On 10/19/2016 01:08 PM, Kirk Wallace wrote: > On 10/19/2016 10:53 AM, andy pugh wrote: >> On 19 October 2016 at 18:34, Roland Jollivet <roland.jolli...@gmail.com> >> wrote: >> >>> While the devices have a high resolution, look at pg.7 for all the >>> non-linearity specs. So while you may discern 16 383 positions, you may be >>> well over 50 counts in error. >> Possibly fixable in software. Especially with a stepper (we don't >> normally worry about whether a _stepper_ is linear) > Another issue that might come about is encoder latency. I may be wrong > but, I seem to recall Jon ran into this problem with capacitive encoders > which had a lag between the position and the sending of the position > signal. The lag also seemed to vary with velocity. > > Most specifically, it was a lag in the encoder's loop to respond to acceleration. Velocity was fine, but when there is acceleration, the encoder's velocity didn't change for a few milliseconds, then it had to produce velocity greater than real for position to catch up. I thought it was a really severe problem, but it seems it may not be all that bad. But, it can make servo tuning more tricky.
Jon ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
