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.

融合多源激光点云数据的亚运场馆建模研究

为了获取体育场馆内外建筑结构的三维信息,构建完整的三维实景模型,在分析多种非接触式测量技术的各自特点和局限性基础上,结合无人机机载LiDAR和地面三维激光扫描仪的优势,提出一种使用空地2种激光点云数据进行初始配准、精确融合,进而实现体育场馆三维重建的方法。以某亚运体育场馆为应用研究对象,结果表明:该方法可以有效地采集、处理海量点云数据,构建的模型纹理清晰,几何结构完整;使用全站仪、手持测距仪实地检测,平面和高程中误差分别是±0.136 m、±0.087 m,边长最大较差15 cm。通过工程实践,验证了上述建模方法具有一定的有效性和实用性,同时进行了深入探讨分析并提出了改进思路。

Study on Estimation Method of Rock Mass Discontinuity Shear Strength Based on Three-Dimensional Laser Scanning and Image Technique

The estimation of shear strength of rock mass discontinuity is always a focal, but difficult, problem in the field of geotechnical engineering. Considering the disadvantages and limitation of exist- ing estimation methods, a new approach based on the shadow area percentage （SAP） that can be used to quantify surface roughness is proposed in this article. Firstly, by the help of laser scanning technique, the three-dimensional model of the surface of rock discontinuity was established. Secondly, a light source was simulated, and there would be some shadows produced on the model surface. Thirdly, to obtain the value of SAP of each specimen, the shadow detection technique was introduced for use. Fourthly, compared with the result from direct shear testing and based on statistics, an empirical for- mula was found among SAP, normal stress, and shear strength. Data of Yujian （~ River were used as an example, and the following conclusions have been made. （1） In the case of equal normal stress, the peak shear stress is positively proportional to the SAP. （2） The formula for estimating was derived, and the predictions of peak-shear strength made with this equation well agreed with the experimental re- suits obtained in laboratory tests.

日本桥梁自动化检测技术研究新进展

桥梁自动化检测技术为桥梁智慧管养提供了有力的技术支持,日本在桥梁自动化检测技术方面开展了斜拉索检测机器人、钢桁架桥检测机器人、搭载3D激光扫描仪的检测机器人的研发和应用研究。斜拉索检测机器人采用螺旋桨驱动,安装全高清画质数码相机,沿索体上升或下降进行全方位摄像,查看照片和视频可检测修补痕迹、锈迹、涂膜剥落、碰撞等,不需要进行交通管制,检测速度快、效率高,不仅适用于斜拉桥,还可用于悬索桥吊索检测。侧面走行检测机器人主要用于检测钢桁架桥桥面板、钢梁及其它构件损伤,走行装置上安装锂电池电机,遥控操作变换前进方向和调整走行速度,机器人万向接头上安装4K高清数码相机,可检测到无法近距离肉眼观测以及视线死角位置。既有桥梁桥面板更换工程中,采用搭载3D激光扫描仪的检测机器人进行桥梁空间坐标全自动检测,扫描的点云数据输入数据处理系统,自动生成检测报告,无需搭设支架和实施交通管制,且检测精度满足目标精度要求,该设备还可用于挂篮悬臂浇筑法施工中成桥空间坐标测量。研发了3D激光扫描仪自动移动装置,使检测更快捷。各桥梁自动化检测设备具有较好的工程实用价值,可为国内同类型桥梁结构智能检测提供参考。

Wind dynamic environment and wind-sand erosion and deposition processes on different surfaces along the Dunhuang–Golmud railway,China

The Dunhuang–Golmud railway passes through different deserts in arid areas,especially drifting-sand desert and sandy-gravel Gobi.The near-surface wind environment and wind-sand transport process vary due to different external factors,such as topography,vegetation,and regional climate,resulting in evident spatial differences in surface erosion and deposition.Consequently,the measures for preventing wind-sand hazards will differ.However,the mechanism and control theory of sand damage remain poorly understood.In this study,we used meteorological observation,three-dimensional(3D)laser scanning,and grain-size analysis to compare and evaluate the spatial distribution of wind conditions,sand erosion and deposition patterns,and grain composition in the drifting-sand desert and sandy-gravel Gobi along the Dunhuang–Golmud railway in China.Results show that the annual mean wind speed,the frequency of sand-driving wind,and the drift potential of sandy-gravel Gobi are higher than those of drifting-sand desert,indicating a greater wind strength in the sandy-gravel Gobi,which exhibits spatial heterogeneity in wind conditions.The major sediment components in sandy-gravel Gobi are very fine sand,fine sand,and medium sand,and that in drifting-sand desert are very fine sand and fine sand.We found that the sediment in the sandy-gravel Gobi is coarser than that in the drifting-sand desert based on mean grain size and sediment component.The spatial distributions of sand erosion and deposition in the sandy-gravel Gobi and drifting-sand desert are consistent,with sand deposition mainly on the west side of the railway and sand erosion on the east side of the railway.The area of sand deposition in the drifting-sand desert accounts for 75.83%of the total area,with a mean deposition thickness of 0.032 m;while the area of sand deposition in the sandy-gravel Gobi accounts for 65.31%of the total area,with a mean deposition thickness of 0.028 m,indicating greater deposition amounts in the drifting-sand desert due to the presence of more fine sediment components.However,the sand deposition is more concentrated with a greater thickness on the embankment and track in the sandy-gravel Gobi and is dispersed with a uniform thickness in the drifting-sand desert.The sand deposition on the track of the sandy-gravel Gobi mainly comes from the east side of the railway.The results of this study are helpful in developing the preventive measures and determining appropriate selection and layout measures for sand control.

成像激光雷达技术概述

简要介绍了成像激光雷达技术的应用特点 ,阐述了成像激光雷达可采用的几种成像技术及部分单元技术包括激光器和可用的扫描系统技术。概括了成像激光雷达在军事和国民经济中的应用。

三维激光扫描点云数据在CloudWorx for MicroStation下的处理

三维激光扫描技术作为一种先进的测量手段应用前景十分广阔,但是,在应用其扫描所得的点云数据进行内处理上又遇到了许多技术性的问题。CAD系统处理大量点云数据过程中存在局限性,一旦用CAD系统处理点云时,CAD程序就会出现错误操作提示,甚至完全停止进程。CloudWorx克服了这些局限性,它避免了直接输入数据,而是利用Cyclone技术作为MicroStation环境下有效管理和解决点云的工具,使MicroStation内点云操作与CAD程序执行再无冲突。本文主要介绍了并且还介绍了CloudWorx模块的功能,并举例就点云数据在CloudWorx for MicroStation软件环境下的处理工作进行了详细的介绍。

计算全息光栅扫描器与制作工艺的研究

简述了计算全息光栅扫描器的特点和优点， 以及它有可能成为解决ＣＯ２ 激光成像雷达的激光扫描这一关键技术的有效途径， 并给出当蚀刻深度为λ／４ ＝ ２－６５ μｍ 时， 传统的加工工艺受到的障碍及给出新的加工工艺和明显的实验效果。最后给出要想使计算全息光栅扫描器成为真正满足ＣＯ２激光成像雷达扫描技术的实用型光栅扫描器，

Effect of proximal contact strength on the three-dimensional displacements of implant-supported cantilever fixed partial dentures under axial loading

Objective:This study investigated the effect of proximal contact strength on the three-dimensional displacements of cantilever fixed partial denture(CFPD) under vertically concentrated loading with digital laser speckle(DLS) technique.Methods:Fresh mandible of beagle dog was used to establish the implant-supported CFPD for specimen.DLS technique was employed for measuring the three-dimensional displacement of the prosthesis under vertically concentrated loading ranging from 200 to 3 000 g.The effect of the contact tightness on the displacement of CFPD was investigated by means of changing the contact tightness.Results:When an axial concentrated loading was exerted on the pontic of the implant-supported CFPD,the displacement of the CFPD was the greatest.The displacement of the prosthesis decreased with the increase of contact strength.When the contact strength was 0,0.95,and 3.25 N,the displacement of the buccolingual direction was smaller than that of the mesiodistal direction but greater than that of the occlusogingival direction.When the force on the contact area was 6.50 N,the mesiodistal displacement of the prosthesis was the biggest while the buccolingual displacement was the smallest.Conclusions:The implant supported CFPD is an effective therapy for fully or partially edentulous patients.The restoration of the contact area and the selection of the appropriate contact strength can reduce the displacement of the CFPD,and get a better stress distribution.The most appropriate force value is 3.25 N in this study.

A shortcut to marking 3D target curves on curved surface via a galvanometric laser scanner

Marking arbitrary three-dimensional(3D) target curves on given objects with curved surface is required in many industrial fields, such as fabric prepreg placement in composite material part fabrication, product assembly, surface painting for decoration, etc. A shortcut to the solution of this intractable problem is proposed by utilizing a galvanometric laser scanner(GLS) with the aid of a camera. Without using the existing tedious GLS calibration procedures,the proposed method directly establishes a mapping between the 3D coordinates of the laser spots on the object surface and the control voltages of the scanner. A single-hidden layer feedforward neural network(SLFN) is employed to model the mapping. By projecting a dense grid of laser spots on the object to be marked and simultaneously taking only one image, the SLFN model is trained in minutes via a linear solving mechanism. Experiments demonstrate that the trained SLFN model has a good generalization performance for marking 3D target curves. The 3D laser marking errors on experimental objects are less than 0.5 mm. The proposed method is especially suitable for on-site use and can be conveniently extended to multiple GLSs for marking large complex objects.

汽车板激光扫描焊接工艺研究

为了研究激光扫描焊接汽车板的工艺方法,采用4k W光纤激光器对0.7mm镀锌板与0.8mm冷轧板SPCC两类汽车板的激光扫描焊接工艺进行了理论分析和实验验证,得到了板间间隙、激光功率、扫描速率等对焊缝成形及强度的影响规律。结果表明,当选取板间间隙0.1mm^0.2mm、激光功率3000W^3400W、焊接速率不小于3m/min等适当参量进行焊接时,焊缝质量可满足电子束及激光焊接接头欠缺质量分级指南C级标准,且强度高于母材。选取合适的工艺参量时,激光扫描焊接在无保护气的作用下可得到高质量的焊缝。

三维激光扫描技术在地表岩移观测中的应用

三维激光扫描技术作为近几年发展起来的一种新兴的测量技术,可用于矿山地表岩移观测。通过实测数据分析,可得出矿山开采沉陷规律及参数,可用以指导优化回采工作面设计,解决建筑物下开采等技术难题。

浅谈地下工程的测量技术

随着社会的发展和城市化进程的不断加快,地下铁道、上下水道、电力通讯等各种地下设施的优势不断突显出来,并不断扩大着建设面积和设施类型。分析了地下工程测量技术的现状,并展望了其未来的发展。