机载/车载激光扫描测距/成像制图系统的新进展

结合机载激光遥感影像制衅系统的特点。论述了机载／车载激光扫描测距／成像制衅系统研制背景、基本原理、研究进展,应用前景和进一步发展应该解决的问题等。     

矿用带式输送机输送量测量方法现状及发展趋势

对目前矿用带式输送机输送量的测量方法即电子胶带秤测量法、核子胶带秤测量法、超声波测距测量法、激光CCD图像测量法、激光扫描测量法进行了分析,并从测量精度、响应时间等方面对各种方法进行了对比分析。接触式测量法中,电子胶带秤测量法测量精度高,但响应速度较慢,稳定性较差;非接触式测量法中,激光扫描测量法测量精度较高,响应速度较快,稳定性较好。指出带式输送机输送量测量方法的发展趋势是提高测量精度、抗干扰性和适应性,非接触式测量法或融合多种技术的方法将逐渐成为主流的输送量测量方法。     

基于扫描激光测距数据的建筑物三维重建

建筑物的三维信息是重要的基础地理信息,可以应用于城市的规划、管理等方面,而机载激光扫描测距系统在城市建筑物的三维重建方面具有重要的应用价值。针对我国自行研制的机载激光扫描测距数据提出了一套利用稀疏激光测距数据自动提取建筑物三维信息的方法。首先根据测量的激光距离和相应的姿态、位置信息计算出激光采样点的三维位置,进而可以生成城市的数字表面模型(DSM)和城市的数字地面模型(DTM),依据它们能准确地提取出建筑物的轮廓信息,最后根据建筑物具有规则的形状这个特点来对建筑物的轮廓线进行规则化处理而最终恢复建筑物的三维信息。通过对北京城市北部地区的实际处理,说明了该方法的可行性。     

辅助机载惯导快速对准的光学测量装置

机载惯导系统在地面静基座对准需要较长的对准时间,严重影响飞机的出动速度。为辅助机载惯导进行快速、精确的对准,设计了一种通过对飞机上的标志点进行激光测距从而获取航向信息的装置。描述了该测量装置的构成和基本原理,推导了利用该装置测量飞机航向角的测量公式,给出了标定和测量的完整流程。通过仿真实验对测量仪测距误差、俯仰及方位测角误差进行了分析,证明该装置能够满足惯导快速对准的精度需求。     

用于油罐容积测量的自动激光扫描的关键技术研究

大型油罐的计量对油储具有重大的意义，而油罐容积测量技术及设备是其中的关键。为了避免传统基于液位进行容积测量的误差，研究了用于油罐容积测量的自动激光扫描的关键技术，通过扫描系统测量油罐表面三维数据，从而实现油罐容积的测量。该系统由主要通过两维电动旋转机构带动激光测距仪进行扫描测量，采用相位式测距原理实现高精度激光扫描测距功能，同时利用视觉识别瞄准系统实现合同目标的瞄准测量，使得系统具有无合作目标和带合作目标两种测量模式。经过复杂光机系统装调与集成，形成测量仪器整机。经实验测试，在60 m处仪器坐标测量精度可达0.3 mm左右，满足油罐计量的性能要求。     

机载激光扫描数据误差分析与精度改善研究进展

回顾了国内外机载激光扫描结果数据精度分析、仪器校正,特别是在利用条带之间的重叠数据调整并提高数据精度等方面的研究进展,为后续的研究提供了参考。     

脉冲测距系统的多径干扰影响及消除

由于地空无线信道的多径特性的影响,采用脉冲测距原理的机载脉冲测距系统的精度受到较大影响。在对机载脉冲测距设备原理进行深入研究的基础上,对多径干扰对脉冲测距系统的影响进行了分析,确定了最为不利的多径形态,进一步提出了一种针对多径消除的基于第一脉冲延迟译码的解决方案,并予以了工程实现。仿真结果表明该方案效果良好。     

基于RANSAC的便携式激光扫描测量臂手眼标定方法

便携式测量臂和激光扫描测头手眼关系的确定是便携式激光扫描测量臂系统中的关键问题。针对测量臂末端相对运动旋转轴之间的夹角和测量臂与扫描测头相对运动的旋转角差值这两个影响手眼标定精度的因素,设定激光扫描测量臂标定数据筛选原则,提出一种基于随机采样一致性的自适应阈值手眼标定算法。蒙特卡洛仿真实验和激光扫描测量臂实测实验结果表明,提出的算法对四元数方法求解的相对旋转轴和平移向量误差标准差精度分别提高了2.42%,4.14%,可以满足便携式激光扫描测量臂系统的测量精度要求。     

基于正态DS 证据理论的机载LIDAR 数据地物分类方法

针对现有方法无法满足机载激光扫描与测距系统(LIDAR)数据地物分类时对算法 精度和速度需求的问题,提出了一种基于非下采样剪切波(NSST)和正态DS 证据理论的LIDAR 数据快速地物分类方法。首先,利用NSST 对LIDAR 数据源图像进行多尺度分解,对得到的各 层高频图像进行中值滤波处理,并进行逆变换合成。其次,构建正态概率分配函数及模糊类别, 对LIDAR 数据进行信任分配,并进行合成与决策。实验证实,该方法的分类精度达到86.12%, 运行时间仅为0.46 s,在保证快速的基础上有效地提高了分类算法的精度。     

超声波测距回波信号处理方法的研究

在分析超声波测距系统回波信号处理存在问题的基础上,提出了两种提高测量精度的回波信号处理方法.采用了时间增益补偿技术和峰值时间检测技术,可正确检测超声波回波的到达时间.经反复试验,在50 cm～5 m的测量范围内,测距精度可达到0.5%,且测量重复性较好.两种方法的采用,提高了超声波测距系统的测量精度.     

Micro-mirror laser scanner combined with a varifocal mirror

A laser beam scanning system consisting of a scanning micro-mirror and a varifocal micro-mirror is fabricated for laser beam sensing with variable beam diameter. The scanning micro-mirror is operated under the resonant oscillation condition with an electrostatic comb-drive actuator. The varifocal micro-mirror is driven by a bending moment generated at the circumference of mirror with a parallel-palate electrostatic actuator. The scanning micro-mirror and the varifocal mirror are fabricated on a silicon on insulator wafer. The rotational angle of 9° at 766 Hz is obtained at the voltage of 300 V. The spot size of the laser beam is adjusted from 0.5 to 3.5 cm at the distance of 43 m by changing varifocal voltage. The proposed scanning system can be useful for several sensing techniques.     

Identification and optimization of key process parameters in noncontact laser scanning for reverse engineering

This Extended Technical Note shows that the final accuracy level of reverse engineered surfaces depends on scanning distance and scanning angle of the laser beam, hence it also depends on the morphology of the scanned objects. On scanning strongly curved objects, such as the ones with free form surfaces, the distance and impact angle of the laser beam are changing continuously during the scanning process. On the basis of these, two critical parameters are specified for the design model, which make it possible to predict these two factors in advance, depending on the morphology of the scanned object. First, a mathematical-statistical design model of the scanning process is generated, which relies on ANOVA (analysis of variance) and DOE (design of experiments). In the next step, a fitness function is optimized by the genetic algorithm (GA) program. This optimization improves the accuracy of the final scanned surfaces, in terms of the minimum standard deviation values of reverse engineered 3D surface model. The proposed approach was confirmed in a case study, which is presented at the end of this Technical Note.     

基于平晶的非线性激光扫描直径测量系统

设计了一种基于平晶扫描的轴类零件直径测量系统。激光透射旋转的平晶产生扫描平行光,扫描光偏移光轴的距离是入射角及平晶自身参数的非线性函数,光电检测及计时电路获得测量周期和对应被测工件边缘的信号跳变时间,根据时间与转动角度的比例关系将所得时间量换算成入射角度,最终实现直径测量。利用刀口法进行标定实验,分别采用参数拟合法和RBF神经网络法确定实际非线性测量方程,完成了各测头的标定,进一步实现多测头系统标定,在100 mm的测量范围内,3σ重复性误差为0.006 mm,测量误差为±0.010 mm。     

The evaluation of speckle contrast with variable speckle generator

Abstract— While laser projection has many advantages, there is a problem with speckle patterns generated as a result of interference of the laser beam and results in bad effects to observers. In 2010, a variable speckle generator, which produces an angular shift of incident light to the screen and generates variable speckle patterns, was suggested. In this study, the performance of a variable speckle generator by using a volume phase holographic beam shaper and scanning mirror was investigated in detail by evaluating both the objective and subjective speckle contrast. The morphology of the speckle pattern was also investigated when the variable speckle generator was activated. With a scanning VPH beam shaper, the objective speckle was effectively reduced because each point of the VPH beam shaper generated different speckle patterns and coherency among each pattern disappeared by using the scan process. On the other hand, subjective speckle was also dramatically reduced by changing the incident angle on the screen, which resulted in generating variable subjective speckle. It was also shown that the speckle reduction rate by using a variable speckle generator did not depend on the coherent length of a laser by evaluating the normalized speckle contrast against the angular shift on the screen.     

Localization algorithm using a virtual label for a mobile robot in indoor and outdoor environments

Scanning laser range sensors provide range data consisting of a set of point measurements. The laser sensor URG-04LX has a distance range of approximately 0.02–4 m and a scanning angle range of 240°. Usually, such an image range is acquired from one viewpoint by “moving” the laser beam using rotating mirrors/prisms. The orientation of the laser beam can easily be measured and converted into the coordinates of the image. This article conducts localization using virtual labels with data about distances in the environment obtained from 2D distance laser sensors. This method puts virtual labels on special features and points which are along the mobile robot’s path. The current location is calculated by combining the virtual label and the range image of the laser range finder.     

激光武器跟瞄精度及其成因分析

本文从激光武器跟瞄系统的跟瞄精度需求入手,结合造成激光光束散射角扩大的主要原因以及跟瞄系统中的误差源,通过分析激光光斑的稳定性导出了激光武器跟瞄系统的精度与激光光束散射角的关系,最后仿真得出了激光武器对跟瞄系统精度的需求.     

回转轴运动精度的干涉测量与误差补偿分析

采用激光干涉仪检测混联数控机床回转轴的运动精度,达到对其综合评价的目的,为机床的运动精度误差补偿做准备.对雷尼绍激光干涉仪的结构和角度测量原理进行了详细探讨,分析了干涉仪在回转轴运动精度测量中的主要影响因素和误差诱因;作出了角度测量中正弦近似误差特性曲线,并提出了该测量误差的数学模型;讨论了激光波长补偿的机理,提出了一种通用、简便易行的回转轴角位移精度检测方法.     

Development and application of miniaturized scanners for laser beam micro-welding

Nowadays, flexible production systems for laser joining of micro parts require high dynamics and precision, as well as increased flexibility regarding the working space. The combination of miniaturized scanner-based laser joining systems and high-performance assembly systems is a new approach for a high accuracy compact micro assembly system with an increased flexibility. Using highly dynamic oscillation techniques leads to a stabilization of the welding process of difficult-to-weld materials, e.g. of zinc-containing alloys on the one hand, and to an increased process velocity and reduction of the joining geometry, e.g. for the welding of plastic materials on the other. Hence, a miniaturized laser processing optics is being developed featuring an integrated beam deflection for laser beam micro welding of metal as well as plastic materials. The requirements on this laser processing optics, the choice of a suitable beam deflection system and the design and simulation of the miniaturized optics are presented and discussed. Furthermore, results of laser beam micro welding applications are presented. These results directly influence the design of new miniaturized laser processing optics. By means of the integration of highly dynamic scanner devices further process improvements can be achieved for laser beam micro welding.     

Force-controllable, optically driven micromachines fabricated by single-step two-photon microstereolithography

We have fabricated optically driven micromechanisms and demonstrated their motion under optical force. All of the movable microcomponents are directly fabricated through an assembly-free process using the high-speed scanning of a femtosecond laser focused inside a photocurable resin. Since these movable micromachines are made from photocurable resin transparent to visible and near-infrared light, they can be driven by the force of optical trapping. We demonstrate a simple, versatile method for driving movable micromachines. Part of the movable component is optically trapped by a single laser beam and manipulated according to the desired trajectory. Various types of motion, including rotation and swinging are demonstrated. In addition, the optically driven micromachines can be force-controlled to femtonewton order by adjusting the position trapped by the laser beam. We demonstrated the femtonewton order force-controllable swing motion of micromanipulators. A microturbine was rotated by circular scanning of a trapping laser beam in a liquid. Such force-controllable optically driven micromachines are promising manipulation tools for biomolecules such as DNA and protein.     

A flexure motion stage system for light beam control

This paper presents the design of an improved tip-tilt-piston compliant/flexure motion stage for steering light beam. The motion stage is actuated by three linear stepper motors in an open-loop control. Using a laser and optical setup, the completed device was tested by making it steer a laser beam, effectively demonstrating its range of movement and level of precision. The testing has proved that the new motion stage system has a maximum bidirectional rotation range of at least 2.89° with a precision and repeatability of 0.0213°, demonstrating a micro-positioning ability.