Fuzzy Logic Control

hal hfeinstein at cox.net
Sun Feb 5 09:43:27 CST 2006

Andre, Frank:

There is something called fuzzy logic.  In a nutshell, it is a method of 
design that gives us instructions on how
to build a much simpler control loop with fewer and simpler parts that 
lead to a very good results.
The underlying idea relies on the observation that many control systems 
can do their job well with much less
information (measurement) about the object being controlled   The 
resulting control loop hardware can
be simplified and manufactured cheaper too.  Although the name throws 
people (a logic) it is really a design
method that is pretty easy to understand.  The Japanese have been using 
it for a decade to solve really
hard control problems.  For example, there is some very tall building 
with elevators that must have fast
speed but be very gentile with riders. The system was designed first the 
traditional way leading to a very
difficult to design and expensive proposal.  A second attempt was made 
using the fuzzy logic design method and
it yielded a much simpler design and one that riders said produced a 
ride so smooth they hardly knew they were
moving.  Well, that sounds like a bit of overstatement to me but similar 
results are reported by other designers
in Europe and Asia who have used the technique in many different types 
of problems.  

Although designers in Japan know all about this technique it never 
really caught on in the US.  I don't know why
that is because the guy that discovered it was at UCB and it got wide 
publicity back in the early '90.
(Maybe same deal as quality control: invented here but ignored. Yup).  I 
tried to think of where in amateur radio
we use control loops and several come to mind.  One might be morse code 
decoding against a noisy signal
Control loops inside a satellite are, of course, a natural application.  
Perhaps an improved battery charger for solar cells.
The fuzzy logic design method is a bit of a different way to view the 
problem but its results are good.  It has been applied to
computers and there is something called a fuzzy algorithm that nicely 
captures the way we do things
like mixing ingredients for baking a cake or  parallel parking a car or 
guiding an elevator.
This is an important technique that can yield some new ways of
looking at  control problems.  I've held off on telling how to use it so 
if there's interest start by exploring the
subject on the web.


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