[Diy_efi] fuzzy logic

[niche at iinet.net.au]

mmm, That sort of mirrors my sentiments and I was in two
minds whether to respond initially. When PID controllers were
expensive and the confluence of microcontroller h/w expense
with vague understandings of control implementation of sampled
data systems some 'clever' companies came up with term fuzzy
logic as a silver bullet to various ill-defined control problems
which were eventually well enough defined so PID type
controls with a few mostly minor exceptions could be used.

True 'so called'  fuzzy logic would require a huge data set
to mirror what goes on in the human brain, if indeed that
was the initial paradigm. Some not so complimentary engineers
who knew PID really well suggested Fuzzy logic was inspired
by fuzzy thinking. The suggestion is still there to some degree
that fuzziness can somehow fill in the blanks for lack of
initial planning, in that the control system can work this out.
Most interpret this as a form of intellectual laziness or
incompetence of misunderstanding of the requirements or
inability to articulate what is the desired goal in more than simple
terms vis a vis - save fuel by adjusting engine mixture over a
wide range of driving style, gearing and road conditions...

Well if you have a train car weighing several tonnes accelerating
whilst handling supply voltage variations or similar real world
heavy and dangerous items - fuzziness is that last thing you
want to tolerate - except perhaps in statistical analysis and
removal of outliers...

The huge number of really effective PIDs soon walked all over
even moderately complex fuzzy logic designs (back then).

I also would be interested to know what you are trying to achieve
and why you are of the impression the keywords fuzzy logic in
some way applies as a first option to a solution ?

Regards from


Mike Massen
Perth, Western Australia
VL Commodore Fuse Rail that wont warp or melt !
Yes the guy with the twin tyres, in Australia ;)
http://niche.iinet.net.au



At 11:56 PM 12/05/05, you wrote:

>Hi,
>
>Some one asked about fuzzy logic the other day.
>
>As an ECU designer it was of great interest to me when it first appeared
>about 15 years ago or so.
>
> It was something that Motorola touted when the 68HC11 was first
>offered to the non OEM market.
>
>Try as I might I could not come up with an automotive use for it.
>
>If you had two broom sticks that you wanted to balance end on end
>it was the ducks guts. but...
>
>Seriously; it's a very, very simple control algorithm that can be used
>for something like fan speed control of a multi speed fan that only has
>speed steps rather than continuously variable control.
>
>It has inputs and tables and outputs  and not much else.
>
>About 2 years later one of the Motorola staff released a full PID
>controller that used about 180 lines of machine code and worked a treat.
>It was quite capable of Class A power generation when used as a governor
>control on a genset.
>
>What were you hoping to do with the said fuzzy logic ?
>
>I love to hear that you've found a use for it.
>
>HTH
>
>Phil
>
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