Re: EMC2 Servo Loop

couple things off the top of my head
-Emc knows where you are at - no re-homing after an estop (as I said in an earlier post)

-Tuning and following error can be done in the control.
emc has a really cool program called halscope which can be used to veiw any signal within hal. Here I am looking at the following error of my x axis. It is at .00017 peak at the moment ;) http://www.electronicsam.com/images/KandT/conversion/testing/tuning.png

-external hardware to run industry standard +/-10 servos drives with emc2 are pretty inexpensive. Look at pico or mesa for their hardware solutions. for starters you could get a 6 axis analog + 24 i/o for under $200. (the same hardware would run steppers also (or a combo of))


I am converting a large hmc. I am going to have about about $566 in interface hardware + some cheap ebay opto22 boards. That gives me 10 axis analog (10 +/-10v and 10 high speed encoder counters) + 96 i/o. (and believe you me - I need it all - I might have to use the printer port also ;) - oh and I can use the printer port if I wanted to :))

emc2 makes me smile everytime I use it.

sam

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Phil@..." <yahoo@...> wrote:
>
> Yes, I get the idea. I just wonder what the main advantage is of having the
> servo loop run through the PC if not to reduce the external hardware. If you
> have to add external encoder counters it doesn't seem the cost would be much
> different from having a self-contained servo controller that simply takes
> step-direction commands and reports errors, etc. Cheap microcontrollers can
> easily handle that computing load.
>
> --Phil M.
>
> ----- Original Message -----
> From: "Jon Elson" <elson@...>
> To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> Sent: Thursday, December 16, 2010 8:40 PM
> Subject: Re: [CAD_CAM_EDM_DRO] EMC2 Servo Loop
>
>
> > Phil@Yahoo wrote:
> >> This is a question mainly for Jon Elson, being the EMC2 guru-
> >>
> >> You mentioned in a recent post that EMC2 can run the servo loop in the
> >> PC,
> >> which I presume means the PC is reading the encoder outputs. My question
> >> is:
> >> how can the PC read the encoder fast enough? I know there are some fairly
> >> significant delays in the parallel port speed, at least on output. Maybe
> >> that's not an issue on input? Also, where do you get enough inputs?
> >>
> > Maybe I should expand on my previous message....
> > The idea here is that the attached hardware counts the encoder pulses
> > and converts them to
> > position. In the case of my boards, that is a 24-bit signed binary
> > count. This is then extended
> > by the device driver to give 32-bits of signed precision, which nobody
> > so far has found
> > insufficient. So, the computer only needs to sample the count
> > periodically and compute a
> > new velocity to minimize following error.
> >
> > Jon
> >
> >
> > ------------------------------------
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