Brian wrote: > I am quite happy with the way EMC handles screw comp and lash. I am > not interested in changing my machine or EMC in these regards. The > ONLY reasons backlash and screw comp have been mentioned at all in > this thread is because it is the reason I can't feed my scale feedback > into axis.N.motor-pos-fb. Thats all. > OK, I have never been a real expert in this area. But, I guess the problem is that screw compensation is in the commanded position path to the motion system, not the measured position back from the axis. Is that right? The obvious reason is it almost has to be that way for an open-loop system that has no measured position. (I guess you could kludge it to look like there is a measured position coming back, and then apply the correction. This probably puts a PID or similar loop back into an open-loop stepper, which was what they were trying to avoid.)
Maybe the proper fix is to always have the screw compensation in the measured position path except for open-loop systems. But, if you have a decent linear encoder on your machine, the measured position should be QUITE accurate, and not need correction, just the correct scale factor overall. So, then, you could throw out backlash and screw compensation, and let the encoder do the hard work. So, I am still lost as to what you are really trying to achieve, here. Jon ------------------------------------------------------------------------------ This SF.net email is sponsored by Make an app they can't live without Enter the BlackBerry Developer Challenge http://p.sf.net/sfu/RIM-dev2dev _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
