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Publications (8)2.43 Total impact

  • Article: Iterative-type evaluation of PSGS fuzzy systems for anytime use
    O. Takacs, A.R. Varkonyi-Koczy
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    ABSTRACT: While fuzzy systems can advantageously be used in system modeling and control, their use in time-critical applications is limited because of complexity problems, especially in cases when not only low, but also flexibly changeable complexity is needed. Previously, a method has been proposed to use fuzzy and other soft-computational tools in the frame of modular anytime architectures; however, the applicability needs the a priori knowledge of the temporarily available time and resources. This paper proposes a new transformation method, which makes possible the iterative-type evaluation of product-sum-gravity-singleton (PSGS) fuzzy systems, with a really flexibly changeable complexity, and with an easily estimable error at any step of the evaluation. Moreover, the transformation also ensures the fastest possible decrease of the error.
    IEEE Transactions on Instrumentation and Measurement 03/2005; · 1.21 Impact Factor
  • Conference Proceeding: SVD-based complexity reduction of "near PSGS" fuzzy systems
    O. Takacs, A.R. Varkonyi-Koczy
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    ABSTRACT: With the help of the SVD-based (singular value decomposition) complexity reduction method, not only the redundancy of fuzzy rule-bases are eliminated, but also further, nonexact reduction are made, considering the allowable error. Namely, in case of higher allowable error, the result is a less complex fuzzy inference system, with a smaller rule-base. This property of the SVD-based reduction method makes possible the usage of fuzzy systems in time-critical applications and makes possible the combining of fuzzy systems with anytime techniques to cope with the changing circumstances during the operation of the system. However, while the SVD-based reduction can be applied to PSGS fuzzy systems, in case of rule-bases, constructed from expert knowledge, the input fuzzy sets are not always in Ruspini-partition. This paper extends the SVD-based reduction to "near PSGS" fuzzy systems, where the input fuzzy sets are not in Ruspini-partition.
    Intelligent Signal Processing, 2003 IEEE International Symposium on; 10/2003
  • Article: SVD-based complexity reduction of rule-bases with nonlinear antecedent fuzzy sets
    O. Takacs, A.R. Varkonyi-Koczy
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    ABSTRACT: With the help of the singular value decomposition (SVD) based complexity reduction method, not only can the redundancy of fuzzy rule-bases be eliminated, but further reduction can also be made, considering the allowable error. Namely, in the case of higher allowable error, the result may be a less complex fuzzy inference system, with a smaller rule-base. This property of the SVD-based reduction method makes possible the usage of fuzzy systems, even in cases when the available time and resources are limited. The original SVD-based reduction method was proposed for rule-bases with linear antecedent fuzzy sets. This limitation remained valid in the later extensions, as well. The purpose of this paper is to give a formal mathematical proof for the original formulas with nonlinear antecedent fuzzy sets and thus to end this limitation
    IEEE Transactions on Instrumentation and Measurement 05/2002; · 1.21 Impact Factor
  • Conference Proceeding: Iterative-type evaluation of PSGS fuzzy systems for anytime use
    O. Takacs, A.R. Varkonyi-Kozy
    [show abstract] [hide abstract]
    ABSTRACT: While fuzzy systems can advantageously be used in system modeling and control, their use in time-critical applications is limited because of complexity problems, especially in cases, when not only low, but also flexibly changeable complexity is needed. Previously a method has been proposed to use fuzzy and other soft-computational tools in the frame of modular anytime architectures; however, the applicability needs the a priori knowledge of the temporarily available time and resources. This paper proposes a new transformation method, which makes possible the iterative-type evaluation of PSGS fuzzy systems, with a really flexibly changeable complexity, and with an easily estimable error at any step of the evaluation. Moreover, the transformation also ensures the fastest possible decrease of the error.
    Instrumentation and Measurement Technology Conference, 2002. IMTC/2002. Proceedings of the 19th IEEE; 02/2002
  • Conference Proceeding: Anytime extension of the iterative fuzzy model inversion
    A.R. Varkonyi-Koczy, O. Takacs
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    ABSTRACT: Model based techniques play very important role in solving engineering problems. Recently, for representing nonlinear systems fuzzy models became very popular for evaluating measurement data and controller design, and the inverse models are of considerable interest. In this paper the extension of the observer based technique to perform fuzzy model inversion is presented. The inversion can be extended towards anytime modes of operation providing short response time and flexibility during temporal loss of computational power and/or time.
    Fuzzy Systems, 2001. The 10th IEEE International Conference on; 01/2002
  • Conference Proceeding: Non-exact complexity reduction of generalized neuro-fuzzy networks
    O. Takacs, A.R. Varkonyi-Koczy
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    ABSTRACT: In modern measurement, control, monitoring and fault diagnosis systems, there is an increasing need for the use of non-classical computing methods. On the other hand, in these systems the available time and resources are usually limited, so methods with lower computational complexity are needed. Thus, the need arises to have formal methods for the complexity reduction of different soft-computing techniques. This paper discusses a possible method for the non-exact reduction of generalized type neuro-fuzzy systems, and gives the necessary error-bounds of the reduction.
    Fuzzy Systems, 2001. The 10th IEEE International Conference on; 01/2002
  • Conference Proceeding: Error-bound for the non-exact SVD-based complexity reduction of the generalized type hybrid neural networks with non-singleton consequents
    O. Takacs, A.R. Varkonyi-Koczy
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    ABSTRACT: The main advantage of neural networks (NNs) is that they are able to solve complicated problems, even if the exact mathematical model is not known. However, there is no universal method for the approximation of the proper size of the neural networks which usually results in the overestimation of the needed size. Therefore, the need arises to have formal methods for the complexity reduction of neural networks. Singular Value Decomposition (SVD) based complexity reduction was first proposed for various fuzzy inference systems. Recently, the method has been extended to generalized neural network, which made possible the use of neural networks in time-critical systems. Beyond the elimination of redundancy, the SVD-based reduction can be used to achieve further reduction, if a certain amount of error can be tolerated. This paper gives an error-bound for this further complexity reduction of generalized type hybrid neural networks with non-singleton consequents
    Instrumentation and Measurement Technology Conference, 2001. IMTC 2001. Proceedings of the 18th IEEE; 02/2001
  • Conference Proceeding: Anytime information processing based on fuzzy and neural network models
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    ABSTRACT: In modern measurement and control systems, the available time and resources are often not only limited, but could change during the operation of the system. In these cases, the so called anytime algorithms could be used advantageously. While different soft computing methods are in widespread use in system modeling, their usability in these cases are limited, because the lack of a universal method for the determination of the needed complexity often results in huge and redundant neural networks/fuzzy rule-bases. This paper proposes a possible way to carry out anytime information processing in fuzzy systems or neural networks, with the help of the SVD-based complexity reduction algorithm
    Instrumentation and Measurement Technology Conference, 2001. IMTC 2001. Proceedings of the 18th IEEE; 02/2001