3D Laser Research Articles

Digital sand patch: Using laser scanning and discrete element simulation for rapider pavement texture depth measurement

The sand patch method is one of the most basic methods for measuring pavement texture depth (TD), which is an important reference index for pavement anti-skid performance evaluation and road maintenance. However, manual sand patch method heavily relies on the experience of the operators. The emergence of laser 3D scanning and simulation has made it possible to conduct digital sand patch. This study introduces a digital sand patch framework based on 3D scanning and discrete element simulation for precise TD measurement. We developed a 3D scanner with an accuracy of 0.04 mm to obtain the pavement texture data, along with algorithms for outlier removal and slope correction in point cloud data. The method of 3D reconstruction of triangular meshes was adopted to transform discrete point clouds into continuous 3D models to build 3D pavement models. In addition, the virtual process of rotation-spreading-measurement of the digital sand patch method was constructed by discrete element simulation with reference to the physical principles of the manual sand patch method. At the same time, an adaptive dynamic feedback control logic was proposed to accurately determine the termination conditions of the sand patching process. To validate our method, we collected 126 samples from over 20 km of pavement surfaces with various gradations. The results demonstrated an average relative error of 2.92 % compared to the manual sand patch method, and a correlation coefficient of 0.9926 with the laser scanning Mean Profile Depth (MPD) algorithm. Stability and accuracy tests, including scanning downsampling and volatility assessments, confirmed the robustness of our method. This innovative technique for rapid and precise TD measurement not only offers immediate practical benefits but also sets the stage for future research on pavement skid resistance.

Mathematical Modeling for Robot 3D Laser Scanning in Complete Darkness Environments to Advance Pipeline Inspection

This paper introduces an autonomous robot designed for in-pipe structural health monitoring of oil/gas pipelines. This system employs a 3D Optical Laser Scanning Technical Vision System (TVS) to continuously scan the internal surface of the pipeline. This paper elaborates on the mathematical methodology of 3D laser surface scanning based on dynamic triangulation. This paper presents the mathematical framework governing the combined kinematics of the Mobile Robot (MR) and TVS. It discusses the custom design of the MR, adjusting it to use of robustized mathematics, and incorporating a laser scanner produced using a 3D printer. Both experimental and theoretical approaches are utilized to illustrate the formation of point clouds during surface scanning. This paper details the application of the simple and robust mathematical algorithm RANSAC for the preliminary processing of the measured point clouds. Furthermore, it contributes two distinct and simplified criteria for detecting defects in pipelines, specifically tailored for computer processing. In conclusion, this paper assesses the effectiveness of the proposed mathematical and physical method through experimental tests conducted under varying light conditions.

3D laser scanning for automated structural modeling and deviation monitoring of multi-section prefabricated cable domes

This paper presents a multi-member automatic structural modeling (MASM) method for high-thrust deviation monitoring of prefabricated cable domes. Point cloud data generated by three-dimensional (3D) laser scanning were segmented into structural modules to effectively reduce the method's computational complexity. A multimember central shrinkage algorithm was developed for skeleton-point recognition. Subsequently, skeleton members were detected with sequentially identified joints, and the structural model of the cable dome was built. The MASM method was validated with respect to its 1) accuracy, ensuring a satisfactory signal-to-noise ratio, and 2) efficiency, ensuring competitive runtime. The use case of the cable-dome deviation monitoring was studied in detail. The proposed MASM method systematically evaluates prefabricated cable domes with multi-section members. This study enables high-fidelity analysis using a structural digital twin for predicting future structural performance.

Accurate extrinsic calibration for the invisible-light 1D laser rangefinder and camera

Abstract A combined sensor, comprising a camera and a one-dimensional laser rangefinder (1D LRF), has wide application across engineering sectors, notably in aerospace. This combined sensor is pivotal for earth observation and deep space exploration. To achieve precise and stable external parameters for this combined sensor, an accurate external calibration method is proposed. Initially, a technique for localized registration of laser spots is introduced to ensure precise determination of their positions, addressing the challenge of laser invisibility in a 1D LRF. Subsequently, a data evaluation criterion known as the data synthesis criterion is presented, addressing the issue of limited constraints in traditional calibration methods. This criterion evaluates relative errors encompassing 1D LRF ranging values, camera external parameters, and laser spot positions. Finally, based on the proposed criteria, a robust extrinsic calibration method is introduced that automatically filters observation data with significant errors and utilizes the growth rate of camera spatial resolution as the termination condition. The efficacy of the proposed method is confirmed through simulation experiments and real-world data experiments.

Virtual Reality Scenario Analysis of Art Design Taking into Account Interactive Digital Media Pattern Generation Technology

In art design, 3D printing technology is crucial, and more and more creators conceive scenes using 3D modeling software to get a three-dimensional and beautiful work. Due to the large amount of noise and redundant points in the raw data collected during the modeling process, the generation speed and rendering effect of 3D models are reduced. Given the above problems, the study designed an interactive 3D lightweight modeling system based on the combination of hand-drawn sketching and laser 3D scanning based on the streamlined algorithm. The experimental results showed that when the hand-drawn speed was 300, the number of triangular slices, model size, and time required to generate the model of the hand-drawn sketching model based on the streamlined algorithm were reduced by 67.39%, 65.48%, and 63.79%, respectively. In the real-time point cloud data streamlining process of the laser 3D scanning model, the point cloud data reduction ratio and the streamlining goodness index of the point cloud streamlining algorithm are 71.99% and 3.06%, respectively. The system performance is robust, and the data processing speed and rendering effect are good.

Experiments on the material and stability performance of slender WAAM plated structures

An experimental study has been carried out to investigate the material and stability performance of WAAM 316L stainless steel plates supported along both edges. The experiments were facilitated by testing a series of square hollow section (SHS) stub columns and tensile coupons extracted from the plates manufactured along with the stub columns. The tensile test results provided the material properties to be used for later analysis of the stub column tests, and indicated anisotropic material behaviour while displaying satisfactory material ductility. The SHS stub column dimensions fall in the range of ‘slender’ cross-sections as defined by Eurocode 3. Their geometric profiles were 3D laser scanned and analysed prior to the compression tests. The failure modes and load carrying capacities of the WAAM SHS stub columns were analysed and compared to the specimens in previous similar studies. The use of the Effective Width Equation in Eurocode 3 and the Continuous Strength Method for the design of slender WAAM stainless steel plates are evaluated.

Tailored silver coated polymer pillar metasurfaces for near-infrared refractive index sensing applications

In this work, we report the design, numerical simulation, and fabrication of plasmonic metasurfaces consisting of two-dimensional array arranged polymer pillars on glass substrate coated by a thin silver layer. Silver coated polymer pillar metasurfaces with various silver thicknesses are designed and their optical characteristics analyzed with a finite-difference time-domain (FDTD) method. The designed structures for near-infrared refractive index (RI) sensing show the sensitivities and figure-of-merits (FOM) of ∼1438.3 nm/RIU and ∼71.5 RIU−1, for gaseous media, and ∼1444.0 nm/RIU and ∼59.2 RIU−1 for liquid media, respectively. By introducing and applying the fabrication processes of 3D laser direct writing combined with sputtering technique, we have demonstrated the facile implementation of the plasmonic metasurfaces working in the near-infrared region without using the precise fabrication techniques. This work will provide general guidelines and useful approaches for plasmonic metasurface device design.

Minimal-Invasive 3D Laser Printing of Microimplants in Organismo.

Multi-photon 3D laser printing has gathered much attention in recent years as a means of manufacturing biocompatible scaffolds that can modify and guide cellular behavior in vitro. However, in vivo tissue engineering efforts have been limited so far to the implantation of beforehand 3D printed biocompatible scaffolds and in vivo bioprinting of tissue constructs from bioinks containing cells, biomolecules, and printable hydrogel formulations. Thus, a comprehensive 3D laser printing platform for in vivo and in situ manufacturing of microimplants raised from synthetic polymer-based inks is currently missing. Here, a platform for minimal-invasive manufacturing of microimplants directly in the organism is presented by one-photon photopolymerization and multi-photon 3D laser printing. Employing a commercially available elastomeric ink giving rise to biocompatible synthetic polymer-based microimplants, first applicational examples of biological responses to in situ printed microimplants are demonstrated in the teleost fish Oryzias latipes and in embryos of the fruit fly Drosophila melanogaster. This provides a framework for future studies addressing the suitability of inks for in vivo 3D manufacturing. The platform bears great potential for the direct engineering of the intricate microarchitectures in a variety of tissues in model organisms and beyond.

3D Laser Writing of Low-Loss Cross-Section-Variable Type-I Optical Waveguide Passive/Active Integrated Devices in Single Crystals.

Optical waveguides fabricated in single crystals offer crucial passive/active optical components for photonic integrated circuits. Single crystals possess inherent advantages over their amorphous counterpart, such as lower optical losses in visible-to-mid-infrared band, larger peak emission cross-section, higher doping concentration. However, the writing of Type-I positive refractive index modified waveguides in single crystals using femtosecond laser technology presents significant challenges. Herein, this work introduces a novel femtosecond laser direct writing technique that combines slit-shaping with an immersion oil objective to fabricate low-loss Type-I waveguides in single crystals. This approach allows for precise control of waveguide shape, size, mode-field, and refractive index distribution, with a spatial resolution as high as 700nm and a high positive refractive index variation on the order of 10-2, introducing new degrees of freedom to design and fabricate passive/active optical waveguide devices. As a proof-of-concept, this work successfully produces a 7mm-long circular-shaped gain waveguide (≈10µm in diameter) in an Er3+-doped YAG single crystal, exhibiting a propagation loss as low as 0.23dBcm-1, a net gain of ≈3dB and a polarization-insensitive character. The newly-developed technique is theoretically applicable to arbitrary single crystals, holding promising potential for various applications in integrated optics, optical communication, and photonic quantum circuits.

SLAM for Indoor Mapping of Wide Area Construction Environments

Abstract. Simultaneous localization and mapping (SLAM), i.e., the reconstruction of the environment represented by a (3D) map and the concurrent pose estimation, has made astonishing progress. Meanwhile, large scale applications aiming at the data collection in complex environments like factory halls or construction sites are becoming feasible. However, in contrast to small scale scenarios with building interiors separated to single rooms, shop floors or construction areas require measures at larger distances in potentially texture less areas under difficult illumination. Pose estimation is further aggravated since no GNSS measures are available as it is usual for such indoor applications. In our work, we realize data collection in a large factory hall by a robot system equipped with four stereo cameras as well as a 3D laser scanner. We apply our state-of-the-art LiDAR and visual SLAM approaches and discuss the respective pros and cons of the different sensor types for trajectory estimation and dense map generation in such an environment. Additionally, dense and accurate depth maps are generated by 3D Gaussian splatting, which we plan to use in the context of our project aiming on the automatic construction and site monitoring.

Acoustic emission and fracture morphology characteristics of thermal-damage granite under mixed mode I/III loading

To explore the fracture morphology and acoustic emission characteristics of thermally damaged granite under mixed mode I/III loading, a series of heat treatment and mixed mode I/III loading tests were conducted on edge-notched disc bend (ENDB) granite samples. First, the thermal damage samples’ strength and crack opening displacement were analyzed. Subsequently, based on 3D laser scanning technology, the fracture morphology of the sample was studied, and the fractal dimension was calculated. Then, the samples’ acoustic emission characteristics were discussed, including the ringing count, b value, spectrum signature, and AF-RA. Finally, an acoustic early warning index was proposed based on the critical slowing down theory, and the influence of temperature on the early warning effect was analyzed. The results show that under mixed mode I/III loading, the samples formed an antisymmetric curved surface with out-of-plane torsion. As the thermal damage effect is enhanced, the peak strength decreases linearly, and the fractal dimension increases linearly. The failure mode changes from sudden instability to progressive instability. Shear cracks gradually dominate the sample failure. The peak frequency signal of the sample is mainly distributed between 80 kHz and 400 kHz. The appearance of the sudden drop in the b value and a zero-frequency signal has an early warning effect. The quadratic function can describe the relationship between warning time and temperature. As the temperature increases, the deterioration effect of historical loading on the sample is enhanced, the development time of sample failure is prolonged, and the early warning effect is better.

Effective Denoising Algorithms for Converting Indoor Blueprints Using a 3D Laser Scanner

This paper focuses on converting complex 3D maps created by LiDAR and SLAM technology into simple 2D maps to make them easier to understand. While 3D maps provide a lot of useful details for robots and computer programs, they can be difficult to read for humans who are used to flat maps. We developed a new system to clean up these 3D maps and convert them into intuitive and accurate 2D maps. The system uses three steps designed to correct different kinds of errors found in 3D LiDAR scan data: clustering-based denoising, height-based denoising, and Statistical Outlier Removal. In particular, height-based denoising is the method we propose in this paper, an algorithm that leaves only indoor structures such as walls. The paper proposes an algorithm that considers the entire range of the point cloud, rather than just the points near the ceiling, as is the case with existing methods, to make denoising more effective. This makes the final 2D map easy to understand and useful for building planning or emergency preparedness. Our main goal is to map the interior of buildings faster and more effectively, creating 2D drawings that reflect accurate and current information. We want to make it easier to use LiDAR and SLAM data in our daily work and increase productivity.

Mechanical behaviour of weakly filled granite and a unified evaluation method for macro-fine-micro multi-scale fracture characteristics

The mechanical properties of weakly filled rock are critical for engineering rock stability control. With the help of 3D DIC (Digital Image Correlation) and AE (Acoustic Emission) monitoring system, and the industrial CT (Computed Tomography), 3D laser scanning and SEM (Scanning Electron Microscope) technology, the mechanical behaviour and fracture characteristics of granite with different inclination angles of planar weak filling were analyzed comprehensively. Firstly, the influence law of the inclination angle of planar weak filling on the basic mechanical properties of the specimens was investigated, and it was confirmed that the specific angle had an obvious weakening effect on the specimen’s ability to resist deformation. Then, the spatial deformation field evolution and failure mode of the specimen were analysed, and it was found that when the inclination angle increased from 0° to 90°, the failure mode of the specimen will gradually change from “Y”-shaped shearing and splitting mixed failure to “chain” splitting failure, and then to overall splitting failure. Then, the spatial distribution of the micro-fracture event was analysed, and the results show that the spatio-temporal evolution and distribution characteristics of the micro-fracture events, the distribution characteristics of the spatio-temporal evolutionary local enlargement zone of the deformation field and the spatial distribution of the main fracture surface at the time of final failure are highly consistent and correlated. The spatio-temporal evolution and distribution characteristics of micro-fracture events provide important references for predicting the location, time and degree of spatial failure in weakly filled rock mass. Finally, based on the fractal theory, the fracture characteristics within the multiscale of the specimen were analysed, and the method of evaluating the unity of the multiscale fracture characteristics of the rock mass was summarised and given.

FEATURES OF COMBINING THE RESULTS OF 3D LASER SCANNING FROM DIFFERENT STATIONS USING MAGNETIC SPHERES

3D laser scanning is becoming an increasingly important technology in the modern world, opening up endless possibilities for obtaining accurate geometric parameters of various objects. So, due to its efficiency and accuracy, this technology is becoming indispensable in such industries as surveying, construction support, executive surveying, geodetic monitoring, and others. However, despite the many advantages of laser scanning, it has a limitation that can significantly affect the results, namely the algorithm for stitching individual scans into a single-point cloud. Most scanners do not have built-in capabilities to stitch together scan results from multiple stations automatically. Therefore, obtaining a single-point cloud requires using alternative methods. Modern laser scanner companies offer a variety of models with unique technical characteristics. The right choice of scanner functionality is crucial when performing various technological tasks throughout the entire process, from scanning to obtaining the result. The technical parameters of laser scanners, such as measurement accuracy, maximum scanning range, and scanning speed, vary depending on the type of objects scanned and the necessary results. The use of magnetic spheres becomes an essential aspect of ensuring scanning accuracy. They facilitate stitching data from different stations and allow automated search for stitching points, simplifying data processing. An algorithm built into Trimble RealWorks software automatically detects magnetic spheres in the point cloud. It uses an appropriate transformation to join two adjacent scans from different stations if more than three identical spheres are present. The article aims to study the peculiarities of combining the results of 3D laser scanning from several stations using magnetic spheres. It discusses the analysis of the technical parameters of the Trimble TX6 laser scanner, variations in the use of magnetic spheres to ensure the accuracy of combining scanning results, and the advantages and disadvantages of this approach. Keywords: 3D laser scanning, magnetic spheres, stitching algorithm, point cloud, Trimble RealWorks.

TECHNOLOGY FOR COMBINING THE RESULTS OF 3D LASER SCANNING FROM DIFFERENT STATIONS USING PLANE MARKS

3D laser scanning is a promising technology gaining popularity and active use worldwide. One of the advantages of 3D laser scanning is the speed of the scanning process and processing of the results. Compared to other geodetic instruments, this technology allows for displaying large objects in a much shorter time and more efficiently. For example, at the construction stage of an industrial plant, scanning enables monitoring the shapes and sizes of all its elements in real time, which is critical for controlling and optimising construction processes. Another important aspect is the geometric complexity of objects. Many objects can have complex shapes or similar elements of considerable length. When combining scanning results from different stations, it is necessary to ensure the accuracy and correct geometry of the object. To combine scan results, designated markers in the form of spheres and plane marks are used. However, unlike spheres, plane markers can be more convenient and economical. In addition, they can be left on the object for a long time, which significantly simplifies the additional scanning or data correction. It is also notable that in our time, the development of laser scanning technologies has led to new scanners that can automatically stitch together scan results by using advanced technology to track characteristic points in the environment. Despite the significant advantages of this new technology in terms of efficiency and accuracy, it is worth noting that it is rather expensive. Accordingly, scanners that do not have this advanced technology rely on alternative methods of stitching together scan results, such as placing plane marks on the object. The article aims to develop a technology for combining the results of 3D laser scanning from different stations using plane marks. The article considers the evaluation of the technical characteristics of the Trimble TX6 laser scanner, the analysis of options for using plane marks to ensure scanning accuracy, and the identification of the advantages and disadvantages of this method. Keywords: 3D laser scanning, plane marks, stitching algorithm, point cloud, Trimble RealWorks.

Experimental investigation on fractal mechanism and shear failure characteristics of cement mortar at different curing ages

In this paper, the NMR and direct shear tests were conducted successively on cement mortar specimens with different curing ages (7 days, 14 days and 28 days). The porosity, shear strength, shear stiffness and shear energy of cement mortar are measured and analyzed through interpreting the pore distribution patterns and their corresponding fractal dimensions. The cross-sections of shear surface were characterized into point cloud data via 3D laser scanning and quantified by three dimensionless parameters (the root mean square value of the first derivative, root mean square value and joint roughness coefficient). The grey relation analysis (GRA) method and principal component analysis (PCA) is employed to analyze the relationship between the pore structures (i.e., gel pores, transition pores, capillary pores and pores or cracks) and distribution and the fractal dimensions. The results indicate that the shear peak strength is linearly correlated with the joint roughness coefficient. Compared to the fractal characteristics of pore size (T2 spectra) and pore distribution (MRI), we demonstrated that there is a strong correlation between the peak shear strength and the fractal dimension of shear fracture surface, which suggests that the quantitative characterization of internal pores and shear strength variations in cement mortar specimens can be achieved through the numerical values of fractal dimensions.

Practicalities of Incorporating 3D Laser Scanning with BIM in Live Construction Projects: A Case Study

The integration of laser scanning technology and Building Information Modelling (BIM) processes offers a transformative approach to managing the complexities in live construction projects. This paper aims to explore the significant impacts of incorporating laser scanning and BIM on construction projects in terms of as-built models, information management, and overall project performance utilising case study analysis of a building that was not BIM-based. The research scope is defined by the need to investigate the integration of laser scanning and BIM in live construction projects. It details the data acquisition process, challenges encountered due to site obstructions, and the methodologies employed for spatial modelling procedures. Key findings reveal that such integration can significantly enhance the accuracy of data collection and improve project outcomes. Results also identify the need for specialised equipment and skills for the effective implementation of such integrations. The research concludes by offering a practical approach to enhancing construction processes, from design to maintenance. This paper contributes to the body of knowledge by providing a detailed analysis of the practical application of laser scanning and BIM in a live construction project, offering insights into the benefits, challenges, and future directions for integrating these technologies in the construction industry.

Hybrid Inspection Method using Three Dimensional Scanning, Lock-in Thermography and Laser Shearography

The proportion of composite materials (such as CFRP) to the metal used on the modern aircrafts is rising, imposing different kind of failure modes. Since the composite structures are known to be sensitive to the impact loading, there is need for means to assess the sub-surface damage in the structure rapidly. Royal Netherlands Aerospace Centre NLR has an extensive track record on contactless non-destructive inspection (NDI) methods based on optical sensors, such as 3D surface scanning, lock-in thermography and laser shearography. The combination of these methods (multi-domain inspection) enables us to assess the structural integrity of an aircraft outer surface in a short time, reducing inspection costs and the “down time” of the aircraft. Recently, NLR is working towards a 3D oriented mesh environment of an object, enhanced with NDI data, providing sub-surface damage information. By automatically stitching the 3D object images, it is possible to expand this method for a complete scan of an aircraft surface. Furthermore, the thermographic and shearography imaging information has been integrated into the 3D surface accounting for the image distortion from the different measurement angles. In this paper, the results from the various studies will be presented involving integration of the 2D measurements with the 3D scan mesh. Keywords: Thermography, Shearography, 3D scanning, Data fusion

Behavior of wire arc additively manufactured 316L austenitic stainless steel single shear bolted connections

This paper aims to investigate the behavior of single shear bolted connections made of wire arc additively manufactured 316L austenitic stainless steel. A set of 44 wire arc additive manufacturing (WAAM) 316L austenitic stainless steel single shear bolted connections were included with consideration of various bolt positions, surface conditions and loading orientations respective to the printing layer direction. The geometric dimensions of the WAAM austenitic stainless steel plates were measured with the assistance of non-contact 3D laser scanning prior to tensile testing. Monotonic tensile tests were carried out to investigate the load-deformation responses, failure patterns and resistances determined by both the deformation and strength criteria of the single shear bolted connections. The effects of geometric and printing parameters on the single shear bolted connections were analyzed. Due to the absence of codified design provisions for WAAM austenitic stainless steel bolted connections, the suitability of the existing design rules originally developed for traditionally manufactured carbon steel and stainless steel bolted connections was examined. Design resistances calculated by the Eurocode 3 (prEN 1993-1-8 and prEN 1993-1-4), the American Specification (ANSI/AISC 370-21) as well as the prevalent design recommendations proposed in existing literature were compared with the obtained experimental results. It is shown that the abovementioned design methods offer conservative predictions for the resistances of WAAM 316L austenitic stainless steel single shear bolted connections. Further study is needed to improve the accuracy of design resistance predictions.

Analysis of Road Surface Texture for Asphalt Pavement Adhesion Assessment Using 3D Laser Technology

Pavement adhesion plays a crucial role in driving safety, while traditional test methods exhibit some limitations. To improve the efficiency and accuracy of asphalt pavement texture characterization and adhesion assessments, this paper uses three-dimensional (3D) laser technology to detect the continuous point cloud data of road surface and reconstruct the 3D topography of pavement texture. On this basis, a volume parameter Volume of peak materials (Vmp) is innovatively proposed to comprehensively characterize the 3D spatial characteristics of road surface texture. The correlation analysis between the proposed Vmp and the traditional adhesion evaluation index Transversal Adhesion Coefficient (CAT) is conducted, and then refined graded adhesion prediction models based on the proposed Vmp are proposed. Results show that the proposed volume parameter Vmp can reliably and accurately characterize the asphalt pavement texture by considering more structural properties of the road surface texture. According to the research findings of this paper, it is feasible to achieve rapid and correct assessment of asphalt pavement adhesion using 3D laser detection technology by comprehensively considering the 3D characteristics of the road surface texture.