nesuro fuzzy inference circuit

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International Journal of Innovative Computing, Information and Control ICIC International c °2007 ISSN 1349-4198 Volume 3, Number 4, August 2007 pp. 1043—1052 AN IMPLEMENT ATION OF THE NEURO-FUZZY INFERENCE CIRCUIT Kuniaki Fujimoto, Hirofumi Sasaki, Yoichiro Masaoka and Ren-Qi Yang School of Engineering Kyushu Tokai University 9-1-1, Toroku Kumamoto 862-8652, Japan { kfuji; hsasaki }@ktmail.ktokai-u.ac.jp Masaharu Mizumoto Faculty of Information Science and Technology Osaka Electro-Communication University Osaka 572-8530, Japan [email protected] Received October 2006; revised February 2007 Abstract. In this paper, we propose a neuro-fuzzy inference circuit applicable to real- time learn ing. We adop ted a ba ck-pr op agatio n algor ithm used in the neura l netwo rk  for learn ing. The high sp eed le arnin g is realized by using the pa r allel pr o ce ssing of the operations and tuning only the parameters of the consequent part. Furthermore, to reduce the circuit scale, we use the membership function of antecedent parts satisfying that the total of the degrees is equal to 1. Through the experimental use of the Field Programmable Gate Array (FPGA), we con  fi rm that a high speed self-tuning of the fuzzy inference rules can be realized on the circuit. Keywords: Neuro-fuzzy inference circuit, Field programmable gate array, Self-tuning method, Triangular-type membership function 1. Introduction. Since L. A. Zadh proposed the idea of fuzzy logic [1] nearly 40 years ago, it has been used widely in the industrial world as a means of like industrial control or nancial management [2- 4]. The rules use d in the se fuzzy appl ica tio n systems have usually been determined by the experts or operators of these elds according to their knowledge or experie nce s. Ho we ver, it is more di cult for us to give desirable fuzzy rules when an iden tifyi ng system is ve ry complicate d. Thus learning techniques of fuzzy inference rules have been studied by many researchers in order to solve such problems [5- 10] . Ichiha shi [5,6 ], Nomur a et al. [7, 8], Wang and Mende l [9] have con tri ved the techniques by using the back-propagation algorithm of the neural network called “neuro- fuzzy lea rni ng alg orithms” independently. However, as the auth ors dis cus sed in [11 ], while these neuro-fuzzy techniques have high generative ability for tuning fuzzy rules, it is sometimes not reasonable and suitable for practical fuzzy applications, due to some disadvantages such as the weak-ring or non- ring. Therefore, we have developed one of the neuro-fuzzy learning algorithms [12] designed to prevent the case of weak-ring or non- ring even after learn ing. However, since the 1043

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International Journal of Innovative Computing, Information and Control  ICIC International c°2007 ISSN 1349-4198Volume 3, Number 4, August 2007 pp. 1043—1052

AN IMPLEMENTATION OF THE NEURO-FUZZY INFERENCECIRCUIT

Kuniaki Fujimoto, Hirofumi Sasaki, Yoichiro Masaoka and Ren-Qi Yang

School of Engineering

Kyushu Tokai University

9-1-1, Toroku Kumamoto 862-8652, Japan

{ kfuji; hsasaki }@ktmail.ktokai-u.ac.jp

Masaharu Mizumoto

Faculty of Information Science and TechnologyOsaka Electro-Communication University

Osaka 572-8530, Japan

[email protected]

Received October 2006; revised February 2007

Abstract. In this paper, we propose a neuro-fuzzy inference circuit applicable to real-time learning. We adopted a back-propagation algorithm used in the neural network   for learning. The high speed learning is realized by using the parallel processing of the operations and tuning only the parameters of the consequent part. Furthermore, to reduce the circuit scale, we use the membership function of antecedent parts satisfying that the 

total of the degrees is equal to 1. Through the experimental use of the Field Programmable Gate Array (FPGA), we con  fi rm that a high speed self-tuning of the fuzzy inference rules can be realized on the circuit.Keywords: Neuro-fuzzy inference circuit, Field programmable gate array, Self-tuning

method, Triangular-type membership function

1. Introduction. Since L. A. Zadh proposed the idea of fuzzy logic [1] nearly 40 yearsago, it has been used widely in the industrial world as a means of like industrial controlor financial management [2-4]. The rules used in these fuzzy application systems haveusually been determined by the experts or operators of these fields according to theirknowledge or experiences. However, it is more difficult for us to give desirable fuzzyrules when an identifying system is very complicated. Thus learning techniques of fuzzyinference rules have been studied by many researchers in order to solve such problems[5-10]. Ichihashi [5,6], Nomura et al. [7,8], Wang and Mendel [9] have contrived thetechniques by using the back-propagation algorithm of the neural network called “neuro-fuzzy learning algorithms” independently. However, as the authors discussed in [11],while these neuro-fuzzy techniques have high generative ability for tuning fuzzy rules, itis sometimes not reasonable and suitable for practical fuzzy applications, due to somedisadvantages such as the weak-firing or non-firing.

Therefore, we have developed one of the neuro-fuzzy learning algorithms [12] designedto prevent the case of weak-firing or non-firing even after learning. However, since the

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