基于点云中心的激光雷达与相机联合标定方法研究

针对激光雷达与相机联合使用遇到的点云稀疏、相机受环境光照影响失真等问题,提出一种基于点云中心的激光雷达与相机自动配准方法,避免了传统联合标定需要手动选择特征点以及连续采集多帧等问题。该方法在对点云与图像预处理后,利用平面法向量的一致性实现多标定板点云自动分割,提取标定板在激光坐标系和相机坐标下的点云;然后通过点云聚集迭代求解中心点,实现两个传感器标定板对应点云中心的粗配准;最终利用迭代最近点算法进行精配准,获得标定参数,完成联合标定。实测表明,在激光雷达误差±3 cm范围内,点云正确投影比例达到97.93%,可以有效获取高精度联合标定参数,满足空间环境对激光雷达和相机数据融合的要求。     

基于SVR回归拟合的摄像机标定算法

在摄像机标定过程中,为得到像素坐标中不同像素坐标值对应的唯一世界坐标值,需要求解相机坐标系和世界坐标系之间的旋转矩阵参数、平移矩阵参数及物理器件特性参数,操作步骤烦琐。因此,提出了一种支持向量回归（Support Vector Regression,SVR）拟合一体化标定算法。首先,为实现图像平面坐标系到世界坐标系的坐标转换,选择大小为26 mm×26 mm的棋盘格作为标定块。每次采集棋盘格,统计图像中的棋盘角点。多次重复采集后,整理图像坐标与世界坐标的数据。其次,训练SVR回归模型,得到SVR的核函数和惩罚因子。最后,定量分析实验结果。相较于传统的标定方法,SVR的方法省略了求解相机畸变的步骤,解决了相机的非线性问题,具有良好的精确度和鲁棒性。     

基于传感器融合里程计的相机与激光雷达自动重标定方法

智能驾驶车辆行驶环境复杂多样,不可避免地导致传感器相对位姿发生变化,此时需要进行重新标定。针对智能驾驶车辆的相机和激光雷达发生漂移后的重标定问题,提出一种基于传感器融合里程计的自动重标定方法。基于点云投影和图像配准原理建立基准点云和观测图像之间的3D-2D点对,利用N点透视投影得到平移尺度不准的相机运动;通过融合估计的激光雷达运动来恢复准确尺度的相机运动,并将基准点云根据相机运动转换到观测位置下,与观测点云通过点云配准求解变换矩阵,使用时域均值滤波得到最终的外参矩阵。基于智能驾驶车辆试验平台进行室内外实车试验。结果表明所提出的基于传感器融合里程计的方法无需设置标定板,不受环境和数据特征限制,能够实现相机和激光雷达的精确重标定,对传感器漂移具有较高的鲁棒性。     

基于双视点特征匹配的激光-相机系统标定方法

针对传统的基于棋盘格的标定方法存在耗时且精度不高的问题,提出一种新的基于双视点特征匹配的激光-相机系统标定方法.采用自然场景中的普通物体作为标定物,通过三维激光扫描仪和相机分别采集两个不同视点下关于标定物的激光点云和图像数据,首先利用迭代最近点(iterative closet point,ICP)法对2组激光特征点集进行注册以获取两视点间的位姿转换关系,并结合立体三角化将第1个视点下获得的二维图像特征点转换到三维相机坐标系中,最后通过匹配同一视点下对应的三维激光与相机特征点集,求解出激光与相机坐标系间的外部标定参数.实验结果表明该方法能有效提高标定精度,缩短标定耗时.     

一种基于棋盘格的高精度分区域相机标定方法

在视觉测量系统中,相机的标定精度至关重要,将影响整个测量系统的精度。针对现有相机标定方法难以兼顾精度和操作复杂度的问题,本文提出了一种基于棋盘格的高精度分区域相机标定方法。首先,将棋盘格置于不同位置,提取不同位置角点的世界坐标和像素坐标,对所有角点用线性变换和非线性最优算法求解出全局标定参数。然后,将角点分为中间区域角点和边缘区域角点,对两区域角点分别标定得到两组分区域标定参数。标定实验结果表明：与全局标定法相比,分区域标定法的图像平均投影误差至少降低16%。该方法操作简单,精度高,可以很好的应用于工业视觉检测。     

一种基于棋盘格的高精度分区域相机标定方法（英文）

在视觉测量系统中,相机的标定精度至关重要,将影响整个测量系统的精度。针对现有相机标定方法难以兼顾精度和操作复杂度的问题,本文提出了一种基于棋盘格的高精度分区域相机标定方法。首先,将棋盘格置于不同位置,提取不同位置角点的世界坐标和像素坐标,对所有角点用线性变换和非线性最优算法求解出全局标定参数。然后,将角点分为中间区域角点和边缘区域角点,对两区域角点分别标定得到两组分区域标定参数。标定实验结果表明:与全局标定法相比,分区域标定法的图像平均投影误差至少降低16%。该方法操作简单,精度高,可以很好的应用于工业视觉检测。     

立体视觉和三维激光系统的联合标定方法

双目立体视觉和三维激光扫描是移动机器人环境探测与建模的常见传感测量方法。为实现两个系统的数据融合应用,必须为二者的测量坐标系建立数学关系,即对其进行传感器之间的位姿联合标定。为此提出了一种基于三维特征点距离匹配的联合标定新方法,设计了一种镂空棋盘格作为标定板。使用双目立体相机提取棋盘格角点三维坐标信息,使用激光测距雷达扫描获取镂空区域中心点三维坐标,最终通过最小化两组特征点的理论与实际测量距离的平方差获取两传感器坐标系之间的旋转矩阵和平移向量。进行的联合标定测量实验结果表明了该方法的准确性和可靠性。     

成像激光雷达与摄像机外部位置关系的标定

为了确定成像激光雷达与摄像机两种不同传感器的相互位置参数,建立两者的一一映射关系,在现有激光雷达与摄像机外部参数标定方法的基础上,通过引入奇异值分解技术,对现有标定算法进行了改进.首先,介绍了改进标定算法的基本原理,采用奇异值分解方法求解超定方程组,得到成像激光雷达坐标系与摄像机坐标系之间的投影变换矩阵.为了降低噪声影...     

二维和三维视觉传感集成系统联合标定方法

为了解决激光雷达三维深度与摄像机二维图像信息融合的关键问题,建立二者的映射关系,提出了一种基于平面实体特征匹配的三维激光雷达与摄像机集成系统的联合标定方法.首先在三维激光雷达与摄像机系统模型的基础上,提取靶标平面在激光雷达和摄像机坐标系中的平面特征,利用平面特征约束求解两坐标系之间的旋转矩阵和平移向量的初值,为了降低噪声影响,使用Levenberg-Marquardt算法优化结果.分别进行了计算机仿真和在自制的集成传感系统上的标定实验,残差深度比达到0.2％,并使用标定结果对激光点云和摄像机图像进行数据融合,验证了该方法的准确性和有效性.     

一种融合二维激光雷达和RGB-D相机的移动机器人建图方法研究

针对单独使用二维激光雷达描述环境信息不足、单独使用RGB-D相机构建地图精度不足以及三维激光雷达使用成本高的问题，提出一种使用低成本二维激光雷达和RGB-D相机点云信息融合的方法。首先，通过Autoware联合标定的方式获取相机的内部参数和外部参数，建立激光雷达数据和相机数据的变换关系。然后，基于体素网格滤波的方式降低相机原始数据的噪声和密度，并将滤波后的数据进行投影转换成伪激光雷达数据。最后，通过将转换后激光雷达数据与相机的伪激光雷达数据叠加的方式，实现两传感器信息融合。实验结果表明，有效弥补了移动机器人搭载单一传感器地图构建精度不足和获取环境信息描述不足的问题，提高了移动机器人建图的可靠性和完整性，为机器人有效导航提供保障。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.