• Journal of Industrial Technology
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• v.26 no.B
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• pp.227-231
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• 2006

This paper presents a robust speed control method of induction motors(IM) using a Non-linear PI controller(NPI). NPI is high gain controller in region of small error, and low gain controller in region of large error. So in steady state, system will be robust against variation of load torque. The simulation and experiment results confirm the validity of proposed control scheme.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.3
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• pp.292-299
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• 1992

A nonlinear feedback linearizing control method for an EMS (Electro-Magnetic Suspension) system is proposed. After linearzing the system using the exact linearizing method, conventional linear system control theory has been applied. Robustness properties of the proposed controller with respect to the load variations is also analysed for a single magnet suspension system. Computer simulation is carried out in order to compare the performance of the proposed controller with that of the existing controller designed by using Taylor series expansion around nominal points.

• Korean Journal of Mathematics
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• v.14 no.1
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• pp.113-123
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• 2006

The arches may buckle in a symmetrical snap-through mode or in an asymmetry bifurcation mode if the load reaches a certain value. Each bifurcation curve develops as pressure increases. The governing equation is derived according to the bending theory. The balance of forces provides a nonlinear equilibrium equation. Bifurcation theory near trivial solution of the equation is developed, and the buckling pressures are investigated for various spring constants and opening angles.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.10a
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• pp.28-31
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• 1997

Buckling analysis of thin compressed beam has been carried out. Pre-buckling and post-buckling are simulated by finite element method incorporating with the incremental nonlinear theory and the Newton-Raphson solution technique. In order to find the bifurcation point, the determinent of the stiffness matrix is calculated at every iteration procedure. For post-buckling analysis, a small perturbed initial guess is given along the eigenvector direction at the bifurcation point. Nonlinear elastic buckling and elastic-plastic buckling of cantilever beam are analyzed. The buckling load and buckled shape of the two models are compared.

• Proceedings of the Korea Concrete Institute Conference
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• 1992.04a
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• pp.47-52
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• 1992

The entire nonlinear behavior of reinforced concrete frames up to collapse, is analyzed by the displacement control method and the combined layered and nonlayered method. All of the rigidities of section are calculated approximately by a sum over all the layers for the layered method, are used the integral values over the cross section area for the nonlayered method. The spurious sensitivity to the chosen element size in the result of analysis by finite element method for the materials with strain-softening can be overcome by modifying the strain distribution based on the concept of fracture energy at plastic hinge considering the applied axial load.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.5
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• pp.88-93
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• 2003

Buckling behavior of stiffened laminated composite cylindrical panel was studied using linear and nonlinear deformation theory. Various buckling load factors are obtained for stiffened laminated composite cylindrical panels with rectangular type longitudinal stiffeners and various longitudinal length to radius ratio, which made from Carbon/Epoxy USN150 prepreg and are simply-supported on four edges under uniaxial compression. Buckling behavior design analyses are carried out by the nonlinear search optimizer, ADS.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.1
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• pp.136-144
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• 2004

In general a hydraulic system which uses a single rod hydraulic as an actuator is modeled as a nonlinear system and reveals uncertain Parameter characteristics such as the density variation of hydraulic oil and is subject to load variations and severe disturbances during operation. A variable design-parameter fuzzy PID controller is adopted to solve these undesirable internal and external problems and its effectiveness is verified through computer simulations for control performance and real time control possibility.

• Earthquakes and Structures
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• v.5 no.4
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• pp.439-459
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• 2013

Main objective of the present study is to determine the statistical properties and suitable probability distribution functions of spectral displacements from nonlinear static and nonlinear dynamic analysis within the frame work of Monte Carlo simulation for typical low rise and high rise RC framed buildings located in zone III and zone V and designed as per Indian seismic codes. Probabilistic analysis of spectral displacement is useful for strength assessment and loss estimation. To the author's knowledge, no study is reported in literature on comparison of spectral displacement including the uncertainties in capacity and demand in Indian context. In the present study, uncertainties in capacity of the building is modeled by choosing cross sectional dimensions of beams and columns, density and compressive strength of concrete, yield strength and elastic modulus of steel and, live load as random variables. Uncertainty in demand is modeled by choosing peak ground acceleration (PGA) as a random variable. Nonlinear static analysis (NSA) and nonlinear dynamic analysis (NDA) are carried out for typical low rise and high rise reinforced concrete framed buildings using IDARC 2D computer program with the random sample input parameters. Statistical properties are obtained for spectral displacements corresponding to performance point from NSA and maximum absolute roof displacement from NDA and suitable probability distribution functions viz., normal, Weibull, lognormal are examined for goodness-of-fit. From the hypothesis test for goodness-of-fit, lognormal function is found to be suitable to represent the statistical variation of spectral displacement obtained from NSA and NDA.

• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.4
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• pp.269-276
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• 2016

Seismic performance evaluation of existing building usually needs much time and man power, especially in case of nonlinear analysis. Many data interaction steps for model transfer are needed and engineers should spend much time with simple works like data entry. Those time-consuming steps could be reduced by applying computerized and automated modules. In this study, computational platform for seismic performance evaluation was made with several computerized modules. StrAuto and floor load transfer module offers a path that can transfer most linear model data to nonlinear analysis model so that engineers can avoid a lot of repetitive work for input information for the nonlinear analysis model. And the new nonlinear property generator also helps to get the nonlinear data easily by importing data from structural design program. To evaluate the effect of developed modules on each stages, seismic performance evaluation of example building was carried out and the lead time was used for the quantitative evaluation.

• Journal of Electrical Engineering and Technology
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• v.9 no.6
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• pp.1935-1943
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• 2014

In recent years, the induction machines are increasingly being used as self-excited induction generators (SEIG). This generator is especially widely employed for small-scale power plants driven by renewable energy sources. The application of power electronic components in the induction generator control (IGC) and the loading of SEIG using nonlinear loads will generate harmonic currents. This paper analyzes the propogation of harmonic currents on the SEIG with nonlinear loads. Transfer function method in the frequency domain is used to calculate the gain and phase angle of each harmonic current component which are generated by a nonlinear loads. Through the superposition approach, this method has also been used to analyze the propagation of harmonic currents from nonlinear load to the stator windings. The simulation for the propagation of harmonic currents for a 4 pole, 1.5 kW, 50Hz, 3.5A, Y-connected, rotor-cage SEIG with energy-saving lamps, have provided results almost the same with the experiment. It can prove that the validity of the proposed models and methods. The study results showed that the propagation of harmonic currents on the stator windings rejects high order harmonics and attenuates low order harmonics, consequently THDI diminish significantly on the stator windings.