双目立体视觉中特征点三维坐标重构校准研究

双目立体视觉是一种商业化较成熟的三维测量技术,左右摄像机内外参数的精确标定是实现三维重构的基础和关键。针对棋盘格和圆点两种标定板图案研究了相应的图像处理技术,实现了标定点的亚像素精度定位及其有效排序。采用基于单映性约束和非线性优化的多视角平面标定算法实现了摄像机光学及空间位置参数求解。用极线约束残差法衡量标定结果的准确度。基于桥式三坐标标准实现标定点三维重构平面度以及多平面空间夹角测量结果的校准,基于光学三坐标标准实现了标定点三维重构空间距离的校准,并分析了校准结果的不确定度。圆标志点三维重构空间距离示值误差为0.029 mm,不确定度U=24 μm（k=2）     

一种实用的双目显微镜视觉系统标定设计

本文针对显微镜光路复杂对三维物体的放大倍数过大使得采集的图像样本不理想的情况,将双目视觉系统的标定原理与显微系统产生的虚拟双目成像原理结合,提出了一种双目显微小孔成像模型。深入分析了显微摄像机系统的标定及畸变模型,然后,根据张正友的平面模板标定方法和Brown的方法,提出了一种双目标定算法,求解了摄像机内外参数和非线性畸变参数。最后结合Bouguet算法对图形进行校正,通过实验验证了本文所提方法的有效性。     

船用光电系统中摄像机参数的标定方法

基于一阶径向畸变的针孔摄像机模型,提出了一种新的线性三步摄像机定标方法,即通过径向排列约束计算摄像机参数的旋转矩阵、X轴平移矢量和Y轴平移矢量;根据透视投影的交比不变性解算一阶径向畸变参数;利用求得的摄像机参数建立有效焦距和Z轴平移矢量的线性方程,采用最小二乘法得到线性解。实验表明,该方法简单快捷,具有较高的标定精度,解决了原有算法采用非线性搜索寻优可能存在的解不稳定性等问题。     

3D测量系统中的高精度摄像机标定算法

本文在分析完整的摄像机镜头畸变模型的基础上,提出了一种新的标定算法.该算法包括三个步骤,首先在不考虑镜头畸变的情况下利用标定块上的中间若干个点,采用线性优化方法求出除畸变系数以外的其他外部参数和主要的内部参数;然后固定上述已求得的参数,利用线性优化方法求解畸变系数;最后对所有内部参数和外部参数进行全局非线性优化.最后对本文的标定算法进行了标定实验,实验结果表明,本文算法的标定精度可以达到0.0367 mm,可以满足高精度三维测量及其他应用的要求.     

基于卡尔曼滤波的摄像机标定方法

本文提出了一种基于迭代扩展卡尔曼滤波的摄像机标定方法.将二维平面靶标图像上的特征点看作是匀速运动的点,以观测到的特征点图像坐标和对应世界坐标作为滤波器的输入,摄像机内外参数的估计值作为滤波器的输出,根据迭代扩展卡尔曼滤波算法得到摄像机内外参数的最优估计.通过仿真和真实实验,结果表明,对于有限数量的平面靶标标定图像数据,该算法具有较高的标定精度和较好的鲁棒性.     

基于两步法的摄像机标定算法

摄像机标定是机器视觉中的一个重要问题.精确的摄像机标定在涉及定量测量的应用中是非常重要的.摄像机标定的目的是得到摄像机的内部参数和外部参数.通过这些参数我们能够将一个点的三维位置与它的图像平面的坐标相匹配.本文提出了一种基于两步法的摄像机标定方法.第一步,使用基于无畸变的相机模型估计标定参数;第二步,在考虑相机畸变的情况下,对第一步中得到的标定参数通过非线性优化进行迭代优化,并求解畸变系数,包括径向畸变系数和切向畸变系数.用单幅图像即可完成标定,标定过程比两步法更为简洁.实验结果表明,这种算法是简单而有效的.     

基于参数分离机器人手眼视觉标定方法研究

提出一种简单,快速、不需要标定摄像机内外部参数的标定方法。详细推导了机器人平面手眼视觉系统变换关系,完成了从视觉平面坐标系到机器人参考坐标系的坐标变换。通过参数分离简化求解过程,实践表明这种方法求解速度快、精度高。     

基于网格靶标快速高精度摄像机标定方法

本文针对单摄像机成像特点,首先建立其实际成像数学模型,为快速高精度的标定摄像机参数,靶标采用平行网格线靶标,有效利用直线的平行性约束条件,可高效的求取目标点,此种方法先求解摄像机纵横比,然后利用参数分离的方法通过迭代求解其余模型参数,从而简化了求解过程,将标定结果与Tsai法相比较可知,标定精度相当。     

带切向畸变的模型可视化摄像机标定

根椐Tsai两步标定方法,在Matlab中首先运用直接线性变换法(DLlr)对摄像机参数进行估计,然后以线性参数为初始值,运用非线性优化方法对摄像机参数进行优化.并对摄像机参数标定过程中的畸变模型进行分析,主要分析了透镜的径向和切向畸变分量.最后根据标定的摄像机参数,实现了摄像机畸变模型可视化.     

大视场星敏感器矢量观测在轨检校模型

针对大视场星敏感器的在轨标定问题,提出了一种基于矢量观测的检校新模型。将3个罗德里格参数代替欧拉角,作为外方位参数与畸变参数、内方位参数一起求解,简化了运算。采用仿真星图分析了模型的性能,结果表明,该模型较采用欧拉角的传统标定模型精度更高,在星点位置噪声方差为0.05 pixels的情况下,仍能准确解算出星敏感器参数,其星内角距的统计偏差为0.483″,x、y方向的残差绝对均值分别为0.019 pixels、0.016 pixels,且算法的参数设置简单,无需计算初值。将检校模型应用于ZY-3号卫星星敏感器的检校,结果表明模型可以有效提高检校的精度。建议在实际应用中采用精度更高的星点中心计算算法。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...