be=20
treated.
Hi Brett,
I would be quite happy to 'go public' if no one=
=20
else objects?
<=
FONT=20
style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
=3D2>I'm=20
uncomfortable with taking the approach that because there exist some fairl=
y=20
small (I think) nonlinear effects, then no quantitative analysis can be va=
lid=20
at all. Although it's somewhat beyond
my experience, I believe t=
hat=20
feedback designers today routinely deal with highly nonlinear, time-varyin=
g,=20
and stochastic system variables and still are able to obtain quite useful=20
results. If they couldn't there would be a lot fewer airplanes=
out=20
there and our cars wouldn't handle as well.
Read through the papers on Randall's Website?=
DIV>
Your car analogy misses the point. We are conce=
rned=20
mostly with microscopic as opposed to macroscopic variations.
The mechanical properties of springs have a 'fi=
ne=20
structure' of discontinuous steps, a bit like ferro magnetic domains. This g=
ives=20
small 'step function' variations and limits the ultimate performance of=20
seismometers, clocks, MEMS devices, etc. The macroscopic propertie=
s=20
are also not quiite linear and are time dependant. Hooke's Law is only an=20
approximation.
How would you suggest incorporating step functi=
ons=20
which are random in time, sense and amplitude into the calculations / proper=
ties=20
of a feedback loop? The stochastic processes you mentioned?
Regards,
Chris Chapman
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