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 ------------------------------------------------------------------------------ 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
