Extension Principle Adriano Cruz ©2002 NCE e IM/UFRJ
@2002 Adriano Cruz NCE e IM - UFRJNo. 2 Fuzzy Numbers n A fuzzy number is fuzzy subset of the universe of a numerical number. –A fuzzy real number is a fuzzy subset of the domain of real numbers. –A fuzzy integer number is a fuzzy subset of the domain of integers.
@2002 Adriano Cruz NCE e IM - UFRJNo. 3 Fuzzy Numbers - Example u(x) x51015 Fuzzy real number 10 u(x) x51015 Fuzzy integer number 10
@2002 Adriano Cruz NCE e IM - UFRJNo. 4 Functions with Fuzzy Arguments n A crisp function maps its crisp input argument to its image. n A fuzzy arguments have membership degrees. n When computing a fuzzy mapping it is necessary to compute the image and its membership value.
@2002 Adriano Cruz NCE e IM - UFRJNo. 5 Functions applied to intervals n Compute the image of the interval. n An interval is a crisp set. x y I y=f(I)
@2002 Adriano Cruz NCE e IM - UFRJNo. 6 Monotonic Continuous Functions n For each point in the interval –Compute the image of the interval. –The membership degrees are carried through. I
@2002 Adriano Cruz NCE e IM - UFRJNo. 7 Monotonic Continuous Functions x y x y u(x) u(y)
@2002 Adriano Cruz NCE e IM - UFRJNo. 8 Monotonic Continuous Ex. n Function: y=f(x)=0.6*x+4 n Input: Fuzzy number - around-5 –Around-5 = 0.3/ / /7 n f(around-5) = 0.3/f(3) + 1/f(5) + 0.3/f(7) –f(around-5) = 0.3/ / /8.2 I
@2002 Adriano Cruz NCE e IM - UFRJNo. 9 Monotonic Continuous Ex. f(x) x 510 u(x) x
@2002 Adriano Cruz NCE e IM - UFRJNo. 10 Nonmonotonic Continuous Functions n For each point in the interval –Compute the image of the interval. –The membership degrees are carried through. –When different inputs map to the same value, combine the membership degrees.
@2002 Adriano Cruz NCE e IM - UFRJNo. 11 Nonmonotonic Continuous Functions x y x y u(x) u(y)
@2002 Adriano Cruz NCE e IM - UFRJNo. 12 Nonmonotonic Continuous Ex. n Function: y=f(x)=x 2 -6x+11 n Input: Fuzzy number - around-4 Around-4 = 0.3/2+0.6/3+1/4+0.6/5+0.3/6 y = 0.3/f(2)+0.6/f(3)+1/f(4)+0.6/f(5)+0.3/f(6) y = 0.3/3+0.6/2+1/3+0.6/6+0.3/11 y = 0.6/2+(0.3 v 1)/3+0.6/6+0.3/11 y = 0.6/2 + 1/ / /11 I
@2002 Adriano Cruz NCE e IM - UFRJNo. 13 Nonmonotonic Continuous Functions x y x y u(x) u(y)
@2002 Adriano Cruz NCE e IM - UFRJNo. 14 Extension Principle n Let f be a function with n arguments that maps a point in X 1 xX 2 x...xX n to a point in Y such that y=f(x 1,…,x n ). n Let A 1 x…xA n be fuzzy subsets of X 1 xX 2 x...xX n n The image of A under f is a subset of V defined by
@2002 Adriano Cruz NCE e IM - UFRJNo. 15 Arithmetic Operations n Applying the extension principle to arithmetic operations it is possible to define fuzzy arithmetic operations n Let x and y be the operands, z the result. n Let A and B denote the fuzzy sets that represent the operands x and y respectively.
@2002 Adriano Cruz NCE e IM - UFRJNo. 16 Fuzzy addition n Using the extension principle fuzzy addition is defined as
@2002 Adriano Cruz NCE e IM - UFRJNo. 17 Fuzzy addition - Examples n A = 0.3/ /2 +1/ / /5 n B = 0.5/10 + 1/ /12 n Getting the minimum of the membership values n A+B=0.3/ / / / / / / / / / / / / / /17 n Getting the maximum of the duplicates n A+B= 0.3/ / /13 + 1/ / / /17
@2002 Adriano Cruz NCE e IM - UFRJNo. 18 Fuzzy addition A, x=3 B, y= C, x=14
@2002 Adriano Cruz NCE e IM - UFRJNo. 19 Fuzzy Arithmetic n Using the extension principle the remaining fuzzy arithmetic fuzzy operations are defined as: