• Journal of Energy Engineering
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• v.10 no.3
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• pp.253-265
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• 2001

This paper investigates a PI control problem for the evaporator superheat, i.e., temperature difference between the two-phase region and the exit region of an evaporator, for multi-type air-conditioning/refrigeration system. Mathematical model describing the characteristics of compressor, condenser, evaporator, and electronic expansion valve are first derived. Then, two transfer function from the current input applied to an electronic expansion valve to the wall-temperatures of an evaporator tube at two-phase region and superheated region, respectively, are derived. The stability of the closed loop system with the PI controller designed it analyzed by using Nyquist stability criterion. Simulation results are provided.

• Journal of the Korean Institute of Telematics and Electronics
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• v.22 no.5
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• pp.75-82
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• 1985

The fuel pump system is developed with the Model Reference Adaptive Control (M.R.A.C.) algorithm based on the Weight Least Square (W.L.S.) algorithm for the parameter Identification and the one step ahead dead-beat control with the reference model. The value of some parameters as the sampling period 7, the weighting coefficient L, and the State Variable Filter (5.V,F.) coefficient f which a(fects the system performance are selected through computer simulation. For the variation of the plante dynamics rspecially due to the change of the fuel viscosity with the ambient temperature condition, the adaptability of the control system is studied in the case of regulation and tracking.

• Review of KIISC
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• v.11 no.3
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• pp.24-37
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• 2001

정보화의 급진전에 따라 역기능의 문제도 대폭적으로 증가되고 있는 추세 속에서 이를 극복하고정보화의 급진전에 따라 역기능의 문제도 대폭적으로 증가되고 있는 추세 속에서 이를 극복하고자 하는 노력이 국제적으로 활발하게 전개되고 있다. 보다 체계적이고 비용 효과성을 고려하여 미국, 유럽, 호주 등 많은 선진국가에서는 지난 수년동안 정보를 보호하는 기준이나 지침 등을 학계, 산업계, 연구기관, 정부기관과 공동 또는 자체적으로 개발하여 활용하고 있거나 활용 예정에 있다. 국내에서도 이러한 접근 방식의 중요성을 인식하고 정보통신망이용촉진및정보보호등에관한법률을 개정하여 정보보호관리체계에 대한 인증 제도를 2001년 7월 1일부터 시행하기에 이르렀다. 이에 따라 국내에서도 동 법에 근거하여 인증업무를 수행하게 될 한국정보보호센터에서 국내의 현실에 맞는 정보 보호관리기준 마련 작업을 1년여 동안 추진하여 왔으며, 각고의 노력을 기울이고 있는 상태이다. 이에 따라 본 고에서 는 정보보호관리체계에 대한 구체적인 소개와 더불어 각 국에서 노력을 기울이고 있는 정보보호 관리를 위해 마련하여 온 지침과 절차 및 기준 등의 내용을 소개하고, 각각이 가지고 있는 특성들을 프레임워크 수준에서 살펴보기로 하며, 제시하고 있는 통제사항들을 간략하게 비교함으로써 정보보호관리체계의 수립과 인증 제도의 효과성에 대하여 많은 관련자들의 인식을 제고하고자 한다. 그리고, 향후 정보보호관리체계 수립 및 인증제도의 도입과 운용이 활발하게 이루어지고 활성화될 경우를 미리 준 비하기 위하여 정보보호관리를 위한 성숙도의 측정에 대한 연구 방향을 나름대로 제시하고자 한다.

• Journal of the Institute of Convergence Signal Processing
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• v.5 no.3
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• pp.210-215
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• 2004

The dynamic model of ac servo motor is influenced very much due to rotor resistance change and nonlinear characteristic. By using the sliding mode control the dynamic behavior of system can be made insensitive to plant parameter change and external disturbance. This paper describes the application of the sliding mode control for position control of ac servo motor. The control scheme is derived and designed. A design method based on external load parameters has been developed for the robust control of ac induction servo drive. The proposed control scheme are given based on the variable structure controller and slip frequency vector control. Simulated results are given to verify the proposed design method by adoption of sliding mode and show robust control for a change of shaft initial J, viscous friction B and torque disturbance.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.5 no.3
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• pp.117-126
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• 2012

This study configuration Vector Control System which is stable and has outstanding Dynamic Characteristics in Very Low Speed Region and Low Speed Region, and proposes Instantaneous Speed Observer and Very Low Speed Control method using Reduced-Dimensional State Observer. The Observer proposed in this system, by appling Reduced-Dimensional State Observer to Load-Torque estimation and using for speed estimation, implements system composition simply and is capable of accurate Instantaneous Speed estimation in Very Low Speed Region. Also, this study reduces influence by System Noise and suggests an induction motor speed control system which is effective in Load Disturbance, modeling error, estimation noise and so on without changing pole of an Observer.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.8
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• pp.1918-1924
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• 2010

This In this paper, we propose an efficient algorithm for motion estimation of the image sequences with luminance fluctuation. For such sequences, conventional motion estimation methods based on the difference of pixel values usually produce the erroneous motion information. The proposed algorithm defines the luminance fluctuation as a linear model with gain and offset parameter, and extracts motion information using gradient and phase of the corresponding local region within consecutive frames. Therefor the method is robust to the luminance change of the frames. We test our algorithm for the ground truth sequence with artificially added luminance change and motion, and real sequences corrupted by the flicker. The results shows that the proposed algorithm outperforms the conventional methods.

• Journal of the Institute of Convergence Signal Processing
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• v.7 no.2
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• pp.53-59
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• 2006

Dynamic neural networks have been applied to diverse fields requiring temporal signal processing such as system identification and signal prediction. This paper proposes the gamma neural network(GAM), which uses gamma memory kernel in the hidden layer of feedforward multilayered network, to improve dynamics of networks and then describes nonlinear adaptive prediction using the proposed network as an adaptive filter. The proposed network is evaluated in nonlinear signal prediction and compared with feedforword(FNN) and recurrent neural networks(RNN) for the relative comparison of prediction performance. Simulation results show that the GAM network performs better with respect to the convergence speed and prediction accuracy, indicating that it can be a more effective prediction model than conventional multilayered networks in nonlinear prediction for nonstationary signals.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.05a
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• pp.180-185
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• 2009

Actuator-induced disturbance is one of the crucial factors of spacecraft attitude pointing and stability in fine attitude control problems. The control moment gyros (CMGs) are known as very attractive actuators from the point of high power and low weight. In order to develop a CMG as an actuator for fine controls, CMG-induced disturbances should be analyzed. Therefore, this paper aims to develop an analytic model and predict the effect of disturbances of CMGs by assuming static and dynamic imbalances. The proposed model is induced by the Lagrangian method on the basis of the small signal assumption. In this research, mechanical system of the CMG is designed and the main components of CMG are producted.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.447-448
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• 2008

The goal of this study is to find flame dynamic behavior using a transverse fuel injection in a model combustor, and is to investigate main causes of unstable combustion in a liquid-fueled combustor. For transverse fuel injection into air cross flow, spray result shows similar tendency with Wu et al.[1998] until spray arrives at flame-holder. However, passing through flame-holder, fuel inflow into recirculation region of flameholder is not sufficient so it makes large difference between shear flame and recirculation flame behind flameholder. In combustion tests, the stable flame shows a kind of shear flames and low peaks of dynamic pressure frequencies. On the other hand, unstable flame shows periodic detached flame in recirculation zone and a strong peak of dynamic pressure frequency. The instability frequency is highly affected by influx air velocity, air temperature, equivalence ratio and wake or vortex shedding frequency behind the flameholder.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.378-385
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• 2012

Vent mixer can provide main flow directly into a recirculation region downstream of the mixer to enhance fuel-air mixing efficiency. Based on experimental results of three-dimensional velocity, vorticity and turbulent kinetic energy obtained by a stereoscopic PIV method, the performance of the vent mixer was compared with that of the step mixer which was used as a basic model. Thick shear layers of the vent mixer induced the increase of the penetration height. The turbulent kinetic energy mainly distributed along a boundary layer between the main flow and the jet plume. This turbulent field activates mass transfer in a mixing region, leading to the mixing enhancement.