• Title/Summary/Keyword: impedance sensing

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Remote Impedance-based Loose Bolt Inspection Using a Radio-Frequency Active Sensing Node

  • Park, Seung-Hee;Yun, Chung-Bang;Inman, Daniel J.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.27 no.3
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    • pp.217-223
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    • 2007
  • This paper introduces an active sensing node using radio-frequency (RF) telemetry. This device has brought the traditional impedance-based structural health monitoring (SHM) technique to a new paradigm. The RF active sensing node consists of a miniaturized impedance measuring device (AD5933), a microcontroller (ATmega128L), and a radio frequency (RF) transmitter (XBee). A macro-fiber composite (MFC) patch interrogates a host structure by using a self-sensing technique of the miniaturized impedance measuring device. All the process including structural interrogation, data acquisition, signal processing, and damage diagnostic is being performed at the sensor location by the microcontroller. The RF transmitter is used to communicate the current status of the host structure. The feasibility of the proposed SHM strategy is verified through an experimental study inspecting loose bolts in a bolt-jointed aluminum structure.

A wireless impedance analyzer for automated tomographic mapping of a nanoengineered sensing skin

  • Pyo, Sukhoon;Loh, Kenneth J.;Hou, Tsung-Chin;Jarva, Erik;Lynch, Jerome P.
    • Smart Structures and Systems
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    • v.8 no.1
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    • pp.139-155
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    • 2011
  • Polymeric thin-film assemblies whose bulk electrical conductivity and mechanical performance have been enhanced by single-walled carbon nanotubes are proposed for measuring strain and corrosion activity in metallic structural systems. Similar to the dermatological system found in animals, the proposed self-sensing thin-film assembly supports spatial strain and pH sensing via localized changes in electrical conductivity. Specifically, electrical impedance tomography (EIT) is used to create detailed mappings of film conductivity over its complete surface area using electrical measurements taken at the film boundary. While EIT is a powerful means of mapping the sensing skin's spatial response, it requires a data acquisition system capable of taking electrical impedance measurements on a large number of electrodes. A low-cost wireless impedance analyzer is proposed to fully automate EIT data acquisition. The key attribute of the device is a flexible sinusoidal waveform generator capable of generating regulated current signals with frequencies from near-DC to 20 MHz. Furthermore, a multiplexed sensing interface offers 32 addressable channels from which voltage measurements can be made. A wireless interface is included to eliminate the cumbersome wiring often required for data acquisition in a structure. The functionality of the wireless impedance analyzer is illustrated on an experimental setup with the system used for automated acquisition of electrical impedance measurements taken on the boundary of a bio-inspired sensing skin recently proposed for structural health monitoring.

Advances and challenges in impedance-based structural health monitoring

  • Huynh, Thanh-Canh;Dang, Ngoc-Loi;Kim, Jeong-Tae
    • Structural Monitoring and Maintenance
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    • v.4 no.4
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    • pp.301-329
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    • 2017
  • Impedance-based damage detection method has been known as an innovative tool with various successful implementations for structural health monitoring of civil structures. To monitor the local critical area of a structure, the impedance-based method utilizes the high-frequency impedance responses sensed by piezoelectric sensors as the local dynamic features. In this paper, current advances and future challenges of the impedance-based structural health monitoring are presented. Firstly, theoretical background of the impedance-based method is outlined. Next, an overview is given to recent advances in the wireless impedance sensor nodes, the interfacial impedance sensing devices, and the temperature-effect compensation algorithms. Various research works on these topics are reviewed to share up-to-date information on research activities and implementations of the impedance-based technique. Finally, future research challenges of the technique are discussed including the applicability of wireless sensing technology, the predetermination of effective frequency bands, the sensing region of impedance responses, the robust compensation of noise and temperature effects, the quantification of damage severity, and long-term durability of sensors.

Measurement of Setting Times of Steel Fiber Reinforced Mortar using Electric-mechanical Impedance Sensing Technique (전기역학적 임피던스 기법을 이용한 강섬유 보강 모르타르의 응결시간 평가)

  • Lee, Jun Choel;Kim, Wha Jung
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2016.05a
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    • pp.183-184
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    • 2016
  • This study investigated the evolution of electro-mechanical impedance (EMI) of piezoelectricity (PZT) sensor embedded in hydrating steel fiber reinforced mortar to determine the setting times of that. Penetration resistance test was also conducted in order to justify the valid of EMI sensing technique. As a result, the setting times of steel fiber reinforced mortar can be effectively monitored through the EMI sensing technique using PZT sensor.

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A New Simple Sensorless Control Method for Switched Reluctance Motor Drives

  • Xin Kai;Zhan Qionghua;Luo Jianwu
    • Journal of Electrical Engineering and Technology
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    • v.1 no.1
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    • pp.52-57
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    • 2006
  • In this paper, a new 'impedance sensing' method is described. This method overcomes the shortcomings of the impedance sensing method. According to the new method, sensing voltage pulse is applied to the idle phase in the minimum inductance region and the beginning of the increasing inductance region to detect rotor position. The negative torque produced by the sensing voltage pulse can be neglected in the minimum inductance region and the efficiency of SRM is improved. In the minimum inductance region the back electromotive force (EMF) can be neglected. And in the increasing inductance region the EMF opposes the rise of current in the phase, so the position estimation scheme is reliable. Therefore the new 'impedance sensing' method is sufficiently precise even under the high back EMF effect. The adjustment of turn-on angle and turn-off angle is also easy to be realized. The technique is very useful in applications where cost or size is primary concerns, such as electric bicycle drives. Experimental results are presented to verify the proposed method.

Autonomous hardware development for impedance-based structural health monitoring

  • Grisso, Benjamin L.;Inman, Daniel J.
    • Smart Structures and Systems
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    • v.4 no.3
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    • pp.305-318
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    • 2008
  • The development of a digital signal processor based prototype is described in relation to continuing efforts for realizing a fully self-contained active sensor system utilizing impedance-based structural health monitoring. The impedance method utilizes a piezoelectric material bonded to the structure under observation to act as both an actuator and sensor. By monitoring the electrical impedance of the piezoelectric material, insights into the health of the structured can be inferred. The active sensing system detailed in this paper interrogates a structure utilizing a self-sensing actuator and a low cost impedance method. Here, all the data processing, storage, and analysis is performed at the sensor location. A wireless transmitter is used to communicate the current status of the structure. With this new low cost, field deployable impedance analyzer, reliance on traditional expensive, bulky, and power consuming impedance analyzers is no longer necessary. A complete power analysis of the prototype is performed to determine the validity of power harvesting being utilized for self-containment of the hardware. Experimental validation of the prototype on a representative structure is also performed and compared to traditional methods of damage detection.

Crack Initiation and Temperature Variation Effects on Self-sensing Impedance Responses of FRCCs (FRCCs의 자가센싱 임피던스 응답에 미치는 균열 발생 및 온도 변화 영향성)

  • Kang, Myung-Soo;Kang, Man-Sung;Lee, Han Ju;Yim, Hong Jae;An, Yun-Kyu
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.22 no.3
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    • pp.69-74
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    • 2018
  • Fiber-Reinforced Cementitious Composites (FRCCs) have electrical conductivity by inserting reinforced conductive fibers into a cementitious matrix. Such characteristic allows us to utilize FRCCs for crack monitoring of a structure by measuring electrical responses without sensor installation. However, the electrical responses are often sensitively altered by temperature variation as well as crack initiation. The temperature variation may disturb crack detection on the measured electrical responses. Moreover, as sensing probes for measuring electrical reponses increase, undesired contact noises are often augmented. In this paper, a self-sensing impedance circuit is specially designed for reducing the number of sensing probes. The crack initiation and temperature variation effects on the self-sensing impedance responses of FRCCs are experimentally investigated using the self-sensing impedance circuit. The experiment results reveal that the electrical impedance response are more sensitively changed due to temperature variation than crack initiation.

Ethanol Gas Sensing Characteristics of Conducting Polymer Sensor Using Impedance (Impedance를 이용한 전도성고분자 센서의 에탄올 가스 감응특성)

  • Lee, Kyung-Mun;Yu, Joon-Boo;Jun, Hee-Kwon;Lee, Byung-Soo;Lee, Duk-Dong;Huh, Jeung-Soo
    • Korean Journal of Materials Research
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    • v.13 no.3
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    • pp.155-159
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    • 2003
  • The polypyrrole and polyaniline thin film sensors which were made by chemical polymerization were employed to detect ethanol gas. With a single sensor element we can obtain characteristic patterns of behaviour across a very wide frequency range when measuring either resistance or capacitance. Impedance spectroscopy was employed to study the gas sensing behavior of both capacitance and resistance based sensors with conducting polymer as the active sensing element.

Assement of setting times of cement mortar with different ratio of sand using Electro-mechanical impedance sensing technique (EMI 센싱 기법을 이용한 잔골재 혼합비에 따른 모르타르의 응결특성)

  • Lee, Jun-Cheol
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2022.04a
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    • pp.51-52
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    • 2022
  • The electro-mechanical impedance(EMI) behavior of piezoelectric sensor embedded in cement mortar was investigated to assess the setting times. EMI signal was continuously measured for 12 hours by the PZT sensor embedded in cement mortar with different ratio of sand. As a result, the setting times by the penetration resistance test were accelerated as the sand ratio increased. However, the setting times by EMI sensing technique were delayed as the sand ratio increased.

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Electrical impedance-based crack detection of SFRC under varying environmental conditions

  • Kang, Man-Sung;An, Yun-Kyu;Kim, Dong-Joo
    • Smart Structures and Systems
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    • v.22 no.1
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    • pp.1-11
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    • 2018
  • This study presents early crack detection of steel fiber-reinforced concrete (SFRC) under varying temperature and humidity conditions using an instantaneous electrical impedance acquisition system. SFRC has the self-sensing capability of electrical impedance without sensor installation thanks to the conductivity of embedded steel fibers, making it possible to effectively monitor cracks initiated in SFRC. However, the electrical impedance is often sensitively changed by environmental effects such as temperature and humidity variations. Thus, the extraction of only crack-induced feature from the measured impedance responses is a crucial issue for the purpose of structural health monitoring. In this study, the instantaneous electrical impedance acquisition system incorporated with SFRC is developed. Then, temperature, humidity and crack initiation effects on the impedance responses are experimentally investigated. Based on the impedance signal pattern observation, it is turned out that the temperature effect is more predominant than the crack initiation and humidity effects. Various crack steps are generated through bending tests, and the corresponding impedance damage indices are extracted by compensating the dominant temperature effect. The test results reveal that propagated cracks as well as early cracks are successfully detected under temperature and humidity variations.