• Structural Engineering and Mechanics
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• 제87권3호
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• pp.211-219
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• 2023

The structural health of a pipeline is usually assessed by visual inspection. In addition to the fact that this method is expensive and time consuming, inspection of the whole structure is not possible due to limited access to some points. Therefore, adopting a damage detection method without the mentioned limitations is important in order to increase the safety of the structure. In recent years, vibration-based methods have been used to detect damage. These methods detect structural defects based on the fact that the dynamic responses of the structure will change due to damage existence. Therefore, the location and extent of damage, before and after the damage, are determined. In this study, fuzzy genetic algorithm has been used to monitor the structural health of the pipeline to create a fuzzy automated system and all kinds of possible failure scenarios that can occur for the structure. For this purpose, the results of an experimental model have been used. Its numerical model is generated in ABAQUS software and the results of the analysis are used in the fuzzy genetic algorithm. Results show that the system is more accurate in detecting high-intensity damages, and the use of higher frequency modes helps to increase accuracy. Moreover, the system considers the damage in symmetric regions with the same degree of membership. To deal with the uncertainties, some error values are added, which are observed to be negligible up to 10% of the error.

• Journal of Advanced Marine Engineering and Technology
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• 제28권8호
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• pp.1299-1312
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• 2004

This paper suggests the simple form of a fuzzy PID controller and describes the design principle, tracking performance, stability analysis and changes of parameters of a suggested fuzzy PID controller. A fuzzy PID controller is derived from the design procedure of fuzzy control. It is well known that a fuzzy PID controller has a simple structure of the conventional PID controller but posses its self-tuning control capability and the gains of a fuzzy PID controller become nonlinear functions of the inputs. Nonlinear calculation during fuzzification, defuzzification and the fuzzy inference require more time in computation. To increase the applicability of a fuzzy PID controller to digital computer, a simple form of a fuzzy PID controller is introduced by the backward difference mapping and the analysis of the fuzzy input space. To guarantee the BIBO stability of a suggested fuzzy PID controller, ‘small gain theorem’ which proves the BIBO stability of a fuzzy PI and a fuzzy PD controller is used. After a detailed stability analysis using ‘small gain theorem’, from which a simple and practical method to decide the parameters of a fuzzy PID controller is derived. Through the computer simulations for the linear and nonlinear plants, the performance of a suggested fuzzy PID controller will be assured and the variation of the gains of a fuzzy PID controller will be investigated.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 2003년도 ISIS 2003
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• pp.98-101
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• 2003

To classify desired and undesired documents on the web according to each user's view, FOCUS (Fuzzy dOCUment ordering System) is developed based on fuzzy concept extraction, fuzzy fish eye matching, and fuzzy selection. Experiments are done using the concept-system-dictionary by EDR (Electronic Dictionary Research Institute) including 140,000 words and web-based documents related to movie.

• 호남수학학술지
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• 제30권1호
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• pp.21-32
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• 2008

We introduce some notions and results which have been discussed, and we define the notion of fuzzy normal B-algebra and obtain the structure of quotient B-algebra via fuzzy normal B-algebra. Moreover, we generalize a fundamental theorem of B-homomorphism for B-algebras via fuzzy normal B-algebras.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1991년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 22-24 Oct. 1991
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• pp.156-161
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• 1991

It is difficult to realize precise control by a fuzzy control scheme alone because control signals are derived from fuzzy inferences. On the other hand, pole-placement control can offer a precise control to a known system. In this paper, a VSC(variable structure control)scheme is proposed, which is an attempt to take merits of pole-placement control and fuzzy control. On the vicinity of the reference point the pole-placement control scheme takes over the role of the fuzzy controller to improve the set point response.

• Journal of applied mathematics & informatics
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• 제20권1_2호
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• pp.315-325
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• 2006

The notion of intuitionistic fuzzy finite switchboard state machines and (strong) homomorphisms of intuitionistic fuzzy finite state machines are introduced, and related properties are investigated. After we give a congruence relation on the set of all words of elements of X of finite length, the quotient structure is discussed. We show that the family of equivalence classes is a finite semigroup with identity.

• 전자공학회논문지B
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• 제31B권4호
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• pp.138-144
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• 1994

An inference network is proposed as a tool for bidirectional approximate reasoning. The inference network can be designed directly from the given fuzzy data(knowledge). If a fuzzy input is given for the inference netwok, then the network renders a reasonable fuzzy output after performing approximate reasoning based on an equality measure. Conversely, due to the bidirectional structure, the network can yield its corresponding reasonable fuzzy input for a given fuzzy output. This property makes it possible to perform forward and backward reasoning in the knowledge base system.

• 한국지능시스템학회논문지
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• 제7권3호
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• pp.102-106
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• 1997

We introduce the category [PFSyn] of saturated fuzzy syntopogenous preordered spaces and continuous isotones ans show that the category [PFSyn] is topological and cotopological. Furthermore, to consdier a compatibility between order structures and fuzzy syntopogenous structure, we introduce a category [IPFSyn] of increasing saturated fuzzy syntopogenous spaces and its dual category [IPFSyn] of decreasing fuzzy syntopogenous spaces, and show that [IPFSyn] and [DPFSyn] are both bireflective in the category [PFSyn].

• 대한전기학회논문지:시스템및제어부문D
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• 제49권11호
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• pp.625-631
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• 2000

In designing fuzzy model, we encounter a major difficulty in the identification of an optimized fuzzy rule base, which is traditionally achieved by a tedious-and-error process. This paper presents an approach to automatic design of optimal fuzzy rule bases for modeling using evolutionary programming. Evolutionary programming evolves simultaneously the structure and the parameter of fuzzy rule base a given task. To check the effectiveness of the suggested approach, 3 examples for modeling are examined, and the performance of the identified models are demonstrated.

• 산업공학
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• 제6권2호
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• pp.67-78
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• 1993

In this paper, we deal with the application of the fuzzy sets theory to evaluate and estimate the system reliability under the fault tree analysis. We formulate the uncertainty of component reliability to fuzzy sets, and propose a procedure for obtaining the system reliability in case the system structure is described by fault tree. An importance measure of each component is proposed. Computer program for fuzzy fault tree analysis(FFTA) is developed using C language to obtain the system reliability and the component‘s fuzzy importance.