• Journal of Electrical Engineering and Technology
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• 제12권6호
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• pp.2268-2277
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• 2017

As constantly increasing wind power penetrates power grid, wind power plants (WPPs) are exerting a direct influence on the traditional power system. Most of WPPs are using variable speed constant frequency (VSCF) wind turbines equipped with doubly fed induction generators (DFIGs) due to their high efficiency over other wind turbine generators (WTGs). Therefore, the analysis of DFIG has attracted considerable attention. Precisely measuring optimum reference speed is basis of utilized maximum wind power in electric power generation. If the measurement of wind speed can be easily taken, the reference of rotation speed can be easily calculated by known system's parameters. However, considering the varying wind speed at different locations of blade, the turbulence and tower shadow also increase the difficulty of its measurement. The aim of this study is to design fuzzy controllers to replace the wind speedometer to track the optimum generator speed based on the errors of generator output power and rotation speed in varying wind speed. Besides, this paper proposes the fuzzy adaptive PID control to replace traditional PID control under rated wind speed in variable-pitch wind turbine, which can detect and analyze important aspects, such as unforeseeable conditions, parameters delay and interference in the control process, and conducts online optimal adjustment of PID parameters to fulfill the requirement of variable pitch control system.

• Transactions on Electrical and Electronic Materials
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• 제9권6호
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• pp.265-272
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• 2008

In this paper, AC losses of long wire Bi-2223 tapes with different twist pitch of superconducting core were fabricated, measured and analyzed. These samples produced by a powder-in-tube method are multi-filamentary tape with Ag matrix. Also, it's produced by non-twist. The critical current measurement was carried out under the environment in Liquid nitrogen and in zero field by 4-prob method. And the Magnetic measurement was carried out under the environment of applied time-varying transport current by transport method. From experiment, the susceptibility measurements were conducted while cooling in a magnetic field. Flux loss measurements were conducted as a function of ramping rate, frequency and field direction. The AC flux loss increases as the twist-pitch of the tapes decreased, in agreement with the Norris Equation. Neutron-diffraction measurements have been carried out investigate the crystal structure, magnetic structures, and magnetic phase transitions in Bi-2223([Bi, Pb]:Sr:Ca:Cu:O).

• 한국기계가공학회지
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• 제12권3호
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• pp.36-40
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• 2013

Recently, electronic equipments become smaller, more functional, and more complex than before. As these trends, MLC(multi-layer ceramic) circuit has been emerged to a promising technology in semiconductor inspection industry. Especially, multi-layer ceramic which is consisted of many fine-pitch multi-hole is used to produce a semiconductor inspection unit. The hole is processed by UV laser. But, working conditions are changed all the time. Therefore real time measurement of fine-pitch multi-hole is very important method for ensuring performance. In this paper we found the best method for illuminating and auto focusing. And, we verified our equipment.

• 한국통신학회논문지
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• 제40권9호
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• pp.1837-1845
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• 2015

도심지환경에서 정확한 차량 위치를 추정하기 위해서는 종방향 속도가 필요하다. 이러한 종방향 속도는 노면경사, 즉 차량의 피치각(Pitch) 산출을 통해서 가능하다. 하지만 단일 센서와 알고리즘을 이용한 피치각 추정에는 정확한 값을 기대할 수 없다. 본 논문에서는 정확한 피치각 추정을 위해 AKF(Adaptive Kalman Filter)와 CF(Complementary Filter)로 구성된 ACF(Adaptive Complementary Filter)를 이용하여 IMU(Inertial Measurement Unit)의 프로세스 노이즈와 측정에러를 주행환경에 맞게 조절하고, 이에 GPS(Global Positioning System)와 OBD(Onboard Equipment) 데이터를 융합한다. 그리고 노면 경사 모델에 따른 필터에 시스템 모델 최적화를 위해 IMMKF(Interactive Multiple Model Kalman Filter)를 사용하여 주행환경에 적합한 최종 피치각을 추정한다.

• 한국항공우주학회지
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• 제39권2호
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• pp.162-169
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• 2011

현대의 고성능 전투기는 공력성능 및 조종성능의 향상을 위하여 대부분 세로축 방향으로 항공기를 불안정하게 설계하는 정안정성 완화 개념을 채택하고 있다. 항공기는 비행제어법칙에 필요한 피치, 롤, 요우각속도, 수직가속도와 같은 항공기 상태정보를 각속도(RSA: Rate Sensor Assembly)와 가속도센서(ASA: Acceleration Sensor Assembly)로부터 획득한다. 항공기에 적용되는 센서는 항공기의 안전을 보장하는 최소한의 허용 가능한 측정 오차를 갖지만, 잡음, 오프셋 등과 같은 허용 범위내의 오차로 인하여 원하지 않는 항공기 운동을 발생시킨다. 비행시험 결과, ASA의 허용 범위내의 측정 오차는 1g 수평비행시에 원하지 않는 기수 숙임 현상을 일으켰다. 본 논문에서는 이러한 오차로 인하여 발생하는 기수 숙임 현상을 개선하기 위해 1g 수평비행 조건에 피치자세각 궤환을 세로축 제어법칙에 적용하였다. 비행시험 결과, 피차자세각 궤환은 1g 수평 비행 시에 기수 숙임현상을 제거하고 항공기의 기본적인 안정성에는 영향을 미치지 않는다는 것을 확인할 수 있었다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 하계종합학술대회논문집
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• pp.607-610
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• 1998

The major objectives of speech coding include high compression ratio for transmission in the band limited channel, high synthesized speech quality in terms of the intelligibility and the naturalness and fast processing speed. In general, speech coding methods are classified into the following three categories: the wavelform coding, the source coding and the hybird coding. In this paper, we proposed a new waveform coding method using PSOLA(pitch-synchronous overlap add) technique. First, we fixed one basic waveform per pitch and measured the formant similarity between basic and neighbor waveform. Second, if the similairy satisfied threshold values, we compress the neighbor waveform per pitch and then store or transmit. When the comparession is about 45%, we obtained about 4 in MOS.

• 동력기계공학회지
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• 제12권4호
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• pp.18-25
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• 2008

This paper investigated the new calibration algorithm of a straight-type five-hole pressure probe necessary for calculating three-dimensional flow velocity components. The new data reduction method Includes a look-up, a geometry transformation such as the translation and reflection of nodes, and a binary search algorithm. This new calibration map was applied up to the application angle, ${\pm}55^{\circ}$ of a probe. As a result, this data reduction method showed a perfect performance without any kind of interpolation errors In calculating yaw and pitch angle from the calibration map.

• 음성과학
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• 제2권
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• pp.95-108
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• 1997

The purpose of this experimental study was to investigate prosodic characteristics of English as spoken by Koreans. Test materials were four English words, a sentence, and a paragraph. Six female Korean speakers and five native English speakers participated in acoustic and perceptual experiments. Pitch and duration of word syllables were measured from signals and spectrograms made by the Signalize 3.04 software program for Power Mac 7200. In the perceptual experiment, accent position, intonation patterns, rhythm patterns and phrasing were evaluated by the five native English speakers. Preliminary results from this limited study show that prosodic characteristics of Koreans include (1) pitch on the first part of a word and sentence is lower than that of English speakers, but the pitch on the last part is the opposite; (2) word prosody is quite similar to that of an English speaker, but sentence prosody is quite different; (3) the weakest point of sentence prosody spoken by Koreans is in the rhythmic pattern.

• KIEE International Transactions on Electrophysics and Applications
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• 제3C권6호
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• pp.211-215
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• 2003

Alternating current (AC) losses of two Bi-2223 ([Bi, Pb] : Sr : Ca : Cu :O = 2:2:2:3) tapes [one untwisted (Tape I, twist-pitch of $\infty$ mm) and the other with a twist-pitch of 8mm (Tape II) ] were measured and compared. These samples, produced by the powder-in-tube (PIT) method, are multi-filamentary and have a Ag/Au and Ag matrix, respectively. Susceptibility measurements were conducted while cooling in a magnetic field. Flux loss measurements were conducted as a function of ramping rate, frequency and field direction. The AC flux loss increases as the twist-pitch of the tapes decreased, in agreement with the Norris Equation.

• 풍력에너지저널
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• 제3권1호
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• pp.61-67
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• 2012

The loading test of wind turbine pitch and yaw bearings have been conducted using special test rig designed for the test of large slewing bearings. Test type was fatigue test that applied fatigue load to each bearing and followed the defined test process. Measurement data during test were rotational torque and raceway temperature, and inspected key components by disassembling the bearing after all test finished. As a results, the raceway temperature during test did not exceed the operational temperature range of lubricant and rotational torque was reduced as the bearing's rotational cycle increased. In the inspection of key components, some plastic deformation and flaking were detected at some raceway sections while other components such as ball, spacer and seal remain indefective conditions.