On Monday 05 March 2018 08:01:58 Mark wrote: > On 03/04/2018 12:53 PM, Gene Heskett wrote: > > That is something that Andy wrote, called lincurve, see man 9 > > lincurve for a basic explanation. What isn't mentioned is that in a > > motion scenario, it will probably feed a pair of sum2's, one summing > > the command from motion to the machine in order to sum the command > > from motion and the correction into the stepgen controlling the x > > (height) axis, and a 2nd sum2 with its input from the lincurve set > > for a gain of -1, and its feedback from the stepgen summed so that > > the effect of the first "offset" is subtracted from the feedback > > back to motion, effectively hiding any corrective motions from the > > motion controller which would generate either corrections, or > > following errors. > > I did a bit of research yesterday. lincurve is not in the elder > version of linuxcnc I have, v2.5.5. I'm willing to upgrade to get the > utility of lincurve, but I'd like to understand the utility a bit > better. Downloaded the latest linuxcnc and burned the DVD yesterday > ever. > > > The confusing part for me would be that the x input would be derived > > from the saws z (length along the trackage) position, and the > > corresponding y output controls the error corrections applied to the > > height motor drive. > > I saw it was an x,y thing. Maybe Andy can help figure how to apply > this to an X and a Z axis. > > > As the man page says, it is a maximum of 16 points long, and I've no > > clue if it could be cascaded to more points, however from your > > description of the errors, 16 points seems like more than enough to > > do a considerable error reduction. The calibration, done with a > > series of setp's in the hal file, can be easily corrected for wear > > error over time. > > 16 points would probably be overkill so no worries. I've already got > the cal numbers for each inch along the X axis. We're talking at most > about a few thou of deviation from the mean at any given point on the > table. > > > Your ability to measure the error will likely determine how accurate > > the correction can be. > > Got that nailed down pretty good with repeatable numbers. > > > Beyond this, Andy can probably explain it better than I can since he > > wrote it. My only experience with it was in trying to linearize the > > spindle speed control, a miserable failure trying to correct the > > errors caused by some bob optoisolators so slow as to need stakes > > set and a surveyer called. > > <snippage> > > > But I have some half built furniture to finish first. I've > > had another blood clot reminder that I am on the downhill side of > > life, and I do want to get them done before I miss roll call. So my > > warfarin dose is back up... > > > > Alone ATM, the missus is in the shop with a broken leg, possible > > cast removal in May. Osteoporosis etc, to go with the COPD. She did > > that the night before I was scheduled to have a sore leg looked at. > > The ultrasound tech called the ER, and they kept me for 6 days, > > pouring in the heperin. Its better, but I've been instructed to get > > the hell out of this chair every 30 minutes. > > Hope you and the Missus are mending. Best wishes. > > > Cheers, > Mark > Thanks Mark. Now I need to go make a lap around the house. And its too darned quiet.
-- 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
