• Title/Summary/Keyword: Approximate sensor

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Lamb wave-based damage imaging method for damage detection of rectangular composite plates

  • Qiao, Pizhong;Fan, Wei
    • Structural Monitoring and Maintenance
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    • v.1 no.4
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    • pp.411-425
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    • 2014
  • A relatively low frequency Lamb wave-based damage identification method called damage imaging method for rectangular composite plate is presented. A damage index (DI) is generated from the delay matrix of the Lamb wave response signals, and it is used to indicate the location and approximate area of the damage. The viability of this method is demonstrated by analyzing the numerical and experimental Lamb wave response signals from rectangular composite plates. The technique only requires the response signals from the plate after damage, and it is capable of performing near real time damage identification. This study sheds some light on the application of Lamb wave-based damage detection algorithm for plate-type structures by using the relatively low frequency (e.g., in the neighborhood of 100 kHz, more suitable for the best capability of the existing fiber optic sensor interrogator system with the sampling frequency of 500 kHz) Lamb wave response and a reference-free damage detection technique.

A Study on 2-Dimensional Sound Source Tracking System IV - Mainly on Approximation of the Relative Bearing and Distance - (2차원적 음원추적에 관한 연구IV -음원위치의 근사적 결정법을 중심으로 -)

  • 문성배;전승환
    • Journal of the Korean Institute of Navigation
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    • v.25 no.4
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    • pp.371-379
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    • 2001
  • We have reported the new measurement system which was substituted digital filter for the analog filter in order to develop the optimal system that could find the time delay between each sensors with high accuracy. And also we have confirmed through the experiments that the accuracy of measurements were differentiated by the methods what kind of digital filter had been adopted. This paper suggests two algorithms which approximate the sound source's bearing and distance. One is that sound source's relative bearing can be approximately regarded as the gradient of hyperbolic asymptote, the other is that the source's range can be approximated under the condition of a long range source relative to the sensor's interval. And a series of experiments were carried out with the source's distance 22.42meters and the random bearing interval within the limits of $-90^{\circ}$~$+90^{\circ}$. As a result, we have recognized that the approximation methods could measure the bearing and distance with higher accuracy than the method using trigonometric relation could do.

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Kalman Filtering with Optimally Scheduled Measurements in Bandwidth Limited Communication Media

  • Pasand, Mohammad Mahdi Share;Montazeri, Mohsen
    • ETRI Journal
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    • v.39 no.1
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    • pp.13-20
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    • 2017
  • A method is proposed for scheduling sensor accesses to the shared network in a networked control system. The proposed method determines the access order in which the sensors are granted medium access through minimization of the state estimation error covariance. Solving the problem by evaluating the error covariance for each possible ordered set of sensors is not practical for large systems. Therefore, a convex optimization problem is proposed, which yields approximate yet acceptable results. A state estimator is designed for the augmented system resulting from the incorporation of the optimally chosen communication sequence in the plant dynamics. A car suspension system simulation is conducted to test the proposed method. The results show promising improvement in the state estimation performance by reducing the estimation error norm compared to round-robin scheduling.

Beam analysis of underwater conformal array by using cylindrical acoustic holography (원통면 음향 홀로그래피를 이용한 수중음향 곡면배열센서의 빔 해석)

  • Kwon, Hyu-Sang;Park, Seong-Chol;Seo, Hee-Seon;Shin, Gu-Kyun;Joh, Ghee-Young
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2009.04a
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    • pp.111-116
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    • 2009
  • As an experimental technique to analyze the far-field characteristics of underwater cylindrical array sensors, cylindrical acoustic holography is studied. Inside an laboratory water tank, far-field directivity patterns as well as near-field source images are reconstructed from the measured hologram by hydrophone array. Approximate equation for far-field directivity estimation is derived based on stationary phase method. The simulation and experiment show well usefulness of the proposed method in application of underwater array sensors.

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Structural Improvement of Extended Kalman Filter using Coordinate Transformation (좌표 변환을 이용한 확장 칼만 필터의 구조적 개선)

  • Yun, Kang-Sup;Kim, Jong-Hwa;Hwang, Chang-Sun;Lee, Man-Hyung
    • Proceedings of the KIEE Conference
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    • 1988.07a
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    • pp.905-908
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    • 1988
  • In recent, Kalman filter technique has been much used as one of technique for tracking of the moving target. But some problem are still remained to be resolved. For example, when Kalman filter technique is applied to nonlinear system, the technique is nonoptimal estimator. Therefore, extended Kalman filter is proposed to reduce modeling error for nonlinear system. In this study, an extended Kalman filter in Cartesian coordinates is described for moving target, when the radar sensor measures range, azimuth and elevation angle in polar coordinates. And an approximate gain computation algorithm is proposed. In this approach, Kalman gains are computed for three uncoupled filter and multiplied by a Jacobian transformation determined from the measured target position and orientation.

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Fault Detection and Isolation System for DC motor driven Centrifugal Pump-Pipe Systems: Parity Relation Approach (직류전동기 구동 원심펌프-파이프 계통의 고장검출진단시스템: 등가관계 접근법)

  • Park, Tae-Geon;Ryu, Ji-Su;Lee, Kee-Sang
    • Proceedings of the KIEE Conference
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    • 1998.07b
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    • pp.819-821
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    • 1998
  • This paper deals with a method or a residual generation for fault isolation in a centrifugal pump with a water circulation system, driven by a speed controlled dc motor. It is based on parity relations derived from the moving-average model of the system and is used to identify sensor faults and two possible brush and impeller faults, where the former is dealt with additive faults, while the latter characterized as discrepancies between the nominal and actual plant parameters of the system is modelled by multiplicative faults. We will represent the propagation of this uncertainty to the model matrices by the approximate handling of partial derivatives of polynomials. With multiplicative faults, the transformation matrix implemented in the residual generator are calculated on-line. The simulation studies demonstrate that small changes of the system can be detected and diagnosed by using the method.

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Compressed Sensing Based Low Power Data Transmission Systems in Mobile Sensor Networks (모바일 센서 네트워크에서 압축 센싱을 이용한 저전력 데이터 전송 시스템)

  • Hong, Jiyeon;Kwon, Jungmin;Kwon, Minhae;Park, Hyunggon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.41 no.11
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    • pp.1589-1597
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    • 2016
  • In this paper, we propose a system in a large-scale environment, such as desert and ocean, that can reduce the overall transmission power consumption in mobile sensor network. It is known that the transmission power consumption in wireless sensor network is proportional to the square of transmission distance. Therefore, if the locations of mobile sensors are far from the sink node, the power consumption required for data transmission increases, leading to shortened operating time of the sensors. Hence, in this paper, we propose a system that can reduce the power consumption by allowing to transmit data only if the transmission range of the sensors is within a predetermined distance. Moreover, the energy efficiency of the overall sensor network can even be improved by reducing the number of data transmissions at the sink node to gateway based on compressed sensing. The proposed system is actually implemented using Arduino and Raspberry Pi and it is confirmed that source data can be approximately decoded even when the gateway received encoded data fewer than the required number of data from the sink node. The performance of the proposed system is analyzed in theory.

A Mobility Support Scheme Achieving High Energy-Efficiency for Sink Groups in Wireless Sensor Networks (무선 센서 망에서 싱크 그룹을 위한 에너지 효율 향상 이동성 지원 방안)

  • Yim, Yongbin;Park, Hosung;Lee, Jeongcheol;Oh, Seungmin;Kim, Sang-Ha
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.38B no.1
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    • pp.63-71
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    • 2013
  • In order to support mobility for sink groups, it is important to get the current location of a mobile sink group and then to offer the location to a source. Typically, previous works calculate a region including all member sinks by flooding; then, it notifies this region information to a source. However, flooding and location updates are periodically performed regardless of the group movement so that it causes considerable control overhead. In this paper, we propose an energy-efficient scheme supporting mobile sink groups. The proposed scheme obtains a location of a group without flooding. It exploits the inherent property of mobile sink groups which could approximate entire group movement by only partial member sinks movement. Also, the scheme learns group location by back-propagation learning method through exploiting overhearing feature in wireless communication environment. Our simulation studies show that the proposed scheme significantly improves in terms of energy consumption compared to the previous work.

Thermo-optic Characteristics of Micro-structured Optical Fiber Infiltrated with Mixture Liquids

  • Wang, Ran;Wang, Yuye;Miao, Yinping;Lu, Ying;Luan, Nannan;Hao, Congjing;Duan, Liangcheng;Yuan, Cai;Yao, Jianquan
    • Journal of the Optical Society of Korea
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    • v.17 no.3
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    • pp.231-236
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    • 2013
  • We present both theoretically and experimentally the thermo-optic characteristics of micro-structured optical fiber (MOF) filled with mixed liquid. The performance of MOF depends on the efficient interaction between the fundamental mode of the transmitted light wave and the tunable thermo-optic materials in the cladding. The numerical simulation indicates that the confinement loss of MOF presents higher temperature dependence with higher air-filling ratios $d/{\Lambda}$, longer incident wavelength and fewer air holes in the cladding. For the 4cm liquid-filled grapefruit MOF, we demonstrate from experiments that different proportions of solutions lead to tunable temperature sensitive ranges. The insertion loss and the extinction ratio are 3~4 dB and approximate 20 dB, respectively. The proposed liquid-filling MOF will be developed as thermo-optic sensor, attenuator or optical switch with the advantages of simple structure, compact configuration and easy fabrication.

Load-Balancing Rendezvous Approach for Mobility-Enabled Adaptive Energy-Efficient Data Collection in WSNs

  • Zhang, Jian;Tang, Jian;Wang, Zhonghui;Wang, Feng;Yu, Gang
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.14 no.3
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    • pp.1204-1227
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    • 2020
  • The tradeoff between energy conservation and traffic balancing is a dilemma problem in Wireless Sensor Networks (WSNs). By analyzing the intrinsic relationship between cluster properties and long distance transmission energy consumption, we characterize three node sets of the cluster as a theoretical foundation to enhance high performance of WSNs, and propose optimal solutions by introducing rendezvous and Mobile Elements (MEs) to optimize energy consumption for prolonging the lifetime of WSNs. First, we exploit an approximate method based on the transmission distance from the different node to an ME to select suboptimal Rendezvous Point (RP) on the trajectory for ME to collect data. Then, we define data transmission routing sequence and model rendezvous planning for the cluster. In order to achieve optimization of energy consumption, we specifically apply the economic theory called Diminishing Marginal Utility Rule (DMUR) and create the utility function with regard to energy to develop an adaptive energy consumption optimization framework to achieve energy efficiency for data collection. At last, Rendezvous Transmission Algorithm (RTA) is proposed to better tradeoff between energy conservation and traffic balancing. Furthermore, via collaborations among multiple MEs, we design Two-Orbit Back-Propagation Algorithm (TOBPA) which concurrently handles load imbalance phenomenon to improve the efficiency of data collection. The simulation results show that our solutions can improve energy efficiency of the whole network and reduce the energy consumption of sensor nodes, which in turn prolong the lifetime of WSNs.