42 research outputs found

    Two Solutions of Soil Moisture Sensing with RFID for Landslide Monitoring

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    Two solutions for UHF RFID tags for soil moisture sensing were designed and are described in this paper. In the first, two conventional tags (standard transponders) are employed: one, placed close to the soil surface, is the sensor tag, while the other, separated from the soil, is the reference for system calibration. By transmission power ramps, the tag’s turn-on power levels are measured and correlated with soil condition (dry or wet). In the second solution, the SL900A chip, which supports up to two external sensors and an internal temperature sensor, is used. An interdigital capacitive sensor was connected to the transponder chip and used for soil moisture measurement. In a novel design for an UHF RFID tag the sensor is placed below the soil surface, while the transponder and antenna are above the soil to improve communication. Both solutions are evaluated practically and results show the presence of water in soil can be remotely detected allowing for their application in landslide monitoring

    Passive low frequency RFID for non-destructive evaluation and monitoring

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    Ph. D ThesisDespite of immense research over the years, defect monitoring in harsh environmental conditions still presents notable challenges for Non-Destructive Testing and Evaluation (NDT&E) and Structural Health Monitoring (SHM). One of the substantial challenges is the inaccessibility to the metal surface due to the large stand-off distance caused by the insulation layer. The hidden nature of corrosion and defect under thick insulation in harsh environmental conditions may result in it being not noticed and ultimately leading to failures. Generally electromagnetic NDT&E techniques which are used in pipeline industries require the removal of the insulation layer or high powered expensive equipment. Along with these, other limitations in the existing techniques create opportunities for novel systems to solve the challenges caused by Corrosion under Insulation (CUI). Extending from Pulsed Eddy Current (PEC), this research proposes the development and use of passive Low Frequency (LF) RFID hardware system for the detection and monitoring of corrosion and cracks on both ferrous and non-ferrous materials at varying high temperature conditions. The passive, low cost essence of RFID makes it an enchanting technique for long term condition monitoring. The contribution of the research work can be summarised as follows: (1) implementation of novel LF RFID sensor systems and the rig platform, experimental studies validating the detection capabilities of corrosion progression samples using transient feature analysis with respect to permeability and electrical conductivity changes along with enhanced sensitivity demonstration using ferrite sheet attached to the tag; (2) defect detection using swept frequency method to study the multiple frequency behaviour and further temperature suppression using feature fusion technique; (3) inhomogeneity study on ferrous materials at varying temperature and demonstration of the potential of the RFID system; (4) use of RFID tag with ceramic filled Poly-tetra-fluoro-ethyulene (PTFE) substrate for larger applicability of the sensing system in the industry; (5) lift-off independent defect monitoring using passive sweep frequency RFID sensors and feature extraction and fusion for robustness improvement. This research concludes that passive LF RFID system can be used to detect corrosion and crack on both ferrous and non-ferrous materials and then the system can be used to compensate for temperature variation making it useful for a wider range of applications. However, significant challenges such as permanent deployment of the tags for long term monitoring at higher temperatures and much higher standoff distance, still require improvement for real-world applicability.Engineering and Physical Sciences Research Council (EPSRC) CASE, National Nuclear Laboratory (NNL)

    Chipless RFID sensor systems for structural health monitoring

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    Ph. D. ThesisDefects in metallic structures such as crack and corrosion are major sources of catastrophic failures, and thus monitoring them is a crucial issue. As periodic inspection using the nondestructive testing and evaluation (NDT&E) techniques is slow, costly, limited in range, and cumbersome, novel methods for in-situ structural health monitoring (SHM) are required. Chipless radio frequency identification (RFID) is an emerging and attractive technology to implement the internet of things (IoT) based SHM. Chipless RFID sensors are not only wireless, passive, and low-cost as the chipped RFID counterpart, but also printable, durable, and allow for multi-parameter sensing. This thesis proposes the design and development of chipless RFID sensor systems for SHM, particularly for defect detection and characterization in metallic structures. Through simulation studies and experimental validations, novel metal-mountable chipless RFID sensors are demonstrated with different reader configurations and methods for feature extraction, selection, and fusion. The first contribution of this thesis is the design of a chipless RFID sensor for crack detection and characterization based on the circular microstrip patch antenna (CMPA). The sensor provides a 4-bit ID and a capability of indicating crack width and orientation simultaneously using the resonance frequency shift. The second contribution is a chipless RFID sensor designed based on the frequency selective surface (FSS) and feature fusion for corrosion characterization. The FSS-based sensor generates multiple resonance frequency features that can reveal corrosion progression, while feature fusion is applied to enhance the sensitivity and reliability of the sensor. The third contribution deals with robust detection and characterization of crack and corrosion in a realistic environment using a portable reader. A multi-resonance chipless RFID sensor is proposed along with the implementation of a portable reader using an ultra-wideband (UWB) radar module. Feature extraction and selection using principal component analysis (PCA) is employed for multi-parameter evaluation. Overall, chipless RFID sensors are small, low-profile, and can be used to quantify and characterize surface crack and corrosion undercoating. Furthermore, the multi-resonance characteristics of chipless RFID sensors are useful for integrating ID encoding and sensing functionalities, enhancing the sensor performance, as well as for performing multi-parameter analysis of defects. The demonstrated system using a portable reader shows the capability of defects characterization from a 15-cm distance. Hence, chipless RFID sensor systems have great potential to be an alternative sensing method for in-situ SHM.Indonesia Endowment Fund for Education (LPDP

    Signals in the Soil: An Introduction to Wireless Underground Communications

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    In this chapter, wireless underground (UG) communications are introduced. A detailed overview of WUC is given. A comprehensive review of research challenges in WUC is presented. The evolution of underground wireless is also discussed. Moreover, different component of UG communications is wireless. The WUC system architecture is explained with a detailed discussion of the anatomy of an underground mote. The examples of UG wireless communication systems are explored. Furthermore, the differences of UG wireless and over-the-air wireless are debated. Different types of wireless underground channel (e.g., In-Soil, Soil-to-Air, and Air-to-Soil) are reported as well

    A Survey on Subsurface Signal Propagation

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    Wireless Underground Communication (WUC) is an emerging field that is being developed continuously. It provides secure mechanism of deploying nodes underground which shields them from any outside temperament or harsh weather conditions. This paper works towards introducing WUC and give a detail overview of WUC. It discusses system architecture of WUC along with the anatomy of the underground sensor motes deployed in WUC systems. It also compares Over-the-Air and Underground and highlights the major differences between the both type of channels. Since, UG communication is an evolving field, this paper also presents the evolution of the field along with the components and example UG wireless communication systems. Finally, the current research challenges of the system are presented for further improvement of the WUCs

    Suivi immergé de durabilité du béton par nano capteurs sans fil

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    Making the construction industry more sustainable requires the extension of the life of structures, achievable through the anticipation of structural deficiencies. Structural deficiencies often originate at the core of concrete structures from micro scale defects, whose detection is the key to predict structural ageing. The in-situ, real-time detection of such defects remains a major scientific and technological challenge and no cost effective technique is currently available. In this thesis, we present the design, fabrication and validation of the first wireless nano sensor node for embedded monitoring of concrete structures.The device is composed of 3 main parts: a sensing element, a conditioning circuit and an antenna. The first is a highly reproducible, hysteresis-free, flexible sensor fabricated by inkjet printing carbon nanotubes (CNTs) on polymer. We achieved the batch production of more than 140 sensors and also demonstrated low dispersion in device resistance as well as in its sensitivity to strain and temperature. The sensor also responds to humidity and pH, indicating that this fabrication process is adapted to the creation of a multifunctional nano sensor.The low-cost, low-power conditioning circuit adapts the sensors’ output to the input requirements of a regular analog-to-digital converter (ADC), compensating for temperature sensitivity. The antenna is specifically designed to maximise transmission through concrete for the wireless communication of the measurements. Power is supplied by a battery enabling the operation of the node for over 5 years. The circuitry is housed in a protective casing to insulate it from the harsh concrete environment. The volume of the assembled device is more than 3 times smaller than state of the art embedded nodes for concrete.The devices are tested both in laboratory conditions and in real-size concrete structures. The outputs of the sensors embedded in a mortar slab under 3-point bending tests suggest that the devices are capable of detecting the opening of micro cracks caused by increasing load. Moreover, continuous outdoor deployment since December 2014 demonstrates that this setup may be capable of detecting thermal-induced micrometric deformations and suggests that our technology provides a higher durability for embedded monitoring than commercial metallic strain gauge. In conclusion, the scientific and technological results of this research show the strong applicative potential of wireless nano sensors for embedded monitoring of concrete materials.Mettre en œuvre le développement durable en construction nécessite de prolonger la durée de vie des structures grâce à la détection précoce des fragilités structurales. Celles-ci trouvent très souvent leur origine au cœur même des structures, au niveau de défauts micrométriques. Détecter ces défauts in situ et en temps réel représente un défi scientifique et technologique majeur et aucune solution bas coût n’est actuellement disponible. Cette thèse présente le premier nanocapteur intelligent sans fil pour le suivi noyé des structures en béton. Le système est composé de trois parties : un élément sensible, un circuit de conditionnement du signal, et une antenne. Le premier est un capteur de déformation fabriqué par impression jet d’encre de nanotubes de carbone sur polymère. Ces capteurs sont fabriquées en série, jusqu’à 140 à la fois. Ils ne présentent pas d’hystérésis, résistent aux cyclages mécaniques, et sont très reproductibles en termes de résistance et de sensibilité (en température et en déformation) au sein d’une même série. Les capteurs sont sensibles également au pH et à l’humidité, ce qui suggère que cette technologie pourrait être adaptée à la création de nano capteurs multifonctionnels. Le circuit de conditionnement est à bas coût et faible consommation énergétique. Il met en forme le signal du capteur tout en compensant sa sensibilité à la température. L’antenne a été conçue pour maximiser sa portée à cœur du béton, permettant ainsi la communication sans fil des mesures du capteur vers l’utilisateur. Le système, protégé par un boitier spécialement conçu, est alimenté par une batterie pour une durée de vie estimée à plus de 5 ans. Le volume total du système final est plus de 3 fois inférieur à l’état de l’art des capteurs noyés.De nombreuses expériences en laboratoire ainsi que dans une structure en béton de taille réelle suggèrent que le dispositif est capable d’observer à la fois l’ouverture de micro fractures dues à des charges appliquées et les déformations micrométriques dues à des dilatations thermiques. De plus, nos capteurs à base de nanotubes ont montré une durabilité plus importante au cœur du béton que des capteurs de déformation métalliques commerciaux. En conclusion, les résultats scientifiques et technologiques de ces travaux montrent le fort potentiel applicatif des nano capteurs sans fil pour l’instrumentation noyée des matériaux cimentaires

    1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface

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    A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance

    Beam scanning by liquid-crystal biasing in a modified SIW structure

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    A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium
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