Monitoreo de salud estructural de aeronaves basado en mediciones de impedancia electromecánica

The structural Health Monitoring (SHM) is theprocess of damage detection in many areas ofengineering, like aerospace, civil and mechanics.One of SHM techniques is based on theelectromechanical impedance measurement. Thistechnique monitors the mechanical impedancevariation of the structure, caused by the presenceof damage, through measurements of theelectrical impedance signal of the piezoelectricmaterial bonded on the surface of the monitoredstructure. As the electrical impedance of thePZT patches is directly related to the mechanicalimpedance of the structure, the impedancemeasurements can be used for damage detection.The quantification of the damage is done by ametric, which is attributed a characteristic scalarvalue. In this context, the project developed byFederal University of Uberlandia with partnershipwith EMBRAER, studied the feasibility of thestructural health monitoring technique based onthe electromechanical impedance measurements todetect incipient damage at inaccessible location inthe airplane. This paper presents the results of thistechnique obtained by UFU for the consolidationof this tool. Despite the method is still applied inlaboratory scale applications, it has shown a greatpotential to detect incipient damage in airplanes’structures, like a rivet loss and cracks. This worksalso describes an impedance measurement systemdeveloped at UFU.Se denomina Monitoreo de Salud Estructuralal proceso de detección de anomalías (dañoso degradación) en varias áreas de ingeniería,tales como, aeroespacial, civil y mecánica,principalmente. Una de las técnicas utilizadaspara monitorear la integridad de una estructuraes basada en la medición de impedanciaelectromecánica. Esta técnica monitorea lavariación de impedancia mecánica de unaestructura, causada por la existencia de uno o másdaños, por medio de la medición de la impedanciaeléctrica de las pastillas de material piezoeléctricoacopladas en la superficie de la estructura. Laimpedancia eléctrica de las pastillas piezoeléctricasestá directamente relacionada con la impedanciamecánica de la estructura, es por eso que a partir dela variación de las señales de impedancia medidasse puede concluir la presencia o no de un daño.La cuantificación del daño se hace por mediode una métrica que es especialmente definidapara atribuirle un valor escalar característico.En el marco del proyecto de investigación enconvenio con la EMBRAER, la UniversidadFederal de Uberlândia (UFU), estudia la viabilidaddel uso de la técnica de Monitoreo de SaludEstructural basada en mediciones de impedanciaelectromecánica como una herramienta dedetección de daños incipientes en lugares dedifícil acceso en aeronaves. El presente trabajopresenta los resultados obtenidos en la UFU parala consolidación de esta herramienta, los cualesa pesar de encontrarse todavía en aplicacionesa nivel de laboratorio han mostrado un granpotencial para la detección de daños incipientesen estructuras aeronáuticas, tales como, pérdida deun remache y fisuras. En este trabajo también serádescrito un sistema de medición de impedanciaelectromecánica desarrollado en la UFU

Recent Developments on Impedance Measurements with DSP based Ellipse Fitting Algorithms

In this paper, recent advances of a new digital-signalprocessor (DSP)-based impedance measurement instrument under development are presented. The digital signal processing algorithms are based on ellipse fitting for the extraction of the acquired sine signal parameters so that the impedance magnitude and phase can be determined. Special attention is devoted to the improvement of the algorithm’s efficiency, i.e., by enabling the acquisition of a large number of samples by processing nonconsecutive data segments with no extra memory requirements. This capability is shown to reduce the experimental uncertainties of the estimated parameters. The systematic errors caused by the two different acquisition channels are measured and taken into account. The combined experimental measurement uncertainty is evaluated for the frequency sweep measurement of a particular impedance

AC/DC differential bridge based solution-electrode interfacial capacitance biosensor, for field-deployable real-time and low-cost detection of MCLR in drinking water.

Microcystin-LR (MCLR, one of the most toxic and commonly found products of cyanobacteria in freshwater resources, threatens human health and the livestock. WHO has set a standard limit of 1 μg⁄l for the concentration of MCLR in drinking water. The lab-based, specialized water quality monitoring tests for this purpose are not only expensive but also slow and require sample preparation and transportation from distant sites. Therefore, there is a need for a handheld, field-deployable and low-cost biosensor to make frequent water quality monitoring easier. Many field-deployable biosensors with applications in environmental monitoring and healthcare where concentrations of interest are on the order of μg/l and fewer face challenges in achieving high dynamic range and lower detection resolution due to the resultant small fractional change in the transducer characteristics. Additionally, non-faradaic label-free biosensors for MCLR type applications face difficulty in real-time data analysis due to signal drift, non-specific binding of non-target particles and last but not least noise coming from both transducer and readout electronics. This dissertation is mainly focused on utilizing electronic circuit methods to fill the gap of reading small responses from the bio-transducer with sufficient accuracy and sensitivity. Differential bridge based transduction as sensitivity booster and careful design of amplification unit and real-time signal processing capable of extracting signal information buried in noise are part of the presented work that achieves 8-bit resolution within a 1% full-scale transducer fractional capacitive change

Advances in Piezoelectric Transducers

The piezoelectric transducer converts electric signals into mechanical vibrations or vice versa by utilizing the morphological change of a crystal which occurs on voltage application, or conversely by monitoring the voltage generated by a pressure applied on a crystal. This book reports on the state of the art research and development findings on this very broad matter through original and innovative research studies exhibiting various investigation directions. The present book is a result of contributions of experts from international scientific community working in different aspects of piezoelectric transducers. The text is addressed not only to researchers, but also to professional engineers, students and other experts in a variety of disciplines, both academic and industrial seeking to gain a better understanding of what has been done in the field recently, and what kind of open problems are in this area