• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.553-558
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• 2003

The boundary estimation problem is used to estimate the shape of organic depend on the phase of the cardiac cycle or interested in the detection of the location and size of anomalies with resistivity values different from the background tissues such as nuclear reactor. And we can use the method to solve the optimal solution such as modified Newton raphson, kalman filter, extended kalman filter, etc. But, this method consumes much time and is sensitive to the initial value and noise in the estimation of the unknown shape. In the paper, we propose that multi-layer neural networks estimate the boundary of the unknown object using Fourier coefficient. This method can be used at the real time estimation and have strong characteristics at the noise and initial value. It uses voltage change; difference the homogeneous voltage to the non-homogeneous voltage, and change of Fourier coefficient change to train multi-layer neural network. After train, we can have real time estimation using this method.

• 대한전자공학회논문지TE
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• 제42권3호
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• pp.19-24
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• 2005

본 연구에서는 일반 주택이나 저전력의 전기를 사용하는 전기환경에서 발생하는 전기 화재의 원인이 되는 아크를 검출하고 부하 전류를 차단하여 화재를 방지할 수 있는 제어기를 설계하였다. 전기 화재를 방지하기 위해 전기가 발명된 이래로 많은 변천이 있어왔다. 휴즈에서 시작하여 일반 누설전류에서 동작하는 차단기를 거쳐 아크를 검출하고 부하전류를 제어할 수 있는 장치까지 개발되기에 이르렀다. 현재 발생하는 많은 전기 화재의 원인은 아크로 인해 발생하는 것으로 확인되었다. 본 연구를 통해서 일반 전기 환경에서 발생하는 전기 화재의 원인을 미연에 검출하여 인명피해는 물론이고 물질적인 피해를 방지할 수 있도록 하였으며, 본 연구를 계속적으로 확대하여 대전력 환경에서도 안정적으로 동작할 수 있는 제어기를 설계하고자 한다.

• 전력전자학회논문지
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• 제23권1호
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• pp.9-15
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• 2018

This study investigates a bidirectional quasi-Z-source inverter (Bq-ZSI) system with bidirectional power transfer capability and a modified space vector modulation scheme for reducing the ripple of the inductor current. By replacing the diode in the impedance network with an active switch, the power flow can be bidirectional. The average inductor current of the Bq-ZSI network is negative in the regenerative braking mode, thereby regenerating the power. In addition, modified space vector modulation scheme is applied to the Bq-ZSI to control shoot-through time effectively. A 5 kW prototype is built and tested to implement the proposed system. Experimental results show that the Bq-ZSI system is capable of regenerative braking of the induction motor and that the modified space vector modulation method is efficient.

• 신재생에너지
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• 제8권3호
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• pp.14-22
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• 2012

Performance of photovoltaic (PV) generator systems relies on its operating conditions. Maximum power extracted from PV generators depends strongly on solar irradiation, load impedance, and ambient temperature. A most maximum power point tracking (MPPT) algorithm is based on a perturb and observe method and an incremental conductance method. It is well known the latter is better in terms of dynamics and tracking characteristics under condition of rapidly changing solar irradiation. However, in case of digital implementation, the latter has some error for determining a maximum power point. This paper presents a PID based MPPT algorithm for such PV systems. We use neural network technique for determining PID parameters by online learning approach. And we construct a boost converter to regulate the output voltage from PV generator system. Computer simulation is carried out to evaluate the proposed MPPT method and we accomplish comparative study with a perturb and observe based MPPT method to prove its superiority.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.470-473
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• 2004

This paper presents conducted emission noise measurement from electronic equipment in frequency range of 1 MHz up to 30 MHz by small loop antenna. Small loop antenna measurement method can measure common-mode (CM) and differential-mode (DM) component of the noise on a pair of power line at the same time. The CM and DM can be measured separately. The theory of this measurement method is introduced and analyzed. The measured results were compared with the conventional measurement by Line Impedance Stabilization Network (LISN) and result a good trend between those methods.

• Journal of electromagnetic engineering and science
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• 제5권2호
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• pp.97-103
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• 2005

This paper describes the measured results of sonobuoy transmitting antenna system for anti-submarine warfare (ASW). Since radiation pattern and power density depend on impedance matching between transmitting RF part and antenna with termination resistance, design of matching circuit is very important for sonobuoy system performance. Matching circuit is designed by Smith chart using control of L and C. In standing wave ratio(SWR) measurement using Network Analyzer, SWR of antenna with matching circuit observed 1.5 below at the assigned VHF band. It shows very excellent performance comparison with conversional product that is used for the same object. The measured vertical and horizontal radiation patterns are also shown the satisfaction of military specifications. A drop out of sonobuoy system on the sea is happened when angle of elevation direction is over 10 degrees, and it is conformed that it takes less than I second return to original signal level. The required electric power density is $83\;mW/m^2$ in the military specification, and measured electric power density is observed over average $110\;mW/m^2$ at all frequency bands.

• Smart Structures and Systems
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• 제7권5호
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• pp.365-378
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• 2011

Piezo-based active structural health monitoring (SHM) requires amplifiers specifically designed for capacitive loads. Moreover, with the increase in number of applications of wireless SHM systems, energy efficiency and cost reduction for this type of amplifiers is becoming a requirement. General lab grade amplifiers are big and costly, and not built for outdoor environments. Although some piezoceramic power amplifiers are available in the market, none of them are specifically targeting the wireless constraints and low power requirements. In this paper, a piezoceramic transducer amplifier for wireless active SHM systems has been designed. Power requirements are met by two digital On/Off switches that set the amplifier in a standby state when not in use. It provides a stable ${\pm}180$ Volts output with a bandwidth of 7k Hz using a single 12 V battery. Additionally, both voltage and current outputs are provided for feedback control, impedance check, or actuator damage verification. Vibration control tests of an aluminum beam were conducted in the University of Houston lab, while wireless active SHM tests of a wind turbine blade were performed in the Harbin Institute of Technology wind tunnel. The results showed that the developed amplifier provided equivalent results to commercial solutions in suppressing structural vibrations, and that it allows researchers to perform active wireless SHM on moving objects with no power wires from the grid.

• 한국진공학회지
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• 제8권1호
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• pp.75-82
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• 1999

내부 삽입형 유도결합 플라즈마를 이온화원으로 하는 I-PVD장치를 이용하여 박막을 형성하는데 중요한 요소의 하나가 이온의 입사에너지이며, 이는 플라즈마 전위와 기판 전위의 차이에 의해서 결정된다. 이를 감소시킬 목적으로 안테나 여기 주파수를 4MHz의 중간주파수에서, 안테나의 정합 회로를 변형형, 부동형의 2가지로 변화시키고, 부동형에서는 바이어스 저항의 값을 가변시켰다. 그 결과 Ar 플라즈마에서 4MHz RF 전력 600 W에서 5 mTorr에서 30 mTorr의 넓은 압력 범위에서 5V 미만의 낮은 평균 플라즈마 전위와 60V의 안테나 전압을 얻었다. 또한 출력측에 설치한 RLC회로의 조절을 통해서 RF전력 500 W에서 RF 입력 및 출력단의 Rf 안테나 유기 전압을 50V의 아주 낮은 값으로 유지시킬 수 있었다. 이때의 안테나 및 플라즈마의 총 임피던스는 약 10$\Omega$이었으며, 리액턴스를 0.05$\Omega$수준으로 유지하였을 때 가장 낮은 전압을 얻었다.

• 한국정보통신학회논문지
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• 제23권12호
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• pp.1659-1665
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• 2019

본 논문에서는 WLAN (wireless local area network) 응용을 위한 소형 인쇄형 모노폴 안테나의 새로운 설계에 대해 연구했다. 선폭이 다른 패치와 계단 모양의 접지면이 있는 복사체는 안테나 크기를 줄이기 위해 사용된다. 안테나의 크기는 16 × 17 × 1 ㎣이며 포토리소그래피(photolithography) 기술로 제작되었다. 시뮬레이션 및 측정 결과가 잘 일치한다. 연구된 안테나의 공진 주파수는 약 5.2 GHz이며 측정 결과 1 GHz의 임피던스 대역폭을 가진다. 또한 측정된 방사패턴을 제시하고 필요한 WLAN 5 GHz 주파수 대역 (5.15 - 5.825 GHz)에서 측정된 이득 및 효율을 제시했으며, 5 GHz 대역 WLAN 안테나로 사용할 수 있음을 확인했다. 연구된 안테나는 소형, 경량, 저비용, 전방향성 복사패턴, 고이득 및 고효율을 갖는다.

• Journal of Electrical Engineering and Technology
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• 제13권2호
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• pp.688-698
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• 2018

Quasi Z-Source Multilevel Inverter (QZMLI) topology has attracted grid connected Photovoltaic (PV) systems in recent days. So there is a remarkable research thrust in switching techniques and control strategies of QZMLI. This paper presents the mathematical analysis of Phase shift- Pulse Width Amplitude Modulation (PS-PWAM) for QZMLI and emphasizes on the advantages of the technique. The proposed technique uses the maximum and minimum envelopes of the reference waves for generation of pulses and proportion of it to generate shoot-through pulses. Hence, it results in maximum utilization of input voltage, lesser switching loss, reduced Total Harmonic Distortion (THD) of the output voltage, reduced inductor current ripple and capacitor voltage ripple. Due to these qualities, the QZMLI with PS-PWAM emerges to be the best suitable for PV based grid connected applications compared to Phase shift-Pulse Width Modulation (PS-PWM). The detailed math analysis of the proposed technique has been disclosed. Simulation has been performed for the proposed technique using MATLAB/Simulink. A prototype has been built to validate the results for which the pulses were generated using FPGA /SPARTAN 3E.