Fuzzy inference apparatus

A 2-input fuzzy inference apparatus having two if-parts corresponding to first and second inputs, each of the if-parts having a membership function defined by one vertex position and a straight line, comprising:

• an if-part membership function position memory for storing the vertex position data of the if-part membership functions respectively corresponding to the first and second inputs;
• a then-part membership function position memory for storing position data of then-part membership functions corresponding to the if-part vertex position data respectively corresponding to the first and second inputs on the basis of inference rules;
• a first selector for selecting, from said if-part membership function position memory, the vertex position data at positions interposing the first input, on the basis of the inference rules;
• a second selector for selecting, from said if-part membership function position memory, the vertex position data at positions interposing the second input, on the basis of the inference rules;
• a third selector for selecting, from said then-part membership function position memory, position data of then-part membership functions corresponding to the vertex position data selected by said first and second selectors;
• a first calculation unit for calculating membership values of the membership functions for the first input as absolute values of differences between the first input and the vertex position data selected by the first selector;
• a second calculation unit for calculating membership values of the membership functions for the second input as absolute values of differences between the second input and the vertex position data selected by the second selector;
• a minimum value calculation unit for obtaining values corresponding to minimum values corresponding to the inference rules on the basis of outputs from said first calculation unit and outputs from said second calculation unit;
• and
• an output calculation unit for calculating inference outputs for the inference rules in accordance with position data of the then-part membership functions selected by said third selector and output values from said minimum value calculation unit.

A fuzzy inference apparatus in which an if-part membership function has a shape of a triangle, and a base of the triangle extends up to vertex positions of adjacent if-part membership functions, comprising:

• if-part membership storing means for storing vertex positions of the if-part membership functions;
• if-part membership function selecting means for selecting the if-part membership function corresponding to input data;
• minimum value calculating means for calculating a minimum value of an in-part membership function value by using the selected if-part membership function and the input data;
• then-part membership function storing means for storing position data of then-part membership functions on the basis of addresses of the if-part membership functions;
• then-part membership selecting means for selecting the position data of the then-part membership function on the basis of the address of the selected if-part membership function;
• and
• center-of-gravity calculating means for calculating a center of gravity on the basis of the selected position data and an output from said minimum value calculating means, wherein said if-part membership function selecting means comprises:
• a vertex position output circuit for sequentially reading and outputting the vertex positions stored in said if-part membership function storing means in response to rule designation address signals;
• a subtractor for calculating differences between the output vertex positions and the input data, said subtractor being arranged to output absolute values of the differences and a borrow signal when a sign of the difference is inverted;
• a stop circuit for stopping outputting the vertex positions from the vertex position output circuit when the borrow signal is output from said subtractor;
• and
• a memory circuit for storing a present absolute value output and a previous absolute value output from said subtractor when said stop circuit stops outputting the vertex positions, the values stored in said memory circuit being values corresponding to if-part membership function values.

A multi-input fuzzy inference apparatus having a plurality of if-parts corresponding to a plurality of inputs, each of the plurality of if-parts having a membership function defined by one vertex position and a straight line, comprising:

• an if-part membership function position memory circuit for storing the plurality of vertex position data of each if-part membership function corresponding to each input;
• a then-part membership function position memory circuit for storing a plurality of position data of a then-part membership function corresponding to the plurality of vertex position data of the if-part membership function for each input on the basis of inference rules;
• a first selector circuit for sequentially comparing each input with the vertex position data stored in said if-part membership function position memory circuit and selecting the vertex position data at positions interposing each input;
• a second selector circuit for selecting, from said then-part membership function position memory circuit, position data of a then-part membership function corresponding to the plurality of vertex position data selected by said first selector circuit;
• a grade calculation circuit for calculating grades of the membership functions for each input as absolute values of differences between each input and the plurality of the vertex position data selected by said first selector circuit;
• a minimum value calculating circuit for obtaining values corresponding to minimum values corresponding to the inference rules on the basis of outputs from said grade calculation circuit;
• a center-of-gravity calculation circuit for calculating a center of gravity as an inference output in accordance with the then-part membership function position data selected by said second selector circuit and outputs from said minimum value calculation circuit;
• and
• a switching signal generator for switching between said grade calculation circuit and a set of said first and second selector circuits in correspondence with each input.

A fuzzy inference apparatus comprising:

• rule storing means for storing a plurality of then-part positions respectively corresponding to pairs each of which has one of a plurality of first if-part membership functions and one of a plurality of second if-part membership functions, the plurality of first and second if-part membership functions having shapes of triangles each having a base corresponding to positions of vertices of triangles of two adjacent membership functions, said rule storing means storing the positions of the vertices of the triangles in correspondence with the plurality of first and second if-part membership functions;
• rule selecting means for sequentially comparing an input value to the plurality of first if-part membership functions with positions of a plurality of vertices of the plurality of first if-part membership functions stored in said rule storing means, retrieving two adjacent vertex positions between which a position of the input value is located, calculating first and second differences between the retrieved two vertex positions and the input value, sequentially comparing an input value to the plurality of second if-part membership functions with positions of a plurality of vertices representing the plurality of second if-part membership functions stored in said rule storing means, retrieving two adjacent vertex positions between which a position of the input value is located, and calculating third and fourth differences between the retrieved two vertex positions and the input value;
• membership value selecting means for selecting a minimum value of each rule on the basis of magnitudes of the first to fourth differences obtained by said rule selecting means;
• membership value storing means for storing the minimum value selected by said membership value selecting means;
• then-part selecting means for selecting then-part positions respectively corresponding to the two vertex positions corresponding to the plurality of first if-part membership functions stored in said rule storing means and selected by said rule selecting means and the two vertex positions corresponding to the plurality of second if-part membership functions stored in said rule storing means and selected by said rule selecting means;
• then-part position storing means for storing the then-part positions selected by said then-part selecting means;
• and
• center-of-gravity calculating means for calculating a position of a center of gravity on the basis of the minimum values stored in said membership value storing means and the then-part positions stored in said then-part position storing means.