2012/11/6 andy pugh <bodge...@gmail.com> > > If 50% improvement is all that you need, then this might be worthwhile. > My scepticism is based on a more subtle consideration which applies to > stepper systems, however I think yours is a step-servo system so this > might not apply. >
A 50 % drop in latency is a 100 % improvement. ;) When you are pushing software step generation to its limits you find > that the gaps between the available step rates get wider. > Taking the example of a 25uS base thread, you can either step every 1, > 2 or 3 threads, giving you top-end pulse frequencies of 40kHz, 20kHz > or 13kHz. At some point the steps become bigger than the physical > system can follow and the motors will stall somewhere short of the > theoretical top speed. > In systems where the step generation clock is a few MHz (Pico or Mesa > FPGAs, SmoothStepper, other stuff I can't recall right now) this > "granularity" limit is well above the practical speed limits of a > stepper system. > A step-servo system will have its own internal position-tracking > control loops and may be immune to this issue. > > Good info. I'm not sure if a servo step/dir is immune, I haven't thought about the technical implementation but I'll ask the vendor where the limits are. If I don't remember it all wrong I think I'm close to the max rpm of the servo's with the figures I'm getting now. I'm in a need of a 5-axis and that will be a Mesa-driven machine, no doubt about that. /S ------------------------------------------------------------------------------ LogMeIn Central: Instant, anywhere, Remote PC access and management. Stay in control, update software, and manage PCs from one command center Diagnose problems and improve visibility into emerging IT issues Automate, monitor and manage. Do more in less time with Central http://p.sf.net/sfu/logmein12331_d2d _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
