查看更多>>摘要：? 2021In this paper, the scale ambiguity in underwater monocular visual odometry is solved with 2-D sonar measurements obtained from three viewpoints. Each measurement value is formulated as geometrical constraint and the recovered scale can be expressed in closed-form. Different from the existing method which assumes the features being on the same plane in order to meet the pre-condition of quasi-homography transformation, our method allows the observation points to be distributed spatially (not limited to a plane), thus extending the proposed method to more general application environments. An error contribution criterion of sonar measurement is proposed to weight the constraints, which further reduces the influence of noisy input. Experiments are performed in both simulated and real environments. For nonplanar case, the proposed method gives improved accuracy after employing constraint weighting. As for planar case, our method achieves comparable accuracy to the existing method, while the time consumption is much lower.
查看更多>>摘要：? 2022 Elsevier LtdGiven that the ionic conductivity of a proton exchange membrane fuel cell is significantly influenced by water concentration in the channel, an elaborate water management strategy is crucial to ensure durability and performance of these types of fuel cells. In this study, the vapour concentration of a gas mixture was observed in the through-plane direction in a bipolar plate. The stainless steel bipolar plate used here has straight channels containing installed relative humidity/temperature micro-sensors such that the vapour flow behaviour can be observed. The vapour concentration in the anode channel is increased by the back diffusion of water vapour from the cathode. The vapour concentration at the cathode channel increases with the water produced during the electrochemical reaction. The distribution of the dew point temperature at the anode/cathode channel shows that water transport to the anode increases the vapour concentration of anode gases.
查看更多>>摘要：? 2022 Elsevier LtdBecause of the occlusion of the railings, the collected animal point clouds become fragmentary and have the large holes. The incomplete point clouds have a great impact on body size measurements of pigs. This paper presents an improved hole repairing algorithm based on cubic B-spline curve for region defining. Meanwhile, by applying approximation fitting and interpolation based on cubic B-spline curve, we can repair the holes of the pig point clouds after slicing longitudinally in the mid-axis plane of the pig body point clouds. In the experiment, comparisons were made among polar coordinate transformation algorithm, surface fitting algorithm, triangularization algorithm, and the algorithm proposed by us to verify hole repairing effect and estimation accuracy of abdominal circumference. The results show that we have proposed an algorithm with a better repairing effect and a higher accuracy in the abdominal circumference measurement of pigs.
查看更多>>摘要：? 2021 Elsevier LtdTo guarantee proper seedbed preparation, it is important to assess and control soil aggregate size in tillage operations. Doing so would lead to higher crop yield and more efficient resource use. This study proposes a portable smartphone-based machine vision system using convolutional neural network (CNN) for the classification of soil texture images taken from 20, 40 and 60 cm heights. The proposed CNN model consists of two blocks with several different layers. The first block (feature extraction) includes Conv, Max-pooling, drop out and batch normalization layers. The second block (classifier) consists of fully connected layers, flatten and SVM classifier. Also in this study, ANN, SVM, RF and KNN algorithms were used to compare the proposed CNN results with other classifiers. The proposed CNN model was able to successfully predict soil images in distances of 20, 40 and 60 cm with the accuracies of 99.89, 99.81 and 99.58%, respectively. The results showed that the best performance was obtained when using fully preprocessed images at the height of 20 cm. Ultimately, a graphical user interface was designed in form of a user-friendly software to predict soil texture based on CNN model. The results revealed the proposed CNN method could quickly and accurately predict the type of soil texture on large scale farms and thus be a good alternative to the costly and time-consuming laboratory methods.
查看更多>>摘要：? 2022 Elsevier LtdTo obtain weak structure damage information, existing methods basically enhance the signal detected by an acoustic emission sensor. There is a risk that the sensor cannot obtain the structural damage information. In response to this problem, this study presents a novel method to enhance the acoustic emission information before it reaches the sensor based on acoustic black holes. First, the enhancement effect of acoustic black holes on acoustic emission signals was determined by simulations. Then, the enhancement effects of the geometric parameters of the acoustic black holes on acoustic emission signals were studied in detail, and the selection method of the best geometric parameters in practical applications was obtained. Finally, broken-lead experiments were performed on the plate to verify the ability and regularity of the proposed method. The results show that the presented method has good prospects for enhancing acoustic emission information.
查看更多>>摘要：? 2021This paper reports on the development of a software platform for acquiring ultrasonic guided waves for the application of structural health monitoring (SHM) of composite fuselage panels. The focus of the developments has been its application at an industrial scale. As part of the CleanSky2 project developments, the application of SHM has been designed, developed and tested following a building block (BB) approach, from a large number of tests at coupon level to element and sub-component levels each with increasing complexity. Therefore, an SHM measurement platform has been developed and tested at different stages of the BB tests under combined operational and environmental conditions, with different sensor technology and sensor network. The platform is demonstrated to be reliable, user friendly and scalable to large sub-components, with optimized data acquisition and handling protocols.
查看更多>>摘要：? 2022 Elsevier LtdThis study proposes an enhanced inverse finite element method (iFEM) to reconstruct the structural displacements based on strain data collected from single surface (top/bottom) of the structure. The method eliminates the drawback of existing iFEM formulations for which the strain sensors must be symmetrically installed on both top and bottom surfaces of the structure with respect to its mid-plane. Therefore, the present approach increases the practical application of shape sensing with a lower number of sensors. To this end, the least-squares variational principle of iFEM is established using scaled boundary method, which represents the displacement field of structure by scaling the boundary in the radial direction with a scaling factor. Moreover, a novel five-node inverse plate element is developed to discretize the geometry and approximate the kinematic variables of the present approach. This element increases the order of interpolation function and thus reduces the number of strain sensors used in shape-sensing process. Overall, the accuracy and applicability of the present iFEM is numerically and experimentally validated by performing shape sensing analyses of various plate structures.
查看更多>>摘要：? 2022 Elsevier LtdDynamic strain measurement is critical in blade vibration monitoring for evaluating the residual life and health condition of rotating blades. Blade tip time (BTT) is recognized as a promising technique to replace traditional strain gauge measurement. This paper presents a method for dynamic strain reconstruction as well as vibration parameter identification based on BTT via the L1/2-norm sparse regularization and response transmissibility. First, a sparse representation model based on the L1/2-norm penalty is developed to identify blade vibration frequency and blade-tip displacement. Second, a displacement-to-strain transmissibility (DST) is proposed for strain reconstruction from identified displacement. The mode shapes of the blade are needed to calculate the DST. The proposed method is named L1/2-DST, which has a great advantage of achieving non-intrusive strain measurement for rotating blades using BTT. Numerical simulation and spin experiment show that the L1/2-DST method enables accurate dynamic strain reconstruction and robustness to noise.
查看更多>>摘要：? 2022 Elsevier LtdCorrosion is one of inevitable problems of constructional steel exposed to atmospheric environment in the long time, of which the quantification usually plays a key role in the accurate safety evaluation of corroded steel structure. Aiming to determine the reasonable quantitative method of corrosion, the morphological parameters were thoroughly investigated based on the surface measurements of 6 groups of corroded steel specimens obtained by accelerated corrosion test. By using the statistical analysis, the corrosion pitting parameters and their evolution rules were systematically analyzed and discussed. The distribution laws of pitting depth, width and spacing distance, and their statistical characteristic parameters (i. e., the expectation and the variance) were revealed. And then, their probability density functions were given at different pitting shape parameter. At last, the fractal character of corroded specimen surface was also researched. The results showed that all the pitting parameters obeyed the chi-square distribution (χ2). The corrosion pit evolved from a single corrosion pit to a double-stepped corrosion pit, and finally to be a single-stepped style. With increase of corrosion degree, the multi-fractal dimension (D) of corroded surface generally increased. Besides, the value of D can be well predicted by the combined effect of all characteristic parameters of corrosion pit. Finally, based on the W-M function and considering the relationship between the characteristic parameters and fractal dimension, and noise reduction and continuous treatment in consideration, the fractal reconstruction model of corroded steel surface was proposed, which can be utilized to accurately simulate the corroded surface of constructional steel.
查看更多>>摘要：? 2022 Elsevier LtdSince worn surfaces contain rich information of the wear mechanisms, in-situ measurements of surface topography can characterize ongoing wear degradation in machines. With the help of photometric stereo vision, three-dimensional (3D) topography of worn surfaces is obtained with a monocular microscope. However, the accuracy of the reconstructed surfaces remains low due to the non-Lambertian reflections of worn surfaces and noise in the image acquisition equipment. To address this issue, an optimized photometric stereo approach is proposed for the improvement of worn surface reconstruction. To accommodate the non-Lambertian reflections, a multi-branch network is constructed to estimate normal vectors from both the photometric images and the incident illumination directions. The estimated normal vectors are adopted to reconstruct worn surface topography by embedding prior knowledge. With this design, the overall distortion caused by image noise is effectively suppressed. The proposed method is verified by comparing with the Laser Scanning Confocal Microscopy (LSCM). As the main result, over 88% similarity on the worn surface roughness can be obtained.
NSTL
Elsevier