Re: Re: Re: Re: EMC, ISA and other Questions...

Alex

Paul is much closer to this networking stuff than I am but I want to thank
you for your work with this. I can immediately see a lot of it's value for
motion control. Folk are worried about not having ISA slots or (free)DOS
compatable PC's but I recently saw a pile of a few hundred 133-266 used
machines on the floor of a nearby PC store -- 30 bucks in singles.

Paul is right on for right now about the single computer to do both the
position reading and motion planning on the same processor. NIST's thinking
here is reflected on the coffee mug I grabbed this morning. It is a NIST
Intelligent Systems Division cup and it says, "Real-Time Control System -
sense - model - act. The EMC currently reads position (sense) at the start
of every motion loop. It compares this with where the trajectory planner
thinks it ought to be (model). Then it develops the motion output signals
(act) for that loop.

I said "right now" Paul's advice is correct but there is a lot of work going
on in the realm of real-time networking and real-time distributed processing
out there. Some of these projects have demonstrated very practical results.
You mention some of your own work and what you say sounds promising. Couple
that with EMC's ease of networking because of the NML language and you have
"tight" control of motion processes.

I've done just a bit of work with paper mills around here. The coordination
of speeds of dozens of motors on a 1500 foot long machine boggles the mind.
More so when you remember that for much of that distance the product is
flimsier than bargain brand toilet paper, it's 40 feet wide, and it's running
at 3000 fpm. If you want to read some interesting stuff about this kind of
coordinated motion, look at Nyquist from the Netherlands.

Keep on! There's a lot going on right now with the EMC and several of the
other systems as well.

Ray

>    From: "alex" <telecomt@...>
> Subject: Re: Re: Re: EMC, ISA and other Questions...
>
> Paul,
> thank you for the guidance.
> This will be the next step.
> Regards, Alex