Download - Fuzzy logic mis
Fuzzy LogicIntelligent Technique
Qamar Wajid Ali
OVERVIEW
Where did it begin? What is Fuzzy Logic? Fuzzy Logic in Control Systems Fuzzy Logic in Other Fields Fuzzy Logic vs. Neural Networks Fuzzy Logic Benefits
Fuzzy Logic began Traces back to Ancient Greece Lotfi Asker Zadeh ( 1965 )
First to publish ideas of fuzzy logic. Professor Toshire Terano ( 1972 )
Organized the world's first working group on fuzzy systems.
F.L. Smidth & Co. ( 1980 ) First to market fuzzy expert systems.
WHAT IS FUZZY LOGIC?
Definition of fuzzy Fuzzy – “not clear, distinct, or precise; blurred”
Definition of fuzzy logic A form of knowledge representation suitable for notions that
cannot be defined precisely, but which depend upon their contexts.
What is Fuzzy Logic? Contd.
Fuzzy logic is a form of many-valued logic In contrast with traditional logic theory, where binary sets
have two-valued logic: true or false, completely true or completely false 0 or 1
WHY FUZZY LOGIC
The reason for the most successful of today's technologies which is very simple. Fuzzy logic addresses such applications perfectly as it resembles human
decision making It fills an important gap in engineering design methods left vacant by
purely mathematical approaches (e.g. linear control design), and purely logic-based approaches (e.g. expert systems) in system design.
WHY FUZZY CONTROL?
The reasoning in fuzzy logic is similar to human reasoning It allows for approximate values and inferences as well as
incomplete or ambiguous data (binary yes/no choices) Fuzzy logic is able to process incomplete data and provide
approximate solutions to problems
Fuzzy Control Procedure
Fuzzy control, which directly uses fuzzy rules is the most important application in fuzzy theory.
Using a procedure originated by Ebrahim Mamdani in the late 70s, three steps are taken to create a fuzzy controlled machine: Fuzzification(Using membership functions to graphically describe a
situation) Rule evaluation(Application of fuzzy rules) DE-fuzzification(Obtaining the crisp or actual results)
Degrees of Truth
Both degrees of truth and probabilities range between 0 and 1 and hence may seem similar at first. For example, let a 100 ml glass contain 30 ml of water. Then we may consider two concepts: Empty and Full. The meaning of each of them can be represented by a certain fuzzy set.
Then one might define the glass as being 0.7 empty and 0.3 full
Applying the Values
In this image, the meaning of the expressions cold, warm, and hot is represented by functions mapping a temperature scale. A point on that scale has three "truth values"—one for each of the three functions.
Fig. below illustrates bivalent sets to characterize the temperature of a room
Example
Traditional Representation of Logic
Slow FastSpeed = 0 Speed = 1
bool speed; get the speed if ( speed == 0) {
// speed is slow} else {
// speed is fast}
Fuzzy Logic Representation For every problem must represent in terms of
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 ]
Fuzzy Logic Representation Cont.
Slowest Fastest
float 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}
Slow Fast
else if ((speed >= 0.5)&&(speed < 0.75)) {
// speed is fast}else // speed >= 0.75 && speed < 1.0 {
// speed is fastest}
How do fuzzy sets differ from classical sets?
In classical set theory we assume that all sets rare well-defined (or crisp), that is given any object in our universe we can always say that object either is or is not the member of a particular set.
CLASSICAL SETS The set of people that can run a mile in 4 minutes or less. The set of children under age seven that weigh more than 1oo pounds.
FUZZY SETS The set of fast runners The set of overweight children
Applications
ABS Brakes Expert Systems Control Units Bullet train between Tokyo and Osaka Video Cameras Automatic Transmissions Washing Machines
Fuzzy Controllers
• Used to control a physical system
TEMPERATURE CONTROLLER A temperature control system has four settings
Cold, Cool, Warm, and Hot
Change the speed of a heater fan, based off the room temperature and humidity.
Anti Lock Break System ( ABS )
Inputs for Intel Fuzzy ABS are derived from Brake 4 WD Feedback Wheel speed Ignition
Outputs Pulsewidth Error lamp
Fuzzy Inference (Expert) Systems
Input_1 Fuzzy IF-
THENRules
OutputInput_2
Input_3
Service Time
Fuzzy IF-THEN
RulesTip Level
Ambiance
Food Quality
Fuzzy Inference (Expert) Systems
Fuzzify: Apply MF on
input
Generalized Modus Ponens with specified aggregation operations
Defuzzify: Method of Centroid,
Maximum, ...
Suggested Fuzzy Inference System
Want to OrderPizza
RecognizeShop
Service Time
Tip LevelFood Quality
Ambiance
Output Fuzzy MF for each Phoneme
Assign a Fuzzy Value for each Phoneme, Output Highest N Values to a
Linguistic model
Image ProcessingBinaryGray LevelColor (RGB,HSV etc.)
Can we give a crisp definition to light blue?
FUZZY LOGIC VS NEURAL NETWORKS
How does a Neural Network work? Both model the human brain.
Fuzzy Logic Neural Networks
Both used to create behavioural systems.
BENEFITS OF USING FUZZY LOGIC
? ?