On Fri, 29 Apr 2011, Jon Elson wrote: > Date: Fri, 29 Apr 2011 00:33:49 -0500 > From: Jon Elson <el...@pico-systems.com> > Reply-To: EMC developers <emc-developers@lists.sourceforge.net> > To: EMC developers <emc-developers@lists.sourceforge.net> > Subject: Re: [Emc-developers] Fanuc converter > > Chris Radek wrote: >> If you really have 65K-1M per rev, though, dP/dt is going to give you >> a better than usual velocity estimate. If your hardware can measure >> the real dt instead of the driver trusting the pc latency to be >> negligible, even better? >> >> > Well, this is somewhat confusing. Apparently, these Fanuc encoders have > an interpolator that increases the resolution of a basic 2048-line > encoder wheel. At low speeds, the absolute position report is good to > either 65K or 1 million counts/rev. At some speed, it apparently zeroes > out the interpolated part and only reports the 4096 count/rev part > direct from the encoder. Probably at those speeds, there is no problem > with that, but it seems there might be some kind of discontinuity as the > interpolation is switched on and off.
Certainly at high speed the interpolation is not of much use, but the interpolator will of course also go bad at 0 speed. We've considered using such and interpolator with our embedded motion controller to avoid the (expensive if embedded) divide used for velocity estimation. The interpolator is just a second order DPLL, fairly easy to build into the encoder logic, and has the advantage that the velocity falls out directly from the first accumulator. > > Well, as none of this seems to be available in external documents, I > will just have to experiment with it. I have a guy sending me a motor > to work with. > > Jon Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your (")_(") signature to help him gain world domination. ------------------------------------------------------------------------------ WhatsUp Gold - Download Free Network Management Software The most intuitive, comprehensive, and cost-effective network management toolset available today. Delivers lowest initial acquisition cost and overall TCO of any competing solution. http://p.sf.net/sfu/whatsupgold-sd _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers