Stuart Stevenson wrote: > The other option is EMC2!!!!!! - that is an option I like. > After review of a previous discussion on the necessary tach signal for the > amp I have questions bouncing around in my head. > > If the 11 control is SOOOO SLOOOWWWW in program execution would that control > not process the tach signal at a relative slow speed compared to today's > capability? > If that generated tach signal was sufficient for the amps in the late 70's > would the current technology be able to at least match it? > If today's tach signal generation is suboptimal for a servo amp how did > Fanuc do it acceptably 30 years ago? > Low bandwidth. You can figure it out, given the encoder resolution. The amplifier would have a velocity bandwidth of maybe 100 Hz at the max, but I'm guessing probably less on that system. So, what speed would the machine need to move at for the encoder counts to be coming in at less than 100 Hz?
Processing the tach signal is not the important factor. Fanuc had a custom chip made to do the conversion, it was literally all in one chip plus an op-amp. There are several outfits making a converter now. US Digital has one with LOTS of options, and there's a guy in Bulgaria making a 2-channel unit for 100 Euros. > If synthesized tach signals are problematic why does/did Fanuc use them as > their primary design? > Yes, I've often wondered that! If you are a control manufacturer, of course, they aren't problematic. They figured the problem out, standardized the solution, and built it into their controls. Problem solved, period. The only problematic thing is replacing the function when you pull the control. > Fanuc seems to have a "decent" reputation for servo systems and controls. > :) > I insist on believing there is no magic nor magic chip in a Fanuc control. > Oh, there IS, INDEED, a magic chip! It is similar to one made by ST microelectronics, a bi-directional frequency to voltage converter, but it has been out of production for years. That is the L290, see http://pdf1.alldatasheet.com/datasheet-pdf/view/87940/STMICROELECTRONICS/L290.html for info on how it works. Pretty sad there's no current replacement, as this does everything you need. Jon ------------------------------------------------------------------------------ This SF.net email is sponsored by Sprint What will you do first with EVO, the first 4G phone? Visit sprint.com/first -- http://p.sf.net/sfu/sprint-com-first _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
