• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1795-1800
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• 2003

An experimental study was carried out to investigate near-wake characteristics of an elliptic airfoil oscillating in pitch. The airfoil was sinusoidally pitched about the half chord point between $-5^{\circ}C$ and $+25^{\circ}C$ angles of attack at the freestream velocities of 3.4 and 23.1 m/s The corresponding Reynolds numbers based on the chord length were $3.3{\times}10^4$ and $2.2{\times}10^5$, respectively. A hot-wire anemometer was used to measure the near-wake flow variable at the reduced frequency of 0.1. Ensemble-averaged velocity and turbulence intensity profile were presented to examine the near-wake characteristics depending on the Reynolds number. The axial velocity deficit in the near-wake region tend to decrease with the increase in the Reynolds number a found in many stationary airfoil test . Turbulence intensity in the near-wake region have a tendency to decrease with the increase in the Reynolds number during the pitch-up motion, whereas it shows different feature during the pitch-down motion either the laminar boundary layer or turbulent boundary layer separation.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.50 no.12
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• pp.624-630
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• 2001

The trend of the regulations on environmental issues are getting tight. Responding to this trend new technologies such as moving electrodes, wide pitch and pulsed power supply are also introduced in the electrostatic precipitator(EP) systems. The introduction of wide pitch and moving electrodes enhances the system performance of the EPs by improving air-flow and by improving the ash reentrainment on rapping. The power supplies for the EPs developed up to date include thyristor-based dc or intermittent type, SMPS(switching mode power supply) type and the pulsed-power supply type. The use of the pulsed ones is known to improve dust-collecting efficiency of high resistivity ash and reduces back corona occurrence in the collecting plate. There are two kinds of pulsed-power supplies; one with pulsed transformers and the other with direct dc switching devices. The latter uses rotary spark gap switches or semiconductor switches. Both have the merits and demerits: the spark gap switches are simple and robust but has short life time, hence, high maintenance cost, whereas the semiconductor switches have long life time but are costly. In this study, A high voltage power supply with superimposing voltage pulse on dc source was developed for EPs. This study describes circuit topology, operating principle of the scheme, and analysis of experimental results on Dong-Hae Power Plant. The pulsed power supply consists of a variable dc power supply with ratings of 60kV, 800mA and pulse generator which is made of high voltage thyristor-diode switch strings, an LC resonant tank and a blocking inductor. The pulse generator generates variable pulse-voltage up to 70kV using a high frequency resonant inverter with a variable dc source. Two prototypes were built and tested on 250MW DongHae power plant to verify the possibility of the commercial use and the normal operation in the transient states.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.8
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• pp.150-157
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• 2005

This paper presents the simulation modeling and analysis of variable wind speed turbine system(VWTS) using the doubly fed induction generator(DFIG) connected the back to back converter system in the rotor side. In the simulation, using the model system which has the 660[kW] rated power, blade control and the dual converter system are modeled for verifying the control characteristics. The VWTS is controlled by the optimal pitch angle for maximum output power under the rated wind speed, and for the rated output power over the rated wind speed. And also power factor is controlled by the reactive power. To verify the effectiveness of the proposed method, simulation results are compared with the actual data from the V47 VWTS located in Hangwon wind farm in Jeju-Do. According to the comparison of these results, this method shows excellent performance.

• Journal of IKEEE
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• v.26 no.4
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• pp.602-613
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• 2022

This paper proposes an algorithm for correcting indirect situations resulting from the wheelchair moving the stairs with wheel-type caterpillar and seat position variable. For analyzing the Yawing movement model, the change of Yaw value was estimated using Roll, Pitch, and Yaw in the driving environment, and it was used as a control variable and the information of the wheel drive controller. The verification confirmed the correction of about 10° of Yawing movement within about 7 seconds. It was confirmed that the angular velocity was reduced by 47.5% in seat position change.

• Proceedings of the IEEK Conference
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• 2003.07e
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• pp.2455-2458
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• 2003

In this paper, the Classification of Energy Labeling has been Proposed. Energy Parameters of input signal which is extracted from each phoneme is labelled. And groups of labelling according to detected energies of input signals are detected. Next, DTW processes in a selected group of labeling. This leads to DTW processing faster than a previous algorithm. In this Method, because an accurate detection of parameters is necessary on the assumption in steps of a detection of speeching duration and a detection of energy parameters, variable windows which are decided by pitch period is used. Extract algorithms don't search for exact frame energy, because 256 frame window-sizes is fixed. For this reason, a new energy extraction method has been proposed. A pitch period is detected firstly; next window scale is decided between 200 frames and 300 frames. The proposed method make it possible to cancel an influence of windows.

• Journal of Institute of Control, Robotics and Systems
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• v.7 no.2
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• pp.173-182
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• 2001

Ascent trajectory optimization and optimal explicit guidance problems for a satellite launch vehicle in a 2-dimensional pitch plane are studied. The trajectory optimization problem with boundary conditions is formulated as a nonlinear programming problem by parameterizing the pitch attitude control variable, and is solved by using the SQP algorithm. The flight constraints such as gravity-turn are imposed. An optimal explicit guidance algorithm in the exoatmospheric phase is also presented, the guidance algorithm provides steering command and time-to-go value directly using the current states of the vehicle and the desired orbit insertion conditions. To verify the optimality and accuracy of the algorithm simulations are performed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.401-407
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• 2004

This study proposes a interim development result for the l-㎾ class small wind turbine system, which is applicable to relatively low wind speed regions like Korea and has the variable pitch control mechanism. In the aerodynamic design of the wind turbine blade, parametric studies were carried out to determine an optimum aerodynamic configuration which is not only more efficient at low wind speed but whose diameter is not much larger than similar class other blades. A light composite structure, which can endure effectively various loads, was newly designed. In order to evaluate the structural design of the composite blade, the structural analysis was performed by the finite element method. Moreover both structural safety and stability were verified through the full-scale structural test.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.512-513
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• 2011

본 논문에서는 PMSG(Permanent Magnet Synchronous Generator)의 가변속-고정피치(Variable-Speed Fixed-Pitch) 풍력발전시스템을 위한 FLC를 기반으로 하는 최대 전력점제어(MPPT) 알고리즘을 제시한다. 최근에는 풍속변화에 대응하여 최대전력을 발생할 수 있는 가변속 풍력발전 시스템에 대한 연구가 활발히 진행 중이다. 국내의 지형적 조건에 따른 바람의 영향으로 풍력발전 시스템의 MPPT제어가 반드시 필요하다. 종래의 풍력발전 MPPT 제어는 응답속도 등에 대한 문제점이 나타난다. 따라서 본 논문에서는 이러한 문제점을 해결하기 위해 파라미터 변동에 강인한 FLC를 기반으로 하는 최대 전력점 제어(MPPT)를 제시한다. 또한 본 논문에서 제시한 알고리즘은 시뮬레이션 결과를 통해 타당성을 입증한다.

• Journal of the Korea Institute of Military Science and Technology
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• v.5 no.2
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• pp.37-49
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• 2002

In this paper, flyout stability of missile that is launched in inclined launcher using sabots is analyzed. To include missile bending motion during flyout, FEA model of missile is converted into eight concentrated mass and equivalent stiffness matrix. Six d.o.f ship motion that have influence on flyout stability is modeled and missile firing time is modeled as probability variable to take arbitrary ship attitude into account. Gap between missile and sabot is modeled as normal distribution probability variable and Monte Carlo simulation is performed. As results, the coriolis acceleration effects by ship motion are analyed and statistical results of missile pitch rate are shown.

• Journal of the Korean Solar Energy Society
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• v.36 no.6
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• pp.1-12
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• 2016

A control algorithm for a 100 kW wind turbine is designed in this study. The wind turbine is operating as a variable speed variable pitch (VSVP) status. Also, this wind turbine is a permanent magnet synchronous generator (PMSG) Type. For the medium capacity wind turbine considered in this study, it was found that the optimum tip speed ratios to achieve the maximum power coefficients varied with wind speeds. Therefore a commercial blade element momentum theory and multi-body dynamics based program was implemented to consider the variation of aerodynamic coefficients with respect to Reynolds numbers and to find out the power and thrust coefficients with respect tip speed ratio and blade pitch angles. In the end a basic power controller was designed for below rated, transition and above rated regions, and a load reduction algorithm was designed to reduce tower vibration by the nacelle motion. As a result, damage equivalent Load (DEL) of tower fore-aft has been reduced by 32%. From dynamic simulations in the commercial program, the controller was found to work properly as designed. Experimental validation of the control algorithm will be done in the future.