Re: [CAD_CAM_EDM_DRO] black box specs

I think that's what, essentially, Jeff is talking about.

<unathoratative response>
EMC can still do the trajectory planning but not to
close the positioning loop. That's the stunt boxs' job
This would be my goal in life also but right now I don't
know enough about emc/emcmot to figure out how the
split can be carried off.
</unathoratative response>

A 100Mb point-2-point full-duplex link you could close the
loop in about 5 uS even accounting for Ethernet frame
overhead. If you consider probabilistic throughput
for Ethernet, then assume only 1 out of every 100 frames
succeeds (which is about 70% Ethernet loading factor versus
something less than 1% for p2p) you still close the loop every
half millisecond.

The caveat here is the proprietary nature of the interface.

-Woody

> > <unlurk>
> >
> > Jeff, it's not as bad as you think.
> >
> > Jon, with the exception of ATM (and Allen-Bradley's ControlNet), few
> > networks are deterministic. All are described in probabilistic.
> > I've worked with _many_ fieldbus type I/O system. Ethernet is
> > becoming very popular because of it price, ease of use, distances,
> > reliability, etc.. Probability is based on loading, network speed,

etc..

> > Do a quick lookup of industrial Ethernet, you may be surprised at what
> > is being done with it in real-time control environments.
>
> Yes, sure, but my Linux-EMC system talks to the motion control
> stuff every 1.0 mS (and could do it more, if I needed it to). If you
> want to have all the motion control in the external box, then it
> can work fine, but if the PC is inside the 'loop' (especially with
> servos and encoders) then you can't have fifos, non-deterministic
> communications between the PC and the motion logic, etc.
>
> Jon
>