• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.567-571
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• 2005

The slender rectangular cantilever beam has vef interesting to study dynamic behaviors of the harmonic base excitation of a cantilever beam shows many nonlinear dynamics due to unstability , energy transfer and mode coupling. Nonlinear phenomenon shows superharmonic, subharmonic, super subharmonic and chaotic motions of the cantilever beam. Experimental observation and verification of these phenomenon carry much importance for the theoretical study as well as in it self. In the experimental cantilever beam, the chaotic motions of the beam appear as a pink noise signal in FFT analysis and as a torus structure in the oscilloscope analyzed to eventually give information of chaotic motions of the cantilever beam.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.270-274
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• 2006

This paper proposes a Chaos Pulse Width Modulation(CPWM) technique. For generating the chaotic numbers by chaos phenomenon, chaos area $\lambda$=0.99 in bifurcation tree of the proposed double tent mapping is used. A micro-controller is used for the generation of chaos numbers and triangular carrier with chaotic frequency is obtained through the process of frequency modulation according to the generated chaos numbers. The experiments are executed with the 1.5kw induction motor coupled with a 2.5A load. The experimental results show that the voltage / current spectra are spread to a chaotic range, and the switching noise of motor is reduced by the proposed method compared to the fixed frequency PWM method.

• Wind and Structures
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• 제36권3호
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• pp.215-220
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• 2023

We study the progressive full-scale wind tunnel tests on a high solidity vertical axis wind turbine (VAWT) for various tip speeds and pitch angles to understand the VAWT shaft system's dynamics using 0-1 Test for chaos. We identify that while varying rotor speed (tip speed) of the turbine, the system's dynamics change from periodic to chaotic through quasiperiodic and strange non-chaotic (SNA) states. The present study is the first experimental evidence for the existence of these states in the VAWT shaft system to the best of our knowledge. Using the asymptotic growth value Kc in 0-1 test, when the turbine operates at the low tip speeds and high pitch angles for low incoming wind speeds, the system behaves periodic (Kc ≈ 0). However, when the incoming wind speed increases further the system's dynamics shift from periodic to chaotic vibrations through quasi-periodic and SNA. This phenomenon is due to the dynamic stalling of blades which induces chaotic vibration in the VAWT shaft system. Further, the singular continuous spectrum method validates the presence of SNA and differentiates the SNA from chaotic vibrations.

• 한국통신학회논문지
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• 제19권7호
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• pp.1414-1420
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• 1994

dead beat 제어법칙을 적용한 적응기구에 존재하는 혼돈신호가 일정한 규칙성과 질서를 갖는다는 특성을 이용하여 낮은 상관관계를 갖는 동적 관계식을 도입하여 반복 추종함으로서 추종오차를 줄이고 제어성능을 향상시킬 수 있었다. 또한 이러한 적응제어를 적용한 경우에도 혼돈현상을 보이는 것을 1) Time series 2) Fourier spectrum 3) Phase portrait 4) Lyapunov exponent 등의 방법을 통하여 증명하고 그 특징을 규명해 보였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 추계학술대회 논문집 학회본부
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• pp.322-325
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• 1994

Mareel and Bitmead proved the presence of chaotic signal in random noise by applying dead beat control theory to adaptive mechanism. In this paper robust adaptive theory is proposed. With the property of chaotic signal that has order and law, the proposed theory can enhance the control Performance by applying the recursive algorithm that uses dynamic relation which have small correlation. The performance of proposed algorithm is demonstrated with the computer simulation of position control of electric motor. In this simulation, the adaptive low is adopted to control electric motor and the Presence of chaotic signal in feedback signal is proved by using several method such as time series, fourier spectrum phase portrait method.

• 자연과학논문집
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• 제6권1호
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• pp.79-87
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• 1993

주기배가 갈래질 본뜨기에서 안정 주기의 궤도는 $2^n$으로 그 주기가 갈래질 하고 또 혼돈에 이르면 그 혼돈 띠는 1/$2^n$로 수렴하여 넓은 영역의 혼돈이 생긴다. 이때 순환식에 따라서 혼돈 띠 (Chaotic Band)의 수렴과정에서 이 혼돈띠들이 갑자기 넓은 영역의 하나의 혼돈띠로 바뀌는 고비현상이 생기기도 하는데 여기서는 우리가 만든 순환식에서 생기는 이러한 내부고비현상 (Interioi Crisis)을 살피고 이 현상의 특성을 Lyapunov Exponent를 얻어 분석하고자 한다.

• The Korean Journal of Ceramics
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• 제3권4호
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• pp.239-244
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• 1997

The Voronoi network can be used to effectively simulate the microstructure of ZnO varistors. The nonuniformity in microstructure of simulated ZnO varistor can be changed by setting different disorder degree of Voronoi network. In the region of disorder degree larger than 3 where the simulated microstructures are similar to those the actual ones of ZnO varistors, a chaotic phenomenon exists in the microstructure characteristics. This chaotic property can simulate the original behavior of nonuniformity of electrical characteristics caused by microstructures of ZnO varistors.

• 조명전기설비학회논문지
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• 제22권12호
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• pp.71-78
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• 2008

본 연구에서는 전동기 소음 저감을 위한 카오스 2중 텐트 사상(double tent mapping) PWM 기법에 대하여 고찰하였다. 카오스 수 발생은 2중 텐트 사상의 카오스 발생 영역인 ${\lambda}=0.99$에서의 분기 트리(bifurcation tree)를 사용하였다. 카오스 수 발생은 80C196 마이크로 콘트롤러가 담당하고 있으며, 80C196으로부터 발생된 카오스 수와 MAX038 주파수 변조기를 이용하여 카오스 특성을 갖는 삼각파 캐리어가 발생한다. 2.5[A] 부하조건에 대한 1.5[kw]급 유도 전동기 구동 시스템에 제안된 방법과 종전의 고정 주파수 방법을 적용하였으며 각각의 방법에 대하여 캐리어 및 전동기 전압 그리고 3차원 스위칭 소음의 고조파 스펙트럼을 비교 검토하였다. 그 결과 제안된 방법의 고조파 스펙트럼은 특정 주파수에 집중되지 않는 카오스 분포를 하였으며, 이로 인하여 전동기에서 발생하는 날카로운 스위칭 소음이 저감됨을 알 수 있었다.

• Journal of Electrical Engineering and Technology
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• 제3권3호
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• pp.314-319
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• 2008

Power quality simulation plays an important role in many practical cases, for example, when deciding the capacity of the related mitigation devices, assessing the influence of installing a nonlinear load in the distribution part, dissolving the quality issues between utilities and customers, and so on. For these purposes, many dedicated tools have been used in order to assess the level of quality distortions by various kinds of PQ indices. However, there are few modules that can accurately simulate the flicker phenomenon, that is, $P_{st}$ and the nonlinear and chaotic behavior of the electrical arc furnace, which is one of the representative nonlinear loads. This paper deals with the useful and simple modules for the voltage flicker simulation in the distribution and transmission level under the environment of Matlab/Simulink. With these modules, the various conditions of distribution systems and the capacities of arc furnaces with the chaotic characteristic can be easily taken into account.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.600-605
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• 2002

The keyhole formed by high energy density laser-material interaction periodically collapses due to surface tension of the molten metal in partial penetration welds. The collapse sometimes traps a void at the bottom of the keyhole, and it remains as welding defects. This phenomenon is seen as one cause of the instability of the keyhole during laser beam welding. Thus, it seems likely that improving the stability of the keyhole can reduce voids and uniform the penetration depth. The goal of this work is to develop techniques for controlling laser weld keyhole dynamics to reduce weld defects such as voids and inconsistent penetration. Statistical analysis of the penetration depth signals in glycerin determined that keyhole dynamics are chaotic. The chaotic nature of keyhole fluctuations and the ability of laser power modulation to control them have been demonstrated by high-speed video images of laser welds in glycerin. Additionally, an incident leading beam angle is applied to enhance the stability of the keyhole. The quasi-sinusoidal laser beam power of 400Hz frequency and 15$^{\circ}$ incident leading beam angle were determined to be the optimum parameters for the reduction of voids. Finally, chaos analyses of uncontrolled signals and controlled signals were done to show the effectiveness of modulation on the keyhole dynamics. Three-dimensional phase plots for uncontrolled system and controlled system are produced to demonstrate that the chaotic keyhole dynamics is converted to regular periodic behavior by control methods: power modulation and incident leading beam angle.