On Wednesday 08 November 2017 11:12:50 andy pugh wrote: > On 8 November 2017 at 16:08, Peter C. Wallace <p...@mesanet.com> wrote: > > You can also see that some of the error is straight quadrature error > > and some looks like code wheel variations. > > I am still rather surprised that the encoder variability is finding a > way past the PID and into the hardware.
> Maybe a lowpass on the PID output would be a better answer than a > lowpass on the encoder reported velocity. I haven't tried that Andy, mainly because the filtering is a lag and lag affects the Nyquist stability of any feedback loop. I was mildly surprised that my averager fifo was actually an improvement. I do have a limit3 in front of the pid input, but that is mainly to limit the rate of change when an auto-reversing command is being used, or a direct m3/m4/m3 is encountered in the code, limiting the acceleration of the reversal to something slow enough the Z motor can do it. Making that into a sine squared waveform puts the max accel of the reversal right at zero speed. A slew rate limit with rounded corners at the higher speeds. Applied to the spindle reversal, it helps to keep the Z running well for a G33.1 when doing coarser threads. That would probably just "wind it up". That thought did cross whats left of my mind though. :) Thanks Andy. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ 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
