On 04/13/2014 08:54 AM, EBo wrote: > On Apr 13 2014 8:03 AM, Kirk Wallace wrote: >> On 04/13/2014 04:00 AM, andy pugh wrote: >>> On 13 April 2014 10:56, Niemand Sonst <nie...@web.de> wrote: >>>> The internal units should be metric in any part of linuxcnc, no >>>> matter >>>> what unit the user selected! >>> >>> >>> The internal units always are Metric. Except, for some reason, in >>> Axis >>> (and Gremlin has its roots in Axis). >>> I do feel that this was a regrettable decision on the part of the >>> Axis >>> author, but fixing it is likely to cause more trouble than it saves. >>> >> >> I am thinking that the machine units should be based on encoder >> counts >> such that all calculations can be done with integer math -- then >> convert >> to any user units as needed for the user interface. But then again, I >> could be way off base. > > That would work well if you were basing all arithmetic on rationals, > but in a machine I would think that settling on a standard would be > best, and I agree that SI units are a very good choice. There is a > reason that NASA chose to standardize all new software on SI units (see > https://en.wikipedia.org/wiki/Mars_Climate_Orbiter). > > But to follow you logic a bit, lets imagine that you have a 4 axis > machine where each of the axises have a different machine count metric. > Now how are you supposed to coordinate movement? While this is a bit > stretch to think that *all* axes are different, it is not a stretch to > have X/Y similar, Z and A different. No, I would go with SI as a > standard. > > EBo --
I think there is a different distance scale per axis problem no matter what units one choses. My guess is that there may be a way to use encoder counts to run the motion back end such that only integer math is needed. If each axis had a machine unit to encoder count factor, then a user unit to machine unit conversion could be pushed out to the user space. The machine scale could be set to, let's say 1000 ticks per smallest distance to encoder count, then calculations could be done without decimal points and still have enough resolution. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/ ------------------------------------------------------------------------------ Learn Graph Databases - Download FREE O'Reilly Book "Graph Databases" is the definitive new guide to graph databases and their applications. Written by three acclaimed leaders in the field, this first edition is now available. Download your free book today! http://p.sf.net/sfu/NeoTech _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
