• 전기학회논문지P
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• 제51권2호
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• pp.60-67
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• 2002

This paper presents a control approach for designing a self tuning fuzzy controller for a synchronous generator excitation and SVC system. A combination of thyristor-controlled reactors and fixed capacitors (TCR-FC) type SVC is recognized as having the most flexible control and high speed response, which has been widely utilized in power systems, is considered and designed to improve the response of a synchronous generator, as well as controlling the system voltage. The proposed parameter self tuning algorithm of fuzzy controller is based on the steepest decent method using two direction vectors which make error between inference values of fuzzy controller and output values of the specially selected PSS reduce steepestly. Using input-output data pair obtained from PSS, the parameters in antecedent part and in consequent part of fuzzy inference rules are learned and tuned automatically using the proposed steepest decent method. The related simulation results show that the proposed fuzzy controller is more powerful than the conventional ones.

• 조명전기설비학회논문지
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• 제23권2호
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• pp.175-181
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• 2009

본 논문에서는 전력계통의 안정도를 향상시키기 위하여 동기 발전기와 정지형 무효전력 보상기에 대한 파라미터 자기조정 퍼지제어기의 설계 기법을 제시한다. 제안된 퍼지제어기의 파라미터 자기조정 알고리즘은 퍼지제어기의 추론값과 전력계통안정화 장치의 출력값들 사이의 오차를 감소시키는 두 개의 방향 벡터를 사용하는 최급강하법에 기초를 둔다. 전력계통안정화 장치로부터 얻어진 입 출력 데이터쌍을 사용하여, 퍼지추론 규칙의 전건부와 후건부에서의 파라미터들은 제안된 최급강하법에 의해 자동조정되고 학습되어진다. 시뮬레이션 결과, 제안된 퍼지제어기가 종래의 제어기보다 우수한 제어성능을 보임을 확인하였다.

• 한국광학회지
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• 제8권5호
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• pp.362-365
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• 1997

Mach-Zehnder형 외부 광 변조기나 Homodyne 검출기 같은 간섭계 원리를 이용한 장치에서 최대 또는 최소의 광 출력을 유지하도록 두 입력 광 사이의 위상 차를 제어하는 새로운 방법을 제시하였다. 이 방법은 Steepest Descent 알고리즘의 변형된 형태로 Delta Modulation 이론으로 성능을 해석할 수 있다. 이 방법은 기존의 흔들림(dithering) 방법을 적용하기 어려운 저속 펄스가 사용되는 간섭계 장치에도 사용할 수 있다.

• Journal of applied mathematics & informatics
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• 제32권5_6호
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• pp.609-619
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• 2014

Nonsmooth equations with finitely many maximum functions is often used in the study of complementarity problems, variational inequalities and many problems in engineering and mechanics. In this paper, we consider the global convergence methods for nonsmooth equations with finitely many maximum functions. The steepest decent method and the smoothing gradient method are used to solve the nonsmooth equations with finitely many maximum functions. In addition, the convergence analysis and the applications are also given. The numerical results for the smoothing gradient method indicate that the method works quite well in practice.

• Journal of Mechanical Science and Technology
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• 제14권9호
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• pp.1005-1012
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• 2000

Numerical optimization techniques combined with a three-dimensional thin-layer Navier-Stokes solver are presented to find an optimum shape of a stator blade in an axial compressor through calculations of single stage rotor-stator flow. Governing differential equations are discretized using an explicit finite difference method and solved by a multi-stage Runge-Kutta scheme. Baldwin-Lomax model is chosen to describe turbulence. A spatially-varying time-step and an implicit residual smoothing are used to accelerate convergence. A steady mixing approach is used to pass information between stator and rotor blades. For numerical optimization, searching direction is found by the steepest decent and conjugate direction methods, and the golden section method is used to determine optimum moving distance along the searching direction. The object of present optimization is to maximize efficiency. An optimum stacking line is found to design a custom-tailored 3-dimensional blade for maximum efficiency with the other parameters fixed.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2005년도 하계학술대회
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• pp.397-405
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• 2005

This paper presents a headphone system which has adopted two algorithm to increase sound clearness and to separate signal from noisy environment. In the field of adaptive signal processing, LMS algorithm which is a kind of steepest decent method, can be implemented with more simple calculation, so that we use it to eliminate unwanted noise elements for the proposed system. Futhermore we generate early echo using some delays, then mix it in signal. This process can increase the clearness of signal. In this paper, we prove that the proposed system can be implemented in real time. The proposed system is satisfied to subject assessment test base on MOS(Mean Opinion Score) of ITU-T.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 학술대회 논문집 전문대학교육위원
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• pp.60-63
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• 2002

This paper presents a control approach for designing a self tuning fuzzy controller for SVC system, A SVC constructed by a Fixed Capacitor and a Thyristor Controlled Reactor is designed and implemented to improve the damping of a synchronous generator, as well as controlling the system voltage, The proposed parameter self tuning algorithm of fuzzy controller is based on the steepest decent method using two direction vectors which make error between inference values of fuzzy controller and output values of the specially selected PSS reduce steepestly, The related simulation results show that the proposed fuzzy controller is more powerful than the conventional ones.

• 융합신호처리학회논문지
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• 제9권2호
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• pp.129-134
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• 2008

본 논문에서는 적자생존 원리에 기반한 유전자 알고리즘을 이용하여 일차원 비선형 광자 결정 구조에 대해 분석하고, 광 트랜지스터로의 적용 가능성을 컴퓨터 시뮬레이션에 의해 증명한다. 이와 같은 형태의 최적 설계는 해석식이 필요한 steepest decent 최적 알고리즘과 달리 유전자 알고리즘은 탁월한 성능을 낼 수 있으며, 광 트랜지스터 뿐만 아니라 다른 광자 결정 광소자의 설계에 유용하게 적용될 수 있다. 또한, global minimum 최적해 부근에서 여러 가지의 해가 얻어지기 때문에 광 트랜지스터가 어떤 모양을 가져야 되는지 분석하는데 많은 도움을 주는 장점을 갖는다. 완전 광 필터 트랜지스터를 설계하기 위해 신경회로망 모델을 이용하여 초기 설계를 수행한 후, 유전자 알고리즘에 의해 최종적인 최적화 설계가 수행된다. 시뮬레이션으로부터 얻어진 일차원 광자 결정 트랜지스터의 스위칭 On/Off 비는 약 27dB 였다.

• 대한의용생체공학회:의공학회지
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• 제27권3호
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• pp.83-88
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• 2006

A new method of measuring pulse arrival time (PAT), which is usually used for the estimation of systolic blood pressure, in an unconstrained manner using a chair, is proposed. The capacitive-coupled ECG (CC-ECG) measurement system and the air cushion with balancing tubes system were used for unconstrained PAT measurement. Firstly, the correlation between the standard PAT (S-PAT) from the photoplethysmography (PPG) and the PAT measured in an unconstrained manner (U-PAT) was evaluated. It was observed that U-PAT, which is the time delay from the R-peak of ECG to the steepest decent point of air cushion pressure wave, is significantly correlated with the S-PAT. Secondly, systolic blood pressure (SBP) measured by the radial tonometer is compared to the U-PAT. The ten-beat averaged U-PAT removed respiration effects and demonstrated a high intra-subject correlation with SBP in all participants. Finally, the tonometry SBP was estimated from these U-PAT values for one participant intermittently during half a day.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 B
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• pp.687-689
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• 1998

This paper represents fundamental developments in Fuzzy and Neural approaches. The Fuzzy Controller(FC) and plant are cascaded in Adaptive framework. Each of which produces its outputs. The adjustable parameters all pertain to the fuzzy controller is implemented as an Adaptive FC to adjust the environments of the plant. There is an error meaure block which is a difference between the actual state and desired state. We introduce error back propagation algorithm in neural method. To speed up convergence, we follow a steepest decent in the sense that each parameter set update leads to a smaller error measure and is learned by this methodology. Inverted pendulum is a typical testbed to measure the effectiveness of nonlinear control system. finally we simulated the adaptive fuzzy controller to be able to bring back to the upright position of the its angle and angular velocity.