So if you missed an A or a B pulse from the encoder I think you should see the position count go in the opposite direction for one count. Another words, instead of a position sequence of 0,1,2,3,4,5,6,7 you might see instead 0,1,2,3,2,3, and in addition the time spent in 3 followed by 2 would each be twice as long. So maybe if you can trigger on a non monotonic position sequence you can capture the event.
John Figie On Sun, Oct 2, 2022, 7:49 PM Jon Elson <el...@pico-systems.com> wrote: > On 10/2/22 19:34, John Dammeyer wrote: > > Oh boy does that bring back memories. > > I started with the US Digital Encoders on the DC Servos. According to > the designer of the PIC upgrade board for the HP_UHU Servo drive the US > Digital were crap and caused nothing but problems. > > I switched to CUI and it appeared to be better. Until one day circle > milled inside a piece was off center. See photo. > > > > That’s when I started doing what you did and discovered that at very > slow speeds I could return to the same 0 position but faster moves lost > steps. The error happened in only one direction. > > > > Eventually I discovered that if I swapped the motor+encoder with the Y > axis the problem moved to the Y so it wasn’t the HP_UHU drive. Further > research showed the X axis motor winding resistance was almost double that > of the working Y axis motor. > > It's possible I might have been able to fix the problem by doubling the > current setting on the motor. They were bought at the same time and were > supposed to be identical. > > > > I don't know why the HP_UHU servo drive didn't catch the position loss. > Like yours, the encoder signals looked nice. The CUI encoders seem to be > high > > > > One other point. I switched to the Bergerda AC Servo drives which to > date have been great. Talking to Donald Chen the sales guy at Bergerda he > mentioned that their encoders are Japanese and more expensive than ones > used on a lot of their competitors. After that conversation I took one > apart and checked part numbers. Sure enough, Japanese design made in China. > > > > So try different encoders. > > Yes, I did see some really strange signals on the scope > before. I tore the whole motor/encoder set apart and cleaned > the inside of the encoder. But, optical components in the > encoder are held in place with glue, 39 year old glue! I'm > having doubts that everything is still properly aligned in > there. > > So, I'm leaning toward replacing the encoders with newer > high-end encoders with higher line count. But, that will > require machining adapter plates and making sure the > encoders are well-centered. > > Thanks, > > Jon > > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
