The growth of sensors and sensing technologies have made significant impact in our day-to-day life. The five principle sensory organs of our body should perform effectively, so that we can lead a good healthy life. Apart from these natural sensors, there are man-made sensors that helps us to cope with diseases, organ failure etc. and enable us to lead a normal life. In recent years, with the prevalence of new kind of diseases, the need for new type of biomedical sensors is becoming very important. As a result, sensors used for biomedical applications have become an emerging technology and rapidly growing field of research. The aim of the present thesis work is to use the piezoelectric property of Polyvinylidene Fluoride (PVDF) film for the development of biomedical sensor and studying its application for human respiration/breathing related abnormalities. PVDF nasal sensor was designed in cantilever configuration and detailed theoretical analysis of the same was performed. Based on theoretical and experimental results, the PVDF nasal sensor dimensions were optimized. Suitable signal conditioning circuitry was designed and a measurement system for biomedical application was developed. The developed PVDF nasal sensor was calibrated using MEMS low-pressure sensor. The PVDF nasal sensor system has been applied in different biomedical applications namely, (i) to monitor human respiration pattern, (ii) to identify different Respiration Rates (RR), (iii) to evaluate Deviated Nasal Septum (DNS) in comparison with other objective method and, (vi) to clinically investigate nasal obstruction in comparison with subjective method. The thesis is divided into seven chapters. Chapter 1 This chapter gives a general introduction about biomedical sensors, piezoelectric sensing principle and PVDF polymer films along with the relevant literature survey. The brief introduction as well as literature survey of techniques used to monitor human respiration and to measure nasal obstruction is also included in this chapter. Chapter 2 This chapter gives details about the design of the PVDF nasal sensor in the cantilever configuration for sensing nasal airflow along with the relevant theoretical equations. Also, the details on the optimization of the PVDF nasal sensor dimensions based on the theoretical and experimental analysis are presented. Chapter 3 This chapter reports the designing of the necessary signal conditioning hardware along with the data acquisition unit for the PVDF nasal sensor. The signal conditioning hardware unit made consists of charge amplifier, low-pass filter and an amplifier. Besides, a complete measurement system for biomedical application was developed using PVDF nasal sensor and its merits and demerits were discussed. Chapter 4 In this chapter, an experimental set-up for measuring human respiration/breathing pressure using water U-tube manometer has been described. Also, the calibration procedure followed for the developed PVDF nasal sensor using a Micro Electro Mechanical Systems(MEMS) low pressure sensor is reported. Apart from these, the details on the measurement of deflection of the PVDF cantilever sensing element using laser displacement setup are provided. In addition, the PVDF nasal sensor was also calibrated for various air flow rates. At the end, a study has been reported on optimizing the position the PVDF nasal sensor with respect to human nose. Chapter 5 This chapter is divided into two sections, Section 5.1: This section describes the applicability of the PVDF nasal sensor using its piezoelectric property to monitor the human respiration pattern of each nostril simultaneously. The results of the PVDF nasal sensor have also been evaluated by comparing with Respiratory Inductive Plethysmograph(RIP) technique in normal subjects. Section 5.2: In this section, PVDF nasal sensor, RIP and Nasal Prongs (NP) techniques were used to measure the RR of healthy adults. The aim here was to evaluate the presently developed PVDF nasal sensor for identifying different RR compared to „Gold standard‟ RIP and NP methods. Chapter 6 This chapter is divided into two sections. Section 6.1: This section reports about the utilization of the developed PVDF nasal sensor for clinical application on the patient population. For this purpose, the performance of the PVDF nasal sensor measurements has been compared with the Peak Nasal Inspiratory Flow(PNIF) objective technique and visual analog scale (VAS). Section 6.2: This section describes about the use of PVDF nasal sensor system to measure nasal obstruction caused due to DNS objectively. Further, the results of the PVDF nasal sensor were compared with subjective techniques namely, VAS and clinician scale in patients and control group. Chapter 7 This chapter is composed of two sections. Section 7.1: This section summarizes the salient features of the work presented in this thesis. Section 7.2: This section reports a scope for carrying out further work.

This thesis focuses on the development of a new method for the continuous<p>monitoring of civil engineering structures in order to locate small damages automatically. A<p>review of the very wide literature on Structural Health Monitoring (SHM) points first out that<p>the methods can be grouped in four categories based on their need or not of a numerical model,<p>as well as their need or not of information of the damaged structure to be applied. This state<p>of the art of the SHM methods highlights the requirement to reach each levels of SHM, which<p>is in particular for the localization of small damages in civil engineering structures the needs<p>for a non-model based output-only damage sensitive feature extraction technique. The origin of<p>the local sensitivity of strains to damages is also analyzed, which justifies their use for damage<p>localization.<p>A new method based on the modal filtering technique which consists in combining linearly<p>the sensor responses in a specific way to mimic a single degree of freedom system and which<p>was previously developed for damage detection is proposed. A very large network of dynamic<p>strain sensors is deployed on the structure and split into several independent local sensor networks.<p>Low computational cost and fast signal processing techniques are coupled to statistical<p>control charts for robust and fully automated damage localization.<p>The efficiency of the method is demonstrated using time-domain simulated data on a simply<p>supported beam and a three-dimensional bridge structure. The method is able to detect and<p>locate very small damages even in the presence of noise on the measurements and variability<p>of the baseline structure if strain sensors are used. The difficulty to locate damages from acceleration<p>sensors is also clearly illustrated. The most common classical methods for damage<p>localization are applied on the simply supported beam and the results show that the modal filtering<p>technique presents much better performances for an accurate localization of small damages<p>and is easier to automate.<p>An improvement of the modal filters method referred to as adaptive modal filters is next<p>proposed in order to enhance the ability to localize small damages, as well as to follow their<p>evolution through modal filters updating. Based on this study, a new damage sensitive feature<p>is proposed and is compared with other damage sensitive features to detect the damages with<p>modal filters to demonstrate its interest. These expectations are verified numerically with the<p>three-dimensional bridge structure, and the results show that the adaptation of the modal filters<p>increases the sensitivity of local filters to damages.<p>Experimental tests have been led first to check the feasibility of modal filters to detect damages<p>when they are used with accelerometers. Two case studies are considered. The first work<p>investigates the experimental damage detection of a small aircraft wing equipped with a network<p>of 15 accelerometers, one force transducer and excited with an electro-dynamic shaker. A<p>damage is introduced by replacing inspection panels with damaged panels. A modified version<p>of the modal filtering technique is applied and compared with the damage detection based principal<p>component analysis of FRFs as well as of transmissibilities. The three approaches succeed<p>in the damage detection but we illustrate the advantage of using the modal filtering algorithm as<p>well as of the new damage sensitive feature. The second experimental application aims at detecting<p>both linear and nonlinear damage scenarios using the responses of four accelerometers<p>installed on the three-storey frame structure previously developed and studied at Los Alamos<p>National Labs. In particular, modal filters are shown to be sensitive to both types of damages,<p>but cannot make the distinction between linear and nonlinear damages.<p>Finally, the new method is tested experimentally to locate damages by considering cheap<p>piezoelectric patches (PVDF) for dynamic strain measurements. Again, two case studies are investigated.<p>The first work investigates a small clamped-free steel plate equipped with 8 PVDFs sensors, and excited with a PZT patch. A small damage is introduced at different locations by<p>fixing a stiffener. The modal filters are applied on three local filters in order to locate damage.<p>Univariate control charts allow to locate automatically all the damage positions correctly.<p>The last experimental investigation is devoted to a 3.78m long I-steel beam equipped with 20<p>PVDFs sensors and excited with an electro-dynamic shaker. Again, a small stiffener is added to<p>mimic the effect of a small damage and five local filters are defined to locate the damage. The<p>damage is correctly located for several positions, and the interest of including measurements<p>under different environmental conditions for the baseline as well as overlapping the local filters<p>is illustrated.<p>The very nice results obtained with these first experimental applications of modal filters<p>based on strains show the real interest of this very low computational cost method for outputonly<p>non-model based automated damage localization of real structures. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

Dans une aviation où la sécurité des vols est au cœur des préoccupations des constructeurs, le contrôle de santé des structures est l'un des nouveaux pôles majeurs de recherche et développement engagé par la communauté aéronautique depuis ces dix dernières années. Un système SHM (structural Heath monitoring) intégré aux structures avioniques (tels que le sont déjà les systèmes de monitoring des moteurs) permettrait de : - rendre l’aviation plus sûre et éviterait certains des accidents aériens ; - réduire les coûts de maintenance ; - alléger, à terme, le poids total car cela permettrait de d’éviter les sur-renforcements structuraux actuels. Le travail développé durant cette thèse, dans le cadre d'un projet industriel, concerne le développement de solutions exploitant l'utilisation de nœuds piezoélectriques au sein de microsystèmes reconfigurables dédiés à la détection de défauts dans des éléments de structure d'avion. L'exploitation de données issues de la génération/capture d'ondes de Lamb ainsi que des techniques se basant sur l'étude de l'impédance électromécanique du capteur ont été développées et étudiées sur différents types de défauts identifiés tels que cracks, corrosion, délaminages etc... La méthode proposée repose sur la comparaison et l'évolution dans le temps de signatures de réseaux de capteurs utilisant l’effet piezoélectrique et placés sur des éléments choisis de structures avions. L'interface capteur-matériau a été spécialement étudiée afin de garantir le couplage le plus efficace possible. Les techniques de « monitoring » ainsi développées ont été testées sur des structures aéronautiques métalliques et des structures en matériaux composites simples/sandwichs extraites d’avions Airbus et ATR. Différentes solutions d’intégration de ces capteurs et nœuds ont été passées en revue et une démarche a été proposée, allant de l’architecture des effecteurs au conditionnement et à la transmission des signaux et informations d’intéret. Une nouvelle vision de l’électronique de détection de défauts, permettant de développer une instrumentation « universelle » de capteurs à travers une combinaison de circuits numériques/analogiques reconfigurables à entrées/sorties versatiles, a été implémentée et testée avec succès / Structural health monitoring (SHM) is certainly one of the key technologies required to provide the safety and the reliability of future aviation. Based on non-destructive testing, current on the ground periodical structural integrity inspections showed their limit as evidenced by the Columbia tragedy. For the time being, structural health monitoring technology has reached a good technology readiness level (TRL). However, the integration of these solutions into future aerospace vehicle will require advanced and innovative system architecture. Further, improved SHM techniques and alleged assessment algorithm will be necessary to ensure an embedded integration, as well as to fully exploit their sensing capability. For now, most of high critical embedded systems are based on federate architectures, where each calculator is dedicated to a specific function and to a unique kind of sensor. By consequence, the integration on the field of conventional SHM solutions is highly difficult due to the scale and the weight of the global electronics systems. Based on a fully reconfigurable micro-system, I propose in this thesis, a novel SHM approach that combines into a unique System on Chip: • Sensors instrumentation and interfacing using reconfigurable analog circuits• Signal management and conditioning using reconfigurable digital electronics • Heath diagnostic assessment algorithms using an embedded CPUBased on elastic guided waves and electromechanical impedance analysis, the presented solution is capable through piezoelectric sensors to detect different kinds of abnormal events such as impacts. Moreover, using advanced wavelet transform and signature comparison algorithms, the system is also capable to detect mechanical damages such as corrosion, cracks or delaminations ; no matter if the probed structure is in simple composite, honeycomb composite or metallic alloy. The feasibility was proven using multiples specimens directly extracted from Airbus and ATR airplanes. To cover large areas, the system is fully scalable and accepts a hardware upgrade through multiple communication ports and protocols. Moreover, the versatility of inputs/outputs interface allows the exploitation of multiple sensors in order to locate and triangulate flaws