• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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• pp.289-292
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• 1995

근래에 서보 제어용 엑투에에터의 사용 경향은, 전기 서보 모터 및 그 제어 기술의 발전으로, 중간 용량이내의 제어 시스템 분야에서 전기 서보 모터를 사용한 시스템의 채용이 급증하고 있는 추세이다. 본 연구에서는 고유 진동수 밍 댐핑이 적은 유압 서보 시스템에 소프트웨어적인 방법으로 부하 압력 또는 가속도를 궤환시키는 방법을 적용하여 시 스템의 bandwidth를 유압 시스템의 고유 진동수 영역까지 확대 시키고, 응답 특성의 신뢰성을 증가시키기 위해 직렬 제어기가 없을 경우에는 적용이 어려운 강인 제어기 (robust controller)를 압력 또는 가속도 궤환제어기의 앞 부 분에 직렬로 배치하여 실험을 통하여 그 성능을 관찰한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.5
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• pp.959-966
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• 2009

Effective transmission distance depending on transmission capacity of WDM systems with inline dispersion management (DM) and optical phase conjugator (OPC) at middle of total transmission length is investigated. The range of net residual dispersion (NRD) resulting 1 dB eye opening penalty (EOP) in 1 Tbps WDM system, in which NRD controlled by only postcompensation, is also investigated. It is confirmed that effective transmission distances are increasedto longer than several hundreds kilometers by applying optimal NRD depending on transmission capacity and distance. And it is confirmed that in 1 Tbps WDM system if NRD is determined to +17 ps/nm, the maximum transmission distance is achieved, and, especially, in long-haul 1 Tbps WDM system the effective NRD range will be determined within positive value.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.4
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• pp.957-966
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• 1998

In this paper an imrpoved Signal-to-Interference ratio(SIR)-based call admission control(CAC) algorithm for DS-CDMA cellular system is proposed and its performance is analyzed. This algorithm uses Residual-Capacity defined asthe additional number of initial calls that a base station can accept such that system-wide outage probability will guaranteed to remain below a certain level. the residual capcity at each cell is calculated according to the reverse-link SIR measured not only at the home cell but also the adjacent cells. Then the adjacent cell interference-coupling coefficient .betha. is used. In this work we propose an improved algorithm that .betha. varies according to the traffic load of the home cell. The influence of traffic condition on system performance, namely blocking probability and outage probability, is then examined via simulation. The performance of the improved algorithm is evaluated both under homogeneous and hot spot traffic loads. The results show that the improved algorithm outperforms conventional algorithms under all load values. Under over-load situation, especially, the improved algorithm gives almost constant outage performance the QoS(quality of service) can be guranted.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.2
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• pp.165-174
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• 2007

Variable displacement type piston pump uses various controllers for controlling more than one state quantity like pressure, flow, power, and so on. These controllers need the mathematical model closely expressing dynamic behavior of pump for analyzing the stability of control systems which usually use various kinds of state variables. This paper derives the nonlinear mathematical model for variable displacement type piston pump. This model consists of two 1st oder differential equations by the continuity equations and one 2nd oder differential equation by the motion equation. To simplify the model we obtain the linear state variable model by differentiating the three nonlinear equations. And we verify this linearized model by comparison of simulation with experimentation and analyze the stability for the flow/pressure control. Finally this paper suggests the design compensation to ensure the stability of the systems.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.5 no.2
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• pp.94-101
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• 1993

Recently, efforts of decreasing energy consumption are continously increased and user's preference is also diversified in refrigeration and air conditioning systems. Thus, in order to satisfy these demands, high efficiency, high intelligence, and energy saving for those systems are essential. As the basic study for diverse functions and intelligence of those systems, we investigated the response characteristics through the compressor capacity control concerned with superheat and refrigeration room temperature. And, response characteristics are investigated experimentally by using micro computer based PWM inverter control method. Experimental result of the conventional on-off control method is given in order to be compared to the results of inverter control method. The results obtained through this study are summarized as follows. It is shown from the experimental results of the on-off control method that the range of temperature variation around the steady state ($-18^{\circ}C$) is very large (about $7{\sim}8^{\circ}C$) and the settling time bringing the steady state is not found. In the inverter control method, we can see that the refrigeration room temperature after reaching the setting temperature is very stable without fluctuation and a robust control for disturbance such as opening the door has been realized.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.7
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• pp.275-280
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• 2013

This paper presents an optimizing method for wireless charging system, specifically focused on the capsule endoscope applications. In order to increase the wireless power transfer efficiency of electro-magnetic resonance coupled coils, this paper investigates the impact factors of the power transfer efficiency in small battery capacity system and proposes a efficiency optimizing method based on frequency control. Simulation results show that the proposed efficiency optimal control method can effectively stabilize the wireless power transfer efficiency so as to successfully solve the main issue of transfer efficiency variation with distance and as well as parasitic element.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.7
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• pp.82-88
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• 2014

An available capacitance increasing phase-locked loop(PLL) with two voltage controlled oscillator gains has been proposed. In this paper, the available capacitance of loop filter is increased by using two positive/negative gains of voltage controlled oscillator (VCO). It results in 1/10 reduction in the size of loop filter capacitor. It has been designed with a 1.8V $0.18{\mu}m$ CMOS process. The simulation results show that the proposed PLL has the same phase noise characteristic and a locking time of conventional PLL.

• The KIPS Transactions:PartC
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• v.9C no.1
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• pp.45-54
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• 2002

MPLS(Multiprotocol Label Switching) is regarded as a core technology for migrating to the next generation Internet. In this paper, we propose an dynamic flow admission control supporting DiffServ(Differentiated Services) to provide QoS in MPLS networks. Our proposed model dynamically adjusts the amount of admissible traffic based on transmittable capacity over one outgoing port. It then transmits the Packets while avoiding congested area resulting traffic loss. Ingress LSRs find out the congested area by collecting network state information at QoS state update for QoS routing table. Our Proposed model manages the resource efficiently by protecting the waste of resources that is a critical Problem of DiffServ and makes much more flows enter the network to be served.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.3
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• pp.307-312
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• 2013

The interest in reducing the emissions and increasing the fuel economy of ICE vehicles has prompted research on hybrid vehicles, which come in the series, parallel, and power-split types. This study focuses on the series-type hybrid electric vehicle, which has a simple structure. Because each component of a series hybrid vehicle is larger than the corresponding component of the parallel type, the sizing of the vehicle is very important. This is because the performance may be greater or less than what is required. Thus, in this research, the optimal fuel economy was determined and simulated in a real-world system. The optimal sizing was achieved based on the motor, engine/generator, and battery for 13 cycles, where DP was used. The model was developed using ASCET or a Simulink-Amisim Co-simulation platform on the rapid controller prototype, ES-1000.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.11 no.5
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• pp.1-6
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• 2012

Unlike the past, modern urban intersections have dramatic growth in size and utilizations. As a result, continual traffic signal control is essential. Hence the individual or regional electrical blackout may bring about uncontrollable traffic congestion. Late summer of 2011 a regional blackout brought about traffic nightmare not including time and revenue loss associated with this disaster. Due to this disaster our national police agency and other government agencies are in process of introducing an UPS (uninterruptible power supply) system into essential intersections. This study estimates the power consumption necessary to sustain at least 2 continuous hours for a standard four-legged intersection. Prototype was studied using these standards. The field experiment of prototype showed positive results and was able to meet standard guidelines set forth. Prototype tested was able to meet standards in medium to large capacity of traffic size.