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Wang, Jing. "Distributed Pressure and Temperature Sensing Based on Stimulated Brillouin Scattering." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/78066.
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Brillouin scattering has been verified to be an effective mechanism in temperature and strain sensing. This kind of sensors can be applied to civil structural monitoring of pipelines, railroads, and other industries for disaster prevention. This thesis first presents a novel fiber sensing scheme for long-span fully-distributed pressure measurement based on Brillouin scattering in a side-hole fiber. After that, it demonstrates that Brillouin frequency keeps linear relation with temperature up to 1000°C; Brillouin scattering is a promising mechanism in high temperature distributed sensing.
A side-hole fiber has two longitudinal air holes in the fiber cladding. When a pressure is applied on the fiber, the two principal axes of the fiber birefringence yield different Brillouin frequency shifts in the Brillouin scattering. The differential Brillouin scattering continuously along the fiber thus permits distributed pressure measurement. Our sensor system was designed to analyze the Brillouin scattering in the two principal axes of a side-hole fiber in time domain. The developed system was tested under pressure from 0 to 10,000 psi for 100m and 600m side-hole fibers, respectively. Experimental results show fibers with side holes of different sizes possess different pressure sensitivities. The highest sensitivity of the measured pressure induced differential Brillouin frequency shift is 0.0012MHz/psi. The demonstrated spatial resolution is 2m, which maybe further improved by using shorter light pulses.Master of Science
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Dusek, Jeff Ernest. "Development of bio-inspired distributed pressure sensor arrays for hydrodynamic sensing applications." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/103496.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 277-284).
The performance of marine vehicles is largely influenced by interactions with the flow around their hull, both self-generated and environmentally driven. To improve performance through flow control, a detailed, real-time measurement of the near-field flow is necessary, yet such sensing capability is presently unavailable. Looking to nature for inspiration, fish employ the distributed pressure and velocity sensing capability of their lateral line sensory organ to mediate navigation and control behaviors that, if replicated, could benefit engineered systems. Through a series of towing tank and field experiments, it was found that while distributed pressure measurements on marine vehicles enabled the detection of near-body flow phenomena, the size, cost, and mounting requirements of commercial sensors lead to sparse arrays and substantial gaps in the characterization of the flow field. To address the challenges associated with obtaining spatially-dense pressure measurements on curved surfaces in marine environments, a new waterproof and conformal pressure sensor array was developed based on a closed-cell piezo resistive foam composed of carbon black-doped-silicone composite (CBPDMS foam). The response of the CBPDMS foam sensor arrays was characterized using periodic hydrodynamic pressure stimuli from vertical plunging and water waves, and a piecewise polynomial calibration was developed to describe the sensor response. The sensitivity and frequency response of the sensor arrays was also documented through a series of biologically-inspired hydrodynamic stimuli, including the flow from a dipole source, and the Karmin vortical wake flow behind a circular cylinder. The CBPDMS foam sensor arrays have significant advantages over existing commercial sensors for distributed flow reconstruction and control. They are found to have sensitivity on the order of 5 Pascal, frequency range of 0.5-35 Hertz, are contained in a waterproof and completely flexible package, and have material cost less than $10 per sensor.
by Jeff Ernest Dusek.
Ph. D.
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大岡, 昌博, Masahiro OHKA, 行宏 毛利, Yukihiro MOURI, 徳宏 杉浦, Tokuhiro SUGIURA, 保永 三矢, Yasunaga MITSUYA, 浩嗣 古賀, and Hiroshi KOGA. "分布圧覚ディスプレイ装置による仮想形状呈示." 日本機械学会, 2002. http://hdl.handle.net/2237/9060.
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Andries, Mihai. "Localisation et suivi d'humains et d'objets, et contrôle de robots au travers d'un sol sensible." Thesis, Université de Lorraine, 2015. http://www.theses.fr/2015LORR0293.
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Cette thèse explore les capacités d’une intelligence ambiante équipée d’un réseau de capteurs de pression au sol. Elle traite le problème de la perception d’un environnement au travers un réseau de capteurs de basse résolution. Les difficultés incluent l’interpretation des poids dispersés pour des objets avec multiples supports, l’ambiguïté de poids entre des objets, la variation du poids des personnes pendant les activités dynamiques, etc. Nous introduisons des nouvelles techniques, partiellement inspirées du domaine de la vision par l’ordinateur, pour la détection, le suivi et la reconnaissance des entités qui se trouvent sur le sol. Nous introduisons également des nouveaux modes d’interaction entre les environnements équipés de tels capteurs aux sols, et les robots qui évoluent dans ces environnements. Ceci permet l’interprétation non-intrusive des événements qui ont lieu dans des environnements dotés d’une intelligence ambiante, avec des applications dans l’assistance automatisée à domicile, l’aide aux personnes âgées, le diagnostic continu de la santé, la sécurité, et la navigation robotiqueThis thesis explores the capabilities of an ambient intelligence equipped with a load-sensing floor. It deals with the problem of perceiving the environment through a network of low-resolution sensors. Challenges include the interpretation of spread loads for objects with multiple points of support, weight ambiguities between objects, variation of persons’ weight during dynamic activities, etc. We introduce new techniques, partly inspired from the field of computer vision, for detecting, tracking and recognizing the entities located on the floor. We also introduce new modes of interaction between environments equipped with such floor sensors and robots evolving inside them. This enables non-intrusive interpretation of events happening inside environments with embedded ambient intelligence, with applications in assisted living, senile care, continuous health diagnosis, home security, and robotic navigation
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Sundman, Dennis. "Greedy Algorithms for Distributed Compressed Sensing." Doctoral thesis, KTH, Kommunikationsteori, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-144907.
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Compressed sensing (CS) is a recently invented sub-sampling technique that utilizes sparsity in full signals. Most natural signals possess this sparsity property. From a sub-sampled vector, some CS reconstruction algorithm is used to recover the full signal. One class of reconstruction algorithms is formed by the greedy pursuit, or simply greedy, algorithms, which is popular due to low complexity and good performance. Meanwhile, in sensor networks, sensor nodes monitor natural data for estimation or detection. One application of sensor networking is in cognitive radio networks, where sensor nodes want to estimate a power spectral density. The data measured by different sensors in such networks are typically correlated. Another type are multiple processor networks of computational nodes that cooperate to solve problems too difficult for the nodes to solve individually. In this thesis, we mainly consider greedy algorithms for distributed CS. To this end, we begin with a review of current knowledge in the field. Here, we also introduce signal models to model correlation and network models for simulation of network. We proceed by considering two applications; power spectrum density estimation and distributed reconstruction algorithms for multiple processor networks. Then, we delve deeper into the greedy algorithms with the objective to improve reconstruction performance; this naturally comes at the expense of increased computational complexity. The main objective of the thesis is to design greedy algorithms for distributed CS that exploit data correlation in sensor networks to improve performance. We develop several such algorithms, where a key element is to use intuitive democratic voting principles. Finally, we show the merit of such voting principles by probabilistic analysis based on a new input/output system model of greedy algorithms in CS. By comparing the new single sensor algorithms to well known greedy pursuit algorithms already present in the literature, we see that the goal of improved performance is achieved. We compare complexity using big-O analysis where the increased complexity is characterized. Using simulations we verify the performance and confirm complexity claims. The complexity of distributed algorithms is typically harder to analyze since it depends on the specific problem and network topology. However, when analysis is not possible, we provide extensive simulation results. No distributed algorithms based on the signal-models used in this thesis were so far available in the literature. Therefore, we compare our algorithms to standard single-sensor algorithms, and our results can then easily be used as benchmarks for future research. Compared to the stand-alone case, the new distributed algorithms provide significant performance gains. Throughout the thesis, we strive to present the work in a smooth flow of algorithm design, simulation results and analysis.Compressed sensing (CS) är en nyutvecklad teknik som utnyttjar gleshet i stora undersamplade signaler. Många intressanta signaler besitter dessa glesa egenskaper. Utifrån en undersamplad vektor återskapar CS-algoritmer hela den sökta signalen. En klass av rekonstruktionsalgoritmer är de så kallade giriga algoritmerna, som blivit populära tack vare låg komplexitet och god prestanda. CS kan användas i vissa typer av nätverk för att detektera eller estimera stora signaler. En typ av nätverk där detta kan göras är i sensornätverk för kognitiv radio, där man använder sensorer för att estimera effektspektrum. Datan som samplas av de olika sensorerna i sådana nätverk är typiskt korrelerad. En annan typ av nätverk är multiprocessornätverk bestående av distribuerade beräkningsnoder, där noderna genom samarbete kan lösa svårare problem än de kan göra ensamma. Avhandlingen kommer främst att behandla giriga algoritmer för distribuerade CS-problem. Vi börjar med en överblick av nuvarande kunskap inom området. Här introducerar vi signalmodeller för korrelation och nätverksmodeller som används för simulering i nätverk. Vi fortsätter med att studera två tillämpningar; estimering av effektspektrum och en distribuerad återskapningsalgoritm för multiprocessornätverk. Därefter tar vi ett djupare steg i studien av giriga algoritmer, där vi utvecklar nya algoritmer med förbättrad prestanda, detta till priset av ökad beräkningskomplexitet. Huvudmålet med avhandlingen är giriga algoritmer för distribuerad CS, där algoritmerna utnyttjar datakorrelationen i sensornätverk. Vi utvecklar flera sådana algoritmer, där en huvudingrediens är att använda demokratiska röstningsalgoritmer. Vi analyserar sedan denna typ av röstningsalgoritmer genom att introducera en ingång/utgångs modell. Analysen visar att algoritmerna ger bra resultat. Genom att jämföra algoritmer för enskilda sensorer med redan befintliga algoritmer i litteraturen ser vi att målet med ökad prestanda uppnås. Vi karaktäriserar också komplexiteten. Genom simulationer verifierar vi både prestandan och komplexiteten. Att analysera komplexitet hos distribuerade algoritmer är generellt svårare eftersom den beror på specifik signalrealisation, nätverkstopologi och andra parametrar. I de fall där vi inte kan göra analys presenterar vi istället genomgående simuleringsresultat. Vi jämför våra algoritmer med de vanligaste algoritmerna för enskilda sensorsystem, och våra resultat kan därför enkelt användas som referens för framtida forskning. Jämfört med prestandan för enskilda sensorer visar de nya distribuerade algoritmerna markant förbättring.
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Kelly, Devin WW. "A Practical Distributed Spectrum Sensing System." Digital WPI, 2011. https://digitalcommons.wpi.edu/etd-theses/378.
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As the demand for wireless communication systems grows, the need for spectrum grows accordingly. However, a large portion of the usable spectrum has already been exclusively licensed to various entities. This exclusive allocation method encourages spectrum to be left unused if the licensee has no need for that spectrum. In order to better utilize spectrum and formulate new approaches for greater spectrum use efficiency, it is imperative to possess a thorough understanding about how wireless spectrum behaves over time, frequency, and space. In this thesis, a practical, scalable, and low-cost wideband distributed spectrum sensing system is designed, implemented, and tested. The proposed system is made up of a collection of nodes that use general purpose, off-the-shelf computer hardware as well as a collection of inexpensive software-defined radio (SDR) equipment in order to collect and analyze spectrum data that varies across time, frequency, and space. The spectrum data the proposed system collects is the power present at a given frequency. The tools needed to analyze the gathered data are also created, including a periodogram and spectrogram function, which visualize average spectrum use over a period of time and as spectrum use varies with time, respectively. The proposed system also facilitates the testing of a spatio-spectrum characterization method using real data. This method has only been simulated up to this point. The characterization technique allows for spatially varying spectrum measurements to be visualized using heat maps.
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Feced, Ricardo. "Nonlinear techniques for distributed optical fibre sensing." Thesis, King's College London (University of London), 1998. https://kclpure.kcl.ac.uk/portal/en/theses/nonlinear-techniques-for-distributed-optical-fibre-sensing(48661ada-da47-4da7-b6db-fc995f840603).html.
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Dhliwayo, Jabulani. "Stimulated Brillouin scattering for distributed temperature sensing." Thesis, University of Kent, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242858.
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Frazier, Janay Amber Wright. "High-Definition Raman-based Distributed Temperature Sensing." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/95934.
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Distributed Temperature Sensing (DTS) has been used in a variety of different applications. Its ability to detect temperature fluctuations along fiber optic lines that stretch for several kilometers has made it a popular topic in various fields of science, engineering, and technology. From pre-fire detection to ecological monitoring, DTS has taken a vital role in scientific research. DTS uses the principle of backscattering by three different spectral components, e.g., Rayleigh scattering, Brillouin scattering, and Raman scattering. Although there have been various improvements to DTS, its slow response time and poor spatial resolution have been hard to overcome. Its repetition rate is low because the pulse must travel the distance of the fiber optic line and return to the detector to record the temperature change along the fiber. A spatial resolution of 7.4 cm with a response time as low as 1 second and a temperature resolution of the 0.196 ℃ is achieved from the current Raman-based DTS system. This research proves that high-spatial resolution can be obtained with the use of a Silicon Avalanche Photodetector with a 1 GHz bandwidth.MS
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Reyda, Caitlin J. (Caitlin Jilaine). "Design of a pressure sensing laparoscopic grasper." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/68854.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 34).
With smaller incisions, laparoscopic, or minimally invasive, surgery is considered safer for patients than open surgery. However, the safety of current laparoscopic grasping instruments can still be improved. Current devices provide surgeons with limited tactile feedback, and the current alligator-style jaws create pinch points that can lead to torn or damaged tissue. Additionally, the angled jaws can result in excessive grasping forces, due to the uneven pressure distribution along the jaws, or slippage when grasping larger organs. Tissue trauma, in the form of mechanical injury (crushing), ischemia (cut off blood supply), or perforation, can occur. A new design uses a symmetric, 10-bar linkage to keep the grasping jaws parallel, creating a uniform pressure distribution along the length of the jaws. A pressure sensor, located near the trigger in the handle, can detect when the grasper jaws are applying too much force on an object. When the force is above a given threshold, a vibration motor in the handle activates, warning the surgeon. This improved tactile feedback can help surgeons control pressures applied during grasping. The grasper design is further enhanced through an ergonomic pistol-grip handle, which also includes a turning wheel to rotate the grasper and a locking mechanism to fix the jaws in place. A working lx scale prototype was built to verify the feasibility of the design.
by Caitlin J. Reyda.
S.B.
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Xu, Yong Tai Yu-Chong. "Flexible MEMS skin technology for distributed fluidic sensing /." Diss., Pasadena, Calif. : California Institute of Technology, 2002. http://resolver.caltech.edu/CaltechETD:etd-12302004-144248.
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Mohamad, Hisham. "Distributed optical fibre strain sensing of geotechnical structures." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612416.
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Liu, Bo. "Sapphire Fiber-based Distributed High-temperature Sensing System." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/82741.
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From the monitoring of deep ocean conditions to the imaging and exploration of the vast universe, optical sensors are playing a unique, critical role in all areas of scientific research. Optical fiber sensors, in particular, are not only widely used in daily life such as for medical inspection, structural health monitoring, and environmental surveillance, but also in high-tech, high-security applications such as missile guidance or monitoring of aircraft engines and structures. Measurements of physical parameters are required in harsh environments including high pressure, high temperature, highly electromagnetically-active and corrosive conditions. A typical example is fossil fuel-based power plants. Unfortunately, current optical fiber sensors for high-temperature monitoring can work only for single point measurement, as traditional fully-distributed temperature sensing techniques are restricted for temperatures below 800°C due to the limitation of the fragile character of silica fiber under high temperature.
In this research, a first-of-its-kind technology was developed which pushed the limits of fully distributed temperature sensing (DTS) in harsh environments by exploring the feasibility of DTS in optical sapphire waveguides. An all sapphire fiber-based Raman DTS system was demonstrated in a 3-meters long sapphire fiber up to a temperature of 1400°C with a spatial resolution of 16.4cm and a standard deviation of a few degrees Celsius.
In this dissertation, the design, fabrication, and testing of the sapphire fiber-based Raman DTS system are discussed in detail. The plan and direction for future work are also suggested with an aim for commercialization.Ph. D.
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Read, Tom Oliver Trevett. "Applications of distributed temperature sensing in subsurface hydrology." Thesis, University of East Anglia, 2016. https://ueaeprints.uea.ac.uk/59401/.
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In the study of dynamic subsurface processes there is a need to monitor temperature and groundwater fluxes efficiently in both time and space. Distributed Temperature Sensing has recently become more accessible to researchers in Earth Sciences, and allows temperatures to be measured simultaneously, at small intervals, and over large distances along fibre optic cables. The capability of DTS in conjunction with heat injection to detect groundwater fluxes, is assessed in this thesis using a combination of numerical modelling, laboratory tests, and field trials at the Ploemeur research site in Brittany, France. In particular, three methodological approaches are developed: thermal dilution tests, point heating, and the hybrid cable method. A numerical model was developed to assess the sensitivity range of thermal dilution tests to groundwater flow. Thermal dilution tests undertaken at Ploemeur showed lithological contrasts, and allowed the apparent thermal conductivity to be estimated in-situ, but failed to detect previously identified transmissive fractures. The use of DTS to monitor in-well vertical flow is then investigated. This is first using a simple experiment deploying point heating (T-POT), which tracks a parcel of heated water vertically through the borehole. The method allowed for the relatively quick estimation of velocities in the well. The use of heated fibre optics is then trialled, and through a field test was shown to be sensitive to in-well vertical flow. However, the data suffered from a number of artefacts related to the cable installation. To address this, a hybrid cable system was deployed in a flume to determine the sensitivity relationship with flow angle and electrical power input. Additionally, a numerical model was developed, which suggested a lower limit for velocity estimation due to thermal buoyancy. With the emergence of Distributed Acoustic Sensing, fibre optics may become an increasingly practicable and complete solution for monitoring subsurface processes.
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Li, Xiaowei. "A weighted ℓ₁-minimization for distributed compressive sensing." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/54836.
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Distributed Compressive Sensing (DCS) studies the recovery of jointly sparse signals. Compared to separate recovery, the joint recovery algorithms in DCS are usually more effective as they make use of the joint sparsity. In this thesis, we study a weighted ℓ₁-minimization algorithm for the joint sparsity model JSM-1 proposed by Baron et al. Our analysis gives a sufficient null space property for the joint sparse recovery. Furthermore, this property can be extended to stable and robust settings. We also presents some numerical experiments for this algorithm.Science, Faculty of
Mathematics, Department of
Graduate
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Tongpadungrod, Pensiri. "Characteristics of distributive tactile sensing systems." Thesis, University of Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390833.
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Bello, Simon Antonio. "Intraocular Pressure Sensing and Control for Glaucoma Research." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6466.
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Animal models of ocular hypertension are important for glaucoma research but come with experimental costs. Available methods of intraocular pressure (IOP) elevation are not always successful, the amplitude and time course of IOP changes are unpredictable and irreversible, and IOP measurement by tonometry is laborious. This dissertation focuses on the development and implementation of two novel systems for monitoring and controlling IOP without these limitations. The first device consists of a cannula implanted in the anterior chamber of the eye, a pressure sensor that continually measures IOP, and a bidirectional pump driven by control circuitry that can infuse or withdraw fluid to hold IOP at user-desired levels. A portable version was developed for tethered use on rats. The system was fully characterized and deemed ready for cage- or bench-side applications. The results lay the foundation for an implantable version that would give glaucoma researchers unparalleled knowledge and control of IOP in rats and potentially larger animals.
Moreover, a novel mathematical technique was developed to efficiently analyze IOP records obtained using the pressure controlling device. The algorithm successfully yields the value of several parameters that influence ocular physiology and are commonly linked to glaucoma development. This unique methodology uses information regarding the amount of volume necessary to maintain IOP at different levels to quantify the outflow facility of perfused eyes. The use of this technology largely simplifies the investigator’s experimental set-up and cuts procedural times in half.
The second device is an implantable pressure sensor for continuously monitoring IOP. The miniature system is equipped with pressure and temperature transducers, on-board amplifiers and a powerful microcontroller that ensure data quality. The sensor is able to obtain measurements with twice the accuracy and precision of any other IOP sensor used to date, avoid electronic drifts commonly seen in commercial sensing devices, and can potentially be used in a variety of animal models. The sensor was characterized and tested in alert rats for weeks on end. Data obtained with this device showed the presence of previously reported circadian rhythms, with IOP significantly increasing during nocturnal cycles. This technology provides researchers with an unprecedented tool to analyze IOP dynamics over time. The characterization of the amplitude, period and phase of the IOP profiles of normal and glaucomatous eyes may help establish a definitive correlation between ocular hypertension and glaucoma progression.
While implantable systems provide investigators with essential physiological data, their implementation can be difficult. Challenges such as reduced operational lifetimes and limited data acquisition capabilities are commonly faced by most bio-devices. These limitations are frequently linked to small battery capacities, however the implementation of bigger batteries is not usually viable due to size requirements. Energy harvesting technologies have surfaced in recent years in an attempt to replace battery applications; however, most technologies provide low power densities and cannot deliver continuous telemetric operation. An innovative wireless powering system was developed to overcome these limitations. The technology uses radio frequency (RF) energy transfer to continuously harvest high energy levels. Taking advantage of the controlled environment under which most research animals are housed, RF transmitters are placed around the cage to form strong, omnidirectional electric fields. An especial antenna was designed to be worn by the animal and collect large energy levels, irrespective of animal movements and positioning. The system was tested on the implantable IOP sensor for weeks, providing robust performances and allowing the sensor to collect data continuously with high precision. The device consistently generated power densities much greater than those required by the sensor. The surplus of energy could be used to operate multiple sensors simultaneously, greatly increasing the investigator’s leverage. The technology is easily adaptable to other bio-sensors and has the potential to revolutionize the biomedical field.
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Clement, Pierre. "Solutions aux limites des interrogateurs B-OTDR pour la surveillance d'infrastructures : augmentation de la portée de mesure et décorrélation des paramètres de température et de déformation." Electronic Thesis or Diss., Institut polytechnique de Paris, 2020. http://www.theses.fr/2020IPPAT042.
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Cette thèse porte sur l’étude des systèmes de mesure répartie de la rétrodiffusion Brillouin dans une fibre optique, que l’on nomme B-OTDR et qui sont sensibles à la température et à la déformation de la fibre. Les solutions d'interrogateurs actuelles permettent l'instrumentation de grandes infrastructures. Cependant, il existe des limites, inhérentes au phénomène physique utilisé, qui ne permettent pas d'adresser certaines applications spécifiques. Ces limites portent sur la distance de mesure maximale accessible par ces interrogateurs mais également sur la décorrélation de la mesure des paramètres de température et de déformation. Nous avons donc cherché, au cours de cette thèse, à adresser des solutions à ces problématiques. Un nouveau système de ré-amplification optique, basé sur les technologies EDFA, a été mis au point. Associé à un système B-OTDR, cette solution nous a permis de réaliser une mesure distribuée de température sur 150 km de fibre avec une répétabilité de 1,5 °C. Cette avancée propose, à notre connaissance, les meilleurs résultats obtenus avec un tel système et nous permet d’envisager son déploiement pour la surveillance d’infrastructures du transport de l’énergie sur de longues distances. Nous avons dans un second temps conçu un nouvel interrogateur, utilisant la rétrodiffusion Brillouin, et permettant la décorrélation des mesures de température et de déformation sur une seule et unique fibre optique. Ce nouvel interrogateur, caractérisé et breveté durant cette thèse, a permis de réaliser une mesure indépendante de température et de déformation sur un câble spécifique inséré dans un puits de forage. Les résultats de ces mesures ont montré à la fois des variations de température et de déformation sur le câble, donnant des informations précieuses à l’opérateur du puits. Le nouvel interrogateur mis au point, permet une séparation de ces deux paramètres avec une répétabilité inférieure à 1 °C et 20 μm/m pour une distance de l’ordre du kilomètre. Pour des distances de l’ordre de la dizaine de kilomètres, la répétabilité de mesure est de 3 °C et 75 μm/m. Ce résultat fait l'état de l'art dans la séparation température/déformation par B-OTDR. Enfin, les différents travaux réalisés pour répondre à ces deux problématiques ont abouti au développement d’un prototype d’interrogateur qui laisse envisager une mesure simultanée de la température, de la déformation, des vibrations acoustiques et de la pression hydrostatique. Ce prototype conduit à des perspectives intéressantes pour une solution complète de surveillance d’infrastructuresThis thesis deals with distributed optical fiber sensors, especially Brillouin sensors called B-OTDR that are sensitive both to temperature and strain. Some actual limitations due to the scattering phenomenon avoid deployment of this technology for some specific applications. These limitations are about the maximum length measured by the sensor but also the double sensitivity to strain and temperature. From our current B-OTDR sensor, we propose solutions to address these issues.A new re-amplification module using EDFA has been developed and characterized associated to a B-OTDR system. A 150 km distributed temperature measurement with 1,5 °C repeatability has been reached. This record performance let us consider a deployment for very long infrastructure monitoring for the energy transport. In another hand, we developed a new sensing device using Brillouin scattering and able to separate temperature and strain. This patented device has been characterized and used on a specific cable inserted in a well drilling. Results have shown a combination of strain and temperature variations on the cable that give very useful information to the well operator. We have reached a temperature repeatability of 1 °C and a strain repeatability of 20 μm/m for 1 km fiber. At 10 km, temperature repeatability has been evaluated to be 3 °C and strain to 75 μm/m. These results are to the state of art for temperature/strain separation using B-OTDR.These works have led to a new distributed measurement prototype that could address simultaneously temperature, strain, acoustic vibrations, and pressure sensing. Some interesting perspectives could result from these works to address a complete infrastructure monitoring using fiber optic sensing
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Fariborzi, Fariborz. "Distributed sensing and control of a simply supported plate." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0012/NQ32829.pdf.
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Duck, Graham Ian. "Distributed Bragg grating sensing, strain transfer mechanics and experiments." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ58592.pdf.
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Sammartino, P. F. "A comparison of processing approaches for distributed radar sensing." Thesis, University College London (University of London), 2009. http://discovery.ucl.ac.uk/16331/.
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Radar networks received increasing attention in recent years as they can outperform single monostatic or bistatic systems. Further attention is being dedicated to these systems as an application of the MIMO concept, well know in communications for increasing the capacity of the channel and improving the overall quality of the connection. However, it is here shown that radar network can take advantage not only from the angular diversity in observing the target, but also from a variety of ways of processing the received signals. The number of devices comprising the network has also been taken into the analysis. Detection and false alarm are evaluated in noise only and clutter from a theoretical and simulated point of view. Particular attention is dedicated to the statistics behind the processing. Experiments have been performed to evaluate practical applications of the proposed processing approaches and to validate assumptions made in the theoretical analysis. In particular, the radar network used for gathering real data is made up of two transmitters and three receivers. More than two transmitters are well known to generate mutual interference and therefore require additional efforts to mitigate the system self-interference. However, this allowed studying aspects of multistatic clutter, such as correlation, which represent a first and novel insight in this topic. Moreover, two approaches for localizing targets have been developed. Whilst the first is a graphic approach, the second is hybrid numerical (partially decentralized, partially centralized) which is clearly shown to improve dramatically the single radar accuracy. Finally the eects of exchanging angular with frequency diversity are shown as well in some particular cases. This led to develop the Frequency MIMO and the Frequency Diverse Array, according to the separation of two consecutive frequencies. The latter is a brand new topic in technical literature, which is attracting the interest of the technical community because of its potential to generate range-dependant patterns. Both the latter systems can be used in radar-designing to improve the agility and the effciency of the radar.
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Neri, Mark L. (Mark Lewis). "An approach to distributed sensing in a virtual fishtank." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/42718.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (leaves 44-45).
by Mark L. Neri.
M.Eng.
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Lees, Gareth P. "Q-switched fibre laser sources for distributed sensing applications." Thesis, University of Southampton, 1998. https://eprints.soton.ac.uk/394390/.
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This thesis examines pulsed fibre sources for distributed sensing applications. A number of Q-switched fibre laser sources optimised for high peak powers, narrow linewidth and short pulse duration are described. The source specifications were dictated by the requirements of Raman and Brillouin distributed sensing systems. The spatial resolution of distributed sensors is related to the pulse width whereas the range is dependent on the power launched into the sensing fibre. Brillouin distributed sensors also require that the source linewidth is less than 10 GHz, the separation between the Rayleigh and Brillouin backscattered light. This constraint on laser linewidth leads to coherent Rayleigh noise on the Rayleigh backscattered trace. This noise can be reduced by a technique of frequency shift averaging. A Q-switched laser incorporating this technique was developed, which resulted in a Brillouin distributed temperature sensor with a temperature resolution of 1.4°C and a spatial resolution of 10 metres over a range of 6.5km. The development of high power Q-switched fibre lasers leads to the possibility of generating Raman shifted pulses at wavelengths of 1.64-1.65µm. Interest in this wavelength region stems from the increase in sensitivity to fibre micro-bend losses at these higher wavelengths and the ability to monitor the fibre whilst carrying out live data transmission. A diode pumped, pulsed source at 1.64µm producing 8 Watt, 10ns pulses through a process of Raman generation was demonstrated. Q-switched laser technology was also used to increase the dynamic range of 1.65µm OTDR. The technique utilised delayed Raman amplification of the 1.65µm signal pulse by a co-propagating 1.53µm pump pulse. Amplification occurs when the two pulses overlap. The position of the overlap is determined by the initial delay between the pulses and the fibre dispersion. An increase in dynamic range of 17.5dB has been observed and the 1.65µm OTDR range was extended to in excess of 100km.
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de, Souza Keith R. C. P. "Fibre-optic distributed sensing based on spontaneous Brillouin scattering." Thesis, University of Southampton, 1999. https://eprints.soton.ac.uk/351507/.
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This thesis reports on the use of spontaneous Brillouin scattering for the purpose of fibre-optic distributed temperature and strain sensing based on a time-domain Landau-Placzek ratio technique. Detection system specifications are dictated by the spatial resolution, range, measurand resolution and measurement time. Pulsed sources are used in these sensors. The minimum spatial resolution depends on both the pulse width and receiver bandwidth. The range and measurand resolution depend on the peak pulse power launched into the sensing fibre as well as the Brillouin signal-to-noise characteristics at the receiver. The maximum launched pulse power is limited by the onset of nonlinear effects in the sensing fibre. Novel interferometric techniques based on low-cost, low loss all fibre Mach-Zehnder interferometric optical filters needed to separate the backscattered Rayleigh and spontaneous Brillouin signals have been developed with enhanced signal-to-noise capabilities. Used in conjunction with a newly developed low noise optical preamplifier /transimpedance receiver system, a distributed temperature sensor having 1.8m spatial resolution, 6.3 °C temperature resolution and a range of 23km is demonstrated. The strain dependence of the spontaneous Brillouin intensity has been determined. This coefficient is crucial for the development of a distributed temperature only sensor and /or a combined distributed temperature and strain sensor. Pulsed narrowband and broadband sources are necessary for resolving the Rayleigh and Brillouin signals as well as reducing coherent Rayleigh noise. The latter has been investigated and its dependence on certain parameters confirmed. A source capable of switching between narrowband and broadband operation has been demonstrated and is particularly appropriate for extended periods of data collection cycles.
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Moa, Sandberg. "Distributed Temperature Sensing för kontroll av inläckage i spillvattenledningar." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-445633.
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Infiltration and inflow (I/I) are common problems in the foul sewer system. A method to detect I/I that is not commonly used in Sweden is DTS, Distributed Temperature Sensing. DTS is based on continuous measurements of temperature over a predetermined distance in the sewer system. The I/I is detected as temperature differences in the temperature data that is registered in the sewer system. The measurements often take place over a couple of weeks or months in the sewer system. The aim of this project was to review previous studies where DTS was used to detect I/I in foul sewers. Data from a wastewater treatment plant in Umeå together with meteorological data were analysed to be able to visualize the problem of I/I and then suggest how DTS can be applied in Sweden. Both automated and visual analyses was performed to find if there were any relationships between wastewater temperature, wastewater flow and precipitation. The outcome was that it is possible to apply DTS in the foul sewages to detect I/I. DTS seemed to be able to detect I/I in all types of sewage material, however it is dependent on that the I/I temperature differs from the temperature of the foul sewage water. It is an expensive technique but if it is meant to be used many times to analyse bigger areas it can be worth the costs. If larger areas are to be investigated, the costs for DTS and current methods are approximately the same. At the wastewater treatment plant in Umeå, a slight relationship between wastewater temperature, wastewater flow and precipitation could be detected. The degree of dilution was calculated to 1,34 which means that about 25% of the sewage water is I/I. The conclusion from this was that I/I exists in the foul sewers in Umeå. The leakage points could not be located with this analysis. DTS could be a possible method to detect the leakage points of I/I in foul sewers. Unlike smoke tests, colouring and video-inspection of the sewers, DTS might be able to detect smaller leakage points.Tillskottsvatten är ett vanligt problem i spillvattenledningsnätet. DTS, Distributed Temperature Sensing är en metod som inte är vanlig i Sverige för kontroll av spillvattenledningar. Tekniken bygger på kontinuerliga temperaturmätningar under en tidsperiod över en förutbestämd sträcka och registrerar temperaturavvikelser som kan uppstå i samband med inläckage av tillskottsvatten. Syftet med projektet var att granska tidigare utförda studier med DTS för att ta reda på hur tekniken kan användas för att lokalisera inläckage i spillvattenledningar. För att vidare illustrera problematiken med tillskottsvatten i spillvattennätet samt föreslå hur DTS kan appliceras i Sverige genomfördes en analys av mätdata på inkommande vatten till reningsverket på Ön, Umeå. Både visuella och automatiserade analyser genomfördes där tolkningar gjordes utifrån mätdata från reningsverket tillsammans med nederbörds- och lufttemperaturdata. En regressionsanalys genomfördes som automatiserad analys för att undersöka eventuella samband mellan spillvattentemperatur, spillvattenflöde och nederbörd. Projektet inleddes med en litteraturstudie där det utreddes hur DTS fungerar teoretiskt och praktiskt. Litteraturstudien visade att DTS är praktiskt möjligt att applicera i spillvattenledningsnätet för att leta inläckagepunkter för tillskottsvatten. Inläckage kan registreras som ökningar eller sänkningar i spillvattentemperaturen beroende på lufttemperaturen. Den är inte beroende av material på ledningarna men däremot är DTS beroende av att tillskottsvattnet är av annan temperatur än spillvattnet. Det är en dyr teknik men kan vara värt investeringskostnaderna om mätningar tänkt ske många gånger under längre perioder. Vid kontroll av större områden med hjälp av röktest kombinerat med färgning av vatten och filmning är kostnaderna ungefär de samma. Utifrån mätdatan från reningsverket och nederbördsdatan från Umeå universitet kunde vissa samband påvisas mellan spillvattentemperatur, spillvattenflöde och nederbörd. Ett visst samband kunde även urskiljas mellan spillvattentemperatur och spillvattenflöde. Utspädningsgraden av spillvattnet beräknades till 1,34 vilket innebär att cirka 25% av vattnet i spillvattenledningarna är tillskottsvatten. Slutsatsen som kunde dras utifrån detta var att tillskottsvatten existerar i spillvattenledningsnätet som leder till reningsverket på Ön i Umeå. Däremot kunde inga slutsatser dras för att säga var inläckage av tillskottsvatten sker. DTS skulle kunna appliceras i ledningsnäten för att undersöka närmare var inläckagepunkterna är och tillskillnad från rökning, färgning av vatten och filmning som används idag kan DTS sannolikt upptäcka fler typer av inläckage.
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Yu, Li. "Multi-Material Fiber Fabrication and Applications in Distributed Sensing." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/99380.
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Distributed sensing has been an attractive alternative to the traditional single-point sensing technology when measurement at multiple locations is required. Traditional distributed sensing methods based on silica optical fiber and electric coaxial cables have some limitations for specific applications, such as in smart textiles and wearable sensors. By adopting the fiber thermal drawing technique, we have designed and fabricated multi-material electrode-embedded polymer fibers with distributed sensing capabilities. Polymers sensitive to temperature and pressure have been incorporated into the fiber structure, and thin metal electrodes placed inside fiber by convergence drawing have enabled detection of local impedance change with electrical reflectometry. We have demonstrated that these fibers can detect temperature and pressure change with high spatial resolution. We have also explored the possibility of using polymer optical fiber in a Raman scattering based distributed temperature sensing system. Stokes and Anti-Stokes signals of a PMMA fiber illuminated by a 532 nm pulsed laser was recorded, and the ratio was used to indicate local temperature change. We have also developed a unique way to fabricate porous polymer by thermal drawing polymer materials with controlled water content in the polymer. The porous fibers were loaded with a fluorescent dye, and its release in tissue phantoms and murine tumors was observed. The work has broadened the scope of multi-material, multi-functional fiber and may shed light on the development of novel smart textile devices.PHD
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Sang, Alexander Kipkosgei. "Distributed Vibration Sensing using Rayleigh Backscatter in Optical Fibers." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/77274.
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Sensing has been essential for the investigation, understanding, exploitation, and utilization of physical phenomena. Traditional single-point sensing methods are being challenged by the multi-point or distributed sensing capabilities afforded by optical fiber sensors. A powerful technique available for distributed sensing involves the use of the Optical Frequency Domain Reflectometry (OFDR).
This work focuses on using OFDR as a means of obtaining distributed vibration measurements using the Rayleigh scatter along a single-mode optical fiber. The effort begins by discussing various distributed measurement techniques currently in use before discussing the OFDR technique. Next, a thorough discussion on how high spatially resolved Rayleigh measurements are acquired and how such measurements can be used to make static strain measurements is presented. A new algorithm to resolve strain at regions of high spatial gradient is developed. This results in enhanced measurement performance of systems using the Rayleigh scatter to determine static strain or temperature measurements by improving measurement fidelity at the high gradient locations.
Next, discussions on how dynamic strain (vibration) couples to optical fiber in a single point and in a distributed setting are presented. Lessons learned are then used to develop a new and unique distributed vibration measurement algorithm. Various consequential benefits are then reviewed before concluding remarks are stated.
A simulation model was developed and used to supplement this investigation in every step of the discussion. The model was used to gain insight on how various physical phenomena interact with the optical fiber. The simulation was also used to develop and optimize the high gradient and vibration algorithms developed herein. Simple experiments were then used to validate the theory and the simulation models.Ph. D.
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Melin, Jessica. "Novel Microsystem Techniques for Liquid Manipulation and Pressure Sensing." Doctoral thesis, Stockholm : Department of Signals, Sensors and Systems, Royal Institute of Technology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-56.
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Minerly, Kathleen. "Polymer nanomaterials for applications in sound and pressure sensing." Diss., Online access via UMI:, 2006.
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Goupil, Marc Y. "Dynamic Pressure Sensing for the Flight Test Data System." DigitalCommons@CalPoly, 2019. https://digitalcommons.calpoly.edu/theses/2115.
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This thesis describes the design, assembly, and test of the FTDS-K, a new device in the Boundary Layer Data System (BLDS) family of flight data acquisition systems. The FTDS-K provides high-frequency, high-gain data acquisition capability for up to two pressure sensors and an additional three low-frequency pressure sensors. Development of the FTDS-K was separated into a core module, specialized analog subsystem, and practical testing of the FTDS-K in a flow measurement mission. The core module combines an nRF52840-based microcontroller module, switching regulator, microSD card, real-time clock, temperature sensor, and trio of pressure sensors to provide the same capabilities as previous-generation BLDS-P devices. An expansion header is included in the core module to allow additional functionality to be added via daughter boards. An analog signal chain comprised of two-stage amplification and fourth-order active antialiasing filters was implemented as a daughter board to provide an AC-coupled end-to-end gain of 7,500 and a DC-coupled end-to-end gain of 50. This arrangement was tested in a wind tunnel to demonstrate that sensors with a full-scale range of 103 kPa can be used to reliably discriminate between laminar and turbulent flows based on pressure fluctuation differences on the order of tens of Pa. A combination of wind-off correction and band-filtering was used to reduce the effect of inherent and induced electrical noise, while two-sensor correlation was tested and shown to be effective at removing certain types of noise. Total power consumption for the FTDS-K in a representative mission is 208 mW, which translates to an operational endurance of 9 hours with 2 AAA LiFeS2 cells at -40°C.
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Mirchandani, Smruti S. "INVESTIGATING LOW-COST OPTICAL SPECTROSCOPY FOR SENSING PRESSURE ULCERS." Miami University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=miami1501240867911294.
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Sundman, Dennis. "Compressed Sensing : Algorithms and Applications." Licentiate thesis, KTH, Kommunikationsteori, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-90074.
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The theoretical problem of finding the solution to an underdeterminedset of linear equations has for several years attracted considerable attentionin the literature. This problem has many practical applications.One example of such an application is compressed sensing (cs), whichhas the potential to revolutionize how we acquire and process signals. Ina general cs setup, few measurement coefficients are available and thetask is to reconstruct a larger, sparse signal.In this thesis we focus on algorithm design and selected applicationsfor cs. The contributions of the thesis appear in the following order:(1) We study an application where cs can be used to relax the necessityof fast sampling for power spectral density estimation problems. Inthis application we show by experimental evaluation that we can gainan order of magnitude in reduced sampling frequency. (2) In order toimprove cs recovery performance, we extend simple well-known recoveryalgorithms by introducing a look-ahead concept. From simulations it isobserved that the additional complexity results in significant improvementsin recovery performance. (3) For sensor networks, we extend thecurrent framework of cs by introducing a new general network modelwhich is suitable for modeling several cs sensor nodes with correlatedmeasurements. Using this signal model we then develop several centralizedand distributed cs recovery algorithms. We find that both thecentralized and distributed algorithms achieve a significant gain in recoveryperformance compared to the standard, disconnected, algorithms.For the distributed case, we also see that as the network connectivity increases,the performance rapidly converges to the performance of thecentralized solution.QC 20120229
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Gagliani, Roberto. "Distributed capacitance sensing for characterization of nuclear power plant cables." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
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Depending on their location in a nuclear power plant, cables are exposed to mechanical stresses, elevated temperature, radiation, humidity and environmental stresses which can lead the cables to an earlier degradation if not well designed. For this reason, it is crucial to understand how materials that insulation and jacket are made of, installed in NPPs, will age during their service life and to develop condition monitoring techniques to assure continued safe operation under the normal operating condition and under Design Basis Event (DBE). Nowadays methods based on tensile tests like Elongation at Break (EaB) are the most used as condition monitoring technique since their direct correlation with the ageing effect. However, these destructive methods consist in the destruction of the cables and their replacement in their initial position which means a decrease of reliability of the entire system. Non-destructive techniques such as Dielectric Spectroscopy (DS) are showing good correlation with ageing. In this work, DS on a three-conductor long cable with a thermally-aged middle section is carried out. Starting with measurements of the electrical properties of a pristine cable and the same type of cable with the aged section for a first preliminary assessment, the latter is made successively shorter and the variation of the capacitance (here considered as specific capacitance, pF/m) and dissipation factor are studied with the increase in Damage Ratio (R), the ratio between the length of the damaged section and the total length of the cable. The goal is to figure out if it is possible to detect ageing effect by measuring electrical properties of the pristine section of the same cable, i.e. if the DS can distinguish between a pristine cable and the same cable containing a middle thermally-aged section.
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Zhang, Jian. "Nonlinear methods for distributed sensing in high birefringence optical fibres." Thesis, King's College London (University of London), 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300417.
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Thomas, Richard. "Spread spectrum and detection techniques for distributed optical fibre sensing." Thesis, King's College London (University of London), 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267159.
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Wait, Peter Collinson. "The application of Brillouin scattering to distributed fibre optic sensing." Thesis, University of Southampton, 1997. https://eprints.soton.ac.uk/394568/.
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This thesis reports on an investigation into the application of Brillouin scattering for the purpose of distributed fibre optic sensing. The main focus of the work has been centred on a Brillouin optical time domain reflectometer (BOTDR) system. The behaviour of short (3m), medium (60m) and long (6km) erbium doped fibre amplifiers using narrow bandwidth pulsed signals has been investigated and the most suitable configuration for the source requirement of the BOTDR identified. The operation of a (BOTDR) system has been demonstrated at the low loss window of 1.5µm wavelength. Multiple Stokes orders of stimulated Brillouin scattering in a medium length erbium doped fibre amplifier using pulsed excitation are reported. The observed stimulated Brillouin threshold power is significantly reduced as a result of optical gain. The points of origin within the fibre of the generated Stokes pulses are located using space-time diagrams and are observed to depend on the Brillouin and Erbium pump powers. This has therefore been identified as a possible mechanism for sensing applications utilizing the novel technique of varying the pump powers to spatially interrogate the fibre. Measurements of the Brillouin scattering coherence length in silica fibre using a fibre Mach Zehnder interferometer are presented. As the Brillouin pump power is increased from below to above stimulated threshold, the line shape narrows and changes from that of a Lorentzian to a Gaussian. It is also shown that the Brillouin bandwidth approaches a limiting value. It is shown experimentally that the ratio of the intensities of Rayleigh and Brillouin backscattered light (Landau Placzek ratio) in an optical fibre has a temperature dependence which may be used for the basis of a distributed temperature sensor. This result, combined with the known frequency dependence of the Brillouin backscattering on temperature and strain, indicates spontaneous Brillouin backscatter may be used for the unique determination of either temperature or strain in a distributed fibre optic sensing system. Because of the coherent nature of Rayleigh scattering, use of the same narrow bandwidth source as required for the Brillouin signal in the Landau Placzek ratio method, results in significant coherent noise in the Rayleigh signal. A novel technique is demonstrated whereby the amplified spontaneous emission noise and amplifying properties of an erbium doped fibre amplifier may be exploited to reduce the coherent noise on the Rayleigh backscatter signal. This results in a significant improvement in both temperature and spatial resolution.
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Bassil, Antoine. "Distributed fiber optics sensing for crack monitoring of concrete structures." Thesis, Nantes, 2019. http://www.theses.fr/2019NANT4057.
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Le travail de thèse présenté dans ce mémoire vise à développer et valider une technique de suivi d’ouvertures de fissures à l'aide de mesures réparties de déformation par fibres optiques. Dans un premier temps les différentes théories existantes sur le transfert de déformation du matériau hôte vers la fibre optique sont présentées avec leurs domaine de validité. Le problème de l’adhésion parfaite entre couche est ensuite étudié et un modèle analytique à trois couches tenant compte d’une adhésion imparfaite est élaboré. Ce modèle est ensuite généralisé aux systèmes multicouches. Les études expérimentales validant ce nouveau modèle sont alors présentées. Elles montrent qu’il est possible de suivre les ouvertures de fissures jusqu’à 1000 μm avec une erreur inférieure à 10% avec un câble à fibre optique collé en surface. Les câbles noyés dans le béton donnent des résultats moins justes. La justesse des mesures est aussi influencée par le type de câble, la longueur d’ancrage et le durcissement du béton. Enfin, les résultats des études de cas sur des échantillons en béton armé de laboratoire sont présentés. Elles montrent la capacité des fibres à détecter des fissures aussi précocement que les capteurs acoustiques à ultrasons et de surveiller l’ouverture de micro fissures multiplesThis thesis work aims to develop and validate a method for monitoring crack openings using distributed fiber optics strain measurements. First, the various existing theories on strain transfer from the host material to the optical fiber are presented, with their validity domain. The problem of perfect interfacial bonding is then studied and a three-layer analytical model capable of handling imperfect bonding case is proposed. This model is then generalized to multi-layer systems. Experimental studies validating this new model are presented. They show that it is possible to monitor crack openings up to 1 mm with an error of less than 10% for a fiber optic cable glued on the surface. Cables embedded in concrete show less accurate results. The type of cable, the bonding length and the hardening of the concrete material also influence the accuracy of the estimated crack openings. Finally, the results of case studies on laboratory-size reinforced concrete samples are presented. They show the optical fibers capacity to detect cracks as early as ultrasonic sensors and to monitor the opening of multiple micro cracks
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Pyrak, Matthew James. "Distributed Sensing Testbed Development for Wavelet Based Global Map Estimation." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/23111.
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The development of a fleet of flexible and ruggedized unmanned ground vehicles for use in autonomy and distributed sensing research has resulted in a mature platform with proven capabilities. Each Mapping Autonomous Ground Vehicle (MAGV) is capable of travel on- and off-road, speeds up to 10 mph, and its sturdy construction with a rugged suspension cushions onboard instruments from vibrations. The large battery capacity can sustain at least eight hours of hard use, including powering all onboard electronics. The MAGV is fitted with a high accuracy GPS/INS system for centimeter-accuracy localization and a powerful but compact onboard computer. The integrated wireless communications allow high-bandwidth data communication between the MAGV fleet and a base station. The platform can additionally be fitted with a wide array of sensors, including LIDAR and stereovision cameras, and is designed with ample space to allow the mounting of any future data gathering devices. The platform has already taken a central role in the development of new algorithms for map creation with modern sensing technology, and was deployed to collect data for the demonstration of the map estimation algorithms outlined in this thesis.A wavelet basis combined with a state estimator is demonstrated to be effective for approximating a global map of a given area with complex features. The recursive least squares state estimator is highly effective at rejecting transient features, such as pedestrians frequently passing through the field of view, while retaining the shape of the walls and terrain features. The ability to vary the map resolution allows the mapping station to trade detail for a faster map update processing time. In its current implementation, the global map estimator supports the acquisition and integration of data from multiple simultaneous mobile sources. Because each scan is registered using the position of the vehicle when it is recorded, there is no difference between receiving all data from a single agent, or multiple agents working cooperatively gathering data in the same area. The wavelet basis also offers several opportunities for reducing communications overhead through data compression. In particular, we have demonstrated that simple thresholding of the least significant wavelet coefficients results in a significant reduction in data size with no noticeable reduction in fidelity of the reconstructed map estimate.
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Ek, Simon. "Distributed Temperature Sensing Using Phase-Sensitive Optical Time Domain Reflectometry." Thesis, KTH, Tillämpad fysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-285902.
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This thesis explores and evaluates the temperature measuring capabilities of a phase-sensitive optical time-domain reflectometer (φ-OTDR), which exploits Rayleigh backscattering in normal single mode optical fibers. The device is constructed and its setup explained, and a protocol for making temperature measurements with it is developed. Performance tests are made and the device is shown to achieve fully distributed temperature measurements on fibers hundreds of meters in length with a spatial resolution of 1 m and a temperature resolution of 0.1 K. In addition, the capabilities of the device to measure normal strain in the measurement fiber are tested using the same approach, albeit with less success. The device is capable of very precise measurements, making it very sensitive to the environmental conditions around the measuring fiber but also susceptible to disturbances. Some discussion is had on how to avoid or deal with these disturbances. Furthermore, the technique is shown to be able to run in conjunction with other φ-OTDR measurement techniques from the same device simultaneously.Det här examensarbetet utforskar och utvärderar förmågorna att mäta temperatur hos en fas-känslig optisk tidsdomän-reflektometer (φ-OTDR), som utnyttjar bakåtriktad Rayleigh-spridning i vanliga optiska singelmodfibrer. Anordningen konstrueras och dess komponentstruktur förklaras, och ett protokoll tas fram för att utföra mätningar med den. Prestandatester utförs och anordningen visas kapabel att göra fullt distribuerade temperaturmätningar längs hundratals meter långa fibrer, med en rymdsupplösning på 1 m och en temperaturupplösning på 0.1 K. Dessutom testas förmågan att mäta normaltöjning hos testfibern med samma metod, dock med mindre framgång. Anordningen är väldigt känslig för förhållandena i omgivningen runt mätningsfibern, vilket gör den kapabel till mätningar med mycket hög precision, men också mottaglig för störningar. Lite diskussion hålls kring hur dessa störningar kan undvikas eller hanteras. Vidare visas att mätningstekniken kan köras samtidigt som andra φ-OTDR-baserade tekniker från samma anordning.
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Rahimi, Mohammad Reza. "Distributed Stress Sensing And Non-Destructive Tests Using Mechanoluminescence Materials." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1430763721.
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Kron, Johannes. "Low-delay sensing and transmission." Doctoral thesis, KTH, Kommunikationsteori, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-33404.
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This thesis studies cooperative sensing and transmission in the context ofwireless sensor networks (WSNs). We especially focus on two means of cooperative sensing and transmission, namely, distributed source coding and relaying. We consider systems where the usefulness of the measured data is dependent on how old the data is and we therefore need low-delay transmission schemes. At first sight, the low-delay criterion may seem to be of little relevance, but it is this aspect in particular that distinguishes this thesis from many of the existing communication theoretic results, which often are asymptotic in the block lengths. The thesis is composed of an introductory part, discussing the fundamentals of communication theory and how these are related to the requirements of WSNs, followed by a part where the results of the thesis are reported in Papers A-H. Papers A-D study different scenarios for distributed source-channel coding. In Paper A, we consider transmission of correlated continuous sources and propose an iterative algorithm for designing simple and energy-efficient sensor nodes. In particular the cases of the binary symmetric channel as well as the additive white Gaussian noise channel are studied. In Paper B, the work is extended to channels with interference and it is shown that also in this case there can be significant power savings by performing a joint optimization of the system.Papers C and D use a more structured approach and propose side-information-aware source-channel coding strategies using lattices and sinusoids. In Paper E, we apply the methods we have used in joint source-channel coding to the famous Witsenhausen counterexample. By using a relatively simple iterative algorithm, we are able to demonstrate the best numerical performance known to date. For the case of systems with relays, we study the transmission of a continuous Gaussian source and the transmission of an uniformly distributed discrete source. In both situations, we propose algorithms to design low-delay source-channel and relay mappings. By studying the structure of the optimized source-channel and relay mappings, we provide useful insights into how the optimized systems work. These results are reported in Papers F and G. In Paper H, we finally consider sum-MSE minimization for the Gaussian multiple-input, multiple-output broadcast channel. By using recently discovered properties of this problem, we derive a closed-form expression for the optimal power allocation in the two-user scenario and propose a conceptually simple and efficient algorithm that handles an arbitrary number of users. Throughout the thesis we show that there are significant gains if the parts of the system are jointly optimized for the source and channel statistics. All methods that are considered in this thesis yield very low coding and decoding delays. In general, nonlinear mappings outperform linear mappings for problems where there is side-information available. Another contribution of this thesis is visualization of numerically optimized systems that can be used as inspiration when structured low-delay systems are designed.The author changed name from Johannes Karlsson to Johannes Kron in January 2011. QC 20110512
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Davis, G. R. "Remote sensing of atmospheric water vapour by pressure modulation radiometry." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233505.
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Smith, Lauren E. "Behavioural and neural correlates of hydrostatic pressure sensing in sharks." Thesis, University of Aberdeen, 2008. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=25327.
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The normal depth usage of the juvenile lemon shark, Negaprion brevirostris was determined using data storage tags which logged pressure and temperature. Sharks were found to predominantly occupy water depths between the surface and 1m. A diel rhythm and a tidal rhythm were found for the pressure data. Simultaneous acoustic tracking showed shallow water use despite the availability of deeper areas within the sharks’ home ranges. All sharks mainly occupied a narrow range of temperatures (29°C - 31°C) at the high end of their range. Temperature data showed mainly diel rhythms with slight tidal influence. Pressures and temperatures used by the sharks seemed to be affected by size of home range, individual preference and predator avoidance. The behaviour of the lesser spotted dogfish Scyliorhinus canicula was investigated during controlled small steps of pressure inside a hypobaric chamber. Swimming occurred in response to decreasing pressure with increased swimming speed and duration suggesting enhanced sensitivity of the shark pressure sensor within a narrow range between 39mbar above and down to 195mbar below barometric pressure. Further studies using a novel tidal tank system showed that Scyliorhinus synchronised their activity with a 12.5 hour tidal cycle but not with a 9 hour cycle. When different resting depths were made available, they were utilised by dogfish, suggesting an individual preference independent of environmental cues or the presence of the opposite sex. Isolated vestibular systems were challenged over a range of pressures. Hair cell afferent activity showed responses to sinuosoidal cycles and step changes of pressure. Temperature effects are complex but were small compared with pressure effects. Knowledge of the pressure sensor and vertical range used by sharks is essential in the present development of marine protected areas in an attempt to ultimately aid the conservation of sharks.
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Lloyd, Jennifer Anne. "An integrated circuit pressure sensing system with adaptive linearity calibration." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10447.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (p. 145-152).
by Jennifer Anne Lloyd.
Ph.D.
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Kornmayer, Páll Magnús. "Pressure difference-based sensing of leaks in water distribution networks." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/68532.
Full textAbstract:
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 34-35).
Human society and civilization rely on the constant availability of fresh water. In regions where a local source of potable water is not available, a transportation and distribution pipe system is employed. When these pipes feature cracks, holes, or leaks, the result is a substantial waste of energy and natural resources. As communities grow the loss due to these flaws becomes more costly, and the motivation to detect leaks increases. The purpose of this thesis project is to develop pressure difference-based sensing cells that can be used in an untethered leak-detection device. This device is to be deployed in water distribution networks to locate leaks so that water loss can be minimized. Design of these sensing cells and of the leak-detection device entails evaluating the size and shape of a leak's low pressure region. In this paper, leaks are investigated in this regard and a number of different pressure difference-sensing sensor technologies are explored and evaluated. A silicone-rubber deflecting membrane is selected for the application. The relationship between pressure-derived force acting on its surface and its maximum deflection is evaluated as a means of leak detection. Ultimately, testing reveals that these types of cells are simple and robust. While they deflect as anticipated, the formula used to predict their behavior does not fit the experimental results. It is concluded that this type of pressure difference-sensing membrane is well-suited for application within an untethered sensor, with the opportunity for deeper material selection and more accurate deflection analysis.
by Pall Magnus Kornmayer.
S.B.
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Siebert, Jan, and Marcus Geimer. "Reduction of System Inherent Pressure Losses at Pressure Compensators of Hydraulic Load Sensing Systems." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-199553.
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In spite of their high technical maturity, load sensing systems (LS) have system-inherent energy losses that are largely due to the operation of parallel actuators with different loads at the same pressure level. Hereby, the pressure compensators of the system are crucial. So far, excessive hydraulic energy has been throttled at these compensators and been discharged as heat via the oil. The research project “Reduction of System Inherent Pressure Losses at Pressure Compensators of Hydraulic Load Sensing Systems” aims to investigate a novel solution of reducing such energy losses. The pressure of particular sections can be increased by means of a novel hydraulic circuit. Therefore, a recovery unit is connected in series with a hydraulic accumulator via a special valve in the reflux of the actuators. The artificially increased pressure level of the section reduces the amount of hydraulic power to be throttled at the pressure compensators. As long as a section fulfills the switching condition of the valve, pressure losses at the respectiv pressure compensator can be reduced. Thus, via a suitable recovery unit excessive energy can be regenerated and can be directed to other process steps eventually.
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Frey, Eric W. "Fluorescence-Based Calcium Ion Sensing at High Hydrostatic Pressures." Miami University Honors Theses / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=muhonors1209176599.
Full text
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Baldwin, Christopher S. "Distributed sensing for flexible structures using a fiber optic sensor system." College Park, Md. : University of Maryland, 2003. http://hdl.handle.net/1903/288.
Full textAbstract:
Thesis (Ph. D.) -- University of Maryland, College Park, 2003.Thesis research directed by: Mechanical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Chen, Po-Yu. "A general solution to detect anomalies in networked distributed sensing systems." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/58277.
Full textAbstract:
Networked distributed sensing systems (NDSSs) have been widely adopted in many real-world applications which can be either described as cyber-physical system (CPS) or indeed the Internet of Things (IoT). The security and trust in such systems are of paramount importance. In practice, sensor readings may be abnormal or faulty due to various unpredictable causes such as the harsh environments in which they are deployed, the sensors are inherently fault-prone, or they experience malicious attacks. However, although a large body of research has been looking at detecting such anomalies, we have yet seen a common solution that can effectively detect all general anomalies in NDSSs. Many current solutions are either simple but limited by rigid assumptions, or powerful but complex and therefore not suited to resource scarce and large-scale NDSSs. To overcome this problem, we have investigated the causes and patterns of anomaly behaviours in NDSS, and propose a lightweight general solution that can identify most general anomalies in resource-limited NDSSs. This solution consists of three different components: feature extraction, sensor grouping, and anomaly classification. In feature extraction, we propose two multi-feature dimensionality reduction algorithms, MFDR and MFDR-N. These algorithms extract distinctive time-series features from raw sensor measurements and provide their dimensionality-reduced (DR) representations. In comparison to traditional time-series approaches, MFDR and MFDR-N can provide multiple types of time-series features which can better approximate the original data with smaller error. In addition, to ensure our solution can scale to different sizes of NDSSs while being able to perform sophisticated detection schemes, we propose a distributed matching-based grouping algorithm, DMGA, which clusters sensors into correlation groups where a strong spatiotemporal correlation exists among all sensors. To the best of our knowledge, this grouping algorithm is the first one to provide performance guarantees in terms of correlation strength. Ultimately, we propose two general anomaly detection classifiers, GAD and FGAD, to capture rapid and gradual pattern changes in sensor measurements, respectively. Both of these are lightweight in terms of computation complexity and can adapt fast to changes in non-stationary environments. Our experimental results show that both GAD and FGAD are very effective against various types of anomalies in real-world NDSS.
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George, Dwyane B. "Distributed sensor network for sensing educational interaction in early childhood classrooms." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/106023.
Full textAbstract:
Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 59-60).
For teachers in Montessori schools, making notes of their observations of students is difficult, error prone, and does not scale well. Observations help teachers individualize their methods in early childhood classrooms. Sensei is the first system designed to measure social and classroom interaction using a distributed sensor network. Unobtrusive sensors measure proximity between each node in a dynamic range-based mesh network and establish interaction context through motion and ambient sound data. In this system, I designed a distributed sensor network protocol to collect sensory data, a synchronized network event scheduling scheme to establish a shared time basis, and a wireless data transfer protocol to facilitate data collection from the network. The network protocol interfaces with the sensor's hardware facilities to capture a high fidelity data set. The network event scheduling scheme creates a synchronized time basis that allows battery efficient data collection at a high time resolution for social interaction. The wireless data transfer protocol provides a teacher-friendly interface for extracting data stored in the network. This system is useful for further research in understanding learning and social networks in early childhood environments. Sensei is currently deployed in three Montessori schools and I have evaluated the effectiveness of the system with teachers. My contributions in this system are a protocol that captures sensory data, an event scheduling scheme that establishes a synchronized time basis, and a wireless data transfer protocol that facilitates data transfer from the network. Sensei helps discover observation insights that would have otherwise been lost.
by Dwyane B. George.
M. Eng.