jros wrote: > Hello, > > I'm the owner of such card, as I read from the documentation, the internal > encoder counter of the card > will go to 0 in the next index pulse after index-enable. > > I suppose that if I activate EMC's option INDEX_ENABLE to true in the INI > file, the I > would get hat behavior. > > That looks nice, as I can get a very fine homing, but I think there is a > caveat: > > Wouldn't the reseting of the card's encoder counter would make the PID to go > crazy?. > > Right, it causes a huge transient in apparent velocity. That's why it needs the PID needs to know when the home to index event has occurred. > I mean, if such a reset is not going to be dealt with internally by EMC, the > pid will > see an abrupt change in the position reference that would in turn produce a > hard kick > or hit on the machine and this hit in turn probably will trigger a following > error. > > Is there a way to avoid or soften the referred problem?. > I can't say for the motenc, but the Mesa and Pico Systems drivers and their associated HAL files handle this. I can't right at the moment recall exactly how this works. The index-enable signal is a bi-directional signal between the encoder counter driver (hal_ppmc.c in the case of my boards) and axis.n.index-enable. When searching for the index pulse, axis raises the index-enable signal, and when the driver sees that the hardware counter has been zeroed by the index pulse, it lowers the index-enable signal. Somehow, axis tells pid that it should ignore any transient on the next servo cycle. There was a patch on this about 18 months ago that smoothed the bump further.
Jon ------------------------------------------------------------------------------ Increase Visibility of Your 3D Game App & Earn a Chance To Win $500! Tap into the largest installed PC base & get more eyes on your game by optimizing for Intel(R) Graphics Technology. Get started today with the Intel(R) Software Partner Program. Five $500 cash prizes are up for grabs. http://p.sf.net/sfu/intelisp-dev2dev _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
