Andy Warren writes:

       Fuzzy-logic has one advantage in control systems:  It's a quick
       and easy way to build software that ALMOST works.  However, this
       is outweighed in most cases by the time required to tweak the
       parameters of your fuzzy model until the software works
       acceptably; most fuzzy-logic "development" is performed by
       trial-and-error guesswork.

       On top of this, it's nearly impossible to prove that your final
       design is optimal.  It's even hard to guarantee (for complex
       fuzzy control systems, anyway) that the software won't exhibit
       wildly pathological behavior at certain points... Not a good
       thing fore control systems that are used in critical safety
       applications.

My own take is that fuzzy logic is a little bit like analog computing:
because of the way it is constructed, it is in a sense 'more linear'.
I don't mean the algorithm that the controller is executing---of
course a PID algorithm is linear in mathematical sense. However,
in presence of faults (software-, hardware- or operator-related),
purely numerical/digital algorithms are more fragile than an
equivalent, say, analog PID controller.  For instance, an analog motor
controller could not fully reverse motor speed from +Vmax to -Vmax in
single cycle, in response to some noise from the control loop, but a
digital system might.

It looks reasonable to me that a fuzzy system would behave more like
an analog system, because of typically broad band assignments for
fuzzy variables. I haven't played extensively with fuzzy controllers,
though, so the above is just my hunch. Maybe instead of my playing
air guitar someone could provide more concrete info...

        p