• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.5
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• pp.379-384
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• 2014

This article describes the dynamic behaviors of a rubber tired gantry crane(RTGC) under typical load conditions which are used in the design of gantry cranes. In order to investigate the dynamic characteristics of an RTGC, we developed a finite element crane model for its huge structure. The finite element model was validated with the modal test results, e.g., natural frequencies and normal modes. And other components of RTGC were converted into detailed 3D CAD models and finally transformed to rigid body models in a dynamic simulation program ADAMS. The load conditions considered in this paper were a normal operating condition(OP1) and container hanging condition with no external loads. As a result, we could find there was large influence of crane's vibration owing to its structural stiffness and deformation. And the vibration of crane could made the movements of RTGC, which occurs crash or malfunction of crane works.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.6
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• pp.855-864
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• 2011

In this paper, a nonlinear controller based on adaptive back-stepping method is proposed for high performance operation of IPMSM(Interior Permanent Magnet Synchronous Motor). First, in order to improve the performance of speed tracking a nonlinear back-stepping controller is designed. Since it is difficult to control the high performance driving without considering parameter variation, a parameter estimator is included to adapt to the variation of load torque in real time. In addition, for the efficiency of power consumption of the motor, controller is designed to operate motor with minimum current for maximum torque. The proposed controller is applied through simulation to the a 2-hp IPMSM for the angular velocity reference tracking performance and load torque volatility estimation, and to test the MTPA(Maximum Torque per Ampere) operation in constant torque operation region. The result verifies the efficacy of the proposed controller.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.8
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• pp.1631-1641
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• 2012

A TDMA system in satellite communication has been utilized. Especially DVB-S2 was standardized and now operated in satellite broadcasting system. In this paper, we propose a TDMA frame structure appropriate for special purpose which has the good reliablilty in a poor RF environment even if frequency efficiency is decreased. TDMA frame duration is 12 seconds which is long duration in comparison with general TDMA system with several ms. Designing the frame structure, time and frequency shift in single frame duration are considered. Simulation results show that the proposed frame structure and synchronization method has robust synchronization performance when the terminal is even in low SNR as well as 25 kHz frequency offsets.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.05a
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• pp.589-592
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• 2011

In this paper, bidirectional DC-DC converter is designed to cover up defects of fuel cell generating system like as low dynamic characteristic, unstable output and lack of storage ability by using bidirectional DC-DC Converter and supercapacitor that available to charge & discharge quickly, high efficient at charge & discharge and semi-permanent. Operating efficiency has been analyzed through simulation and examination. According to these design and data, hybrid system has been made and operation test, evaluation and results evaluation have been performed.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.3
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• pp.163-170
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• 2008

Switching characteristics in both linear and nonlinear loads are analysed for a 3-phase voltage disturbance generator applicable to the performance test of custom power devices. Since the line current of the linear load is continuous the natural commutation of the SCR thyristors comprising the generator is carried out with ease. However, in case of nonlinear load the natural commutation scheme is different from that of the linear load due to the discontinuous load current. Through the analysis it is found that a specific switching condition can provide the voltage sag, swell, outage, and voltage unbalance generation in nonlinear load too. The operation of the voltage disturbance generation is described and the usefulness of the generator is verified through simulation and experimental results. It is expected that the generator can be used in the performance test of the custom power devices with low implementation cost and easy control.

• Journal of the Korean Institute of Intelligent Systems
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• v.8 no.2
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• pp.9-20
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• 1998

In this paper, a new distance relaying scheme is proposed. Artificial neural networks are applied to the distance relaying system composed of pattern recognition based. The proposed distance relaying scheme has two blocks of pattern recognition stages to estimate the fundamental frequency and to classify the fault types. In the first block, a filtering method using neural networks called a neural networks mapping filter(NMF) is presented to efficiently extract the features. And in the sec'ond block, the estimator called neural networks fault pattern estimator(NFPE) is also presented to classify the fault types by the extracted effective features obtained from NMF. Each block of these applied schemes is trained by back-propagation algorithm of multilayer perceptron and show the fast and accurate pattern recognition by ability of multilayer neural networks. The test result of this approach are obtained the good performance from the fault transient wave signals of EMTP(e1ectromagnetic transients program) in the various fault conditions of power systems.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.10
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• pp.955-962
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• 2016

In this paper, we propose a design method for speed controller, current control of a Brushless Direct Current(: BLDC) motor using disturbance rejection techniques. Disturbance assumes a back electromotive force occurring in the electrical system and the variation of the load acting on the rotary shaft from the outside of the motor. And it assumed to be constant during the time interval and the Luenberger's observer design. So that the error of the observer about the system status can converge to zero show how to set the appropriate gain. Further, to stabilize the whole system, and proposes a method for setting the appropriate PI gain control to improve the tracking performance. By applying the proposed controller to 120W BLDC motors were tested for the ability to follow the velocity and current reference. Since the simulation results of the steady state error is within 0.1%, we were able to show the usefulness of the tracking performance of the proposed controller.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.5
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• pp.558-563
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• 2008

Vibration/shock affects biggest taking a train subtraction of vehicle and durability decline. Therefore, absorber is used for vibration/shock isolation and various qualities of the material and design are applied to isolation. This paper proposes vibration/shock absorber that applies 'Disc' spring. Through comparison with 'Disc' spring that has nonlinearity and coil spring that is having linearity, see effect that nonlinearity of isolation gets in vibration/shock Isolation. Coil spring and 'Disc' spring are non-linear numerical analysis and simulation through theory for this, get and investigate comparison result through an experiment finally. Expressed and formulated shock through 'Runge-Kutta' method/impact response to nonlinear-vibration-equation of 1 degree of freedom for numerical analysis. Double half sine pulse of excitation used and analyzed result through spectrum response analysis here. Response of disc spring is compared to response of coil spring by changing $h_o/t$ ratio with computer simulation and the usage of disc spring is increased through analysis of effect of design factors. The purpose of this paper is that the shock response of disc spring is calculated through numerical simulation and to design the optimal absorber under the limited condition. And then, the isolation effect was analyzed through the shock test.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.1
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• pp.47-55
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• 2012

A structural health monitoring technique for locating impact position in a plate structure is presented in this paper. The method employs a single sensor and spatial focusing of time reversal (TR) acoustics. We first examine the TR focusing effect at the impact position and its surroundings through simulation and experiment. The imaging results of impact points show that the impact source location can be accurately estimated in any position of the plate. Compared to existing techniques for locating impact or acoustic emission source, the proposed method has the benefits of using a single sensor and not requiring material properties and geometry of structures. Furthermore, it does not depend on a particular mode of dispersive Lamb waves that is frequently used in other ultrasonic testings of plate-like structures.

• Journal of the Korea Society of Computer and Information
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• v.9 no.4 s.32
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• pp.33-39
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• 2004

In this paper. we design the learning algorithm of LVQ which is used Forward Counter Propagation Networks to improve classification performance of LVQ networks. The weights of Forward Counter Propagation Networks which is between input layer and cluster layer can be learned to determine initial reference vectors by using SOM algorithm and to learn reference vectors by using LVQ algorithm. Finally. pattern vectors is classified into subclasses by neurons which is being in the cluster layer, and the weights of Forward Counter Propagation Networks which is between cluster layer and output layer is learned to classify the classified subclass, which is enclosed a class. Also. kr the number of classes is determined, the number of neurons which is being in the input layer, cluster layer and output layer can be determined. To prove the performance of the proposed learning algorithm. the simulation is performed by using training vectors and test vectors that ate Fisher's Iris data, and classification performance of the proposed learning method is compared with ones of the conventional LVQ, and it was a confirmation that the proposed learning method is more successful classification than the conventional classification.