• Smart Structures and Systems
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• 제15권3호
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• pp.769-785
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• 2015

Although timber structures have been extensively used in underground temporary supporting system, their actual performance is poorly understood, resulting in potentially conservative and over-engineered design. In this paper, a novel wireless sensor technology, SmartPlank, is introduced to monitor the field performance of timber structures during underground construction. It consists of a wooden beam equipped with a streamlined wireless sensor node, two thin foil strain gauges and two temperature sensors, which enables to measure the strain and temperature at two sides of the beam, and to transmit this information in real-time over an IPv6 (6LowPan) multi-hop wireless mesh network and Internet. Four SmartPlanks were deployed at the London Underground's Tottenham Court Road (TCR) station redevelopment site during the Stair 14 excavation, together with seven relay nodes and a gateway. The monitoring started from August 2013, and will last for one and a half years until the Central Line possession in 2015. This paper reports both the short-term and long-term performances of the monitored timber structures. The grouting effect on the short-term performance of timber structures is highlighted; the grout injection process creates a large downward pressure on the top surface of the SmartPlank. The short and long term earth pressures applied to the monitored structures are estimated from the measured strains, and the estimated values are compared to the design loads.

• Smart Structures and Systems
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• 제8권5호
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• pp.433-447
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• 2011

The present paper addresses the nonlinear response of a FG square plate with two smart layers as a sensor and actuator under pressure. Geometric nonlinearity was considered in the strain-displacement relation based on the Von-Karman assumption. All the mechanical and electrical properties except Poisson's ratio can vary continuously along the thickness of the plate based on a power function. Electric potential was assumed as a quadratic function along the thickness direction and trigonometric function along the planar coordinate. By evaluating the mechanical and electrical energy, the total energy equation can be minimized with respect to amplitude of displacements and electrical potential. The effect of non homogenous index was investigated on the responses of the system. Obtained results indicate that with increasing the non homogenous index, the displacements and electric potential tend to an asymptotic value. Displacements and electric potential can be presented in terms of planar coordinate system. A linear analysis was employed and then the achieved results are compared with those results that are obtained using the nonlinear analysis. The effect of the geometric nonlinearity is investigated by using the comparison between the linear and nonlinear results. Displacement-load and potential-load curves verified the necessity of a nonlinear analysis rather than a linear analysis. Improvement of the previous results (by the linear analysis) through employing a nonlinear analysis can be presented as novelty of this study.

• Smart Structures and Systems
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• 제9권2호
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• pp.127-143
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• 2012

The present paper deals with the nonlinear analysis of the functionally graded piezoelectric (FGP) annular plate with two smart layers as sensor and actuator. The normal pressure is applied on the plate. The geometric nonlinearity is considered in the strain-displacement equations based on Von-Karman assumption. The problem is symmetric due to symmetric loading, boundary conditions and material properties. The radial and transverse displacements are supposed as two dominant components of displacement. The constitutive equations are derived for two sections of the plate, individually. Total energy of the system is evaluated for elastic solid and piezoelectric sections in terms of two components of displacement and electric potential. The response of the system can be obtained using minimization of the energy of system with respect to amplitude of displacements and electric potential. The distribution of all material properties is considered as power function along the thickness direction. Displacement-load and electric potential-load curves verify the nonlinearity nature of the problem. The response of the linear analysis is investigated and compared with those results obtained using the nonlinear analysis. This comparison justifies the necessity of a nonlinear analysis. The distribution of the displacements and electric potential in terms of non homogenous index indicates that these curves converge for small value of piezoelectric thickness with respect to elastic solid thickness.

• 센서학회지
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• 제6권3호
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• pp.172-179
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• 1997

간섭형 광섬유 센서의 경우 소자의 구성만 적절히 바꾸어 다른 종류의 측정에도 사용될 수 있다는 점에 착안하여 여러 종류의 센서를 동시에 신호처리할 수 있는 원격 다중화 광섬유 센서 시스템을 구현하였다. 구현된 센서 시스템의 신호처리는 간단한 광학 구성으로 원격 다중화 측정이 가능하도록 광섬유 Fabry-Perot 간섭형 센서배열을 가정하여 피측정량의 변화에 의한 간섭 무늬의 수만 카운트하는 디지털 신호처리로 구성되었다. 광섬유의 광학 효과에 대한 데이터를 종합함으로써 센서 시스템에 부착할 센서를 구현하기 위해 적합한 광학효과를 선택하는 기준을 제시하였으며, 한 예로서 반경 4.3 cm의 원형 다이아프램 중앙에 광섬유 Fabry-Perot 간섭계를 부착하여 광섬유의 스트레인 광학 효과를 이용하게 구성한 압력센서 1개를 센서 시스템에 연결하여 간섭형 광섬유 압력 센서 시스템을 구성하였다. 압력센서의 동작을 수조실험에서 확인함으로써 압력의 원격 측정이 가능함을 보였으며, 수조 실험의 길과 2 m의 측정범위에서 오차는 ${\pm}3.6\;cm$이내인 것으로 나타났다.

• 대한전자공학회논문지TC
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• 제43권1호
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• pp.33-40
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• 2006

Single phase unidirectional transducer (SPUDT), 리플렉터, 웨이퍼 본딩 패키지로 구성된 표면탄성파 (surface acoustic wave, SAW) 기반 압력센서가 개발되어 졌다. Coupling of Mode (COM) 모델링에 의한 소자의 시뮬레이션 및 최적 설계 변수가 얻어졌다. Finite Element Methods (FEM)를 통해 주어진 압력에 따른 다이어프램 벤딩, 스트레인/스트레스 변화 및 SAW 속도변위가 미리 예측되어졌다. 유출된 최적 설계 변수를 이용 440 MHz SAW 기반 압력센서가 41o YX LiNbO3 기판 위에서 제작되어졌다. 고 S/N 비, 임펄스 리프렉션 피크, 작은 에러 피크가 관찰되어졌다. 측정된 S11 결과는 COM 모델링 및 FEM 시뮬레이션 결과와 일치함을 보였다.

• 한국구조물진단유지관리공학회 논문집
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• 제20권4호
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• pp.35-43
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• 2016

최근 지속적으로 증가하는 생활폐기물의 배출과 처리가 사회적인 문제로 대두됨에 따라 새로운 폐기물의 수거 및 운반방식으로 쓰레기 이송관로시스템이 최근 부각되고 있다. 이러한 이송관로시스템은 긴 연장을 갖기 때문에 이송관로에 문제가 발생할 경우 즉각적으로 해당 위치를 파악하여 조치할 수 있는 적절한 장기계측시스템을 적용하는 것이 필요하다. 본 연구에서는 FBG 광섬유 변형률 센서를 이용한 계측시스템의 적용성을 검토하고, 이를 이용한 최적의 계측시스템을 도출할 수 있는 자료를 확보하기 위한 실험적 연구로서, 이송관로에 발생할 수 있는 대표적인 손상유형으로 압력누출, 관로변형 및 관로폐색의 3가지 현상을 실제규모의 모형 이송관로실험체에 모사한 후 관로에 설치된 FBG센서로부터 응답을 측정하였다. 실험결과를 바탕으로 실험변수로 적용한 각각의 손상유형에 따른 효과적인 센서설치 방법과 배치방법을 도출하였다. 특히 관로변형실험 결과는 변형발생지점으로부터의 센서와의 거리에 따른 응답 상관관계를 통해 센서배치간격을 산출하여 FBG센서를 이용한 계측설계를 수행하였다.

• 한국산학기술학회논문지
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• 제18권4호
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• pp.578-583
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• 2017

본 논문은 최근에 모바일 기기에 적용되고 있는 차세대 터치 기술로서 압력터치 센서를 이용한 3D 터치패드 기술에 관한 것이다. 3D터치 기술은 터치 위치 및 터치 압력을 동시에 검출할 수 있고 멀티터치 기능이 있어야 한다. 본 논문의 목적은 스트레인 게이지를 이용하여 압력터치 센서를 제작하고 2점을 동시에 터치 가능한 압력터치 패드 제작이다. 하드웨어 부분은 터치 인식 센서에 금속 박막형 스트레인 게이지를 이용하였고 각 스트레인 게이지 센서마다 휘스톤 브리지 회로로 미세한 터치 신호를 검출하였다. 또한, 터치 신호 증폭기를 사용하여 터치 신호를 증폭하고 마이크로프로세서를 통해 디지털 데이터로 변환하여 화면에 디스플레이하는 터치 인식 시스템을 만들었다. 소프트웨어 부분은 2점 동시터치가 가능하고 터치 압력에 따라 구별 가능한 터치 인식 알고리즘을 C언어로 제작하였다. 터치 강도와 터치 위치가 다른 두 개의 터치 신호를 동시에 검출하여 화면에 나타내는 실험을 성공적으로 수행하였다. 본 연구를 통해 스트레인 게이지를 이용한 터치 인식 방법으로 3D 터치패드의 응용 가능성을 확인하였다.

• 로봇학회논문지
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• 제19권2호
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• pp.221-228
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• 2024

As the importance of cardiovascular health is highlighted, research on its correlation with blood pressure, the most important indicator, is being actively conducted. Therefore, extensive clinical data is essential, but the measurement of the central arterial blood pressure waveform must be performed invasively within the artery, so the quantity and quality are limited. This study suggested a mock circulatory robot and artificial aorta to reproduce the blood pressure waveform generated by the overlap of forward and reflected waves. The artificial aorta was fabricated with biomimetic silicone to mimic the physiological structure and vascular stiffness of the human. A pressurizing chamber was implemented to prevent distortion of the blood pressure waveform due to the strain-softening of biomimetic silicone. The reproduced central arterial blood pressure waveforms have similar magnitude, shape, and propagation characteristics to humans. In addition, changes in blood pressure waveform due to aging were also reproduced by replacing an artificial aorta with various stiffness. It can be expanded to construct a biosignal database and health sensor testing platform, a core technology for cardiovascular health-related research.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 추계학술대회 논문집 학회본부
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• pp.296-298
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• 1997

The performance of thin film pressure sensors with polyimide and silicon oxide as a insulating layer between the stainless steel diaphragm and the Cu-Ni strain gauges is presented. The polyimide was spun on the stainless steel diaphragm and cured in an oven. The silicon oxide was deposited by rf sputtering. The thin film pressure sensor with silicon oxide as a insulating layer showed a better nonlinearity and a lower hysteresis.

• 센서학회지
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• 제20권5호
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• pp.343-350
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• 2011

The compliance and stiffness of artery are closely related with disease of arteries. Pulse wave velocity(PWV) in the blood vessel is a basic and common parameter in the hemodynamics of blood pressure and blood flow wave traveling in arteries because the PWV is affected directly by the conditions of blood vessels. However, there is no standardized method to measure the PWV and it is difficult to measure. The conventional PWV measurement has being done by manual calculation of the pulse wave transmission time between coronary arterial proximal and distal points on a strip chart on which the pulse wave and ECG signal are recorded. In this study, a pressure sensor consisting of strain gauges is used to measure the blood pressure of arteries in invasive method and regular ECG electrodes are used to record the ECG signal. The R-peak point of ECG is extracted by using a reference level and time windowing technique and the ascending starting point of blood pressure is determined by using differentiation of the blood pressure signal and time windowing technique. The algorithm proposed in this study, which can measure PWV automatically, shows robust and good results in the extraction of feature points and calculation of PWV.