• Journal of Mechanical Science and Technology
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• 제19권7호
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• pp.1449-1459
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• 2005

This paper shows the results of local flow speed measurement using tunable AC thermal anemometry, which is suitable for the accurate measurement of wide range flow speed. The measurement accuracy is verified through the comparison between the measurement data and the analytic solution of the sensor temperature oscillation in stationary fluid. The relation between the phase lag and the flow speed is experimentally investigated at various conditions. The measurement sensitivity for low flow speed improves in a low frequency region and that for high flow speed improves in a high frequency region. Also, the sensitivity increases with decreasing thermal conductivity of the surrounding fluid. The local flow speed could be measured as low as 1.5 mm/s and the highest measurement resolution was 0.05 mm/s in the range of 4.5 $\~$5.0 mm/s at 1 Hz in this experiment.

• 전자공학회논문지T
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• 제35T권1호
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• pp.90-98
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• 1998

본 논문은 유도전동기를 저속에서 강건하게 제어할 수 있도록 개선된 벡터 제어에 관한 연구이다. 유도전동 기가 정격 속도의 10% 이하인 저속에서 구동될 경우 고조파에 의하여 발생하는 단위 벡터각 오차를 보상하는 알고리즘을 제안하였다. 또한 저속 및 과도상태에서 회전자 파라미터 변화에 대하여 강건하게 운전하도록 회전 자 시정수에 동조하는 알고리즘을 제시하였다. 제안한 벡터 제어를 이용하여 자속과 토오크 리플을 감소시킴으로써 저속에서 안정된 출력특성을 얻을 수 있었다. 입출력이 정현적인 상태일 때, 제안한 벡터 제어와 직접 벡터 제어 및 간접 벡터 제어의 저속 특성을 비교 분석하였고, 고조파가 함유된 상태에서 각각의 제어 특성을 비교 분석하였다. 그리고 회전자 시정수의 추종 성능은 시뮬레이션으로 확인하였다. 전체 제어 시스템을 실제의 하드웨어로 구현하고, 제안한 벡터 제어와 직접 벡터 제어를 비교 분석하였다. 두 제어 기법을 저속에서 실험 한 결과, 정상상태에서 직접 벡터를 기준으로 할 경우 토오크 리플이 45% 개선된 특성을 얻었다. 또한 자속 전류 리플은 0.2 p.u. 감소하였고, 토오크 전류 리플은 0.6 p.u. 감소함을 확인하였다. 그리고 회전자 시정수의 변화에 대하여 동조됨을 확인하였다. 따라서 저속에서 제안한 벡터 제어의 타당성과 강건성을 입증하였다.

• 전력전자학회논문지
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• 제9권3호
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• pp.231-239
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• 2004

A new scheme to estimate the moment of inertia in the motor drive system in very low speed is proposed in this paper. The simple estimation scheme, which is usually used in most servo system for low speed operation, is sensitive to the variation of the machine parameter, especially the moment of inertia. To estimate the motor inertia value, Reduced-Order Extended Luenberger Observer (ROELO) is applied. The effectiveness of the proposed inertia identification method using the RORLO is verified by simulation and experiment.

• 한국전산유체공학회지
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• 제9권2호
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• pp.36-42
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• 2004

Low-speed gas flows in micro-channels are investigated using a kinetic theory analysis. The Boltzmann equation simplified by a collision model is solved by means of a finite difference approximation with the discrete ordinate method. Calculations are made for flows in simple micro-channels and a micro-fluidic system consisting of two micro-channels in series. The results are compared well with those from the DSMC method and an analytical solutions to the Wavier-Stokes equations. It is shown that the present method is a useful tool for the modeling of low-speed flows in micro-channels.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.416-422
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• 2007

Prime movers in most large merchant ships adapt two stroke low speed diesel engine which has higher efficiency, mobility and durability. However, severe torsional vibration in these diesel engines may be induced by higher fluctuation of combustion pressures. Consequently, it may lead sometimes to propulsion shafting failure due to the accumulated fatigue stresses. Shaft fatigue strength analysis had been done traditionally in time domain but this method is complicated and difficult in analysing bi-modal vibration system such as the case of cylinder misfiring condition. In this paper authors introduce an assessment method of fatigue strength estimation for propulsion shafting system with two stroke low speed diesel engine in the frequency domain.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.533-534
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• 2006

This paper presents the architecture design of a high-speed, low-complexity 128-point radix-$2^4$ FFT processor for ultra-wideband (UWB) systems. The proposed high-speed, low-complexity FFT architecture can provide a higher throughput rate and low hardware complexity by using 2-parallel data-path scheme and single-path delay-feedback (SDF) structure. This paper presents the key ideas applied to the design of high-speed, low-complexity FFT processor, especially that for achieving high throughput rate and reducing hardware complexity. The proposed FFT processor has been designed and implemented with the 0.18-m CMOS technology in a supply voltage of 1.8 V. The throughput rate of proposed FFT processor is up to 1 Gsample/s while it requires much smaller hardware complexity.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 A
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• pp.179-181
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• 1999

Sensorless PMSM is much studied for the industrial applications and home appliances because a mechanical sensor reduce reliability and increases cost. Most of sensorless algorithm have poor performances in a low speed range. This paper investigates Performance improvement in a low speed range of PMSM. The proposed control scheme is based on the optimization of ratio between the command and dc-link voltages. The experiment is performed in this study. and the result shows the improved Performance in a low speed range.

• Journal of the Korean Physical Society
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• 제73권12호
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• pp.1889-1894
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• 2018

An innovative small-scale piezoelectric energy harvester has been proposed to gather wind energy. A conventional horizontal-axis wind power generation has a low generating efficiency at low wind speed. To overcome this weakness, we designed a piezoelectric windmill optimized at low-speed wind. A piezoelectric device having high energy conversion efficiency is used in a small windmill. The maximum output power of the windmill was about 3.14 mW when wind speed was 1.94 m/s. Finally, the output power and the efficiency of the system were compared with a conventional wind power system. This work will be beneficial for the piezoelectric energy harvesting technology to be applied to the real world such as wireless sensor networks (WSN).

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 F
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• pp.2171-2173
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• 1997

In this paper space vector PWM method is proposed to implement an indirect vector control for an induction motor with excellent dynamic stability and performance in a very low speed resin. The proposed method can detect the instantaneous speed in very low speed resin and a speed control system with robustness to the load disturbance, modeling error, and measured noise is suggest to decrese their influence on the control system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.190-192
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• 2003

Single phase induction motor is used widely in various electronic appliances by advantage that is simple structure and a low-cost. As high starting torque characteristic is mostly used capacitor run single phase induction motor. In this paper, it is applied that speed controller of Capacitor run single phase induction motor of digital way used general microprocessor, and phase control method used average voltage. Torque get non-linearity to domain of low speed. Unstable domain of low speed is applied of integral cycle control. so it is wide that Speed control domain. Also, PID controller is used to improve characteristic of fast response. The validity of proposed method is verified from simulation and experiment result