• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.192-195
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• 2002

The thesis proposes the sensorless vector control method that estimates the rotor speed and rotor time constant at the same time using stator current. In the proposed method, stator current error in the stationary reference frame is proportional to estimated speed error, and stator current error in the synchronous reference frame is proportional to estimated rotor time constant error. The proposed method can simultaneously produce a fast speed estimation and rotor time constant estimation. Therefore, this new method offers an improvement in the performance of a sensorless vector controller. And, the superiority of the proposed method is verified by simulation.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.28 no.4
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• pp.14-19
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• 2005

In general, cell transmission delay is more sensitive for real time video service rather than cell losses in a wireless ATM network. Existing handoff schemes, which are emphasizing the prevention of cell losses, have limitations in cell transmission delay to satisfy QoS. In this paper, we propose a scheme to minimize transmission delay generated during the handoff and to maintain the sequence of cells. Transmission delay can be reduced by transmitting ATM cells with low CLP(i.e., CLP=0) prior to others and by discarding cells with high CLP(i.e., CLP= 1). The simulation results show that the proposed scheme is suitable for delay sensitive real time VBR service as well as fast handoff by giving high CLP to less meaningful MPEG frames.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.246-248
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• 2004

In this paper, we propose an optimal power control algorithm for CDMA cellular systems. The proposed power control algorithm is based on linear quadratic control theory. As the cellular system includes the changeability of system environment or various noise, Kalman filter is adapted to estimate the time-varying interference. This is the well-known linear quadratic Gaussian (LQG) theory. Through this algorithm, power transmission of each mobile with optimal one is more realistic. Simulation results show a fast convergence rate to optimal power value, and a rapid decreasing outage probability.

• ETRI Journal
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• v.36 no.1
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• pp.179-182
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• 2014

This letter presents a very simple yet very effective solution for fast reference frame (RF) selection in H.264/AVC. By efficiently making use of the correlation between the best RF indices in various inter modes, the proposed method significantly reduces the number of RFs to be examined at the expense of a very small miss rate. Simulation results show that the proposed method not only improves upon the coding performance of conventional methods but also reduces the encoding time significantly.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.567-573
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• 2006

An efficient typhoon wave-generating model is applied to northeast Asia sea zone presented that can be used by civil defense agencies for real-time prediction and fast warnings on typhoon-generated wind wave and storm surge. Instead of using commercialized wave models such as WAM, SWAN, the wind waves are simulated by using a new concept of wavelength modulation to enhance broader application of the hyperbolic wave model of the mild-slope equation type. The results simulated along the Korean coasts during Typhoon Nabi (2005) showed reasonable agreement with the recorded wind waves.

• International Journal of Aeronautical and Space Sciences
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• v.11 no.3
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• pp.184-192
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• 2010

In this paper, an initial fine alignment algorithm, which is developed for the strap-down inertial navigation systems of satellite launch vehicles, is considered. For fast and accurate alignment, a simple closed-loop estimation algorithm using a proportional-integral controller is introduced. Through computer simulation for the sway condition in the launch pad, it is shown that a simple filter structure can guarantee fast computational speed that is adequate for real-time implementation as well as the required alignment accuracy and robustness. In addition, its implementation results are presented for the Naro-1 flight test.

• Journal of Electrical Engineering and Technology
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• v.6 no.6
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• pp.769-775
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• 2011

Custom power devices such as dynamic voltage restorer (DVR) and DSTATCOM are used to improve the power quality in distribution systems. These devices require real power to compensate the deep voltage sag during sufficient time. An interline DVR (IDVR) consists of several DVRs in different feeders. In this paper, a neural network is proposed to control the IDVR performance to achieve optimal mitigation of voltage sags, swell, and unbalance, as well as improvement of dynamic performance. Three multilayer perceptron neural networks are used to identify and regulate the dynamics of the voltage on sensitive load. A backpropagation algorithm trains this type of network. The proposed controller provides optimal mitigation of voltage dynamic. Simulation is carried out by MATLAB/Simulink, demonstrating that the proposed controller has fast response with lower total harmonic distortion.

• Journal of the Korea Institute of Military Science and Technology
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• v.19 no.4
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• pp.462-468
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• 2016

In this paper, we present the results of the numerical analysis employing CONWEP, LS-DYNA FSI(Fluid Structure Interaction), AUTODYN FSI, LS-DYNA ALE(Arbitrary Lagrange Eulerian) and combination of CONWEP and LS-DYNA ALE for blast door fracture and wave propagation through the tunnel by the external explosion. We compared the numerical analysis results with the subscale test data and selected combination of CONWEP and LS-DYNA ALE method as adequate data generation method for the FRM(Fast Running Model) software development. It is expected to save much time and costs by using the numerical simulation data for the various test conditions.

• Proceedings of the KAIS Fall Conference
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• 2002.11a
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• pp.246-248
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• 2002

This paper presents computer simulations of the stacking and transfer system for the fast freeform fabrication system. The stacking and transfer system is essential for the fast freeform fabrication system and its stable motion is very important fer the consistent stacking of the cut slices. The stacking and transfer system cane be modeled as a pneumatic system. The system consists of air compressor, the control valve, and the cylinder. The governing parameters have been changed and the simulation results are shown to predict the time response of the system. The results shows some parameters should be correctly tuned to obtain stable system response.

• Proceedings of the KIEE Conference
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• 1999.11c
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• pp.718-720
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• 1999

This paper describes a charge pump PLL architecture which achieves high frequency operation and fast acquisition. This architecture employs multi-phase frequency detector comprised of precharge type phase frequency detector and conventional phase frequency detector. Operation frequency is increased by using precharge type phase frequency detector when the phase difference is small and acquisition time is shortened by using conventional phase frequency detector and increased charge pump current when the phase difference is large. By virtue of this multi-phase frequency detector structure, the maximum operating frequency of 694MHz at 3.0V and faster acquisition were achieved by simulation.