Research

16 pages, 3756 KiB

Open AccessArticle

Automatic Registration Algorithm for the Point Clouds Based on the Optimized RANSAC and IWOA Algorithms for Robotic Manufacturing

by Guanglei Li, Yahui Cui, Lihua Wang and Lei Meng

Appl. Sci. 2022, 12(19), 9461; https://doi.org/10.3390/app12199461 - 21 Sep 2022

Cited by 8 | Viewed by 1748

Abstract

In order to solve the problems of low accuracy and low efficiency of point cloud registration for stereo camera systems, we propose a binocular stereo camera point cloud registration method based on IWOA and Improved ICP. We propose the following approaches in this [...] Read more.

In order to solve the problems of low accuracy and low efficiency of point cloud registration for stereo camera systems, we propose a binocular stereo camera point cloud registration method based on IWOA and Improved ICP. We propose the following approaches in this paper—the registration process is divided into two steps to complete the initial coarse registration and the exact registration. In the initial registration stage, an improved Whale Optimization Algorithm (IWOA) based on nonlinear convergence factor and adaptive weight coefficients was proposed to realize the initial registration in combination with the RANSAC algorithm, and the obtained transformation matrix was used as the initial estimate of the subsequent exact registration algorithm. In the second step of the exact registration stage, an IICP algorithm with the introduction of normal vector weighting constraints at key points was proposed for achieving point cloud exact registration. This algorithm was verified by using Stanford point clouds (bunnies and monkeys) and our own point clouds algorithm, and the proposed algorithm in this paper has high registration accuracy, improved registration speed, and convergence speed. Full article

(This article belongs to the Special Issue Advanced Digital Non-Destructive Testing Technology)

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14 pages, 3793 KiB

Open AccessArticle

Applications of Stretching Technique and Time Window Effects on Ultrasonic Velocity Monitoring in Concrete

by Bibo Zhong and Jinying Zhu

Appl. Sci. 2022, 12(14), 7130; https://doi.org/10.3390/app12147130 - 14 Jul 2022

Cited by 10 | Viewed by 1562

Abstract

Coda wave interferometry (CWI) has been used to measure the relative wave-velocity change (

d V / V

) caused by small changes in materials. This study uses the stretching processing technique which has been used for CWI analysis to investigate velocity changes [...] Read more.

Coda wave interferometry (CWI) has been used to measure the relative wave-velocity change (

d V / V

) caused by small changes in materials. This study uses the stretching processing technique which has been used for CWI analysis to investigate velocity changes of direct longitudinal (P) wave, direct shear (S) wave, and coda wave in concrete by choosing different time windows of ultrasonic signals. It is found that the obtained wave-velocity change depends on the time window position, because the relative contribution of P wave and S wave is different in each signal window. This paper presents three experimental scenarios of velocity change in concrete: early-age hydration, temperature change, and uniaxial loading. In early-age concrete, the S wave has a larger relative velocity change than the P wave, which is consistent with the microstructure development due to the hydration process. Temperature change causes a larger

d V / V

on the P wave than on the S wave, and the difference between P and S wave-velocity changes may be used to determine nonlinear elastic constants of materials. In the uniaxial loading experiment, analysis of the direct P wave can distinguish the acoustoelastic effects in the stress direction and the non-stress direction, which may potentially be used for stress evaluation in prestressed structures. However, the coda wave does not show this directional property to stress due to multiple scattering in the medium. Full article

(This article belongs to the Special Issue Advanced Digital Non-Destructive Testing Technology)

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17 pages, 17530 KiB

Open AccessArticle

New On-Line MFL Testing Method and Apparatus for Winding Mine Hoist Wire Rope

by Xiaoyuan Jiang, Yanhua Sun, Bo Feng, Mengqi Liu, Xiaotian Jiang, Ran Li, Lingsong He and Yihua Kang

Appl. Sci. 2022, 12(14), 6970; https://doi.org/10.3390/app12146970 - 09 Jul 2022

Cited by 2 | Viewed by 1480

Abstract

Based on the introduction and analysis of difficulties encountered during technical inspection of the wire rope of a winding mine hoist (WMH) working at high speed, an open-loop permanent magnet magnetizer was used to simulate and analyze the effect of the structural dimensions [...] Read more.

Based on the introduction and analysis of difficulties encountered during technical inspection of the wire rope of a winding mine hoist (WMH) working at high speed, an open-loop permanent magnet magnetizer was used to simulate and analyze the effect of the structural dimensions of this magnetizer on the magnetic leakage field of a defect, and the results of the simulation analysis were initially verified by experiments. Additionally, in order to keep the axial position of the probe in line with the axial position of the wire rope, a rocker arm was proposed to act in coordination with a motor to drive the clutching open and closed probe, thereby creating an on-line nondestructive testing device to float and track the movement of the wire rope in different directions. Finally, the device was applied to testing of WMH wire rope on site to validate the effectiveness and feasibility of the method. Full article

(This article belongs to the Special Issue Advanced Digital Non-Destructive Testing Technology)

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18 pages, 3430 KiB

Open AccessArticle

Weak Signal Processing Methods Based on Improved HHT and Filtering Techniques for Steel Wire Rope

by Shiwei Liu, Yanhua Sun, Lingsong He and Yihua Kang

Appl. Sci. 2022, 12(14), 6969; https://doi.org/10.3390/app12146969 - 09 Jul 2022

Cited by 6 | Viewed by 1464

Abstract

As one of the most important processes in steel wire rope inspection, defect signal processing is of great significance in guaranteeing safety and precision measurement. Aiming at the weak signal detection of steel wire rope with mixed strands and noise, a combined signal [...] Read more.

As one of the most important processes in steel wire rope inspection, defect signal processing is of great significance in guaranteeing safety and precision measurement. Aiming at the weak signal detection of steel wire rope with mixed strands and noise, a combined signal processing method based on magnetic flux leakage testing and multi-step filtering techniques are proposed in this paper. The experiments are first introduced and performed on three typical types of steel wire rope with diameters of 28 mm, 32 mm, 45 mm, and different wire broken defects detected under liftoff distances of 13 mm and 20 mm; the acquired signals are then analyzed both in time and frequency domain. According to the weak signal characterizations, the principle of the proposed methods and algorithm are given concretely. Afterwards, comparison of signal processing results between the traditional lowpass filtering, wavelet denoising, median filtering, and the proposed method are presented. Finally, the influence factors of smoothing types and moving average span of the proposed methods are investigated. The processing results of the proposed methods are shown through short-time Fourier transform and signal-to-noise ratio analysis, which not only demonstrates the validity and feasibility of the combined methods with the highest signal to noise ratio of 90.37 dB, but also exhibits a great potential of precision defect detection and practical application in steel wire rope inspection. Full article

(This article belongs to the Special Issue Advanced Digital Non-Destructive Testing Technology)

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21 pages, 10042 KiB

Open AccessArticle

The Research of 30 mm Detecting Distance of Testing Device for Wire Rope Based on Open Magnetizer

by Mengqi Liu, Chi Zhang, Xiaoyuan Jiang, Yanhua Sun, Xiaotian Jiang, Ran Li and Lingsong He

Appl. Sci. 2022, 12(10), 4829; https://doi.org/10.3390/app12104829 - 10 May 2022

Cited by 4 | Viewed by 1506

Abstract

Wire rope will have defects such as local faults (LF) and loss of metal area (LMA) during the long-term using process. The nondestructive testing method of magnetic flux leakage (MFL) has been widely used in wire rope defect detection. Currently, the detecting distance [...] Read more.

Wire rope will have defects such as local faults (LF) and loss of metal area (LMA) during the long-term using process. The nondestructive testing method of magnetic flux leakage (MFL) has been widely used in wire rope defect detection. Currently, the detecting distance between magnetic sensors and wire rope with the MFL method is relatively small (2–5 mm). Considering the inner surface of the sensor head is close to the wire rope, it quickly leads to the sensor head scraping off the surface oil of the wire rope or being stuck by a cut wire in the course of MFL detection. Therefore, it is challenging to realize the sensor with MFL detection of wire rope obtaining the weak signal at a large lift-off (>30 mm). This study used finite element analysis to verify if the MFL signal exists at the large lift-off (>30 mm). Meanwhile, the sensor head was improved using an open magnetizer to make the wire rope reach saturation and excite enough magnetic leakage field. By combining magnetic sensing and coupling and a weak analog signal processing method, not only was the signal effectively detected, but also the signal-to-noise ratio (SNR) was improved. Finally, experiments verify the feasibility of detecting defects at a large distance. The method also has been applied in the high-speed detection of wire rope, which can detect broken wire of 1 mm diameter. Full article

(This article belongs to the Special Issue Advanced Digital Non-Destructive Testing Technology)

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14 pages, 4062 KiB

Open AccessArticle

Automatic Defect Identification Method for Magnetic Particle Inspection of Bearing Rings Based on Visual Characteristics and High-Level Features

by Yun Yang, Yao Yang, Long Li, Cuili Chen and Zhou Min

Appl. Sci. 2022, 12(3), 1293; https://doi.org/10.3390/app12031293 - 26 Jan 2022

Cited by 12 | Viewed by 2531

Abstract

Fluorescent magnetic particle inspection (MPI) is a conventional non-destructive testing process for railway bearing rings that still needs to be completed manually. Due to the complexity of bearing ring surfaces in inspection, automatic detection for bearing rings based on image processing is difficult [...] Read more.

Fluorescent magnetic particle inspection (MPI) is a conventional non-destructive testing process for railway bearing rings that still needs to be completed manually. Due to the complexity of bearing ring surfaces in inspection, automatic detection for bearing rings based on image processing is difficult to apply. Therefore, we proposed a bearing ring defect identification method based on visual characteristics and high-level features. Inspired by the mechanism of human visual perception, defects can be identified from the complex background conveniently by human eyes. According to the linear structure characteristics and greyscale distribution characteristics of cracks in the acquired images, we introduce the centerline extraction and Gaussian similarity measure to reduce background noise and obtain the crack candidate regions. Then, an improved MobileNetV3 is used to extract high-level features of the candidate regions and determine whether they are defective, which uses a new attention module, Coordinate Attention (CA), to substitute the Squeeze-and-Excitation (SE) attention to improve the performance. The experimental results show that the detection accuracy rate of the proposed method is 96.5%. Compared with traditional methods, the proposed method can efficiently extract crack defects in a complex textured background and shows high-quality performance in recall and precision. Full article

(This article belongs to the Special Issue Advanced Digital Non-Destructive Testing Technology)

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16 pages, 36634 KiB

Open AccessArticle

Research on Sparse Representation Method of Acoustic Microimaging Signals

by Kun Wang, Tao Leng, Jie Mao, Guoxuan Lian and Changzhi Zhou

Appl. Sci. 2022, 12(2), 642; https://doi.org/10.3390/app12020642 - 10 Jan 2022

Viewed by 1168

Abstract

Acoustic microimaging (AMI), a technology for high-resolution imaging of materials using a scanning acoustic microscope, has been widely used for non-destructive testing and evaluation of electronic packages. Recently, the internal features and defects of electronic packages have reached the resolution limits of conventional [...] Read more.

Acoustic microimaging (AMI), a technology for high-resolution imaging of materials using a scanning acoustic microscope, has been widely used for non-destructive testing and evaluation of electronic packages. Recently, the internal features and defects of electronic packages have reached the resolution limits of conventional time domain or frequency domain AMI methods with the miniaturization of electronic packages. Various time-frequency domain AMI methods have been developed to achieve super-resolution. In this paper, the sparse representation of AMI signals is studied, and a constraint dictionary-based sparse representation (CD-SR) method is proposed. First, the time-frequency parameters of the atom dictionary are constrained according to the AMI signal to constitute a constraint dictionary. Then, the AMI signal is sparsely decomposed using the matching pursuit algorithm, and echoes selection and echoes reconstruction are performed. The performance of CD-SR was quantitatively evaluated by simulated and experimental ultrasonic A-scan signals. The results demonstrated that CD-SR has superior longitudinal resolution and robustness. Full article

(This article belongs to the Special Issue Advanced Digital Non-Destructive Testing Technology)

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15 pages, 64673 KiB

Open AccessArticle

Dynamic Wind Turbine Blade Inspection Using Micro-Polarisation Spatial Phase Shift Digital Shearography

by Zhiyao Li, Mohammad Osman Tokhi, Ryan Marks, Haitao Zheng and Zhanfang Zhao

Appl. Sci. 2021, 11(22), 10700; https://doi.org/10.3390/app112210700 - 12 Nov 2021

Cited by 5 | Viewed by 1516

Abstract

Shearography, as a novel non-destructive evaluation technique, has shown notable ability in the detection of composite materials. However, in current shearography practices, the phase shifting and loading methods applied are mainly static. For instance, vacuum hood or force loading facilities are often used [...] Read more.

Shearography, as a novel non-destructive evaluation technique, has shown notable ability in the detection of composite materials. However, in current shearography practices, the phase shifting and loading methods applied are mainly static. For instance, vacuum hood or force loading facilities are often used in phase-shifting shearography, and these are hard to realise with robotic control, especially for on-board inspection. In this study, a dynamic process for detecting defects in the subsurface of a wind turbine blade (WTB) using spatial phase shift with dynamic thermal loading was proposed. The WTB sample underwent a dynamic thermal loading operation, and its status is captured by a Michelson interferometric-based spatial phase shift digital shearography system using a pixelated micro-polarisation array sensor. The captured images were analysed in a 2D frequency domain and low-pass filtered for phase map acquisition. The initial phase maps underwent a window Fourier filtering process and were integrated to produce a video sequence for realisation of visualising the first derivative of the displacement in the process of thermal loading. The approach was tested in experimental settings and the results obtained were presented and discussed. A comparative assessment of the approach with shearography fringe pattern analysis and temporal phase shift technique is also presented and discussed. Full article

(This article belongs to the Special Issue Advanced Digital Non-Destructive Testing Technology)

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