• Proceedings of the Korean Ceranic Society Conference
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• 2004.10a
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• pp.90.3-90.3
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• 2004

• New & Renewable Energy
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• v.7 no.2
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• pp.59-69
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• 2011

5MW wind turbine is regarded as a promising system for offshore wind farms in the western sea of Korean. And the wind turbine is developed in many companies but not much information is known about it. In this study, aerodynamics and control characteristics depending on several control methods is reviewed on 5MW wind turbine, in which configuration data of the turbine are used from the previous study of NREL. For the calculations, GH_Bladed, which is certificated software by GL, is used and compared with data from FAST code of NREL. This study shows that how much power production, and aerodynamic performances and loads can be obtained with different controls in the operation of 5MW wind turbine, which is expected to be useful in the design of the wind turbine system.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.537-538
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• 2015

최근 자전거의 활용범위가 출퇴근뿐만 아니라, 친환경 헬스케어 부각으로 자전거 타는 것에 많이 이용되고 있는 실정이다. 근래 몇 년 사이에 정부에서도 자전거 전용도로를 도시외각뿐만 아니라 자전거로 출퇴근 이용자들을 위해 안전하게 운행할 수 있도록 자전거 전용도로를 전국에 확대설치 하여 자전거 보급을 확대 하고 있다. 하지만 현재 국내에 많이 보급되어 있는 자전거는 대부분이 외국에서 반제품이 수입되어 국내에서 완제품으로 조림하여 판매되는 제품들이 주를 이루고 있으며, 자전거 부품 중에도 최근 외국에서 개발이 진행되고 있는 전자변속기 또한 외국의 기술들이 도입되어 제품들이 출시되고 있는 실정이다. 이에 외국의 기술적 우위로 인하여 한국의 자전거 산업발전에 어려움이 많은 것이 현실이다. 본 연구에서는 리니어모터를 이용하여 디지털 전동 변속기를 개발 하여, 변속의 신속성, 정확성을 확보하면서, 동시에 외국의 기술적 장벽을 넘고자 한다. 현행 자전거 뒤 변속기의 정확한 변위위치 확보하기 위하여 자전거 핸들에 장착되어 있는 변속레버를 디지털화 하여, 변속을 제어하게 되면 뒤쪽에 설치되어 있는 리니어모터를 위치 제어함으로써 가이드 샤프트 피치에 의하여 변속위치가 정밀하게 제어 할 수 있는 전동 변속기 제어시스템을 제안하고자 한다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.10a
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• pp.210-214
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• 2004

This study proposes a design method for blade pitch control mechanism in order to regulate the power and to improve the starting characteristic. This power control unit which is assembled by spring and mass is planing to equip with 1kW class wind turbine system which is developed for low wind speed area like Korea. For the design of this control unit, the proper geometry of the hub was designed and the calculation of the mechanics was carried out. Especially, It is expected that the operational efficiency will be improved because of additional high pitch starting function by using 2 step spring structure.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.5
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• pp.383-388
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• 2021

Air-breathing engines used in aircraft have a performance limit as the altitude increases, and this determines the service and absolute ceiling altitude. The method of maintaining altitude and speed in a fixed-wing aircraft in level flight using classical control method is generally using thrust for speed increase/deceleration and pitch attitude for altitude increase/decrease. If this method is used near the service ceiling altitude, increasing the pitch to reduce the altitude error results in a speed reduction. Therefore, it is necessary to use a control method that maintains the speed first using the pitch attitude. Especially in the case of unmanned aerial vehicles, these two methods should be automatically available at the right time. In this paper, we propose a method of switching the speed and altitude maintenance algorithm near service ceiling altitude.

• The KSFM Journal of Fluid Machinery
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• v.15 no.2
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• pp.36-40
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• 2012

Pitch control of wind turbine is activated above rated wind speed for the purpose of rated power regulation. When we design pitch controller, its gain-scheduling is essential due to nonlinear characteristics of aerodynamic torque. In this study, 2-mass model including a vibration mode of drive-train for a 2 MW wind turbine is considered and pitch control with gain-scheduling using a linearization analysis of the nonlinear aerodynamic torque is applied. Some simulation results for the pitch gain-scheduling under step wind speed are presented and investigated. It is shown that gain-scheduling in pitch control is important especially in the region of high wind speeds when there exists a vibration mode of drive-train.

• Applied Chemistry for Engineering
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• v.29 no.6
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• pp.652-656
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• 2018

In this study, effects of the reaction pressure were studied for petroleum-based pitch synthesis. A two-stage reaction process was performed based on different reaction pressure conditions. Each stage experiments for the two-stage reaction were consecutively carried out. The first stage was consisted of three different pressure conditions; high (10 bar), normal and low (0.1 bar). And the second stage was carried out at the normal and low (0.1 bar) pressure. The pitch synthesis was realized at $400^{\circ}C$ for 2 h. Thermal properties and molecular weight distributions of each samples were investigated by analyzing the softening point and MALDI-TOF data. Volatilized components during the pith synthesis were measured by GC-SIMDIS. In case of the first-step reaction with the high pressure condition, the low molecular weight component participated to the pitch formation more effectively and the pitch with the low softening point was obtained. However, for the case of the first-step with the low pressure, the low molecular weight component was vent outside and the partial coke formation occurred. Eventually, pitch properties such as the softening point and yield were controlled effectively by changing the pressure in the pitch synthesis reaction.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3347-3352
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• 2007

This paper describes a research for the performance improvement of the straight-bladed vertical axis wind turbine. To improve the performance of VAWT, the individual blade pitch control method is adopted. For the wind turbine, CFD analysis is carried out by changing blade pitch angle according to the change of wind speed and wind direction. By this method, capacity and power efficiency of VAWT are obtained according to the wind speed and rotating of rotor, and could predict the overall performance of VAWT. It was manufactured to verify performance of the experimental system that consists of rotor including four blades and base. Furthermore, torque sensor and power generator were installed. Also, active controller which can change the pitch angle of the individual blade according to the wind speed and direction was used.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.374-377
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• 2007

This paper deals with a pitch control for reducing load of the wind turbine system. To make a model of the wind turbine system, the Momentum Theory and Blade Element Theory are used. Considering wind shear, wind model was also built. Due to a difference of the wind speed between upper parts and lower parts of the sweep area, overturning moment of the wind turbine is generated. So, in this paper through analyzing of the system model of the wind turbine, a control algorithm which was able to achieve both maintaining power and reducing overturning moment was proposed. Using matlab simulink, controller performance was verified.

• The Journal of the Acoustical Society of Korea
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• v.12 no.2
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• pp.14-27
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• 1993

본 논문은 매 40ms 정도의 음성파형으로부터 추출된 6내지 9ms 정도의 1피치주기 파형을 합성단위로 사용하여 합성시킨 시간영역에서의합성방식을 한국어 문어 변환 시스템내에서의 음성합성기에 적용시킨 연구결과이다. 시험 결과, 4가지 유형의 한국어 음절 합성이 가능하고, 장단강약과 같은 운율요소의 제어가 용이하고, 또한 합성 알고리즘이 간단하여 실시간 처리가 가능하였으나, 문장 단위의 음성을 합성하기 위하여는 문장내에서의 다양한 피치 패턴에 대한 연구와 이의 효율적인 제어에 관한 연구가 이루어져야 할 것이다. 합성음에 대한 평가방법으로는 원음과 합성음에 대한 시간영역에서의 파형비교, 주파수 영역에서의 스펙트럼 포락선 유사성 비교 및 합성음에 대한 청취도 실험을 행하였다.