• Journal of the Korea Computer Industry Society
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• v.3 no.1
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• pp.95-104
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• 2002

This paper presents some studies on the Internet TCP/IP(Transmission Control Protocol-Internet Protocol) traffic over ATM(Asynchronous Transfer Mode) UBR(Unspecified Bit Rate) and ABR(Available Bit Rate) classes of service. Fuzzy logic prediction has been used to improve the efficiency and fairness of traffic throughput. For TCP/IP over UBR, a novel fuzzy logic based cell dropping scheme is presented. This is referred to as fuzzy logic selective cell drop (FSCD). A key feature of the scheme is its ability to accept or drop a new incoming packet dynamically based on the predicted future buffer condition in the switch. This is achieved by using fuzzy logic prediction for the production of a drop factor. Packet dropping decision is then based on this drop factor and a predefined threshold value. Simulation results show that the proposed scheme significantly improves TCP/IP efficiency and fairness. To study TCP/IP over ABR, we applied the fuzzy logic ABR service buffer management scheme from our previous work to both approximate and exact fair rate computation ER(Explicit cell Rate) switch algorithms. We then compared the performance of the fuzzy logic control with conventional schemes. Simulation results show that on zero TCP packet loss, the fuzzy logic control scheme achieves maximum efficiency and perfect fairness with a smaller buffer size. When mixed with VBR traffic, the fuzzy logic control scheme achieves higher efficiency with lower cell loss.

• Proceedings of the KIEE Conference
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• 2005.07d
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• pp.2474-2476
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• 2005

본 논문에서는 슬라이딩 평면에 도달 조건을 이용하여 균일한 계단 반응을 얻을 수 있는 퍼지 슬라이딩 모드 제어기 설계방법을 제시한다. 슬라이딩 평면에 도달할 조건을 퍼지 논리로 설계하여 과도한 입력이 플랜트에 가해지지 않도록 비선형 제어기를 설계한다. 슬라이딩 평면 도달 속도의 가변 조건을 퍼지화 하여 퍼지슬라이딩 모드 제어기를 설계한다. 각각의 제어기에 대하여 고주파 공진이 있는 2차 강성 모델에 대하여 모의 실험을 실시하여 그 특성을 비교하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.3
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• pp.676-683
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• 2005

In this paper, we proposed a method that optimal values of fuzzy control rule base and quantization of membership function are searched by genetic algorithm. Proposed method searched the optimal values of membership function and control rules using genetic algorithm by off-line. Then fuzzy controller operates using these values by on-line. Proposed fuzzy control system is optimized the control rule base and membership function by genetic algorithm without expert's knowledge. We investigated proposed method through simulation and experiment using DC motor and one link manipulator, and confirmed the following usefulness.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1997.10a
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• pp.346-349
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• 1997

칼만 필터는 피드백 제어의 형태를 사용하는 플랜트를 추정한다. 플랜트의 잡음이나 측정 외란이 발생하더라도 상태를 추정하여 최적의 제어를 행한다. 상태를 추정하기 위하여 칼만 필터의 이득 Kk를 저절하고, 이 이득은 칼만 필터의 파라메터인 측정 오차 공분산 Rk과 프로세서 잡음 오차 공분산 Qk를 조정함으로써 뛰어난 필터 수행을 얻을 수 있다. 그러나 필터 파라메터 Rk, Qk는 필터 연산 이전에 측정되어야 하지만, 현재는 전문가가 전문적인 지식을 바탕으로 파라메터를 조정하여 시스템을 제어하고 있다. 따라서 이러한 비효율적인 작업을 퍼지 논리 제어기를 이용하여 온-라인에서 최적의 파라메터 Rk를 구하고자 한다.

• Journal of the Korea Society of Computer and Information
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• v.1 no.1
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• pp.159-170
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• 1996

In this paper, we propose a generating method for the optimal rules for the nonlinear control system using evolution algorithms and fuzzy controller. With the aid of evolution algorithms optimal rules of fuzzy logic system can be automatic designed without human expert's priori experience and. knowledge. and ran be intelligent control. The approachpresented here generating rules by self-tuning the parameters of membership functions and searchs the optimal control rules based on a fitness value which Is tile defined performance criterion. Computer simulations demonstrates the usefulness of the proposed method In non -linear systems.

• Journal of the Korean Institute of Intelligent Systems
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• v.23 no.5
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• pp.479-486
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• 2013

There exist two major difficulties in developing flight control system: nonlinear dynamic characteristics and time-varying properties of parameters of aircraft. Instead of the difficulties, many high reliable and efficient control methodologies have been developed. But, most of the developed control systems are based on the exact mathematical modelling of aircraft and, in the absence of such a model, it is very difficult to derive performance, robustness and nominal stability. From these aspects, recently, some approaches to utilizing the intelligent control theories such as fuzzy logic control, neural network and genetic algorithm have appeared. In this paper, one advanced intelligent lateral control system of a high speed fight has been developed utilizing type-2 fuzzy logic, which can deduce the uncertainty problem of the conventional fuzzy logic. The results will be verified through computer simulation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.11
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• pp.2474-2479
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• 2012

A sensorless vector control of an induction motor provides a good performance in the middle and high speed region. However, in the low speed region, it is very difficult to implement the sensorless vector controller because the feeding voltage measured by the motor is very low. In this paper, to improve the performance of a sensorless vector control of an induction motor in the low speed region under 3Hz, we proposed the fuzzy logic controller using the zooming algorithm. To verify the performance of the proposed controller, an experiment has been performed.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1997.10a
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• pp.194-198
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• 1997

본 연구는 용접게에 퍼지이론을 적용하여 작업자의 비숙련성 및 용접모재의 형상에 따라 변동되는 아크상태에 항상 일정하게 유지되도록 하는 제어방식ㅇ르 제안한다. 기존의 방식은 작업자 스스로 아크상태를 판단하고 아크길이의 변화를 주었다. 이에 비하여, 퍼지 용접기는 적업자가 기준 용접전압 및 용접전류를 설정한 후, 용접을 할 때 발생하는 아크상태를 숙련자의 경험에 바탕을 둔 퍼지제어기를 이용한다. 그러므로써 퍼지제어기의 출력부가 출력전압을 조절하여 균일한 용접효과가 나오도록 하는데 목적을 두었다.

• Journal of KIISE:Information Networking
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• v.31 no.3
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• pp.289-297
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• 2004

State-of-the-art wireless communication networks allow dynamic relocation of mobile terminals. A location management mechanism is required to keep track of a mobile terminal for delivering incoming calls. In this paper, we propose a fuzzy logic-based selective paging method to reduce paging cost. In the proposed fuzzy logic-based location management method, the location update uses the area-based method that uses direction-based together with movement-based methods, and the location search uses the fuzzy logic-based selective paging method based on the mobility information of mobile terminals. A partial candidate paging area is selected by fuzzy control rules, then the fuzzy logic-based selective paging method pages only the cells within the partial candidate paging area. The performance of proposed fuzzy logic-based location management method is to be evaluated by both an analytical model and a simulation, and is compared with those of LA and BVP methods. From these evaluation results, we know that the proposed fuzzy logic-based location management method provide better performance than other location management methods.

• The Transactions of the Korea Information Processing Society
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• v.4 no.10
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• pp.2485-2492
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• 1997

Nowadays the traffic conditions have been getting worse due to continuous increase in the number of vehicles. So it has become more important to manage traffic signal lights efficiently. Recently fuzzy logic is introduced to control the cycle time of traffic lights adaptively. Conventional fuzzy logic controller adjusts the extension time of current green phase by using the fuzzy input variables such as the number of entering vehicles at the green light and the number of waiting vehicle during the red light. However this scheme is inadequate for an intersection with variable traffic densities. In this paper, a new FLC with asymmetric membership functions that reflects more exactly traffic flows than other FLCs with symmetric ones regardless of few control rules is propsed. The effectiveness of the proposed method was shown through simulation of a single intersection. The experimental results yielded the superior performance of the proposed FLC in terms of the average delay time, the number of passed vehicles, and the degree of saturation.