• 전력전자학회논문지
• /
• 제18권1호
• /
• pp.45-53
• /
• 2013

Fuel cell power system is one of the most promising energy source for the alternative energy because it has unique advantages such as high energy density, no power drop during operation, and feasible to make compact size. However, due to very low response time, fuel cell is difficult to correspond to drastic load changes and start-up operation. For solving these problem, fuel cell power system must include energy storage device such as Li-Poly battery or super capacitor. Therefore, bi-directional DC-DC converter must be required for this storage device and fuel cell-PCS control. This paper presents a design and modeling of the bi-directional DC/DC converter. Firstly, we present modeling the boost and buck mode of the bi-directional converter through both PWM switch model and state space averaging technique. Secondly, in order to minimize output ripple and transient response overshoot, we have two identical DC-DC converters interleaved and adopt two-loop voltage-current controller. The proposed bi-directional DC-DC converter's modeling method and control design have been verified with computer simulation and experimentation.

• 대한전자공학회논문지SD
• /
• 제41권10호
• /
• pp.77-83
• /
• 2004

VLSI 시스템에서 전력 소모를 줄이기 위해서는 메가블록이 동작하지 않는 동안 전원을 차단하여 누설 전류를 억제하는 방법이 효과적이다. 최근 들어 다중 문턱 전압 CMOS를 사용하여 전원을 차단하는 방법이 널리 연구되고 있으나, 동작 주파수가 증가함에 파라 전원 복귀에 필요한 시간이 짧아지게 되고, 짧은 시간에 전원이 복귀되면서 전원선에 대량의 전류가 순간적으로 흐르게 된다. 이에 따라 매우 큰 전원 잡음이 생겨서 전원 전압이 안정적이지 못하고 흔들리게 되며 이는 많은 경우 시스템의 오동작을 초래하게 된다. 본 논문에서는 이러한 문제점을 해결하기 위하여 새로운 전원 복귀 기법을 제안한다. 제안하는 기법은 메가블록의 전원이 차단되었다가 다시 복귀할 때 한꺼번에 전원을 켜는 것이 아니라 파이프라인 방식으로 몇 단계로 나누어 전원을 켬으로서 전원선에 흐르는 최대 전류 및 이에 따른 전원 잡음을 크게 억제한다. 제안하는 파이프라인 전원 복귀 기법을 검증하기 위해서 컴팩트 플래시 메모리 제어기 칩에 본 기법을 적용하여 곱셈기 블록의 전원을 차단하고 복귀할 때의 전원 잡음을 모의실험하고 분석하였다. 모의실험 결과, 제안하는 기법은 기존의 전원 차단 기법에 비해 전원 잡음을 매우크게 줄일 수 있음을 확인하였다.

• Journal of Power Electronics
• /
• 제6권1호
• /
• pp.38-44
• /
• 2006

In this paper, a speed sensorless control for an ultrasonic motor (USM) using a neural network (NN) is presented. In the proposed method, rotor speed is estimated by a three-layer NN which adapts nonlinearities associated with load torque and motor temperature into control. The intrinsic properties of a USM, such as high torque for low speeds, high static torque, compact size, etc., offer great advantages for industrial applications. However, the speed property of a USM has strong nonlinear properties associated with motor temperature and load torque, which make accurate speed control difficult. These properties are considered in designing a control method through the application of mathematical models. In these strategies, a detailed speed model of the USM is required which makes actual applications impractical. In the proposed method, a three-layer NN estimates the speed of the USM from the drive frequency, the root mean square value of input voltage and the surface temperature of the USM, where no mechanical speed sensor is needed. The NN speed based estimator enables inclusion of variations in driving conditions due to input signals of the NN involved during the driving state of the USM. The disuse of sensors offers many advantages on both the cost and maintenance front. Moreover, the model free sensorless control method offers practical controller construction within a small number of parameters. To validate the proposed speed sensorless control method for a USM, experiments have been executed under several conditions.

• 천문학회보
• /
• 제39권2호
• /
• pp.90-90
• /
• 2014

The Immersion Grating Infrared Spectrometer (IGRINS) is the first astronomical spectrograph that uses a silicon immersion grating as its dispersive element. IGRINS fully covers the H and K band atmospheric transmission windows in a single exposure. It is a compact high-resolution cross-dispersion spectrometer whose resolving power R is 40,000. An individual volume phase holographic grating serves as a secondary dispersing element for each of the H and K spectrograph arms. On the 2.7m Harlan J. Smith telescope at the McDonald Observatory, the slit size is $1^{{\prime}{\prime}}{\times}15^{{\prime}{\prime}}$. IGRINS has a plate scale of 0.27" pixel-1 on a $2048{\times}2048$ pixel Teledyne Scientific & Imaging HAWAII-2RG detector with a SIDECAR ASIC cryogenic controller. The instrument includes four subsystems; a calibration unit, an input relay optics module, a slit-viewing camera, and nearly identical H and K spectrograph modules. The use of a silicon immersion grating and a compact white pupil design allows the spectrograph collimated beam size to be 25mm, which permits the entire cryogenic system to be contained in a moderately sized ($0.96m{\times}0.6m{\times}0.38m$) rectangular Dewar. The fabrication and assembly of the optical and mechanical components were completed in 2013. From January to July of this year, we completed the system optical alignment and carried out commissioning observations on three runs to improve the efficiency of the instrument software and hardware. We describe the major design characteristics of the instrument including the system requirements and the technical strategy to meet them. We also present the instrumental performance test results derived from the commissioning runs at the McDonald Observatory.

• 천문학회보
• /
• 제39권1호
• /
• pp.52.2-52.2
• /
• 2014

The Immersion Grating Infrared Spectrometer (IGRINS) is an unprecedentedly minimized infrared cross-dispersed echelle spectrograph with a high-resolution and high-sensitivity optical performance. A silicon immersion grating features the instrument for the first time in this field. IGRINS will cover the entire portion of the wavelength range between 1.45 and $2.45{\mu}m$ accessible from the ground in a single exposure with spectral resolution of 40,000. Individual volume phase holographic (VPH) gratings serve as cross-dispersing elements for separate spectrograph arms covering the H and K bands. On the 2.7m Harlan J. Smith telescope at the McDonald Observatory, the slit size is $1^{\prime\prime}{\times}15^{\prime\prime}$. IGRINS has a $0.27^{\prime\prime}$ pixel-1 plate scale on a $2048{\times}2048$ pixel Teledyne Scientific & Imaging HAWAII-2RG detector with SIDECAR ASIC cryogenic controller. The instrument includes four subsystems; a calibration unit, an input relay optics module, a slit-viewing camera, and nearly identical H and K spectrograph modules. The use of a silicon immersion grating and a compact white pupil design allows the spectrograph collimated beam size to be 25mm, which permits the entire cryogenic system to be contained in a moderately sized rectangular vacuum chamber. The fabrication and assembly of the optical and mechanical hardware components were completed in 2013. In this presentation, we describe the major design characteristics of the instrument and the early performance estimated from the first light commissioning at the McDonald Observatory.

• 한국정보통신학회논문지
• /
• 제11권2호
• /
• pp.257-264
• /
• 2007

사진을 찍을 때 카메라는 보기 좋은 사진을 얻을 수 있도록 많은 기능을 제공하고 있다. 대표적인 기능으로 자동 초점거리 조정(Auto Focus), 자동 색온도 보정(Auto White Balance), 자동 노출 조정(Auto Exposure)이 있다. 본 논문에서는 편리한 기능들 중 하나로서 새로운 자동 노출제어 시스템을 제안한다. 본 논문에서 제안하는 자동 노출제어 시스템은 가변 시상수(Variable Time Constant)를 가지는 IIR Filter를 이용한다. 먼저 노출제어의 기준을 정하기 위해서 사진에서 밝기변화와 Zone System에서 보여주는 사물의 휘도정보를 비교하여 이상적인 휘도변화 특성 그래프를 얻는다. 얻어진 이상적인 휘도 변화 그래프와 현재의 노출설정을 비교하여 적정 노출의 설정을 찾는다. 제안하는 자동 노출제어 시스템은 적정 노출을 얻을 수 있는 설정으로 조정하기 위해 기존의 마이크로 콘트롤러 등을 이용하여 구현하는 방법과 달리 IIR Filter를 사용하므로 간단한 구성을 가지며 콤팩트 이미지 센서모듈(ISM)를 구성하기 위하여 사용할 수 있다.