On Wednesday 08 November 2017 16:50:40 Gene Heskett wrote: > On Wednesday 08 November 2017 11:08:29 Peter C. Wallace wrote: > > On Tue, 7 Nov 2017, Jon Elson wrote: > > > Date: Tue, 07 Nov 2017 22:07:36 -0600 > > > From: Jon Elson <[email protected]> > > > Reply-To: "Enhanced Machine Controller (EMC)" > > > <[email protected]> > > > To: "Enhanced Machine Controller (EMC)" > > > <[email protected]> Subject: Re: [Emc-users] PID > > > refresher for Gene? > > > > > > On 11/07/2017 08:58 PM, Gene Heskett wrote: > > > Hmmm, your raw encoder signals seem to have a LOT of width > > > variation. Since your time scale is 20 ms, there are 20 samples > > > between screen divisions, so the sampling rate is not likely to be > > > the cause. Generating encoder velocity from timing the edges > > > suffers if there is poor accuracy of the state transitions, and > > > would be expected to produce a jumpy velocity just like what you > > > showed in a previous Halscope trace. A very poor eyeball guess at > > > the A-B trace looks like you might get 10 - 20% velocity error > > > easily with those duty cycle variations. This ought to show up on > > > an actual scope, to verify it isn't in the Mesa -> HAL part of the > > > system. > > > > > > 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 > > > [email protected] > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > Just counting graticle dots I see some places where theres almost a > > 2-1 difference in time from edge to edge (take a look at the violet > > edges before and after green falling edge roughly 1 graticle line > > left of center) The velocity trace seems to be correctly reflect > > this timing difference. > > > > You can also see that some of the error is straight quadrature error > > and some looks like code wheel variations. > > > > With less than 2 counts per sample, the peak noise is proportional > > 1/T_err. With 2 or more counts per sample the peak noise is > > proportional to 1/T_errN where N is the number of counts per sample > > interval. > > > > So higher quadrature accuracy will always improve things and higher > > resolution encoders will improve things if they have 2 or more > > counts per sample period at normal machining speeds. > > I have a 1000 line Omron encoder on order. I'll fix it to the butt of > the motor shaft, and use its a/b, but the z will the index pulse from > this one, changing the encoder scale according to the gear selection > switches. Or doing it automatically with hal. Hopefully that will put > a stop to this male Bovine output. :) > > I've made the gear switch mounting sandwitch pieces, out of chewing > gum that looks like alu, and sticks to the tool really bad, then found > the back of the knob is hollow, and runs about 5 thou from the casting > when its properly seated on the shaft. So my 8mm dimple will have to > become a bump glued into it, and projecting up high enough to engage > the switch rollers. > > But my bottle of rapid fuse, which seems to work better than regular > superglue is about spoiled, so I'll have to go get another after I > feed the missus. > But that got put on hold, she is not doing very well with the onset of winter weather. Very hard time breathing & not a strong enough cough to keep the airways clear. Got me worried. A huge change from this morning.
> > Peter Wallace > > Mesa Electronics > > > > -------------------------------------------------------------------- > >-- -------- 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 > > [email protected] > > https://lists.sourceforge.net/lists/listinfo/emc-users > > Cheers, Gene Heskett 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 [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
