A novel autonomous strategy for multi-bolt looseness detection using smart glove and Siamese double-path CapsNet

Recently, the issue of bolt looseness has attracted more attention due to its severe consequences. Among different methods for bolt looseness detection, the active sensing method that is based on stress wave signals is preferred since it is low cost and high robust. However, current active sensing method depends on permanent contact sensors, which may be impractical. Moreover, the investigation of multi-bolt looseness detection via the active sensing is very limited so far. With the above deficiency in mind, we propose a new robotic-assisted active sensing method based on our newly designed PZT-enabled smart gloves (SGs) and position-based visual servoing (PBVS) technique. Particularly, another main contribution is that we develop a new Siamese CapsNet to classify stress wave signals under different cases for multi-bolt looseness detection. Compared to machine learning (ML) and traditional deep learning techniques such as Convolutional Neural Networks (CNN), the proposed Siamese CapsNet model can achieve better performance and realize the recognition of signals that is never used during the training, which is impossible for common classification methods. Finally, an experiment is conducted to verify the effectiveness of the proposed method and Siamese CapsNet, which can guide future research significantly.

Communication with self, friends and foes in active-sensing animals

ABSTRACT Animals that rely on electrolocation and echolocation for navigation and prey detection benefit from sensory systems that can operate in the dark, allowing them to exploit sensory niches with few competitors. Active sensing has been characterized as a highly specialized form of communication, whereby an echolocating or electrolocating animal serves as both the sender and receiver of sensory information. This characterization inspires a framework to explore the functions of sensory channels that communicate information with the self and with others. Overlapping communication functions create challenges for signal privacy and fidelity by leaving active-sensing animals vulnerable to eavesdropping, jamming and masking. Here, we present an overview of active-sensing systems used by weakly electric fish, bats and odontocetes, and consider their susceptibility to heterospecific and conspecific jamming signals and eavesdropping. Susceptibility to interference from signals produced by both conspecifics and prey animals reduces the fidelity of electrolocation and echolocation for prey capture and foraging. Likewise, active-sensing signals may be eavesdropped, increasing the risk of alerting prey to the threat of predation or the risk of predation to the sender, or drawing competition to productive foraging sites. The evolutionary success of electrolocating and echolocating animals suggests that they effectively counter the costs of active sensing through rich and diverse adaptive behaviors that allow them to mitigate the effects of competition for signal space and the exploitation of their signals.

Real-Time Monitoring of Timber-Surface Crack Repair Using Piezoelectric Ceramics

Real-time assessment of timber-surface crack repair is crucial to the stability and safety of timber structures. Epoxy resin was used to repair timber cracks, and the active sensing technique using piezoelectric ceramics was applied to monitor the repair process of timber surface cracks in real time. Sixteen wood samples were designed for axial compression tests and active monitoring tests. A pair of lead zirconate titanate patches was pasted on the surface of the timber specimens as actuators and sensors for signal transmission and reception, through wavelet packet analysis, the variations in the signal amplitude, and wavelet coefficients. The relationship between the wavelet packet energy of the monitoring signal and the ultimate bearing capacity of the specimens at different periods after grouting was established. Based on the root-mean-square deviation, the damage index, DI, was introduced to evaluate the repair degree of timber surface cracks quantitatively. The results showed that the active sensing method can evaluate the strength development in timber-surface crack repair in real time.

Structural Integrity Assessment of Composites Plates with Embedded PZT Transducers for Structural Health Monitoring

Active sensing using ultrasonic guided waves (UGW) is widely investigated for monitoring possible damages in composite structures. Recently, a novel diagnosed film based on a circuit-printed technique with piezoelectric lead zirconate titanate (PZT) transducers has been developed. The diagnostic film is a replacement for the traditional cable connection to PZT sensors and has been shown to significantly reduce the weight of the host structure. In this work, the diagnosed films were embedded into composite structures during manufacturing using a novel edge cut-out method during lay-up, which allowed for edge trimming after curing. In this paper, the effect of fatigue loading on the integrity of PZT transducers is initially investigated. The electro-mechanical impedance (EMI) properties at different fatigue loading cycles were used as the diagnostic measure for the performance of the sensors. At the same time, the behaviours of UGW were investigated at different fatigue loading cycles. It was found that the EMI properties and active sensing behaviours remained stable up to 1 million cycles for the force ranges of 0.5~5 kN and 1~10 kN. Next, the effect of embedding the diagnosed film on the mechanical properties of the host composite structure was investigated. Tensile and compressive tests were conducted and the elastic modulus of composite coupons with and without embedded PZT diagnosed films were compared. The elastic modulus of composite coupons with PZT diagnosed films embedded across the entire coupon reduced by as much as 20% for tensile tests and just over 10% for compressive tests compared to the coupons without embedded sensors. These reductions are considered the worst-case scenario, as in real structures the film would only be embedded in a relatively small area of the structure.

Enhanced Propanol Response Behavior of ZnFe2O4 NP-Based Active Sensing Layer Induced by Film Thickness Optimization

Development of gas sensors displaying improved sensing characteristics including sensitivity, selectivity, and stability is now possible owing to tunable surface chemistry of the sensitive layers as well as favorable transport properties. Herein, zinc ferrite (ZnFe2O4) nanoparticles (NPs) were produced using a microwave-assisted hydrothermal method. ZnFe2O4 NP sensing layer films with different thicknesses deposited on interdigitated alumina substrates were fabricated at volumes of 1.0, 1.5, 2.0, and 2.5 µL using a simple and inexpensive drop-casting technique. Successful deposition of ZnFe2O4 NP-based active sensing layer films onto alumina substrates was confirmed by X-ray diffraction and atomic force microscope analysis. Top view and cross-section observations from the scanning electron microscope revealed inter-agglomerate pores within the sensing layers. The ZnFe2O4 NP sensing layer produced at a volume of 2 μL exhibited a high response of 33 towards 40 ppm of propanol, as well as rapid response and recovery times of 11 and 59 s, respectively, at an operating temperature of 120 °C. Furthermore, all sensors demonstrated a good response towards propanol and the highest response against ethanol, methanol, carbon dioxide, carbon monoxide, and methane. The results indicate that the developed fabrication strategy is an inexpensive way to enhance sensing response without sacrificing other sensing characteristics. The produced ZnFe2O4 NP-based active sensing layers can be used for the detection of volatile organic compounds in alcoholic beverages for quality check in the food sector.

Old - New Concrete Interfacial Bond Slip Monitoring in Anchored Rebar Reinforced Concrete Structure Using PZT Enabled Active Sensing

Post-installed anchor technology is widely used for structural strengthening and for retrofitting existing constructions. The old–new concrete interface associated with using this technology is of great significance in the shear capacity of concrete structural member under shear forces. For such members, interface failures usually occur with bond slip. In this paper, an application of a piezoceramic enabled active sensing technique is put forward to monitor Old - New concrete interfacial bond slip. Three concrete specimens (S1, S2, and S3) are fabricated and each specimen consists of two parts. Each part is made of concrete poured at different times, and both are bonded with an anchored rebar embedded inside the specimen. Two PZT aggregates bonded to opposing sides of the concrete specimen helped to realize active sensing. During the shear loading test, both the load values and the signals from sensors are acquired every 20 s. The test durations of S1, S2 and S3 lasted 960, 1,120, and 1,110 s, respectively. Furthermore, the received signal energies are quantified through wavelet packet analysis to monitor the Old - New concrete interfacial bond slip process. The experimental results show that the change of WPEI in the received signals has a direct relation with the severity of the Old - New concrete interfacial bond slip. Moreover, the PZT-based active sensing approach is feasible to monitor the shear-induced bond slip in Old - New concrete interfaces.