Integration system research and development for three-dimensional laser scanning information visualization in goaf

An integration processing system of three-dimensional laser scanning information visualization in goaf was developed. It is provided with multiple functions, such as laser scanning information management for goaf, cloud data de-noising optimization, construction, display and operation of three-dimensional model, model editing, profile generation, calculation of goaf volume and roof area, Boolean calculation among models and interaction with the third party soft ware. Concerning this system with a concise interface, plentiful data input/output interfaces, it is featured with high integration, simple and convenient operations of applications. According to practice, in addition to being well-adapted, this system is favorably reliable and stable.

Development of an In-Situ Laser Machining System Using a Three-Dimensional Galvanometer Scanner

In this study, a three-dimensional (3D) in-situ laser machining system integrating laser measurement and machining was built using a 3D galvanometer scanner equipped with a side-axis industrial camera. A line structured light measurement model based on a galvanometer scanner was proposed to obtain the 3D information of the workpiece. A height calibration method was proposed to further ensure measurement accuracy, so as to achieve accurate laser focusing. In-situ machining software was developed to realize time-saving and labor-saving 3D laser processing. The feasibility and practicability of this in-situ laser machining system were verified using specific cases. In comparison with the conventional line structured light measurement method, the proposed methods do not require light plane calibration, and do not need additional motion axes for 3D reconstruction;thus they provide technical and cost advantages. The insitu laser machining system realizes a simple operation process by integrating measurement and machining,which greatly reduces labor and time costs.

Laser ultrasonic testing for near-surface defects inspection of 316L stainless steel fabricated by laser powder bed fusion

The laser powder bed fusion(L-PBF)method of additive manufacturing(AM)is increasingly used in various industrial manufacturing fields due to its high material utilization and design freedom of parts.However,the parts produced by L-PBF usually contain such defects as crack and porosity because of the technological characteristics of L-PBF,which affect the quality of the product.Laser ultrasonic testing(LUT)is a potential technology for on-line testing of the L-PBF process.It is a non-contact and non-destructive approach based on signals from abundant waveforms with a wide frequency-band.In this study,a method of LUT for on-line inspection of L-PBF process was proposed,and a system of LUT was established approaching the actual environment of on-line detection to evaluate the method applicability for defects detection of L-PBF parts.The detection results of near-surface defects in L-PBF 316L stainless steel parts show that the crack-type defects with a sub-millimeter level within 0.5 mm depth can be identified,and accordingly,the positions and dimensions information can be acquired.The results were verified by X-ray computed tomography,which indicates that the present method exhibits great potential for on-line inspection of AM processes.

Development of an automatic post-weld inspection system based on laser vision

In order to overcome the limitations of manual post-weld visual inspection approach, an automated inspection system is developed which uses three-dimensioual laser vision system based on the principle of optical triangulation. The system hardware consists of a modular development kit （MDK）, a computer, an actuating mechanism and so on. In image processing algorithms, extraction accuracy of centric line of laser stripe is the critical factor that determines the system performance. So according to the features of laser stripe image, a novel algorithm is developed to detect the central line of laser stripe fast and accurately. Experiments have demonstrated that this system can be used in various weld features inspection of both butt and fillet types of weld. Compared with traditional manual inspection method, this method has obvious dominance. The three-dimensional reconstruction result shows that this system has high accuracy and reliability.

On-line quality inspection in laser blank welding using ART2 neural network

Laser blank welding is becoming more and more important in the automotive industry and the quality of the weld is critical for a successful application. A fully automated solution is required to inspect the quality of the blanks. This paper presents a vision inspection system with a CMOS camera which uses ART2 network to inspect the defects on-line to obtain the geometry and the quality of the weld seam. The neural network ART2 has the capability of self-learning fiom the environment. It can distinguish the defects that have been learned before and give new outputs for new defects. So ART2 network is suitable for weld quality inspection in laser blank welding. Additionally, a CO2 laser is used for the blank butt-welding.

Three-dimensional Deposition of Silicon Structure from Silicate Glass with Dispersed Metallie Muminum by Femtosecond Laser Irradiation

We fabricated a silicon structure in silicate glass prepared with metallic aluminum in the starting material, using femtosecond laser irradiation. Small Si-rich structures such as Si clusters were transformed into larger, but still nano-sized, Si particles by laser irradiation. These structures grew to microsize particles due to the thermite reaction promoted by heat treatment. We determined the effect of focused laser pulses on the Si deposition process using the time-resolved transient lens method. Localized high-temperature, high-pressure, and the generation of shock waves appear to be very important in forming the Si-rich structures that ultimately grow into Si particles.

A fast and precise three-dimensional measurement system based on multiple parallel line lasers

This paper conducts a trade-off between efficiency and accuracy of three-dimensional(3 D)shape measurement based on the triangulation principle,and introduces a flying and precise 3 D shape measurement method based on multiple parallel line lasers.Firstly,we establish the measurement model of the multiple parallel line lasers system,and introduce the concept that multiple base planes can help to deduce the unified formula of the measurement system and are used in simplifying the process of the calibration.Then,the constraint of the line spatial frequency,which maximizes the measurement efficiency while ensuring accuracy,is determined according to the height distribution of the object.Secondly,the simulation analyzing the variation of the systemic resolution quantitatively under the circumstance of a set of specific parameters is performed,which provides a fundamental thesis for option of the four system parameters.Thirdly,for the application of the precision measurement in the industrial field,additional profiles are acquired to improve the lateral resolution by applying a motor to scan the 3 D surface.Finally,compared with the line laser,the experimental study shows that the present method of obtaining 41220 points per frame improves the measurement efficiency.Furthermore,the accuracy and the process of the calibration are advanced in comparison with the existing multiple-line laser and the structured light makes an accuracy better than 0.22 mm at a distance of 956.02 mm.

Controlling Three-Dimensional Electron-Electron Correlation via Elliptically Polarized Intense Laser Field

The three-dimensional electron-electron correlation in an elliptically polarized laser field is investigated based on a semiclassical model. Asymmetry parameter α of the correlated electron momentum distribution is used to quantitatively describe the electron-electron correlation. The dependence of α on elliptieity e is totally different in three directions. For the z direction （maJor polarization direction）, α first increases and reaches a maximum at ε = 0.275, then it decreases quickly. For the y direction in which the laser field is always absent, the ellipticity has a minor effect, and the asymmetry parameter fluctuates around α = -0.15. However, for the x direction （minor polarization direction）, α increases monotonously with ellipticity though starts from the same value as in the y direction when ε = 0. The behavior of α in the x direction actually indicates a transformation from the Coulomb interaction dominated correlation to the laser field dominated correlation. Therefore, our work provides an efficient way to control the three-dimensional electron electron correlation via an elliptically polarized intense laser field.

Application of Three-dimensional Laser Scanning Technology in the Teaching Practice of Surveying and Mapping of Ancient Buildings

Based on the study of the application of three-dimensional laser scanning technology in ancient building surveying and mapping,this paper briefly describes the working principle and flow of three-dimensional laser scanning technology.Based on the practical application,this paper puts forward the discussion of related problems and matters needing attention.This has a certain reference significance for the study of new technology in surveying and mapping of ancient buildings.

Investigation of the factors affecting the limit of detection of laser-induced breakdown spectroscopy for surface inspection

Laser-induced breakdown spectroscopy(LIBS) was examined to detect a trace substance adhered onto Al alloys for the surface inspection of materials to be adhesively bonded. As an example of Si contamination, silicone oil was employed and sprayed onto substrates with a controlled surface concentration. LIBS measurements employing nanosecond UV pulses(λ?=?266 nm) and an off-axis emission collection system with different detecting heights were performed. Because surface contaminants are involved in the plasma formed by laser ablation of the substrates, the relative contribution of the surface contaminants and the substrates to the plasma emission could be changed depending on the conditions for plasma formation. The limit of detection(LOD) was evaluated under several detecting conditions for investigating the factors that affected the LOD. A significant factor was the standard deviation values of signal intensities obtained for the clean substrates. This value varied depending on the measurement conditions.For the Al alloy(A6061), the smallest LOD obtained was 0.529 μg?·?cm^(-2). Furthermore, an improved LOD(0.299 μg?·?cm^(-2)) was obtained for the Al alloy with a lower Si content.

On the possible ultrasonic inspection of micro-bubbles generated by the optical fiber tip

We demonstrate the possibility of detection and monitoring of bubbles emerging near the tip of an optical fiber by means of ultrasonic method.The excitation of bubbles at their resonant frequencies is performed using short ultrasonic pulses having a wide frequency range simulta-neously with their modulation by means of a long pulse of a monochromatic frequency.This method allows detection of bubbles of various sizes.Used signal processing method,which allows increased bubble detection accuracy,is proposed for ressearch in envir onments of biological-like medium which show continuous variations in structure and properties when exposed to optical emission.The method has been demonstrated on model objects:in a liquid and in a biological tissue phantom using various methods of bubble generation(hydrolysis and optical enission).We studied bubble formation by the tip of a fiber of the surgical laser LSP-007/10 "IRE Polus"with a wavelength of 0.97μm coated with a highly absorbing graphite layer.

Analysis of Cr Atoms Three-Dimensional Deposition Characteristics

The semi-classical model is used to simulate the three-dimensional trajectory and deposition distribution of the chromium atoms in the Gaussian laser standing wave field using the Runge-Kutta method, and then the three-dimensional deposition stripes are also given, besides, the effects of atomic beam divergence, chromatic aberration and spherical aberration on deposition structure are also analyzed.

Method for visualizing the shear process of rock joints using 3D laser scanning and 3D printing techniques

This study presents a visualized approach for tracking joint surface morphology.Three-dimensional laser scanning(3DLS)and 3D printing(3DP)techniques are adopted to record progressive failure during rock joint shearing.The 3DP resin is used to create transparent specimens to reproduce the surface morphology of a natural joint precisely.The freezing method is employed to enhance the mechanical properties of the 3DP specimens to reproduce the properties of hard rock more accurately.A video camera containing a charge-coupled device(CCD)camera is utilized to record the evolution of damaged area of joint surface during the direct shear test.The optimal shooting distance and shooting angle are recommended to be 800 mm and 40?,respectively.The images captured by the CCD camera are corrected to quantitatively describe the damaged area on the joint surface.Verification indicates that this method can accurately describe the total sheared areas at different shear stages.These findings may contribute to elucidating the shear behavior of rock joints.

基于微型激光雷达的无人机智能化电力线路巡检技术研究

介绍了一种利用激光探测和测距(LiDAR)进行实时电力线检测的算法,并且对微型激光雷达无人机进行电力线路巡检抽象建模。通过使用平面分析法对巡检现场进行距离的比较来分割点云,并提取一组电力线候选点,这些点被拟合到线段上,线段根据它们的共线性质进一步分组比较。该方法可利用图像的共线特性完成特征检验,并在光线条件差以及线路背景复杂的环境下仍可获得较为可靠的巡检结果。案例中电力线路垂直平均误差最大为0.49 m,其他所有直线的估计平均误差都小于0.07 m,水平拟合时,所有平均误差都在0.14 m以内。验证了所提出基于微型激光雷达的无人机技术进行电力线路智能化巡检方法的有效性与可行性。

基于图像视觉检测技术的激光标线仪校准装置研究

针对传统激光标线仪靶标测量方法难度大、人工读数困难且效率低的问题,基于图像视觉检测技术,设计了激光标线仪校准装置硬件系统及软件算法。通过数据采集单元、靶标系统单元和多功能升降工作台单元搭建出系统硬件装置。采用图像预处理方法将原始图像激光线与背景分割,提取出基准中心原点并进行系统标定,利用骨架提取算法拟合出激光测量线,计算出计量特性的偏移量,并根据算法设计出交互软件,自动测量和保存数据。最终通过所研制的校准装置和传统校准方法,校准同一激光标线仪进行比对实验,实验结果|E_(n)|≤1,结果判定为满意,验证了校准系统的可行性。

室内巡检机器人的定位方法

针对巡检机器人在室内环境进行巡检任务时无法准确到达指定位置的问题,提出一种基于激光雷达和里程计的分区域定位方法。当机器人工作在定位精度要求不高的非目标区域时,采用激光雷达加里程计的定位算法进行导航;而当机器人进入包含指定位置的目标区域时,则利用搭载在机器人上的激光测距传感器和已知位置的地标来推算机器人的当前位姿,并根据机器人的当前误差进行位姿矫正,实现机器人在目标位置的精确定位。实验结果表明:该定位方法的位置误差<2 cm,偏转角误差<1°,满足巡检机器人的定位精度要求,具备可行性和实际价值。

融合A^(*)和TEB算法的巡检机器人路径规划研究

针对激光雷达智能巡检机器人在复杂环境下静态障碍物路径规划复杂,动态障碍物躲避效果不佳等问题,提出一种路径规划融合算法以提高机器人避障效果。采用Karto-SLAM进行激光SLAM建图,将A^(*)算法与TEB算法有效融合完成机器人的全局路径规划与局部路径规划。仿真实验与实测表明,通过Karto算法所建地图的平均误差约为1.259%,A^(*)与TEB的融合算法在完成单一A^(*)算法最优路径生成的同时还具备良好的避障功能,有效避障率达到90%以上,满足巡检机器人移动避障等要求。

废钢检验的现状分析与展望

在双碳背景下,废钢的综合利用尤为重要。而废钢质量的好坏和成本高低则直接影响了企业的生产效率和经济效益,故国家标准《GB/T 39733-2020再生钢铁原料》对废钢的质量检验提出了更高的要求。本文从放射性污染物、爆炸性物品、危险废物、夹杂物、化学成分、锈蚀和镀层方面分析了废钢检验的现状,并对废钢检验技术的发展进行了展望。指出,利用通道式放射性检测装置对进厂废钢进行初检非常有必要;危险废物鉴别标准与技术规范有待完善,鉴别程序可操作性不强;利用激光诱导击穿光谱法可对废钢成分进行快速测量,相关决定系数和均方根误差较满意;基于颜色特征和纹理特征的废钢锈层识别算法,可准确识别训练集和预测集的废钢锈层。加强废钢检验标准体系建设、加大按化学成分对废钢进行精细分类的研发力度,尤其是基于激光诱导击穿光谱技术对废钢成分进行在线、快速、准确、定量分析是其未来的发展方向。

基于移动三维激光扫描技术的地铁隧道接触网导高检测新方法

[目的]地铁隧道内接触网导高是保证列车正常受电的重要参数,需定期进行检测。针对其他导高检测方式存在的误差大、精度低的问题,需提出基于移动三维激光扫描技术的地铁隧道接触网导高检测新方法。[方法]基于移动三维激光扫描技术提出了导高检测的新方法,分析了误差来源;提出通过在移动式三维激光扫描仪上增设刚性倾斜组件来改变扫描仪激光线入射角度,进而减少隧道断面点云模型的毛刺数量,并采用等角兰勃特投影来获取隧道真实点云模型。与导高仪检测结果进行对比,以验证其导高检测精度是否满足相关要求。[结果及结论]基于移动式三维激光扫描技术建立的隧道断面点云模型存在毛刺,是因激光脚点垂直入射接触网发生散射和漫反射导致的。增加倾斜组件,可有效减少隧道断面点云模型的毛刺数量。移动式三维激光扫描仪与导高仪的导高检测数据对比结果表明,基于移动式三维激光扫描技术的导高检测精度基本在±3 mm以内,能够满足相关规范对导高检测的精度要求。

基于激光联动扫描的单目动态三维主动热成像研究

为了满足对非平面碳纤维复合材料无损检测的需求,文中提出了一种仅使用一台热像仪对运动试件进行主动三维热成像的系统,称为单目动态三维主动热成像。该系统融合了检测对象的三维轮廓与和主动热成像检测,能够对具有复杂几何形状的复合材料试件进行检测,并给出直观的热成像缺陷检查结果。不同于传统的三维主动热成像检测方法需要额外的三维相机获取检测对象表面轮廓信息;该系统不需要独立的三维传感器,而热像仪同时作为三维传感器与温度传感器。为了实现这一功能,在线激光联动扫描热成像的基础上,文中提出了一个统一联动扫描模型和针孔相机投影模型的数学模型,将线激光作为主动热成像的热激励和三维重建的空间编码。在算法中,该模型实现了对重构热图序列和三维形状点云的无特征配准,该配准方法工作快速、稳健,不需要关键点。标准高度试件标定实验结果表明:在1~150mm的高度测量范围,平均误差0.16mm,最大误差不超过0.25 mm。碳纤维进气管实验表明,该方法具有大尺寸碳纤维复合材料三维温度场重建与检测检测能力。文中提出的单目三维动态热成像系统结构简单、工作稳定,可用于在生产线的三维测量、缺陷检测和质量控制。