On 2 February 2017 at 00:16, Dan Bloomquist <z...@lakeweb.net> wrote: > Next surprise is that what > I thought were pulsing tachs on the motor shafts are really DC > generators
That's the very definition of a tachometer. A tachometer outputs a DC voltage proportional to speed, and a negative one for reverse rotation. What you have is a very conventional (and very effective) system. The servo amps take a voltage input to command a velocity. This voltage is wired to the tachometer output, such that if the two are equal, there is zero resulting voltage. Then that sum is amplified to servo drive current. This is all analogue, but means that you have a very stiff velocity control, with none of that digital-realm PID nonsense. Separate from that, the new-fangled computer looks at the glass scales and decides how fast to go to correct the current position error, converts that to a voltage, and applies that to the amps. So, keep the amps and tachs, that's actually a good system. Like resolvers, it hasn't been superseded for being bad, it has been superseded for being expensive. Put LinuxCNC between the glass-scale input and the servo velocity command output. -- atp "A motorcycle is a bicycle with a pandemonium attachment and is designed for the especial use of mechanical geniuses, daredevils and lunatics." — George Fitch, Atlanta Constitution Newspaper, 1916 ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
