Dissertation (PhD)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: A standard fuzzy logic controller is not robust enough to guarantee consistent closed-loop
performance for highly non-linear plants. A finely tuned closed-loop response loses relevance as
the system dynamics change with operating conditions. The self-adaptive fuzzy logic controller can
track changes in the system parameters and modify the controller parameters accordingly. In most
cases, self-adaptive fuzzy logic controllers are complex and rely on some form of mathematical
plant model.
The multi-mode fuzzy logic controller extends the working range of a standard fuzzy logic
controller by incorporating knowledge of the non-linear system dynamics into the control rule-base.
The complexity of the controller and difficulty in finding control rules have limited the application
of multi-mode fuzzy logic controllers.
An automated design algorithm is proposed for the design of a multi-mode control rule-base using
qualitative plant knowledge. The design algorithm is cost function-based. The closed-loop
response, local to a domain of the non-linear state space, can be tuned by manipulation of the cost
function weights. Global closed-loop response tuning can be done by manipulation of the controller
input gains. Alternatively, a self-learning or self-adaptive algorithm can be used in a model
reference adaptive control architecture to optimise the control rule-base. Control rules responsible
for unacceptable closed-loop performance are identified and their consequences modified.
The validity of the proposed design method is evaluated in five case studies. The case studies
illustrate the advantages of the multi-mode fuzzy logic controller. The results indicate that the
proposed self-adaptive algorithm can be used to optimise a rule-base given a required closed-loop
specification. If the system does not conform to the model reference adaptive architecture then the
intuitive nature of the cost function based design algorithm proves to be an effective method for
rule-base tuning. / AFRIKAANSE OPSOMMING: Standaard wasige logika beheerders is nie noodwendig robuust genoeg om goeie geslote lus
werkverrigting vir hoogs nie-liniere aanlegte te waarborg nie. In Perfek ge-optimeerde beheerder se
geslote lus werkverrigting mag verswak indien die aanleg-parameters weens bedryfstoestande
verander. Self-aanpassende beheerders kan die verandering in die aanleg-parameters volg en die
beheerder dienooreenkomstig optimeer. As In reël is In self-aanpassende beheerder kompleks en
afhanklik van In wiskundige model van die aanleg.
Die multi-modus wasige logika beheerder vergroot die werksbereik van die standaard wasige logika
beheerder deur kennis aangaande die stelsel se bedryfstoestand en stelselparameters in die reël-basis
in te bou. Die aanwending van die multi-modus beheerder word tans beperk deur die struktuur
kompleksiteit en moeilike optimering van die reël-basis.
In Ge-outomatiseerde multi-modus reël-basis ontwerps-algoritme wat gebruik maak van
kwalitatiewe kennis van die aanleg en In kostefunksie word in hierdie proefskrif voorgestel. Die
geslote lus gedrag beperk tot In gebied in die toestands-ruimte kan ge-optimeer word deur die
kostefunksie gewigte te manipuleer. Die globale werkverrigting kan ge-optimeer word met die
beheerder intree aanwinste. In Self-aanpassende algoritme in In model-verwysings aanpassende
argitektuur word as altematieftot reël-basis optimering voorgestel. Reëls verantwoordelik vir swak
werkverrigting word ge-identifiseer en verbeter deur modifikasie van die reëls se gevolgtrekkings.
Die voorgestelde ontwerps-metode word deur middel van vyf gevallestudies ondersoek. Die studies
dui die voordele van die multi-modus struktuur aan. Die self-aanpassende argitektuur is In kragtige
hulpbron om In reël-basis te optimeer vir In gegewe geslote lus spesifikasie. Hierdie proefskrif toon
aan dat indien die stelsel nie aan die vereistes van In model verwysingstelsel voldoen nie, is die
kostefunksie benadering tot reël-basis ontwerp In aantreklike en intuïtief verstaanbare opsie om die
reël-basis te optimeer.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/51631 |
| Date | 12 1900 |
| Creators | Hugo, Etienne Martin |
| Contributors | Du Plessis, J. J., Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 145 p. : ill. |
| Rights | Stellenbosch University |
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