US 5,179,629 AGranted

Device for computing membership functions in fuzzy computers

AssigneeMitsubishi Denki Kabushiki Kaisha

InventorKazuo Nakamura

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Abstract

A fuzzy computer which is provided with a control part for generating control information to define a trapezoidal membrship function, an operating unit for calculating the both oblique sides of the trapezoid by operating input data according to the control information, a comparator (overflow detection circuit) for comparing operation results of the operating unit with a predetermined value which is based on the control information, and a data elector for selecting, according to the comparison results of the comparator, either of the operation results of the operating unit or the predetermined value in order to obtain the both bases of the trapezoid, that is, both of the maximum and minimum values of the membership function, in order to generate the membership function, as a result, the fuzzy computer entails neither a large-storage memory nor complicated software operations which need processing time.

Claims24

Dependent claims

A digital device for computing a fuzzy membership function comprising:

a first operation unit coupled to receive an input variable and a first control signal having:
(i) a first subtractor having a minuend input coupled to said input variable and a subtrahend input coupled to said first control signal and wherein said first subtractor outputs a first difference signal;
(ii) a first comparator, coupled to receive said first difference signal for asserting a first overflow signal when said first difference signal exceeds a maximum value and for deasserting a second overflow signal when said first difference signal exceeds a minimum value;
a second operation unit coupled to receive said input variable and a second control signal having:
(i) a second subtractor having a minuend input coupled to said second control signal and a subtrahend input coupled to said input variable wherein said subtractor outputs a second difference signal;
(ii) a second comparator, coupled to receive said second difference signal for asserting a third overflow signal when said second difference signal exceeds said maximum value and for deasserting a fourth overflow signal when said second difference signal exceeds said minimum value;
and
a data selector coupled to receive said first difference signal, said second difference signal, said first, said second, said third and said fourth overflow signals for outputting:
(i) said maximum value when said first and said third overflow signals are asserted and said second and fourth overflow signals are deasserted;
(ii) said minimum value when said first and said fourth overflow signals are asserted and said second and third overflow signals are deasserted;
(iii) said minimum value when said second and said third overflow signals are asserted and said first and said fourth overflow signals are deasserted;
(iv) said first difference signal when said third overflow signal is asserted and said first, said second and said fourth overflow signals are deasserted;
and
(v) said second difference signal when said first overflow signal is asserted and said second, said third and said fourth overflow signals are deasserted.

11 more elements

A digital device for computing a fuzzy membership function comprising:

a first operation unit coupled to receive an input variable and a first control signal having:
(i) a first subtractor having a minuend input coupled to said input variable and a subtrahend input coupled to said first control signal and wherein said first subtractor outputs a first difference signal;
(ii) a first shifter coupled to receive said first difference signal wherein said first shifter outputs a first shifted difference signal;
(iii) a first comparator, coupled to receive said first shifted difference signal for asserting a first overflow signal when said first shifted difference signal exceeds a maximum value and for deasserting a second overflow signal when said first shifted difference signal exceeds a minimum value;
a second operation unit coupled to receive said input variable and a second control signal having:
(i) a second subtractor having a minuend input coupled to said second control signal and a subtrahend input coupled to said input variable wherein said subtractor outputs a second difference signal;
(ii) a second shifter coupled to receive said second difference signal wherein said second shifter outputs a second shifted difference signal;
(iii) a second comparator, coupled to receive said second shifted difference signal for asserting a third overflow signal when said second shifted difference signal exceeds said maximum value and for deasserting a fourth overflow signal when said second shifted difference signal exceeds said minimum value;
and
a data selector coupled to receive said first shifted difference signal, said second shifted difference signal, said first, said second, said third and said fourth overflow signals for outputting:
(i) said maximum value when said first and said third overflow signals are asserted and said second and fourth overflow signals are deasserted;
(ii) said minimum value when said first and said fourth overflow signals are asserted and said second and third overflow signals are deasserted;
(iii) said minimum value when said second and said third overflow signals are asserted and said first and said fourth overflow signals are deasserted;
(iv) said first shifted difference signal when said third overflow signal is asserted and said first, said second and said fourth overflow signals are deasserted;
and
(v) said second shifted difference signal when said first overflow signal is asserted and said second, said third and said fourth overflow signals are deasserted.

13 more elements

A digital device for computing a fuzzy membership function having trapezoidal shape, wherein the trapezoidal shape is defined by a top and a bottom bases and two oblique sides comprising:

a first operating unit, having a minuend input coupled to receive an input variable and a subtrahend input coupled to receive a first control signal, for outputting a first straight line function corresponding to said first oblique side;
a second operating unit, having a minuend input coupled to receive a second control signal and a subtrahend input coupled to receive said input variable, for outputting a second straight line function corresponding to said second oblique side;
a first comparator, coupled to said first operating unit, for asserting a first overflow signal when a value of said first straight line function exceeds a top base value, and for deasserting a second overflow signal when said value of said first straight line function exceeds a bottom base value;
a second comparator, coupled to said second operating unit, for asserting a third overflow signal when a value of said second straight line function exceeds said top base value and for deasserting a fourth overflow signal when said value of said second straight line function exceeds said bottom base value;
and
a selector circuit coupled to said first and said second operating units and to said first and second comparators for outputting:
(i) said top base value when said first and said third overflow signals are asserted and said second and fourth overflow signals are deasserted;
(ii) said bottom base value when said first and said fourth overflow signals are asserted and said second and third overflow signals are deasserted;
(iii) said bottom base value when said second and said third overflow signals are asserted and said first and said fourth overflow signals are deasserted;
(iv) said first straight line function when said third overflow signal is asserted and said first, said second and said fourth overflow signals are deasserted;
and
(v) said second straight line function when said first overflow signal is asserted and said second, said third and said fourth overflow signals are deasserted.

9 more elements

Dependencies are inferred from the claim text.