Just wanted to point out that there are millions of inkjet printers and plotters in operation right now that use this exact technique. It's certainly practical. I think the reason they do it is to lower the cost. I imagine it also improves reliability by eliminating failure-prone parts (switches, connectors, etc).
The reason I would do it is to lower the moving mass, as I'm attempting to build a very agile machine, and every ounce counts. If it's too complicated though, I'll rig up some optical sensor that can have low mass. On the other axis, I already have a reflective optical sensor that adds no moving mass and works well, but that's more difficult on this axis. Sam's point about the Integral term is important, and raises another question: is it possible to alter the PID tuning parameters after the .ini file has been read. I think the answer must be yes, because the calibration tool in the GUI does this, but not having read the code yet, I don't know how that works. But even assuming that's possible, I don't have a clear idea of where I would need to hook into EMC to do what I want. Neil On Sun, Jun 6, 2010 at 1:25 PM, Viesturs Lācis <[email protected]>wrote: > Can You explain the reason, why would You want to do it this way? I > think that such approach is breaking machine, it creates unnecesary > loads and stresses to the construction of machine and simple switches > are cheap and wiring them is easy. I think that it is trying to > reinvent the wheel in some painful way. > No offense, just my personal opinion :)) > > Viesturs > > 2010/6/6 sam sokolik <[email protected]>: > > I could maybe see monitoring following error... When the servo hit the > > limit - the error would increase. You could then use some logic that > > says when the following error reaches a certain amount - trip the > > 'virtual' limit switch. Maybe.. I could see lots of issues and as > > gene says - you would want to limit the output to the servos. If you > > have any I (in the pid) the pid loop will 'wind up' pretty quick sending > > the servos to maximum. > > > > Big picture it seems possible... :) (but I am just thinking out loud) > > > > sam > > > > On 6/6/2010 11:09 AM, Neil Baylis wrote: > >> Many printers& plotters do not use limit switches. Instead, they move > the > >> print head slowly towards the end stop until the motor stalls, and then > back > >> off from that point a certain distance and that's the home position or > soft > >> limit. > >> > >> What, roughly, do I need to do with EMC to get this behavior? > >> > >> Neil > >> > ------------------------------------------------------------------------------ > >> ThinkGeek and WIRED's GeekDad team up for the Ultimate > >> GeekDad Father's Day Giveaway. ONE MASSIVE PRIZE to the > >> lucky parental unit. See the prize list and enter to win: > >> http://p.sf.net/sfu/thinkgeek-promo > >> _______________________________________________ > >> Emc-users mailing list > >> [email protected] > >> https://lists.sourceforge.net/lists/listinfo/emc-users > >> > >> > > > > > > > ------------------------------------------------------------------------------ > > ThinkGeek and WIRED's GeekDad team up for the Ultimate > > GeekDad Father's Day Giveaway. ONE MASSIVE PRIZE to the > > lucky parental unit. See the prize list and enter to win: > > http://p.sf.net/sfu/thinkgeek-promo > > _______________________________________________ > > Emc-users mailing list > > [email protected] > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > ------------------------------------------------------------------------------ > ThinkGeek and WIRED's GeekDad team up for the Ultimate > GeekDad Father's Day Giveaway. ONE MASSIVE PRIZE to the > lucky parental unit. See the prize list and enter to win: > http://p.sf.net/sfu/thinkgeek-promo > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > -- http://www.pixpopuli.com ------------------------------------------------------------------------------ ThinkGeek and WIRED's GeekDad team up for the Ultimate GeekDad Father's Day Giveaway. ONE MASSIVE PRIZE to the lucky parental unit. See the prize list and enter to win: http://p.sf.net/sfu/thinkgeek-promo _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
