|
@@ -1,95 +0,0 @@
|
|
|
-# Soft Computing
|
|
|
-#### Andrea Bonarini
|
|
|
-##### 5 October 2015
|
|
|
-
|
|
|
-#### What is Soft Computing?
|
|
|
-
|
|
|
-The term was introduced by Lotfi Zadeh, the father of fuzzy sets,
|
|
|
-to denote programming techniques not related to *traditional* programming languages:
|
|
|
-- Fuzzy systems
|
|
|
-- Neural networks
|
|
|
-- Stochastic systems
|
|
|
-
|
|
|
-##### definition
|
|
|
-A set of techniques to model systems (input-output mapping) by approximating them.
|
|
|
-
|
|
|
-##### Modelling technique: generalization
|
|
|
-Considers a small sample of the entity to make an approximate model,
|
|
|
-
|
|
|
-
|
|
|
-#### Model
|
|
|
-
|
|
|
-- Is a *representation* of some entity, defined for a *specific purpose*.
|
|
|
-
|
|
|
-- Is limited to aspects of the entity represented which are *relevant for the purpose*
|
|
|
-
|
|
|
-- A model is different to the represented entity ex: map vs land
|
|
|
-
|
|
|
-- Models lead to *approximation, uncertainty, imprecision*.
|
|
|
-
|
|
|
-##### Approximation
|
|
|
-The model features are similar to the real ones but not the same.
|
|
|
-##### Uncertainty
|
|
|
-We are not sure that the features of the model are the same of the entity.
|
|
|
-##### Imprecision
|
|
|
-The model features values are not precise.
|
|
|
-
|
|
|
-#### Techniques
|
|
|
-
|
|
|
-- ##### Fuzzy sets:
|
|
|
- Correct model in a finite number of points, smooth transistion (approximation) among them.
|
|
|
-
|
|
|
- ex: in a thermal control system we fix the normal working point and the critical one, and the system approximates the behaviour between.
|
|
|
-
|
|
|
-- ##### Neural networks
|
|
|
- input-output samples, learning algorithms to define output values for unknown values.
|
|
|
-
|
|
|
-- ##### Genetic algorithms
|
|
|
- Optimal solution, obtained by evaluating populations of tentative solutions and combining their parts (sort of copying from nature).
|
|
|
-
|
|
|
-#### Applications:
|
|
|
-
|
|
|
-From washing machines to helicopters, to rice cookers
|
|
|
-
|
|
|
-### Fuzzy Sets
|
|
|
-
|
|
|
-Were created in 1965 by Lotfi Zadeh
|
|
|
-
|
|
|
-The principle is to make computation with words.
|
|
|
-
|
|
|
-#### What is a fuzzy set?
|
|
|
-Is a set whose membership function can range on the interval [0,1].
|
|
|
-
|
|
|
-On contrary to __crisp sets__ that admit only {0,1}
|
|
|
-
|
|
|
-###### A membership function defines a set
|
|
|
-###### Defines the degree of membership of an element to the set
|
|
|
-μ: U -> [0,1]
|
|
|
-
|
|
|
-#### How to define membership functions
|
|
|
-- select a variable
|
|
|
- - distance
|
|
|
-- define a range of the variable
|
|
|
- - [0..10]
|
|
|
-- identify labels
|
|
|
- - close, medium, far
|
|
|
-- for each label identify the charachteristic points
|
|
|
- - 0, max, middle values, where MF=1, ...
|
|
|
-- identify function shapes
|
|
|
- - linear
|
|
|
-- check
|
|
|
-
|
|
|
-#####Membership functions can also overlap,
|
|
|
-and this quality is useful for example in classification of a noisy input,
|
|
|
-in fact with overlapping MF we have a *smooth transition* from a label to another
|
|
|
-
|
|
|
-#### MF and concepts
|
|
|
-
|
|
|
-__MFs__ define __fuzzy sets__
|
|
|
-
|
|
|
-__Labels__ denote __fuzzy sets__
|
|
|
-
|
|
|
-__Fuzzy sets__ can be considered as conceptual representations
|
|
|
-
|
|
|
-#### Symbol grounding
|
|
|
-Reason in terms of concepts and grounds them to reality.
|