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Perhaps the sentiments contained within the following
pages, are not yet sufficiently fashionable to procure them general
favor; a long habit of not thinking a thing wrong, gives it a
superficial appearance of being right, and raises at first a formable
outcry in defense of custom. But tumult soon subsides. Time makes more
converts then reason.
--Common Sense; Thomas Paine, February 14, 1776
In the spirit of Thomas Paine, I'd like to offer a few comments
concerning personal computers (PC's) and programmable controllers
(PLC's). We've managed in the last year or so to give the market
something interesting to talk about and let the trade magazines try to
digest new buzzwords. Somehow we seem to have fallen into this pitched
battle between PLC's and PC's. The debate over PC control versus PLC
control, however, provides a misplaced focus for the real issues. This
discussion is not one hardware/OS versus another; it's about whole new
business strategies trying to emerge against a status quo feudal
system. The current state of the controls market, whether it be PLC,
CNC, or DCS, can really be summarized by looking at a structure that
takes proprietary hardware and software though captive channels to
customers held hostage by the sunk costs of their installed base and
training.
Now the interesting thing about this is that a lot of people are
comfortable in their current position. Change is not comfortable. And,
if you're on top, it is down right scary! Yet the mere mortals on the
office side of the enterprise have been forced to adapt to
ever-changing technology since circa 1982. Somehow we have convinced
ourselves that the factory floor is quite different from the office.
Really? I think we spend lots of time trying to come up with arguments
just to keep the MBAs out of our hair. Oh, we can make arguments that
nobody lost their life because the copier went down, etc. But can we
really look at the vast majority of control applications and say that
the environment is all that technologically different from the rest of
the world.
In many plants and factories the physical environment is even better
then the office, given strict temperature, humidity, power,
particulate, and static control. To be sure there are applications
where life is at risk if controls fail. In those cases you need
redundancy, back up systems, and physical intervention procedures to
ensure that the process will not fail. For most of us, however, systems
are designed to work until they fail, and then we want them to fail in
a predicable manner. Getting them back up and keeping the failure
frequency to a minimum is how we get into these arguments of who has
the better technology.
Now in the commercial area we have cost, speed, ease of use, packaging,
support, delivery, optimization, and databases. Shouldn't we take a
look at the technology that has serviced the necessary quality shakeout
of a high-volume, low-margin business, whose costs have been driven
down at the same time the familiarity curve as risen? Shouldn't we try
o take advantage of the R&D resources of Microsoft, Intel and 3Com,
which every day produce high volume, high-quality technology that mere
mortals make work every day? Has the commercial world finally produced
technology robust enough for the factory or plant floor? Or, is it that
those in the factory and plant floor environments have finally become
familiar enough with the technology to at least try it? Or, is it that
he proprietary price premium has become high enough that we can
overcome the pain of change? Maybe the incremental cost of using
leveraged technology (e.g. Windows NT, Ethernet, etc.) is now so far
below the incremental cost of sustaining the sunk cost curve, that it
makes sense to look at what we're really doing. Why should a scanner
card with a sub 500 kHz performance cost $2000.00 when a 10 megabit
Ethernet card costs $80.00?
The calculator and the spreadsheet
This is not about PCs versus PLCs. The answer to the question, "Which
do we need?," is that we need both! Chances are you have a high powered
computer right on your desk at work and at home. You likely have a
calculator nearby also. Now why would you need a calculator when all
those MIPS are eagerly waiting? The answer is that for some problems,
it is easier to use. When you multiply 117 times 235, it is easier to
do it on your TI than in Excel. On the other hand, when you've got a
multivariate problem you will reuse or move to other places, you can't
beat the power and flexibility of a computer spreadsheet. The point is,
you have to know enough about your problem to know if you have a
spreadsheet or calculator problem. If it's a calculator problem,
chances are your small PLC will do just fine. If you have a spreadsheet
problem, life will be more fun with PLC-based control.
Aha! Now you've got it. Let's just put the PLC on a PC. Problem is
relay ladder logic (RLL) on a PC costs you more and does less then a
PLC. This doesn't make much sense to us. We often hear the argument
that everyone knows RLL. We don't think so. Explaining it to recent
engineering school graduates is usually met with the expression,
"You've got to be kidding!" The best description we've heard is, "Oh,
this is sort of a graphical assembly language." So why not take an
in-vogue approach and find a simple language tuned to the problem?
Well, if you're talking about solving a process problem, flow charts
appear quite logical. It's a technique that everyone does seem to know,
or can be picked up intuitively. In Ann Arbor we teach this technique
in elementary school.
A new marketing theme
We've become convinced that products and companies never really go
away. Remember when PLCs were going to replace relays? Actually, a lot
of relay panels disappeared, but the relay itself is alive and well. In
fact the relay market is almost twice as large as it was in 1974 when
we were just fooling around with this PLC stuff. Similarly, the
argument that PLCs are dead is a little presumptuous. Our view of this
PC control technology is that it is a new wave--or theme. Relays were a
theme and had their own technology adaptation curve (e.g., the product
life cycle). Later, this spawned a PLC life cycle curve. PC control is
now a third curve and market theme.
Various business reference books (e.g., Inside the Tornado by Geoffrey
A. Moore) refer to this as a discontinuous innovation! Or, it could be
the dreaded paradigm shock! What we find in our travels around the
market is a resignation that PC control is not an if but a when.
This is dependent on a change in user expectation. To explain this
let's turn back the clock to when the IBM Selectric was king and the
first word processors appeared. Sometimes it's hard to imagine life
before laser printers, hundreds of TrueType fonts, thesaurus, spell
checkers, and a grammar checker. But, in the early days all we had was
soft typewriter. Many secretaries stayed with the tried and true, top
of the line IBM Selectric--feeling that, if IBM didn't give them
permission to try one of these things then they couldn't even be
tempted to try! In fact, the early PC didn't do much more then the
Selectric and it wasn't always as convenient.
But then IBM came out with one of these computers the technology was
blessed! Later, something even more dramatic happened. New companies,
software companies, emerged with stuff that suddenly let these new
boxes do all sorts of cool things that the variable Selectric just
couldn't match. At this point, the user expectation changed. Today,
when we sit down to type something we expect it to check our spelling,
have wizards, templates, fonts and so on.
The Selectric disappeared into the room where we go to make carbon
copies. When control engineers expect their controls to network
seamlessly, share data painlessly, import/export information in a well
recognized format, be table driven, and run on ubiquitous computers,
the users expectations will change! Then the debate won't be one of PCs
versus PLCs, but rather new thinking companies versus the beleaguered
defenders of the old empire. Who becomes whom will be fun to watch!
Ken Spencer
President & CEO
Think & Do Software, Inc.
Ann Arbor, MI 48108
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