Another way is looking at these differences from 'conventional', or
crisplike controllers. As Feijun Song mentions, there is this
singlepoint construction which 'slides' smoothly from one [crisplike]
to another. As far as the good *old* PIDcontrollers go, it is interesting
to note that most 'standard' FLC's use a structure known as the
FuzzyPI[D], and there are a reasonable number of papers that "prove" the
equivalence: that an FLC is a nonlinear PI! But if one inspects Mamdani's
pathbreaking 1974/5/6 papers on FLC's, it is clear that the inspiration
for the 1st FLC was indeed the humble PI controller, to start with.
Fuzzy Logic can be called a "subscience" since it is so universally
applicable, and provides a powerful alternative approach to crisp
problems, often complementing or simply outdoing them: Fuzzy {Regression,
Image Processing, Optimization, and many more}.
Pramit
On Mon, 21 Jun 1999, Mohammad Fazle Azeem wrote:
> Dear Fuzzy Member Hello!
> I am very much strange about the number of response of my comments according
> to my understanding of Fuzzy logic (enclosed at the last). Though I have
> mentioned in my comments about my needs. I received the comments from Dr.
> Feijun Song (enclosed after this message). I am sending this email in the
> hope to receive some expert comments from the people working in this area. I
> think all fuzzy friends put their effort to stop me from going on forward on
> wrong track and guide me towards the right track. Thanks in advance for
> their precious time spending to read this email and for making a response.
>
> M.F. Azeem
> EED, IIT Delhi,
> Hauz Khas, New Delhi110 016,
> INDIA
>
>
>
> >From: Feijun Song <fsong@oe.fau.edu>***********************
> Hi, Azeem, you made a very good comment. the power of fuzzy logic in control
> field lies in its ablity to imcoorperate different methodologies into a
> systematic way, thus achieving better global performance which a single
> methodology can not do. For example, one can suggest: Fuzzy Sliding Mode
> Controller, or Sliding Mode Fuzzy Controoller, ( they are different ) to
> achieve broader operating range, while keeping the transition from one SMC
> to another SMC smooth.
>
> My comments********************
> Yes, Fuzzy Logic allows it. There is general misconception that Fuzzy logic
> is independent of other methodologies, i.e., classic and modern system
> approach. One can incorporate different methodologies in Fuzzy Logic. Fuzzy
> Logic gives different possible ways to combine methodologies for a
> particular situation. The best implementation of an Fuzzy Logic can be
> achieved by selecting a suitable type of model and Inferencing mechanism.
> This selection is depend upon the situation. For example around an operating
> point (in nonlinear system) a PI controller (with particular set of
> parameter) works very well. As soon as either operating points or initial
> conditions get change we need to update PI parameters. With the use of Fuzzy
> Logic we can design a controller which can work for all feasible operating
> with the use of multiple PI controller. In this operation Fuzzy Logic
> function as supervisor in smooth switching from one PI controller to another
> PI controller. In a similar way we can incorporate different type of
> controller (not strictly PI) for a particular application. The broad
> spectrum of this suggestion is we can incorporate different methodologies in
> Fuzzy logic to get best feasible results. It is my view regarding Fuzzy
> logic after working on this subject since July'95. I am in need of
> correction or support of my view abou fuzzy logic. Both correction and
> support will be highly appreciable.
> Thanks
>
>
> ______________________________________________________
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>
>
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============================================================================
Pramit "Jake" Sarma
[Home] [IITB]
email: jake_n_jazz@yahoo.com email: psarma@che.iitb.ernet.in
Process Systems and Control
The PROCISS Group

{Mathematics/Physics}<Applied NonLinear Control>{Industrial World}

Process Control, Identification & Simulation Systems
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