Re: [CAD_CAM_EDM_DRO] EMC2 Servo Loop

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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