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C00002 00002 \\M1BDR25\M2SIGN57\M3NGR25\M4NGR20\F2\CVICARM
\F3\C154 EAST DANA STREET
\CMOUNTAIN VIEW, CA. 94041
\F1\CAugust 24, 1974
Prof. David Waltz
Coordinated Sciences Laboratory
University of Illinois
\J Enclosed are the drawings of the proposed Stanford PDP-11/45
interface and the arm driver electronics. As I have mentioned to you
several times, not all of this is complete, and none of the various
circuits have been tested on the PDP-11.
The arm power amplifiers, the brake drivers, and some of the
circuitry associated with the actual drive of the arm has already
been implemented on one of our arms conected to the PDP-6 and PDP-10.
This works fine, and is being duplicated for our older arm which has
switching power amplifiers which create bothersome noise spikes. The
big difference is the interface itself.
The fellow who his handling the design of the PDP-11
interface at Stanford is Tom Gafford (tel. 415-497-4971). The
enclosed drawings signed TAG were done by him. They are reasonably
complete, but no doubt there will be some changes made before
everything works properly. The entire interface in going to be
placed out near the arm. The Unibus from the PDP-11 will be brought
all the way out to this small rack which is about 24 inches high and
the standard panel width of 19 inches. Mounted on the front of this
rack are two DEC racks containing a total of 10 single density blocks
and 6 double density DEC blocks. The pin side faces foward, and all
the electronics, cables to the arm and other peripherals, and the
Unibus cable plug into these blocks via DEC cards. The only
electronics not on this part of the rack is the forced convection and
natural convection heat sink amplifiers. These are mounted on the
bottom and back of the rack unit with a muffin fan blowing directly
on the forced convection heat sink amplifiers. The main arm power
supply used at Stanford consistes of two Wanlass "Brute" type
supplies with 20 or so amp capability at 28-30 volts. Two are used
as we use a bipolar supply. These supplies are mounted on their own
chassis, and are separate from the rack unit. The A-D reference
supply, the op-amp and logic supplies are mounted in the rack.
The reasoning for bringing the Unibus out to the arm is that
the longer distance we run analog signals, the more noise and errors
we are apt to get. Thus, bring the Unibus out. Gafford feels that
he can do better than a DEC DR-11-C or DR-11-B card, so he has
designed his own way of connecting the Unibus to the interface.
In parallel with all this, I am having my own simple and low
cost interface developed for running either a Stanford or M.I.T. type
arm from a PDP-11, or a NOVA, etc. This interface is simply a 16
channel 12 bit A-D, an 8 channel 9 bit DAC, and 7 brake drivers.
All this is mounted on three double height DEC cards (about 75 ic's,
and interfaces to a PDP-11 via a DR-11-C card (from DEC). This
simple interface does not have sample and holds ( I dont think they
are necessary), nor does it have DMA capability, as I dont feel it
has to operate very fast. For the encoder version of the arm (which
you have ordered), three quadrature decoder and counter cards are
required for the three encoded joints.
I am having Fred Dhrenkenhan of the MIT- AI lab make up the
quadrature decoder and counter boards for me. I will include the
boards with the kit, so that problem will be solved for you.
As for the Vicarm version of the arm driver electronics, we
are using our MIT arm electronics package with a larger power supply,
and beefier amplifiers. The amplifiers are similar to what Gafford
is using at Stanford, and so are most of the other drive details.
The difference is that I am making these amplifiers and brake drivers
as a single unit with pc boards instead of DEC cards and blocks. The
power supply is a much less expensive transformer and capacitor
filtering type which is unregulated (I dont think regulation is
required for the power amplifiers). This arm driver package is
similar to what I supplied to SRI, only it uses built up amplifiers
instead of RCA HC2000H power hybrid amplifiers which are hard to get
I don't know whether I mentioned it or not, but I am building
a Stanford arm for the National Bureau of Standards. Their driver
unit will be similar to what you want. We could make a complete
driver unit (minus the interface, but including a hand controller)
for about $2000. I know that this sounds like a sales pitch- it
isn't, as that price is about cost. Regardless of whether you do
things yourself or buy I will give you details as we generate them.
I suggest you have some people in the know look over the
Stanford arm interface plans, and maybe even call up Tom Gafford
(best in the afternooons or evening here, as he's usually at Stanford
2 pm to 2 am). The decision is between a full blown, able to do
almost anything interface versus one tailored just to the arm, with
no regard to operating super fast, etc.
Now to the arm machining details. In a day or so you will
recieve some of the bearings for the arm. Also will be some of the
corrected drawings. In a couple of cases I said wait. That was
because the wiring details were being changed. We have worked out
what appears to be an alternative solution, and will be testing it
out shortly, and will let you know what hole patterns are necessary
to mount the connector blocks when we know ourselves. This is not a
big thing, and I hope you will be patient on the wiring slots and
holes in the square tubes. I might also add that we intend to do
another thing to help you out. We will be supplying some of the
assemblies complete- including some of the parts you were supposed to
machine. This will be on an exchange sort of basis. The reason is
that I feel it wise to have us assemble the joint 1,2,3,4,and 5 motor
assemblies as the brush and tachometer assemblies are fragile and
some careful fitting is required. As I also mentioned, all the parts
listed on the parts list will be supplied, and they will be machined
to the drawings. This will eliminate the possibility of your
accidentally scrapping a part, and having to reorder or whatever.
Most of the parts have arrived at Vicarm, and we will be machining
them within the next two weeks. When a reasonable number are done,
we will send them to you. We will probably have to send another batch
later, as some items are back ordered. In any event, I feel sure that
we will have everything for you by October 10 or so.
Dave, I hope this letter clears up some of your concerns.
Call me should you have any other furthur questions. I admit to not
being too prompt on my promises, but I'm trying to get everything
right the first time, and its taking a lot longer than expected.\.