• 한국소음진동공학회논문집
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• 제24권9호
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• pp.667-674
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• 2014

선박의 추진축계는 외부 변동 부하에 의해서 축계 손상을 일으킬 수 있다. 이러한 추진축계의 동역학적인 특성은 운전 중에 일어나는 공진을 견딜 수 있거나 또는 피하도록 설계 및 최적화 해야 한다. 이러한 공진은 대빙급 선박의 추진시스템의 설계에 요구되는 프로펠러에서 유체역학적인 상호작용에 기인한다. 추진축계는 프로펠러와 대빙 사이의 상호관계로 인한 과도부하와 시스템의 공진에 의해서 진지한 응력을 받게 된다. 이 논문은 대빙이 적용된 극지 연구 선박에서 추진축계의 과도비틀림 진동응답을 검토하고자 한다. 추진축계는 전기모터로 구동되는 원동기, 탄성커플링 기어 및 프로펠러로 구성되어 있다. 이론적인 해석은 프로펠러의 대빙 부하를 기진력으로 과도비틀림진동 해석을 수행하였다. 그리고 실선에서 비틀림 진동을 계측하고 공진점을 확인하고 이를 이용하여 추진축계 한계 설계 토크에 대한 적용된 평가 요소를 국제선급연합 규정과 비교하였다. 전기모터를 갖는 추진축계에서 공진을 초래하는 탄성커플링의 강성 선정의 영향을 검토하였다.

• 대한기계학회논문집A
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• 제41권10호
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• pp.1005-1009
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• 2017

본 연구에서는 수중폭발에 의한 가스터빈 패키지에 작용하는 충격하중을 평가하고, 충격하중에 대한 가스터빈 패키지의 내충격 안전성을 검토하였다. 이를 위해 먼저 BV043에 따른 시간이력 충격하중을 산출하고, 산출된 충격하중을 바탕으로 이상화된 WEM(Whole Engine Model, 전체시스템)에 대한 시간영역에서의 과도응답해석을 수행하였다. 이를 통해 가스터빈 패키지의 주요구성품에 전달되는 하중을 평가하였으며, 평가된 전달하중을 바탕으로 주요구성품의 상세모델에 대한 내충격 안전성 검토를 수행하였다. 검토결과 가스터빈 패키지는 기준응력 대비 최소 1.0 이상의 안전율을 가지는 것을 확인하였다. 그리고 실물테스트를 통해 가스터빈 패키지 엔진제어시스템(EMS : Engine Management System) 구조 및 제어기능의 내충격 건전성을 검증하였다.

• Journal of Electrical Engineering and Technology
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• 제13권1호
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• pp.168-180
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• 2018

In order to achieve the high quality output voltage of single-phase voltage source inverters, in this paper an Adaptive Complementary Sliding Mode Control (ACSMC) is proposed. Firstly, the dynamics model of the single-phase inverter with lumped uncertainty including parameter variations and external disturbances is derived. Then, the conventional Sliding Mode Control (SMC) and Complementary Sliding Mode Control (CSMC) are introduced separately. However, when system parameters vary or external disturbance occurs, the controlling performance such as tracking error, response speed et al. always could not satisfy the requirements based on the SMC and CSMC methods. Consequently, an ACSMC is developed. The ACSMC is composed of a CSMC term, a compensating control term and a filter parameters estimator. The compensating control term is applied to compensate for the system uncertainties, the filter parameters estimator is used for on-line LC parameter estimation by the proposed adaptive law. The adaptive law is derived using the Lyapunov theorem to guarantee the closed-loop stability. In order to decrease the control system cost, an inductor current estimator is developed. Finally, the effectiveness of the proposed controller is validated through Matlab/Simulink and experiments on a prototype single-phase inverter test bed with a TMS320LF28335 DSP. The simulation and experimental results show that compared to the conventional SMC and CSMC, the proposed ACSMC control strategy achieves more excellent performance such as fast transient response, small steady-state error, and low total harmonic distortion no matter under load step change, nonlinear load with inductor parameter variation or external disturbance.

• Tribology and Lubricants
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• 제23권5호
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• pp.219-227
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• 2007

The dynamic performance of air foil bearings relies on a coupling between a thin air film and an elastic foil structure. A number of successful analytical techniques to predict dynamic performance have been developed. However, the evaluation of its dynamic characteristic is still not enough because of the mechanical complexity of the foil structure and strong nonlinear behavior of friction force. This work presents a nonlinear transient analysis method to predict dynamic performance of foil bearings. In this method, time dependent Reynolds equation is used to calculate pressure distribution and a finite element method is used to model the bump foil structure. The analysis is treated with a direct implicit integration technique that can handle nonlinear problems and the stick-slip algorithm is used to consider friction force. Using this method the response to the mass unbalance excitation is investigated for various design parameters and operating conditions. The results of analysis show that foil bearing is very effective on the restriction of vibration at the resonance frequency compared to the rigid surface bearings and the effectiveness depends on the operating conditions, static load and a amount of mass unbalance. In addition, there exist optimum values of friction coefficient, bump foil stiffness and number of circumferential slit with regards to minimizing dynamic response at the resonance frequency. These optimum values are system dependent.

• 한국구조물진단유지관리공학회 논문집
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• 제11권3호
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• pp.87-94
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• 2007

구조물의 동적해석은 크게 시간영역과 주파수영역해석으로 나눌 수 있다. 시간영역해석은 직접적분법과 모드중첩법 등을 사용하며 주파수영역해석은 DFT법을 적용하고 있다. 일반적으로 DFT법은 주기함수에 대한 응답을 산정할 경우 효과적인 해석방법이지만 비주기함수인 경우 정확한 해석결과를 얻을 수 없어 주기를 크게 하거나 응답을 수정하여 해의 정확성을 향상시키고 있다. 따라서 본 연구는 비주기함수인 이동하중을 받는 구조물에 대해 시간영역과 주파수영역에서 동적응답을 산정하였다. 그 결과 구조물의 자유진동주기를 크게 하거나 응답을 수정하여 DFT법을 적용한다면 주파수영역에서도 충분히 정확한 해석결과를 얻을 수 있을 것으로 판단된다.

• 한국해양공학회지
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• 제22권4호
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• pp.65-71
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• 2008

In many cases, open-type plate breakwaters use plates with multiple holes; the holes serve as energy dissipaters and weight reducers. Because of the multi-holes configuration, stress concentration should be considered during the design process. Among several design loading conditions, the loads from a possible collision with a man-made vessel or other unexpected events many damage a multi-perforated steel plate. In that case, the structural behavior of a multi-perforated steel plate is quite significant, and is not well understood. This study presents a collision analysis for a multi-perforated steel plate. First, four different perforation topologies (three with circles and one with squares) were selected to investigate the effect of different hole shapes on the structural response. Second, the wave force at a specific site was calculated and loaded onto a steel plate as a static load. The static stresses were used for reference values. Third, two rigid body impacters (cubical & cylindrical) were applied to the steel plates to investigate the transient stress responses. In addition, two different impacting angles ($45^{\circ}\;&\;90^{\circ}$) were selected to investigate the angle effect. From the collision analysis, the significance of the transient stresses was emphasized.

• Journal of Electrical Engineering and Technology
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• 제10권1호
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• pp.195-204
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• 2015

In this paper, the development of a cost-effective active power filter/uninterruptible power supply (APF/UPS) system with seamless mode transfer is described. The proposed scheme employs a pulse-width-modulation (PWM) voltage-source inverter and has two operational modes. First, when the source voltage is normal, the system operates as an APF, which compensates for the harmonics and power factor while boosting the DC-link voltage to be ready for the disturbance, without an additional DC charging circuit. A simple algorithm to detect the load current harmonics is also proposed. Second, when the source voltage is out of the normal range (owing to sag, swell, or outage), it operates a UPS, which controls the output voltage constantly by discharging the DC-link capacitor. Furthermore, a seamless transfer method for the single-phase inverter between the APF mode and the UPS mode is also proposed, in which an IGBT switch with diodes is used as a static bypass switch. Dissimilar to a conventional SCR switch, the IGBT switch can implement a seamless mode transfer. During the UPS operation, when the source voltage returns to the normal range, the system operates as an APF. The proposed system has good transient and steady-state response characteristics. The APF, charging circuit, and UPS systems are implemented in one inverter system. Finally, the validity of the proposed scheme is investigated with simulated and experimental results for a prototype APF/UPS system rated at 3 kVA.

• 한국정밀공학회지
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• 제34권3호
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• pp.211-215
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• 2017

This research analyzes bucket elevator roller chain pins by finite element (FE) analysis and static structural analysis for a lightweight pin design. The stress distribution of light weight roller chain pins under static load is analyzed for safety factors and damping effect. The results show that the stress distribution is higher on the plate than on the bush pin. In order to compare experimental and FE analysis results, a light weight design approach was used to produce a prototype base pin. Because the inner diameter of the pin was different, the impact damping effect was most appropriate when the inner diameter was 34.05 mm, and it is used as basic research data on the impact of the roller chain and sprocket.

• 조명전기설비학회논문지
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• 제25권2호
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• pp.53-60
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• 2011

The available power generated from the FC power plant may not be sufficient to meet sustained load demand, peak demand or transient events. An supercapacitor bank(SCB) can supply a large burst of power, but it cannot store a significant amount of energy. The combined use of FC and SCB has the potential for the better energy efficiency, reducing the cost of FC technology and improved dynamic response. In this paper, A single PEMFC and PEMFC operated in parallel with a SC bank are presented, A new dynamic model of PEMFC system, the converter and controller has been developed for stand-alone applications. The simulation results are presented using Matlab/Simulink, and SimPowerSystems environments. It is confirmed that the results show a good performance and stable DC-link voltage for proposed dynamic and mathematical models developed for the combined FC/SCB.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.997_998
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• 2009

Nowadays DC-DC converter has been used widely in electronic production. It has a high requirement in wide input voltage, load variations, stability, providing a fast transient response and the most important thing is that it can be applied easily and efficiently. However, it is not easy to be controlled because of nonlinear system. This study introduces a fuzzy linear control design method for nonlinear systems with optimal $H^{\infty}$ robustness performance. First, the Takagi and Sugeno fuzzy linear model is employed to approximate a nonlinear system. Next, based on the fuzzy linear model, a fuzzy controller is developed to stabilize the nonlinear system, and at the same time the effect of external disturbance on control performance is attenuated to a minimum level. Thus based on the fuzzy linear model, ��$H^{\infty}$ performance design can be achieved in nonlinear control systems. Linear matrix inequality (LMI) techniques are employed to solve this robust fuzzy control problem. PI control structure is used and the control gains are determined based on $H^{\infty}$ control.