[rescue] Anyone Familiar with VMEbus?

Christopher Purdy escher.beretta.2112 at gmail.com
Fri Sep 17 15:23:35 CDT 2021

Well.... A good side note - I got my VT420 working!!!


Now I'm ready once I get a working controller.

On Fri, Sep 17, 2021 at 4:15 PM John Hudak <jjhudak at gmail.com> wrote:

> One doesn't need 'modern hardware' to control that arm.  I was doing it wan
> a DEC LSI11 and later with a 11/73.  There was a Intel 86x box in the lab
> which could have been used as well.  Most of the code I developed was in
> assembler, and some C.  Yea, standard approach is to take the small voltage
> outputs of the d/a's and have that as inputs to the servo amps.  My gig was
> applying/developing modern control theory approaches to construct observers
> to refine the time to position and accuracy in 3-space, avoiding the
> dreaded overshoot problem.   Had to prove to one of my instructors that you
> can't change physics/law of nature with software..the beauty was in the
> math model...but that is another story.....
> On Fri, Sep 17, 2021 at 2:44 PM Mouse <mouse at rodents-montreal.org> wrote:
> > >>> [...PUMA arm...robotics control...]
> > >> I don't recall what we were using for interface hardware once it
> > >> left the host system (I wasn't dealing with it much past that
> > >> point), but I *think* there was no VME anything involved.  [...]
> > > Building new control hardware for PUMA robots is a favorite college
> > > project, it seems.  Lots and lots of college robotics courses do
> > > exactly that, with that hardware.
> >
> > Nice!  That must be fun for the hardware hackers.
> >
> > This grad student's work was more about the software, though.  There
> > was hardware, but the point was to run the control loop on the host.
> > This being the late '80s, we didn't have now-modern hardware for it; we
> > were using Qbus MicroVAXen (hence the finding a bug in the KA630), one
> > of the (I gather) few sites actually using multiprocessor MicroVAX-IIs
> > (one CPU for the host OS, the other for the real-time low-level control
> > loop).  I don't recall much about the interface electronics we used,
> > but IIRC the OP said something about wanting to talk to the arm with a
> > VT420.  If so, that means not just the minimal interface electronics we
> > had but some smarts - we wanted the interface from the host to the
> > robot to be about as dumb as possible, since the whole point of the
> > research was the control software.
> >
> > My memories are thirty years old and somewhat fuzzy, but I _think_ we
> > used a hand-built Qbus board as the interface hardware.  I don't recall
> > how much there was between that and the motors, but there must have
> > been some driver transistors at a bare minimum, because I'm fairly sure
> > it was still logic levels when it left the host enclosure.
> >
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Christopher Purdy
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