[From Fred Nickols (970930.1835 ET)]
Mary Powers (970929)
Fred Nickols (970928.10:20 ET)
I read this post and was surprised by your statement "COMPLETELY MISSING
FROM THAT WEAPONS SYSTEM IS INTENT! and following remarks to the effect that
servomechanisms have no intention or purposiveness. It inspired me to look
at your long exposition of the servomechanism you knew best.
<snip>
But apparently signals from the gun motors never get back to the computer -
once the computer has given its orders. This makes the computer-gun motor
system open loop, although the gun-motor system itself is a control system.
Thus, while the two lower level system have reference signals (intentions},
and are control systems, the over-all system doesn't, and isn't. So you are
quite right that the weapons system does not have intent, but wrong about
the gun mount, and the radar system.
True enough; down in the plotting room, where the computer was located, we
never knew where the gun mount was. I always longed for a "correspondence
dial" that would tell me if the gun mount was lined up with the gun orders,
but never had one. The gun mount, however, had information about ordered
and actual position, so it "knew" where it was in relation to the reference
or ordered position.
You are talking about the infancy of control systems,
I'd never thought of it in those terms but, now that you mention it, it
seems true enough. My first computer was a MK1A Rangekeeper, an
electro-mechanical device full of gleaming cams and shafts and gears and
brightly-colored wiring harnesses looking for all the world like ribbons of
multi-colored spaghetti. The next one, a MK47, was a vast improvement; it
was much more electro- than mechanical. Both were manufactured by Ford
Instrument Company, a division of Sperry-Rand. By the late 1960s, the fleet
was beginning to install digital computers (mostly for use with missile
launchers and other applications where the smooth, continuous positioning of
gun mounts wasn't involved. This was because the computation time in the
digitals was still too slow to use in positioning gun mounts).
when positive feedback
was used to make a "sluggish" negative feedback system more responsive -
that sort of arrangement became obsolete with the development of more
sensitive, etc. negative feedback systems. And about a system design that
included a few simple control systems without the whole system being a
control system.
I'm beginning to feel "obsolete" myself. Anyway, the gun mount and the
radar, as you observe, were control systems a la PCT, and the overall
gunfire control system was not.
This is interesting, because one (incorrect) criticism of
PCT is that feedback is too slow (sluggish). Another is that there is
nothing new about the idea of living control systems (that people HAVE
control systems here and there) - which misses the enormously different
point of PCT that people ARE control systems - numerous levels of them, with
huge numbers of them at each level.
So far as I know, when it comes to people and organizations, "feedback" or
information about the consequences of one's actions, is often "far removed
in space and time" from the actions themselves. In the absence of feedback
of this kind, most people seem to settle for other forms; for example,
keeping their behavior aligned with mental models of "effective behavior."
In other words, we act in ways we think are having the desired effects but
we don't really have any information about the effects themselves.
In your description, the computer processes the radar information and gun
behavior and issues orders to the gun mount to assume such-and-such a
position (this is the way psychologists think the brain works - calculate,
then order actions).
I know, and it drives me up the wall, because I don't believe it and never
have. Although, it's not as bad as it might sound in the case of the gun
mount. Remember, this was an analog, continuous processing system, so, as
folks on this list are fond of saying, "everything was going on everywhere,
simultaneously."
If the whole system were a set of control system, the radar information plus
gun firing characteristics plus the offset between the radar signal in
present time and the presumed location of the target when the shell would
get to the area would all constitute inputs to a system of which the output
would be a reference signal - the intended position of the gun.
That's essentially the way it worked. All the inputs you describe were
there, and the output was a reference signal, an intended position for the
gun, which was transmitted to the gun as an "order," with which the gun
mount complied. In PCT terms, "control" was local; the gun mount was being
provided with a reference condition instead of generating its own.
The gun orders would not be to move the gun to a calculated position, but
for the gun to move, while continuously reporting its status back to the
computer, until the difference between where it is pointing and where the
computer wants it to point is zero.
That's what it did, Mary. The main difference between the way it worked
isn't that the gun did or didn't move to the position the computer ordered,
because it did, but that the computer never knew where the gun mount was.
Essentially, the gun mount said to the computer, "Trust me." Keep in mind
that the target was moving, the orders were changing, and the mount was
keeping pace.
At which point the computer could fire
the gun. (Or if the gunnery officer wanted to feel in control, it could
flash a red light and he could push a button to fire the gun. Or he could
yell "Fire!' and the gunner could push the button...)
In my day, the computer never fired the gun. That is probably different
nowadays. In my day, there were three sets of firing keys, one in the
director, where the gunnery officer could see what was going on; one in the
plotting room (normally for use in shore bombardment); and one in each of
the gun mounts. All were used at one point or another.
The whole point of PCT is that people ARE like "servomechanisms" (most
people these days call them control systems). The idea behind the
development of control systems was to design devices that had certain
specific characteristics of people: some representation in them of an
intended state of affairs, and some means of changing the actual state so
that it matched the intended state. This required a means of sensing the
actual state, and a means of comparing the reference and actual states.The main difference between living and artificial control systems (in the
context of this discussion) is that you can't get at the reference signals
of living systems from the outside. You say "[People] are not gun mounts to
be issued orders and expected to comply with great alacrity. No? People in
the Navy and elsewhere are issued orders all the time and expected to hop to
it. But they don't do it like the gun mount receiving a reference signal
from the computer. The order doesn't get inside their heads and say "do it".
Instead the order goes into their ears and up their control systems, as a
perception of intensity, of sounds, of words, of meaning, etc. to points
where what they are told to do is compared with all kinds of reference
standards such as their commitment as sailors to obey orders. When a person
with a reference signal for obeying an order gets an order, there is then an
error signal until the order is carried out - all kinds of lower level
control systems are activated to enable this to happen, and activity
continues until the error is zero.
Or until "reorganization" occurs, as is the case when a sailor "decides" to
stop taking orders.
Unlike the gun mount, a person may have numerous high level control systems
which conflict with the perceived order and with reference signals that say
orders should be obeyed. So sometimes sailors mutiny, and soldiers fire
their guns in the air instead of at the enemy, etc. But that is beside the
point here, which is that control systems, like microorganisms, although far
less complex than people, do have intentions.
I agree that "living" control systems, like micro-organisms and people, do
have intentions (although I suspect the micro-organisms's might be a little
less elaborate than mine). I don't agree that a weapons control system has
intentions, just reference conditions.
Anyhow, whatever technical knowledge I might have had at one point is
clearly out of date by now. I took my initial electricity and electronics
training in 1955. That was a loooooonnnnnngggggg time ago.
Thanks for your thoughtful posting, Mary. It has been very helpful
Regards,
Fred Nickols
Senior Consultant
The Distance Consulting Company
nickols@worldnet.att.net