I'd be very interested in what Ren¨¦ has to say on the topic. I think it could be done without gearing using a Heidenhain (maybe a 23-bit encoder) mounting it directly to the rear of the RA shaft.
-esy
Erik Sigurd Young
"My punctuality is well known. When The Revolution takes place, I'll be late,
and I'll be shot as a traitor."
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--- In Gemini-II@..., "tom@..." <tom@...> wrote:
This feature was talked about in the beta group quite a while ago. Here
is one of Ren¨¦'s responses. I will say no more and maybe Ren¨¦ can shed
further light on his thinking.
> > We've been thinking about this for a while. Oh yes, I would prefer a
> > closed loop to a stored PEC solution. I think Gemini is well capable to
> > do it. According to Shannon's law the encoders must have about the
> > double resolution of the accuracy requested. At the worm they could
only
> > reduce the spur gear error with higher frequency, for eliminating the
> > worm PE they must reside at the main axis. That means that for
achieving
> > 1" PE about 2 million ticks/rev are needed. Maybe they can be attached
> > to the worm wheel using some gearing.
> >
> > Ren¨¦
Tom Hilton
