• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 추계학술대회
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• pp.131-136
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• 2003

Five expensive sensors are necessary to control a magnetic bearing system. The sensor price rate of magnetic bearing system is high. So it is necessary that cheap and good sensor is developed. The optical fiber displacement sensor is adaptive to satisfy this condition. We can design magnetically suspended spindle based on static characteristic of optical fiber displacement sensor developed. The controller can be designed by decoupled feedback PD. Therefore, it is simpler than any other controller comparatively.

• 한국소음진동공학회논문집
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• 제19권11호
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• pp.1126-1132
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• 2009

Bridge structures are designed to support ordinary loadings such as vehicles, wind, temperature and current as well as unexpected loadings like earthquakes and storm. Especially, the displacement of Flexible bridges like an suspension bridge under ordinary loading conditions is necessary to be monitored. In case of long span bridges, there are some difficulties in monitoring the displacement of center of the main span using traditional laser displacement sensors. In this study, the static and dynamic displacement responses due to vehicle loadings were measured by DGPS(differential global positioning system) technique. The displacement response data were compared with data obtained from traditional laser displacement sensors so that the static and dynamic behavior of the bridge under vehicle loadings was examined and the applicability of the displacement response measurement using DGPS technique was verified. The static and dynamic loading test for an self-anchored suspension bridge, So-rok Bridge, was performed using vehicles. The displacement response from DGPS technique and that from laser displacement sensors of the bridge monitoring system were compared. The amplitude of white noise from DGPS based measurement was about 7 mm and that of laser displacement sensor based measurement was about 3 mm. On the other hand, dynamic behavior of the center of main span from DGPS based measurement showed better agreement with influence line of the bridge than that from laser displacement sensors. In addition, there were some irregular and discontinuous variation of data due to the instability of GPS receivers or frequent appearance of GPS satellites. Post-processing via the reference station close to an observation post provided by NGII(National Geographic Information Institute) will be a counter-plan for these defects.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2011년도 추계 학술논문 발표대회
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• pp.157-158
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• 2011

The monitoring to crack damages is studied using the radio frequency system and static displacement sensors. If load is received on the center of the flexible specimen, bonded sensors will be destroyed, and these are become to send signals of damages at the radio frequency system connected with sensors. This study is fundamental research of the monitoring damage system for diagnostic concrete elements using the radio frequency system and static displacement sensors.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2002년도 추계학술대회 논문집(II)
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• pp.1065-1073
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• 2002

A new damage identification technique using static displacement data is developed to assess the structural integrity of bridge structures. In the conventional damage assessment techniques using dynamic response, it is usually difficult to obtain a significant natural frequencies variation from the measured data because the natural frequencies variation is intrinsically not sensitive to the damage of a bridge. In this proposed identification method, the stiffness reduction of the bridges can be estimated using the static displacement data measured periodically and a specific loading test is not required. The static displacement data due to the dead load of the bridge structure can be measured by devices such as a laser displacement sensor. In this study, structural damage is represented by the reduction in the elastic modulus of the element. The damage factor of the element is introduced to estimate the stiffness reduction of the bridge under consideration. Finally, the proposed algorithm is verified using various numerical simulation and compared with other damage identification method. Also, the effect of noise and number of damaged elements on the identification are investigated. The results show that the proposed algorithm is efficient for damage identification of the bridges.

• Smart Structures and Systems
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• 제16권3호
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• pp.521-535
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• 2015

Vibration-based monitoring is one approach used to perform structural condition assessment. By measuring structural response, such as displacement, dynamic characteristics of a structure may be estimated. Often, the primary dynamic responses in civil structures are below 5 Hz, making accurate low frequency measurement critical for successful dynamic characterization. In addition, static deflection measurements are useful for structural capacity and load rating assessments. This paper presents a DC coupled continuous wave radar to accurately detect both dynamic and static displacement. This low-cost radar sensor provides displacement measurements within a compact, wireless unit appropriate for a range of structural monitoring applications. The hardware components and operating mechanism of the radar are introduced and a series of laboratory experiments are presented to assess the performance characteristics of the radar. The laboratory and field experiments investigate the effect of factors such as target distance, motion amplitude, and motion frequency on the radar's measurement accuracy. The results demonstrate that the radar is capable of both static and dynamic displacement measurements with sub-millimeter accuracy, making it a promising technology for structural health monitoring.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2011년도 춘계학술대회 논문집
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• pp.133-134
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• 2011

• 대한기계학회논문집
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• 제17권9호
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• pp.2381-2389
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• 1993

In this paper the design and test results of a dynamic flow rate sensor was reported. This sensor comprises an 2-way cartridge valve as standard hydraulic component and a displacement sensor. Its working principle bases on the linear relationship between the flow rate and the piston displacement of 2-way cartridge valves under constant pressure drop. This principle is well known, however it is not easy to develop a flow rate sensor with the measurement range of 300 1/min, pressure loss of less than 8 bar at 300 1/min, maximum linearity error of less than $\pm$1% and the maximum rising time of 10 ms. This paper describes the design procedure of the flow rate sensor, the improvement procedure of static performance and test method and results of dynamic performance.

• 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.

• 드라이브 ㆍ 컨트롤
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• 제9권4호
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• pp.32-41
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• 2012

Most diagnosis methods for servo valves requires installing spool displacement sensor or flow sensor as well as pressure sensor. The measurement of flow is hard to implement and many kinds of servovalves or proportional direction valves do not have a built-in spool displacement sensor. In this study, static performances of servovalve or proportional-direction-valve are studied theoretically and a diagnosis technique, which uses only load pressure and input current signal, is assessed. An experimental setup was made based upon a personal computer and the LabVIEW graphical language. A series of diagnosis tests were performed and the analysis results showed it possible to measure the pressure gain, hysteresis and null bias in a relatively simple methodology.

• 한국강구조학회 논문집
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• 제14권5호통권60호
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• pp.641-646
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• 2002

본 논문에서는 정적 처짐데이터를 이용한 교량의 강성추정에 관한 기법을 개발하였다. 제안된 기법은 주기적으로 교량의 자중에 의한 처짐을 계측하여 이들 처짐값의 변화량을 이용하여 손상의 진행정도를 규명하는 기법으로써 재하시험이 필요하지 않으며, 최근 활발히 진행되고 있는 계측모니터링 시스템으로부터 획득된 계측데이터를 정량적으로 분석하는 기법으로 활용이 가능하리라 판단된다. 손상평가를 위한 정식화과정에서 부재의 손상은 강성의 저감으로 표현하였으며, 부재의 질량과 초기강성은 실측 또는 도면을 통하여 획득이 가능하다고 가정하였다. 제안된 기법의 타당성 검증을 위하여 수치모형을 통한 손상도 추정결과를 제시하였으며, 기존의 손상도 추정기법 중 비교적 손상에 대한 민감도가 높은 모드형상을 이용한 기법과 손상도 추정결과를 비교하였다. 또한, 손상추정결과를 정확도를 감소시키는 노이즈의 영향을 분석하기 위하여 정적응답자료에 백색잡음을 추가하여 손상도를 추정하였으며, 손상부재의 수가 손상추정 결과에 미치는 영향을 검토하였다.