• Journal of Power Electronics
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• 제13권4호
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• pp.656-668
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• 2013

This paper presents a wavelet-fuzzy based controller for indirect field oriented control of three-phase induction motor drives. The discrete wavelet transform is used to decompose the error between the actual speed and the command speed of the induction motor drive into different frequency components. The transformed error coefficients along with the scaling gains are used for generating the control component of the motor. Self-tuning fuzzy logic is used for online tuning of the scaling gains of the controller. The proposed controller has the ability to meet the speed tracking requirements in the closed loop system. The complete indirect field oriented control scheme incorporating the proposed wavelet-fuzzy based controller is investigated theoretically and simulated under various dynamic operating conditions. The simulation results are compared with a conventional proportional integral controller and a fuzzy based controller. The speed control scheme incorporating the proposed controller is implemented in real time using a digital processor control board. Simulation and experimental results validate the effectiveness of the proposed controller.

• 제어로봇시스템학회논문지
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• 제18권10호
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• pp.902-911
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• 2012

This paper proposes a robust adaptive fuzzy backstepping control scheme for trajectory tracking of an electrically driven nonholonomic mobile robot with uncertainties and actuator dynamics. A complete model of an electrically driven nonholonomic mobile robot described in this work includes all models of the uncertain robot kinematics with a nonholonomic constraint, the uncertain robot body dynamics with uncertain frictions and unmodeled disturbances, and the uncertain actuator dynamics with disturbances. The proposed control scheme uses the backstepping control approach through a kinematic controller and a robust adaptive fuzzy velocity tracking controller. The presented control scheme has a voltage control input with an auxiliary current control input rather than a torque control input. It has two FBFNs(Fuzzy Basis Function Networks) to approximate two unknown nonlinear robot dynamic functions and a robust adaptive control input with the proposed adaptive laws to overcome the uncertainties such as parameter uncertainties and external disturbances. The proposed control scheme does not a priori require the accurate knowledge of all parameters in the robot kinematics, robot dynamics and actuator dynamics. It can also alleviate the chattering of the control input. Using the Lyapunov stability theory, the stability of the closed-loop robot control system is guaranteed. Simulation results show the validity and robustness of the proposed control scheme.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제10권1호
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• pp.12-18
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• 2010

This paper proposes an adaptive robust fuzzy control scheme for path tracking of a wheeled mobile robot with uncertainties. The robot dynamics including the actuator dynamics is considered in this work. The presented controller is composed of a fuzzy basis function network (FBFN) to approximate an unknown nonlinear function of the robot complete dynamics, an adaptive robust input to overcome the uncertainties, and a stabilizing control input. Genetic algorithms are employed to optimize the fuzzy rules of FBFN. The stability and the convergence of the tracking errors are guaranteed using the Lyapunov stability theory. When the controller is designed, the different parameters for two actuator models in the dynamic equation are taken into account. The proposed control scheme does not require the accurate parameter values for the actuator parameters as well as the robot parameters. The validity and robustness of the proposed control scheme are demonstrated through computer simulations.

• 정보처리학회 논문지
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• 제13권2호
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• pp.13-17
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• 2024

본 논문에서는 규칙의 수를 줄여 간결한 지식 기반을 보장할 수 있는 합 기반의 전건부를 가지는 뉴로-퍼지 제어기를 제안하였다. 제안된 뉴로-퍼지 제어기는 모든 입력 변수의 AND 조합을 전건부로 하는 구조의 퍼지 규칙보다 더 큰 입력 영역을 커버하기 위해 전건부에 입력 퍼지 집합의 합집합 연산을 허용하였다. 이러한 뉴로-퍼지 제어기를 구성하기 위해 본 논문에서는 OR 및 AND 퍼지 뉴런으로 구성된 multiple-term unified logic processor (MULP)를 고려하였다. 이러한 OR 및 AND 퍼지 뉴런은 조정 가능한 연결 강도 집합을 가지므로 학습을 통하여 최적의 연결 강도 집합을 찾을 수 있다. 초기 최적화 단계에서 유전 알고리즘은 제안된 뉴로 퍼지 제어기의 최적화된 이진 구조를 구성하고, 이후 확률에 기반한 강화 학습은 성능 지수를 더욱 향상시켜서 유전 알고리즘에 의해 최적화된 제어기의 이진 연결을 개선하였다. 역진자 시스템을 제어하기 위한 모의실험 및 실험을 통해 제안된 방법의 유효성을 검증하였다.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제5권2호
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• pp.119-123
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• 2005

This paper describes a fuzzy-based system for analyzing the stress intensity factors (SIFs) of three-dimensional (3D) cracks. 3D finite element method(FEM) was used to obtain the SIF for subsurface cracks and surface cracks existing in inhomogeneous materials. A geometry model, i.e. a solid containing one or several 3D cracks is defined. Several distributions of local node density are chosen, and then automatically superposed on one another over the geometry model by using the fuzzy theory. Nodes are generated by the bucketing method, and ten-noded quadratic tetrahedral solid elements are generated by the Delaunay triangulation techniques. The singular elements such that the mid-point nodes near crack front are shifted at the quarter-points, and these are automatically placed along the 3D crack front. The complete FE model is generated, and a stress analysis is performed. The SIFs are calculated using the displacement extrapolation method. The results were compared with those surface cracks in homogeneous materials. Also, this system is applied to analyze cladding effect of surface cracks in inhomogeneous materials.

• 대한산업공학회지
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• 제16권2호
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• pp.37-44
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• 1990

In selecting the best project in multi-criteria decision making problems, the imperfect information of consequence and the vague preference of the decision maker(DM) would make the decision analysis more complex together with the conflict of several criteria. In this context, a method is proposed to deal the fuzzy information mentioned before instead of reducing it to a single representative value. And, based on the given imprecise information, projects are ranked completely or partially according to DM's vague preference. The procedure consists, for each pair of projects, of calculating the degree of supporting over all criteria and the degree of opposing with respect to each criterion for their outranking relation. Together with weights for each criterion, these indices produce fuzzy outranking relations for each pair of projects. And a complete or partial ranking of projects is obtained according to outranking degrees considering the interdependence among projects.

• 한국지능시스템학회논문지
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• 제5권4호
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• pp.12-17
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• 1995

지금까지 전문가들에 의해 만들어진 퍼지규칙들은 종종 모순되었고 불완전하였다. 본 논문에서 우리는 모순되지 않고 거의 완전한 퍼지규칙을 자동생성 하는 새로운 기법을 제안한다. 이러한 퍼지규칙의 자동생성은 제어경험으로 부터 퍼지규칙을 얻어내는 사람의 지식 축적과정을 모사한 방법이다. 이 방식은 기존의 방식들보다 보다간단하면서도 보다 효율적인 방법이다. 잘 조절된 파라메터상에서 우리의 방식이 전문가들보다 더욱 좋은 퍼지규칙을 생성함을 시뮬레이션을 통하여 보인다.

• 한국지능시스템학회논문지
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• 제20권6호
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• pp.875-883
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• 2010

We introduce the concept of intuitionistic smooth topology in Lowen's sense and we prove that the family IST(X) of all intuitionistic smooth topologies on a set is a meet complete lattice with least element and the greatest element [Proposition 3.6]. Also we introduce the notion of level fuzzy topology on a set X with respect to an intuitionistic smooth topology and we obtain the relation between the intuitionistic smooth topology $\tau$ and the intuitionistic smooth topology $\eta$ generated by level fuzzy topologies with respect to $\tau$ [Theorem 3.10].

• 한국지능시스템학회논문지
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• 제5권4호
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• pp.18-32
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• 1995

퍼지 정보 검색 기법을 이용한 가중치 선정 전락은,주어진 입력 문제로 부터 가중치의 패턴과 가중치를 자동적으로 선정함으로써, 추론 시간과 공간을 줄인다. 퍼지 가중치 선정 전략은 퍼지 삼각 관계곱 및 퍼지 신속관계 알고리즘을 사용하기 때문에 선택하는 퍼지 조건연산자와 $-cut에 따라서 결론을 추출하는 시간과 추론 단계의 수가 틀린다. 본 논문에서는, 퍼지 정보 검색을 이용한 추론 전략의 조절 방법에 대하여 개괄적으로 보이고, 잘 알려진 블럭 문제에 적용하여 주어진 영역에서 가장 적합한 퍼지 조건연산자와 $-cut을 선정한다.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제9권2호
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• pp.115-127
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• 2009

In the present paper we introduce and study L-pre-$T_0$-, L-pre-$T_1$-, L-pre-$T_2$ (L-pre-Hausdorff)-, L-pre-$T_3$ (L-pre-regularity)-, L-pre-$T_4$ (L-pre-normality)-, L-pre-strong-$T_3$-, L-pre-strong-$T_4$-, L-pre-$R_0$-, L-pre-$R_1$-separation axioms in (2, L)-topologies where L is a complete residuated lattice.Sometimes we need more conditions on L such as the completely distributive law or that the "$\bigwedge$" is distributive over arbitrary joins or the double negation law as we illustrate through this paper. As applications of our work the corresponding results(see[1,2]) are generalized and new consequences are obtained.