CM3112 Artificial Intelligence
Fuzzy logic: Computing with words
Steven Schockaert
SchockaertS1@cardiff.ac.uk
School of Computer Science & Informatics Cardiff University
Principle of incompatibility
“As the complexity of a system increases, our ability to make precise and yet significant statements about its behavior diminishes until a threshold is reached beyond which precision and significance (or relevance) become almost mutually exclusive characteristics.”
Lotfi Zadeh
Computing with words
The traditional way of modelling systems is by using a well-defined function, mapping inputs of the system to outputs
Computing with words
For complex systems, it is often not feasible to precisely characterise the underlying functional behaviour
Computing with words
Problem: How to encode imprecise knowledge about a system (which may have multiple inputs)
Solution: model imprecise knowledge using fuzzy if-then rules if X1 is Small and X2 is Small then Y is Large
if X1 is Small and X2 is Medium then Y is Very Large …
if X1 is Very Large and X2 is Very Large then Y is Medium
variable
fuzzy set restricting the possible values of that variable
Computing with words
A fuzzy rule base approximates a function as a collection of fuzzy patches
Applications
Sendai subway 1000 series (Japan 1985) uses fuzzy logic to control speed:
‣ smoother starts and stops ‣10% more energy efficient
Applications: consumer electronics
Applications: automatic transmission
http://www.renault.com/en/lists/archivesdocuments/automatic-transmission.pdf
Applications: MASSIVE simulation