# Re: PID Control and fuzzy logic

From: P. Sarma (psarma@seas.upenn.edu)
Date: Tue Nov 06 2001 - 07:27:41 MET

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It's not as simple as that. A careful, focused look at FLC's show that in
fact it is very closely related to PID's. This is not apparent from the
direct construction, which as we all know is quite intricate, with (i)
fuzzification, (ii) fuzzy partitions, (iii) fuzzy manipulations in the FRB,
and (iv) defuzzification. This is partly the classical effect of "missing
the forest for the trees".

A sequence of papers that spans from works such as Tong and Mullholland
(1987), and onwards, clearly show that the general FLC, which is the Mamdani
or M-FLC, is *precisely* a Nonlinear PID controller - in fact it is a
Gain-Scheduled PID, where the schedulors are the inputs to the FLC. For more
details on this, have a look at a series of papers by Gosine et al
(~1999-2000) in IEEE SMCB.

Pramit

----- Original Message -----
From: "Techoji" <techoji@yahoo.com>
To: "Multiple recipients of list" <fuzzy-mail@dbai.tuwien.ac.at>
Sent: Sunday, November 04, 2001 7:23 PM
Subject: Re: PID Control and fuzzy logic

> Thank you Arjun,
> At least, Now I am clear that PID control and fuzzy control are different.
> I'll read thro' some fuzzy logic stuff.
> Techoji
>
> arjun_kakkar@yahoo.com (Arjun Kakkar) wrote in message
> > Nope, PID control is different from fuzzy logic based control.
> >
> > Fuzzy logic has multiple advantages over PID control - it is more
> > effective with less mathematical complexity. PID control usually would
> > require quite a complex mathematical model for it to be sufficiently
> > effective. Fuzzy logic, on the other hand can directly control the
> > variable(/s) in question with a simple set of rules. Moreover, fuzzy
> > logic would keep your system in a narrow band with lesser overshoots.
> >
> > Hmmm... guess it would be be better if you read up some introductory
> > text on fuzzy logic. That would help.
> >
> > Cheers,
> > Arjun Kakkar
> >
> >
> > techoji@yahoo.com (Techoji) wrote in message
> > > Hi,
> > >
> > > A question to the Fuzzy logic gurus.
> > >
> > > As a part of my B.E. Project I implemented
> > > PID(Proportional-Integral-Derivative) Controller for controlling DC
> > > Motor.
> > >
> > > This type of control shows much resemblance with all the examples
> > > given for any
> > > fuzzy logic implementations.
> > >
> > > I was wondering if PID Control is really a fussy logic implementation
> > > or what ?
> > >
> > > Regards,
> > > techoji
>
>
>
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