Re: [CAD_CAM_EDM_DRO] Re: Re: EMC, ISA and other Questions...

Jon,
sampling rate of an original DRO program is 0.5 of ms - that's what I use.
Ping time between two machines under DOS is 0.00 ms.
It would be reasonable to suggest that transmission time, in this case,
is 10 us.
Normally they send 64 bytes packet for ping. In my case I'm writing an array
of 16
bytes into the socket - should be a bit faster.
I'm using UDP which is faster then TCP.
I think it would be reasonable to suggest that between two computers network
update
can be held close to real time, based on this data.
I'm not saying that this is the best way to facilitate exchange of data in
real time.
In fact, I believe it has to be done differently.
I think "slave" computer should be DOS based, it should have Kulaga DRO card
and servo D/A card or stepper driver arrangement (parallel port) in it - all
the real
time staff should work within the same machine.
Then "master" would communicate to the "slave" via the network by
sending/receiving
a structure of data based on a preprocessor commands and updates from the
"slave".
That's probably how they did it for CNC player(via serial)..
Program which I wrote is in public domain and can be easily modified by
interested
people to do all kinds of network communication, if they have desire to do
so.

Regards, Alex

----- Original Message -----
From: Jon Elson <elson@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Wednesday, March 12, 2003 1:23 AM
Subject: Re: [CAD_CAM_EDM_DRO] Re: Re: EMC, ISA and other Questions...


>
>
> alex wrote:
>
> >Ray,
> >I made a program to transmit DRO data from Mauch/Kulaga board to another
> >machine in real time.
> >
> >It can be helpful if Linux machine doesn't have ISA slots, then it can be
> >networked
> >to a cheap old computer which does DRO readout. Then closed-loop
operation
> >can be facilitated.
> >
> No, you are dreaming. A DRO is fine for a person who can handle 2 or 3
> updates a second.
> Closed-loop motion control requires very repeatable sampling intervals,
> because velocity
> is calculated from how much the position changed sinde the last update.
> If the interval of the
> samples, or the interval of the packets transmitted, varies, the program
> is unable to give
> predictable speeds. I run EMC at 1000 samples/second, with less than 10
> uS of jitter in
> the sampling interval. Most commercial CNC systems have very high
> sampling rates,
> from 10 KHz to 60 KHz and above.
>
> If there is nothing else but the 2 computers on the ethernet, this might
> work out OK, but
> even with that limitation, the time of packet transmissions may not be
> dependable.
>
> Jon
>
>
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