• 조명전기설비학회논문지
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• 제26권7호
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• pp.45-51
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• 2012

In this paper, the wireless power transfer system using the magnetic resonance was designed and the effect of resonant coil radius and load resistance to this system was analyzed by the circuit analysis method. As a result, the calculated transmitted-power is similar to measured one, and the coil size has a small effect to the coupling coefficients in the resonant frequency band. In addition, the fact that the calculated transmitted-power according to the source frequency is similar to measured one confirms that the circuit analysis methode in this paper is valid. The input side transmission efficiency ${\eta}_i$ including only the loss in the power transfer circuit is almost 90[%] with the large coil in the 10[cm] transfer distance, and 65[%] with the small coil in 1[cm]. The source side transmission efficiency ${\eta}_s$ is 30~40[%] at both coil when load resistance below 4.7[${\Omega}$] has been connected. Considering that the maximum ${\eta}_s$ is 50[%], this is valid in the practical applications.

• 조명전기설비학회논문지
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• 제20권10호
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• pp.35-40
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• 2006

이 논문에서는 주파수 가변형 무선 personal area network(PAN) 통신시스템 및 단말에 적용이 가능한 응용 회로로써, 탭계수(tap coefficient) 회로를 가변시련 수 있는 전류모드 아날로그 finite impulse response (FIR) 필터를 제안한다. 가변되는 7-tap FIR 필터의 동작은 컴퓨터 모의실험으로부터 확인하였고, $0.8[{\mu}m]$ CMOS 공정기술을 사용하여 0.0625-step 탭계수 회로가 제작되었다. 제안된 FIR 필터는 탭계수의 길이와 계수를 가변시킬 수 있기 때문에 주파수 가변형 무선 PAN통신 시스템 및 단말기에 적용 가능한 유용한 특성을 갖는다.

• 조명전기설비학회논문지
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• 제28권12호
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• pp.90-94
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• 2014

Recently, various types of trains are being operated in the same railroad whose designated stop stations are not the same. In other words, each train does not stop at every station. This could cause the pass-through accidents in which a train passes a station where it is supposed to stop. Although the number of train accidents is on the decrease, this type of error is still an important problem to be resolved. It is true that the burdens of train drivers are growing because the number of high speed trains and non-stop stations is increasing in the current railway system. However, another major reason for this accident is that there is no prevention system for these errors in the current train control system although it is being constantly improved. The purpose of this study is to reinforce the train stop system with wireless communication equipment in order to decrease this type of accident and to maximize the safety of railway transportation.

• 조명전기설비학회논문지
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• 제20권6호
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• pp.43-48
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• 2006

본 논문에서는 마이크로파를 이용한 무선전력전송시스템을 구현하기 위해 2.45[GHz] 마이크로파를 수신하여 직류전력으로 변환하는 렉테나를 설계, 구현하고, RF-DC변환효율을 높이기 위한 임피던스 매칭 및 튜닝 방법을 제시하였다. 구현된 렉테나는 넓은 Open Stub를 사용하여, 쉽게 튜닝이 가능하며, 정류회로의 RF-DC변환효율은 5[dBm]입사전력에 대하여, 최대 59[%]를 얻을 수 있었다. 제작된 패치안테나와 정류회로를 이용하여 소전력무선전송시스템을 구현한 결과, 송수신거리가 1[m]떨어진 거리에서 2.2[V], 1.5[mW]의 직류전력송신이 이루어졌으므로, 소전력 디지털시스템의 운용에 적용가능한 값을 얻을 수 있었다.

• 조명전기설비학회논문지
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• 제28권1호
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• pp.69-78
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• 2014

In this paper, characteristics of wireless power transfer (WPT) systems using magnetically coupled resonance scheme with relay coils are investigated and modeled. Especially, asymmetric frequency splitting characteristics in over-coupled region of WPT with relays are measured and accurately modeled. Transmitter, receiver, and relay coils are modeled with R, L, C equivalent circuits. Using these circuit models and mutual inductances between coils, a WPT system is described with a linear matrix equation. For under-coupled region, a matrix is simplified considering only mutual inductances between adjacent coils. An analytical transfer characteristic of WPT system vs. distance is extracted using an inverse matrix that is acquired by Gauss elimination method for the simplified matrix. For over-coupled region, a matrix considering mutual inductances between non-adjacent coils is used to predict a frequency splitting characteristics accurately. A 6.3MHz WPT system with relay coils is implemented and measured. An accuracy of the model is investigated by comparing the output of the model with the measured results.

• Structural Engineering and Mechanics
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• 제17권3_4호
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• pp.393-408
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• 2004

There exists a clear need to monitor the performance of civil structures over their operational lives. Current commercial monitoring systems suffer from various technological and economic limitations that prevent their widespread adoption. The wires used to route measurements from system sensors to the centralized data server represent one of the greatest limitations since they are physically vulnerable and expensive from an installation and maintenance standpoint. In lieu of cables, the introduction of low-cost wireless communications is proposed. The result is the design of a prototype wireless sensing unit that can serve as the fundamental building block of wireless modular monitoring systems (WiMMS). An additional feature of the wireless sensing unit is the incorporation of computational power in the form of state-of-art microcontrollers. The prototype unit is validated with a series of laboratory and field tests. The Alamosa Canyon Bridge is employed to serve as a full-scale benchmark structure to validate the performance of the wireless sensing unit in the field. A traditional cable-based monitoring system is installed in parallel with the wireless sensing units for performance comparison.

• 정보처리학회논문지A
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• 제10A권6호
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• pp.685-690
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• 2003

새로운 무선인터넷 디바이스로써 주목받고 있는 PDA는 기능 개선을 위해서 다양한 애플리케이션 개발이 이루어지고 있으며 수시로 응용프로그램이 설치되어지고 있다. 또한 PDA는 전원이 방전 될 경우에 RAM(Random Access Memory)에 저장되어 있는 데이터가 모두 삭제되는 단점이 있어서 그때마다 프로그램을 다시 복원해야 한다. 본 논문에서는 PDA의 응용 프로그램을 설치할 경우에 사용자가 직접 애플리케이션을 설치해야 하는 기존의 문제점을 해결하기 위하여 자동으로 PDA 응용프로그램이 설치되는 시스템(PAIS : PDA Automatic Installation System)을 제안하였다. 이 시스템을 적용한 경우 사용자에게는 설치에 소요되는 시간과 노력을 감소시켜 편의를 제공하고, 기업에게는 프로그램 설치관련 홍보물 제작에 소요되던 비용을 절감 할 수 있는 효과가 있다.

• Smart Structures and Systems
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• 제12권3_4호
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• pp.415-426
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• 2013

Condition assessment and monitoring of bridges is critical for safe passenger travel, public transportation, and efficient freight. In monitoring, displacement measurement capability is important to keep track of performance of bridge, in part or as whole. One of the most important parts of a bridge is the expansion joint, which accommodates continuous cyclic thermal expansion of the whole bridge. Though expansion joint is critical for bridge performance, its inspection and monitoring has not been considered significantly because the monitoring requires long-term data using cost intensive equipment. Recently, a wireless smart sensor network (WSSN) has drawn significant attention for transportation infrastructure monitoring because of its merits in low cost, easy installation, and versatile on-board computation capability. In this paper, a rapid wireless displacement monitoring system, wireless hybrid sensor (WHS), has been developed to monitor displacement of expansion joints of bridges. The WHS has been calibrated for both static and dynamic displacement measurement in laboratory environment, and deployed on an in-service highway bridge to demonstrate rapid expansion joint monitoring. The test-bed is a continuous steel girder bridge, the Founders Bridge, in East Hartford, Connecticut. Using the WHS system, the static and dynamic displacement of the expansion joint has been measured. The short-term displacement trend in terms of temperature is calculated. With the WHS system, approximately 6% of the time has been spent for installation, and 94% of time for the measurement showing strong potential of the developed system for rapid displacement monitoring.

• Structural Engineering and Mechanics
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• 제15권3호
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• pp.285-297
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• 2003

Complementing recent advances made in the field of structural health monitoring and damage detection, the concept of a wireless sensing network with distributed computational power is proposed. The fundamental building block of the proposed sensing network is a wireless sensing unit capable of acquiring measurement data, interrogating the data and transmitting the data in real time. The computational core of a prototype wireless sensing unit can potentially be utilized for execution of embedded engineering analyses such as damage detection and system identification. To illustrate the computational capabilities of the proposed wireless sensing unit, the fast Fourier transform and auto-regressive time-series modeling are locally executed by the unit. Fast Fourier transforms and auto-regressive models are two important techniques that have been previously used for the identification of damage in structural systems. Their embedment illustrates the computational capabilities of the prototype wireless sensing unit and suggests strong potential for unit installation in automated structural health monitoring systems.

• Structural Engineering and Mechanics
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• 제30권2호
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• pp.191-209
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• 2008

A structural monitoring system based on cheap and wireless monitoring system is investigated in this paper. Due to low-cost and low power consumption, micro-electro-mechanical system (MEMS) is suitable for wireless monitoring and the use of MEMS and wireless communication can reduce system cost and simplify the installation for structural health monitoring. For system identification using wireless MEMS, a finite element (FE) model updating method through correlation with the initial analytical model of the structure to the measured one is used. The system identification using wireless MEMS is evaluated experimentally using a three storey frame model. Identification results are compared to ones using data measured from traditional accelerometers and results indicate that the system identification using wireless MEMS estimates system parameters with reasonable accuracy. Another smart sensor considered in this paper for structural health monitoring is Lead Zirconate Titanate (PZT) which is a type of piezoelectric material. PZT patches have been applied for the health monitoring of structures owing to their simultaneous sensing/actuating capability. In this paper, the system identification for building structures by using PZT patches functioning as sensor only is presented. The FE model updating method is applied with the experimental data obtained using PZT patches, and the results are compared to ones obtained using wireless MEMS system. Results indicate that sensing by PZT patches yields reliable system identification results even though limited information is available.