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ADVANCED FUZZY CONTROL SYSTEMS
NAVEEN TAMANAM(EEE)
B.TECH
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Overview of Fuzzy logicAdvanced control systems by fuzzyconclusion
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Contents
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I ntroduction to fuzzy
Fuzzy Logic - 1965 Lotfi Zadeh, Berkely
Definition : A form of knowledge representation suitable for notions that cannot be defined precisely, but which depend upon their contexts.
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Fuzzy logic is a form of multi-valued logic derived from fuzzy set theory
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According to Aristotles logical calculus
there are 2 truth valuesi.e true or false
Similarly boolean algebra have
i.e 1 or 0in modern systems there 3 values
* true , fault and unknown
but in fuzzy logic there are infinite truthvalues range form 0 to 1
n>2 in multi valued logic
where n=number of truth values
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logic illustration
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Take the glass of having water
From boolean logic we can representonly 2 states
Logic 1 Logic 0
fillempty
But in fuzzy logic we can representeach and every condition also
Logic 1 for fully fill
Logic 0 for empty
0.75
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TRAD I TI ONAL REPRESENTAT I ON OFLOG I C
Slow Fast
Speed = 0 Speed = 1 bool speed;
get the speed
if ( speed == 0) {// speed is slow}else {// speed is fast}
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FUZZY LOG I C REPRESENTAT I ON
For every problemmust represent in termsof fuzzy sets.
What are fuzzy sets?
Slowest
Fastest
Slow
Fast
[ 0.0 0.25]
[ 0.25 0.50 ]
[ 0.50 0.75 ]
[ 0.75 1.00 ]
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FUZZY LOG I C REPRESENTAT I ON CONT.
Slowest Fastestfloat speed;get the speed if ((speed >= 0.0)&&(speed < 0.25)) {// speed is slowest}else if ((speed >= 0.25)&&(speed < 0.5)){
// speed is slow}else if ((speed >= 0.5)&&(speed < 0.75)){// speed is fast}else // speed >= 0.75 && speed < 1.0{
// speed is fastest}
Slow Fast
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Fuzzy setFuzzy sets are sets whose elements havedegrees of membership
Definition
A fuzzy is a pair of (A ,m) where A is a set &m:A [0 ,1]
X is called not included in the set (A,m) if m(x)=0,x is fully included if m(x)=1
And x is a fuzzy number if 0
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OR I GI NS OF FUZZY LOG I C
Traces back to Ancient Greece
Lotfi Asker Zadeh ( 1965 )
y First to publish ideas of fuzzy logic.
Professor Toshire Terano ( 1972 )
y Organized the world's first working group on fuzzy systems.
F.L. Smidth & Co. ( 19 8 0 )y First to market fuzzy expert systems.
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Advanced control system by fuzzy logic
Fuzzy Logic provides a more efficient and resourceful
way to solve Control Systems.
Some Examplesy Temperature Controller
y Anti Lock Break System ( ABS )
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Anti lock break systemThis system is work on the fuzzy logic
This is a simple control systemthe control is done by the fuzzy set
members
the system is controlled by speed andtemperature
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The block diagram of fuzzy control
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ANT I -LOCK BRAKES
Anti-Lock
Brake Module
Speed
Sensor
PressureValve Dump/VentValve
Master Cylinder Assembly
AntiLock
12V
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CONCLUS I ON
Fuzzy logic provides an alternative way to represent
linguistic and subjective attributes of the real world in
computing.I t is able to be applied to control systems and other
applications in order to improve the efficiency and
simplicity of the design process.
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