• International Journal of Control, Automation, and Systems
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• 제6권1호
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• pp.24-34
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• 2008

A novel neural network model, termed the standard neural network model (SNNM), similar to the nominal model in linear robust control theory, is suggested to facilitate the synthesis of controllers for delayed (or non-delayed) nonlinear systems composed of neural networks. The model is composed of a linear dynamic system and a bounded static delayed (or non-delayed) nonlinear operator. Based on the global asymptotic stability analysis of SNNMs, Static state-feedback controller and dynamic output feedback controller are designed for the SNNMs to stabilize the closed-loop systems, respectively. The control design equations are shown to be a set of linear matrix inequalities (LMIs) which can be easily solved by various convex optimization algorithms to determine the control signals. Most neural-network-based nonlinear systems with time delays or without time delays can be transformed into the SNNMs for controller synthesis in a unified way. Two application examples are given where the SNNMs are employed to synthesize the feedback stabilizing controllers for an SISO nonlinear system modeled by the neural network, and for a chaotic neural network, respectively. Through these examples, it is demonstrated that the SNNM not only makes controller synthesis of neural-network-based systems much easier, but also provides a new approach to the synthesis of the controllers for the other type of nonlinear systems.

• 한국소음진동공학회논문집
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• 제12권12호
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• pp.921-928
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• 2002

Main sources of the nitration of a gear-pair system are backlash and transmission error, the difference between required and actual rotation during gear meshing. This paper presents the nonlinear dynamic characteristics of gear motions due to the existence of backlash and periodic variation of meshing stiffness, which is assumed as a one-term harmonic component. Gear motions are classified as three types with the consideration of backlash. Each response is calculated using the harmonic balance method and confirmed by numerical integration. The responses with the increase of the rotating speed show abrupt changes in its magnitude for the variation of the preload, exciting force, and damping coefficient. The result also shows that there is a chaotic motion with some specific design parameters and operating conditions In gear diving system. Consequently the design of gear driving system with low nitration and noise requires the study on the effects of nonlinear dynamic characteristics due to stiffness variation and backlash.

• 한국공간구조학회논문집
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• 제14권1호
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• pp.85-91
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• 2014

The purpose of this paper is to study comparative of dynamic instability characteristic of Geiger-typed cable dome structures by load condition, which is well-known among the cable dome structures that are the lightweight hybrid structure using compression and tension element continuously. Dynamic buckling process in the phase plane is very important thing for understanding why unstable phenomena are sensitively originated in nonlinear dynamic by various initial conditions. But there is no paper for the dynamic instability of hybrid cable dome by Sinusoidal Excitations, many papers which deal with the dynamic instability for shell-structures under the step load have been published. As a result of Geiger-typed cable dome, which shows chaotic behavior in dynamic nonlinear analysis with initial imperfection.

• 전기학회논문지
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• 제66권12호
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• pp.1852-1865
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• 2017

The vibration of the structures with restrained motion has long been observed in various engineering fields. When the motion of vibrating structure is restrained due to the adjacent objects, the frequencies and the mode shapes of the structure change and its vibration characteristics becomes unpredictable, in general. Although the importance of the study on this type of vibration model increases in many engineering areas, most studies conducted so far are limited to the theoretical study on dynamic responses of the structure with stops, including some experimental works. Specially, the study on the nonlinear phenomena due to the impact between the structure and the stops have been mainly performed theoretically. In the paper, both numerical analyses and experiments are conducted to study the chaotic vibration characteristics of the nonlinear motion and the dynamic response of a cantilevered beam which has restrained motion at the free end by the stops. Results are presented for various magnetic forces and gaps between the beam and stops. The conclusions are as follows : Firstly, Numerical simulation results have a good agreement with experimental ones. Secondly, the effect of higher modes of beams are increased with increasing magnitude of exciting force, and displacement and velocity curves become more complicated shapes. Thirdly, nonlinear characteristics tend to appear greatly with increasing magnitude of exciting force, and fractal dimension is increased.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1994년도 춘계학술대회
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• pp.72-74
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• 1994

This paper describes the effect of autonomic nervous activity on Heart rate variability and peripheral blood pressure with power spectral analysis and its characteristics of chaotic attractors. The aim of this paper is to access the applicability of spectral and dimension analysis of heart rate variability and peripheral blood pressure, attributed to changes in autonomic nervous system activity. About 60 mininutes of Heart rates and synchronized peripheral blood pressure were recorded on 10 healthy man while various mental and physical conditions. The results shows the availability to evaluate the autonomic nervous activities.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.270-275
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• 2003

The nonlinear dynamic characteristic of a straight tube conveying fluid with constraints and an attached mass on the tube is examined in this study. An experimental apparatus composed of an elastomer tube conveying water which has an attached mass and constraints is made and comparisons are done between the theoretical results from non-linear equation of motion of piping system and experimental results. And the results show that the tube is destabilized as the mass of the attached mass increases, and stabilized as the position of the attached mass close to the fixed end. In case of a small end-mass, the system shows rich and different types of periodic solutions. For a constant end-mass, the system undergoes a series of bifurcations after the first Hopf bifurcation, as the flow velocity increases, which causes chaotic motion of the tube eventually.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 B
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• pp.627-629
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• 1997

In this paper, fuzzy logic system equipped with the back-propagation training algorithm as identifiers for nonlinear dynamic systems is described. To improve its performance, Jacob's delta-bar -delta rule is adapted in adjusting stepsize ${\alpha}$, and only y and ${\alpha}$ updating algorithm is suggested. In identifying and predicting the chaotic time series, suggested method is better than Li-Xin Wang's method,[1]

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 B
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• pp.962-964
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• 1995

In this paper, an integrated chaos analysis system for EEG (ICASE) is designed for the analysis of brain functions based on the chaos theory. Nonlinear dynamic characteristics of EEG such as 3-D attractor, Poincare section, correlation dimension, Lyapunov exponents and power spectrum are extracted by this system. The results show that chaotic attractors which indicate the presence of deterministic, dynamics of complex nature could be identified from a routine EEG recording for normal and pathological activity. This proves that the chaotic analysis of EEG may be an appropriate tool in the classification of brain activity and thus a possible diagnostic tool.

• 대한전기학회논문지:전력기술부문A
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• 제48권3호
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• pp.197-202
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• 1999

Electric arc furnaces (EAFs) use bulk electrical energy to create heat in metal refining industries. The electric arc process is a main cause of the degradation of the electric power quality such as voltage flicker due to the interaction of the high demand currents of the load with the supply system impedance. The stochastic models have described the aperiodic physical phenomena of EAFs. An alternative approach is to include deterministic chaos in the characterization of the arc currents. In this parer, a chaotic approach to such modeling is described and justified. At the same time, a DLL(Dynamic Link Library) module, which is a FORTRAN interface with TACS (Transient Analysis of Control Systems), is developed to implement the chaotic load model in the Electromagnetic Transients Program (EMTP). The details of the module and the results of tests performed on the module to verify the model and to illustrate its capabilities are presented in this paper.

• Journal of information and communication convergence engineering
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• 제9권4호
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• pp.369-374
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• 2011

Generally the neural network and the Fuzzy compensative algorithms are applied to forecast the time series for power demand with the characteristics of a nonlinear dynamic system, but, relatively, they have a few prediction errors. They also make long term forecasts difficult because of sensitivity to the initial conditions. In this paper, we evaluate the chaotic characteristic of electrical power demand with qualitative and quantitative analysis methods and perform a forecast simulation of electrical power demand in regular sequence, attractor reconstruction and a time series forecast for multi dimension using Lyapunov Exponent (L.E.) quantitatively. We compare simulated results with previous methods and verify that the present method is more practical and effective than the previous methods. We also obtain the hourly predictability of time series for power demand using the L.E. and evaluate its accuracy.