1,721,224 research outputs found
Sushi Drop - SUstainable fiSHeries wIth DROnes data Processing
No full textWithin SUSHI-DROP, a customized unmanned underwater vehicles will be developed and equipped with acoustical and optical technologies in order to implement a non-invasive mean to assess environmental status of habitats, fish stocks population and, in general, to monitor the biodiversity of marine ecosystems. We are planning to assess the accuracy of the opto-acoustic surveys in deriving single-species abundance indices (in numbers or weight) for direct input into stock assessments, and to evaluate the benefits brought by these new technologies with respect to the classical procedures based on fish sampling. Moreover, a dedicated open-access database system will be created to collect, maintain and share the scientific data acquired by the UUVs
Sviluppo e progettazione di sistemi innovativi per il monitoraggio in tempo reale dell’integrità strutturale di parti di veicoli racing/automotive e confronto con tecniche diagnostiche tradizionali
No full textSviluppo e progettazione di sistemi innovativi per il monitoraggio in tempo reale dell’integrità strutturale di parti di veicoli racing/automotive e confronto con tecniche diagnostiche tradizional
Sensors
No full textSensors provides an advanced forum for the science and technology of sensors and biosensors. It publishes reviews (including comprehensive reviews on the complete sensors products), regular research papers and short notes
A piezoelectric coded-excitation scanning acoustic transducer for Lamb wave inspections
Full text linkSeveral techniques for Guided Wave (GW) inspections have already been developed. Most of them rely on extensive sensor deployment and damage localization algorithms characterized by significant computational costs. However, there is a growing demand for simpler, more autonomous, and more affordable systems across various fields. In particular, the implementation of wireless, battery-powered systems with a reduced number of sensor nodes and simpler processing would greatly facilitate the transition of this inspection technology on the field. Following this direction, this work presents the design of a novel piezoelectric transducer composed of four different patches, i.e. with only four input/output channels, to scan a given area. The peculiar piezo-load distributions allow the association of different spectral binary sequences for each 6∘ discrete angular step. By evaluating the distance-of-flights (DoFs) of detected peaks, the range coordinates for multiple defects are identified. Meanwhile, the angular information is extracted by demodulating binary sequences of peaks with comparable DoFs across several frequency bands. Since the transducer is designed as an encoder, it is referred to as coded-excitation scanning acoustic transducer (CESAT). More specifically, the Gray code is used to generate spectral patterns to reduce the uncertainty between two adjacent angular steps. A new quantization procedure for the optimal generation of the piezo distributions is also proposed. Ad hoc signal processing algorithms, suitable for embedded applications, were developed to extract multi-target range and angle information. The processing is based on the frequency decomposition of the recorded signal using an FIR filter bank and on dispersion compensation procedures for pulse 're-compression'. The transducer encoder behavior is validated through a finite element analysis. Finally, numerical simulations were performed to assess the effectiveness of the CESAT and associated signal processing in multi-defect detection and localization tasks
Transducer-to-Transducer Communication in Guided Wave Based Structural Health Monitoring
No full textSystems for guided wave (GW) based structural health monitoring are limited in the frequency bandwidth of the excitation signal due to the underlying wave’s dispersion that causes a broadening of the waveform along the waveguide. Hence, bandlimited waveforms such as toneburst or chirp signals are widely employed. Recently, the authors have investigated the potential of phase-modulated signals, known from CDMA-communication systems, as a possible way to overcome such limitation. It was found that this class of excitation enables a parallel transmission and reception of all piezoelectric transducers which may lead to a significant reduction in the overall system complexity, because of channel switching is not required anymore. In particular, by means of matched filtering a pulse compression and signal demodulation can be achieved. In addition, the signal-to-noise ratio can be improved by considering phase modulation signals of longer code length. In this paper, we investigate additional properties of phase-modulated signals in terms of their capability to transmit digital information on the health status of the structure through the structure itself [1]. This may lead to autonomous GW-based SHM system where the sensor nodes do not communicate with each other through a wireless module, but where the information are being delivered through the waveguide. A proof-of-concept will be demonstrated here on an isotropic plate using both simulated signals and experimental measurements. The implementation of the concept requires to compensate the guided wave signals from dispersion. Here a suitable Warped Frequency transform [2] designed on the group velocity of the guided modes, is applied. Such transformation has two beneficial effects: 1) it compensates for the detrimental effect of dispersion, 2) it preserves the pseudo-orthogonality of the encoded pulses, because it is computed with a unitary operator
Improving Damage Localization Through Gaussian Process Regression and Enhanced Acoustic Emissions Time of Arrival Estimation
No full textAccurate localization of structural flaws through time of arrival (ToA) estimation is fundamental for structural health monitoring (SHM). However, current methods suffer from inaccuracies in noisy environments, particularly when using standard statistical approaches like the Akaike information criterion (AIC). To overcome these limitations, we propose a new approach built on an adaptive picking technique (APT) combined with gaussian process (GP) regression. APT employs frequency-based mode separation and adaptive envelope analysis to reliably identify first arrivals without prior modal knowledge, while GP regression provides probabilistic damage localization with confidence intervals. Experimental validation on an aluminum plate instrumented with six sensors demonstrates superior performance across multiple conditions, achieving a median error of 13.7 mm with 4.9× improvement over AIC-only alternatives. Under noise conditions down to 18 dB), representative of operational scenarios, our approach not only maintains significant robustness, improving up to 8.2× with respect to AIC, but also generalizes across training and testing conditions, confirming its reliability for real-world SHM applications
A design strategy to improve the directivity of wavenumber-spiral frequency-steerable acoustic transducers
Full text linkDrastic hardware simplification and cost reduction of Guided Wave (GW) based systems can be achieved by using piezoelectric transducers that, shaped according to a frequency based beam steering concept, present inherent directional capabilities exhibiting preferential radiation/sensing directions. In particular, directional GWs generation and sensing can be achieved by patterning the piezoelectric material lay-out and the electrodes. Frequency steerable acoustic transducers (FSATs) peculiar electrodes' shape produces a spatial filtering effect which is frequency-dependent, so that a direct relationship can be established between the direction of propagation (wavenumber) and the spectral content of the transmitted/received signal. In this paper we present a novel design strategy of FSAT that enables enhanced sensor directivity by using a local variation of the density of the piezoelectric material
A stamp size, 40mA, 5 grams sensor node for impact detection and location
No full textIn this work, a stamp-size footprint, low power, and light weight sensor node for impact detection and location on laminate composite and metallic structures is presented. This device passively exploits the guided waves originated by the impacts and is meant as a basic building block for smart structure sensor networks development. It draws power from a two-wire differential data-over-power (DoP) network communication interface, which is also used for half-duplex communication at 200 kbps with a gateway device and the other nodes in the network. Each node measures roughly 30mm×23mm, consumes less than 35mA, and weighs less than 5 g, making it attractive for aerospace systems where size, power and weight reduction are crucial. Elastic waves generated from impacts and propagating on the structure
to be monitored are converted to electrical signals by an innovative, patent-pending, spiral shaped piezoelectric transducer. Signals are simultaneously acquired at 1 Msps on each channel and processed by an embedded STM32F3 low-voltage 32-bit mixed-signal MCU with DSP and FPU instructions. A 128 KiB SPI serial SRAM is used for data storage while program instructions are stored in the MCU embedded 256 KiB flash. A low-voltage, high-speed, half-duplex RS485 transceiver is used to interface the MCU to the bus through a filtering mesh of passive components. This mesh also connects to a low-dropout voltage regulator, allowing it to draw power from the DoP bus without interfering with data transmission. A separate gateway device is also presented: it is capable to simultaneously interface and
feed the DoP bus by drawing power either from a common PC USB2.0 port or from an external power supply. A network counting up to 64 nodes on a single wire can be implemented and interfaced to a PC for real-time impact detection applications. This network can be extended to an arbitrary number of nodes by means of signal repeaters
A design strategy for highly directional piezoelectric transducers for Lamb waves inspections
No full textDrastic hardware simplification and cost reduction of Guided Waves (GWs) based systems can be achieved by using shaped transducers that present inherent directional capabilities when generating and sensing elastic waves. Directional transducers for GW generation and sensing are achieved by patterning the piezoelectric material lay-out and the electrodes. The peculiar electrodes’ shape produces a spatial filtering effect which is frequency-dependent,
so that a direct relationship can be established between the direction of propagation (wavenumber) and the spectral content of the transmitted/received signal. This kind of transducer has been named Frequency Steerable Acoustic Transducers (FSATs). In this work, a transducer’s shape design strategy is presented which is able to enhance the
accuracy of the desired Directivity function approximation. The proposed design strategy is based on Dithering techniques. The effectiveness of the novel transducer design methodology is shown through a numerical validation with application to defect detection in an aluminum plate
A New Generation of Frequency Steerable Transducers for Lamb Waves Inspections
No full textGuided Waves (GW) inspection is a popular methodology employed by many Structural Health Monitoring (SHM) systems. GW inspection is typically achieved through phased arrays featuring a large number of piezoelectric transducers. The weight penalty, the complex circuitry, and maintenance concerns associated with wiring a large number of transducers have to be addressed for widespread field deployment of these type of SHM systems. Drastic hardware simplification and cost reduction of Guided wave (GWs) based systems can be achieved by using shaped transducers that present inherent directional capabilities when generating and sensing elastic waves. In particular, Frequency steerable acoustic transducers (FSATs) are based on a spatial filtering effect which is frequency-dependent, so that a direct relationship can be established between the direction of propagation and the spectral content of the transmitted/received differential signals [1]. However, in the first practical realizations of FSATs, two main limitations appeared: i) waves are excited or sensed contemporarily in one direction and in the opposite direction (180° ambiguity), ii) just a relatively rude approximation of the desired directivity has been achieved, resulting in a wave generation/detection even in directions other than the desired one. In this work, a new generation of FSATs is proposed, which allows overcoming the above mentioned limitations. In particular, the 180° ambiguity is eliminated by combining the information of 2 differential signals rather than one [1], as happened for the 1st generation FSATs. The result of this combination is a signal whose spectrum peaks at a frequency “f_d”. The piezoelectric load distribution of the 2nd generation FSAT is designed so that the value of “f_d” varies as a function of the wave direction of propagation in the whole angular range [0-360°]. The proposed embedded system allows to operate on composite panels tackling anisotropic and dispersive propagation, and to implement a SHM system with lower weight and size w.r.t. the actual structural monitoring systems. References [1] E. Baravelli et al., IEEE TIM, 62(8), 2013. [2] L. De Marchi et al., “Piezoelectric sensor, method and apparatus for guided waves inspections in real time,” 2015, temporary patent no. MI2015A000556
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