RE: dither, hunting. was re: G320s, New and Improved!

Hi Jon, list,

I seem to recall a servo system we had in the submarine (I can't
remember which), and it had dither intentionally introduced in it, to
increase accuracy (I think). That was a long time ago! Is what you are
describing possibly called "HUNTING", an not dither, which I thought was
intentional? (I said it was a l-o-n-g time ago!)

Alan KM6VV
(back from vacation #2, now to get some rest!)


Jon Elson wrote:

>
> cadcamcenter@... wrote:
>
> >
> > > First off there is virtually no dither noise. I do have one axis
> > that you
> > > can hear the motor shift back and forth very slightly and at a very
> > slow
> > > rate (maybe one or two cycles per second) when it is stopped in
> > certain
> > > positions. There is absolutely no humming noise that I used to get
> > on the
> > > old G320's.
> >
> > The presence of dither means that the servo is always seeking
> > the "correct" position means that servo is always overcorrecting,
> > then undercorrecting. Re: the old servo vs stepper "controversy".
>
> It can be argued that any servo which dithers with no other input is not
> properly tuned. I can say that my servos do NOT dither, except under
> very rare circumstances when a mechanical resonance has been excited.
> That, in itself, is indication that I could tune it better, but it is very
> much
> "Good Enough".