PSN-L Email List Message
Subject: Re: fine structure nonlinearity vs dithering
From: "Charles R. Patton" charles.r.patton@........
Date: Fri, 08 Feb 2008 11:50:54 -0800
One brief thought -- I''m familiar with dithering to solve frictional
problems. So why not dither the force feedback at the A/D sample rate?
The friction non-linearity would generate harmonics of the dither
frequency, but these would also be rejected by the synchronous sampling
of the A/D (they would show up as a DC offset -- i.e., it would appear
as if the seismometer had a tilt that was not there in reality.) The
question is, "Does the "fine structure nonlinearity" show up as random
stiction/rachetting?" I.e., if one was to dither the force feedback,
would the result be a lifting of the noise spectrum floor and result in
overwhelming broadband noise?
As an aside, Brett asked you to start a direct email of this discussion
off the PSN list. I would hope this doesn't happen. I can't learn from
a discussion I don't have contact with. :-)
Charles R. Patton
Randall Peters wrote:
> As an engineer you will appreciate something that is needed for the improvement
> of force balance instruments. Friction-limited systems have to be dithered to
> overcome the adversities of the friction.
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