• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2004년도 학술발표회
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• pp.124-133
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• 2004

Global climate variations are expected to affect local hydro-meteorological variables like precipitation and temperature. The Southern Oscillation (SO) is one of the major driving forces that give impact on regional and local climatic variation. The relationships between SO and local climate variation are, however, characterized by strong nonlinear variation patterns. In this paper, the nonlinear dynamic relationship between the Southern Oscillation Index (SOI), precipitation, and temperature in Fukuoka, Japan, is investigated using by a nonlinear multivariable approach. This approach is based on the joint variation of these variables in the phase space. The joint phase-space variation of SOI, precipitation, and temperature is studied with the primary objective to obtain a better understanding of the dynamical evolution of local hydro-meteorological variables affected by global atmospheric-oceanic phenomena.

• International Journal of Aeronautical and Space Sciences
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• 제12권3호
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• pp.266-273
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• 2011

This paper deals with missile autopilot design for agile turn phase in air-to-air engagement scenarios. To attain a fast response, angle-of-attack (AOA) is adopted for an autopilot command structure. Since a high operational AOA is generally required during the agile turn phase, dealing with the aerodynamic uncertainties can be a challenge for autopilot design. As a remedy, a new controller design method based on robust nonlinear control methodology such as time delay control is proposed in this paper. Nonlinear observer is also proposed to estimate the AOA in the presence of the model uncertainties. The performance of the proposed controller with variation of the aerodynamic coefficients is investigated through numerical simulations.

• 융합신호처리학회논문지
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• 제2권1호
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• pp.95-100
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• 2001

본 논문에서는 불확실성을 갖는 비선형 시스템에 제어기를 설계하기 위해서 출력제환 선형화 방법을 통하여 비선형 시스템을 선형시스템으로 변환하고 슬라이딩 모드 제어기법을 사용하여 파라미터들을 갱신하고 이를 통하여 제어입력을 갱신하는 강인성제어기를 제안하고자 한다. 비선형시스템은 최소 위상시스템이고, 시스템의 상대차수는 r＜n 이며, 제로 다이나믹스는 안정하다고 가정한다. 제안된 제어기에 대해서 대역적 점근적 안정도가 보장됨을 보였으며, 제안된 제어기에 대해서 컴퓨터 시뮬레이션을 통하여 타당성을 검증하였다.

• 한국정밀공학회지
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• 제14권5호
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• pp.108-117
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• 1997

To prove the stability and the effectiveness of the robust non-linear friction control suggested and proved analytically in the previous paper, the describing function analysis is introduced. The instability of the Southward's nonlinear friction compensation for a digital position control and the improvement of phase margin of the robust nonlinear friction compensation are verified qualitatively through the describing function analysis. Those controls are applied to a single-axis digital servo driving experimental setup which has inherent stick-slip friction and experimental results confirm the results obtained in and the effectiveness of the robust nonlinear friction compensation for a digital position control.

• 대한기계학회논문집
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• 제18권8호
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• pp.1985-1996
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• 1994

A new design method of sliding hyperplanes is proposed in the synthesis of a variable structure controller for robust tracking of general nonlinear multi-input-output(MIMO) uncertain systems of relative degree higher than two. Input/ output(I/O) linearzation is firstly undertaken by employing the concept of relative degree and minimum phase followed by the construction of sliding mode controllers. Sliding hyperplanes are then derived from the inherent properties of companion matrix and ideal sliding mode characterized in I/O linearized system. Subsequently, the gradient magnitudes of the sling hyperplanes are determined in an optimal manner by considering a quadratic performance index to be evaluated at two phases; a reaching phase and a sliding phase. The proposed design methodology is relatively straightforward and systematic compared with conventional strategies such as geometric approach or pole assignment technique. A nonlinear governor and exciter control problem for a power system is adopted herein in order to demonstrate the design efficiency and also favorable and robust control performances.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.1480-1482
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• 2005

The major causes of power quality deterioration are harmonic current through semiconductor switching device, due to use of nonlinear loads such as diodes rectifier or thyristor rectifiers. In response to this concerns, this paper presents a new control method of single-phase active power filter(APF) for the compensation of harmonic current components in nonlinear loads. In order to make the complex calculation to be possible, the single-phase system that has two phases was made by constructing a imaginary second-phase giving time delay to load currents. In the conventional method, a imaginary-phase lagged to the load current T/4(here T is the fundamental cycle) was made. But in this proposed method, the new signal, which has the delayed phase through the filter, using the phase-delay property of low-pass filter, was used as the second phase. As this control method is applied to the system of single phase, an instantaneous calculation was done rather by using the rotating reference frames that synchronizes with source-frequency than by applying instantaneous reactive power theory that uses the conventional fixed reference frames.

• Steel and Composite Structures
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• 제46권5호
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• pp.637-647
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• 2023

Nonlinear free vibration and stability responses of a carbon nanotube reinforced composite beam under temperature rising are investigated in this paper. The material of the beam is considered as a polymeric matrix by reinforced the single-walled carbon nanotubes according to different distributions with temperature-dependent physical properties. With using the Hamilton's principle, the governing nonlinear partial differential equation is derived based on the Euler-Bernoulli beam theory. In the nonlinear kinematic assumption, the Von Kármán nonlinearity is used. The Galerkin's decomposition technique is utilized to discretize the governing nonlinear partial differential equation to nonlinear ordinary differential equation and then is solved by using of multiple time scale method. The critical buckling temperatures, the nonlinear natural frequencies and the nonlinear free response of the system is obtained. The effect of different patterns of reinforcement on the critical buckling temperature, nonlinear natural frequency, nonlinear free response and phase plane trajectory of the carbon nanotube reinforced composite beam investigated with temperature-dependent physical property.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제3권1호
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• pp.55-69
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• 1999

In this paper we analyze the error estimates for a single-phase nonlinear Stefan problem with Neumann boundary conditions. We apply the modified Crank-Nicolson method to get the optimal order of error estimates in the temporal direction.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1995년도 Proceedings of the Korea Automation Control Conference, 10th (KACC); Seoul, Korea; 23-25 Oct. 1995
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• pp.135-137
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• 1995

A new design method is proposed for a fuzzy PD controller. By analyzing phase plane characteristics we can build and optimize the rule base of fuzzy logic controller. Also, a new gain tuning method is used to improve performance in the transient and steady state. The improved performance of the new methodology is shown by an application to the design of control system with a highly nonlinear actuator.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1987년도 한국자동제어학술회의논문집; 한국과학기술대학, 충남; 16-17 Oct. 1987
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• pp.652-657
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• 1987

The Dynamic Matrix Control(DMC) technique was applied to nonlinear and nonminimum phase system. System model was identified by using Least Square method. Desired output trajectory was prespecified and input suppression parameter was also introduced. It was shown that DMC technique worked with great success in solving both nonminimum phase system and nonlinear system.