非合作目标在轨服务最终接近段视觉导航算法

为解决在轨服务最终接近段传统单目视觉相对导航方法受相机视场限制以及非合作航天器无法设置人工靶标的问题,提出了以非合作航天器太阳帆板三角形支架的部分结构为测量目标的视觉相对导航算法.首先,设计了"自拍杆"相机安装结构和相机实时标定方案,给出了视觉相机安装角的计算方法;然后,基于逆投影原理构建满足三角形支架实际空间几何构型约束的优化模型,采用蚁群搜索算法求解特征点的景深,并应用绝对定位方法估计航天器之间的相对位置和姿态;最后,以非合作航天器在轨服务最终2 m~0 m的接近段为背景进行数学仿真,在相对距离小于1 m时,航天器之间的相对位置和相对姿态确定精度分别优于3 mm和0.2°,验证了算法的有效性和可行性.数学仿真结果表明:该相对导航方案可行,导航算法具有较高的精度,且相对导航的精度随着航天器之间的相对距离的逐渐减少而逐渐提高;同时,该算法对投影点测量误差具有较好的鲁棒性,在投影点测量误差较大时仍具有较高的精度.     

视觉测量中光学测头姿态估计方法

基于光学测头特征点成像的单机视觉坐标测量系统具有测量空间大、测量精度高及可进行现场测量等优点,是替代传统的大型坐标测量机的最有发展前途的技术方案之一.为实现该测量方法,必须先解决光学测头姿态估计问题,为此,提取一种利用SVD与矢量观测值的姿态确定方法.首先,通过基于SVD的5点优化算法确定特征点的空间坐标;然后,利用特征点的测头坐标和空间坐标建立关于测头坐标矢量、像机坐标矢量的矩阵方程,优化求解矩阵方程确定光学测头(测头坐标系)相对于像机坐标系的姿态.该算法利用所有数据冗余信息,提高了测量系统的精度和稳定性.实验证明,该算法切实可行,系统的单点重复性及测量不确定度<0.1 mm.     

利用数字图像处理技术实现音圈电机运动检测

为了精确分析音圈电机的运动（特性）规律,运用IMPERX公司生产的高速相机,采用非接触式测量的方法;运用数字图像处理技术,在MATLAB平台上通过追踪特征点的运动轨迹,实现音圈电机运动的精确测量,并分析其运动特性.实验结果表明,音圈电机直线运动特性较好,视频运动分析可行.     

基于GPS差分技术的无控制点或少控制点航测精度分析

主要介绍了通过对GPS差分数据进行无控制点或少控制点的内业空三解算结果的分析得出,基于GPS差分技术的无控制或少控制航空摄影测量的精度完全可以满足航摄测图的精度要求。     

基于线阵CCD的大视场二维平面定位系统

为了克服当前交互式电子白板系统技术复杂、定位精度低等缺点,提出一种基于线阵电荷耦合器件（CCD）的大视场二维平面定位系统,该系统由待定位物体、CCD摄像装置和信号处理电路组成.CCD获取待定位物体的信息送入信号处理电路处理,通过坐标变换快速校正CCD光学系统引起的畸变,得到待定位物体的位置.系统定位距离为1 360 mm,二维定位平面大小为1 574 mm×1 260 mm,定位误差小于2 mm,定位精度高于0.2%.搭建了相应的大视场二维平面定位系统.实验结果表明,该系统可实现大角度非接触式二维物体的精确动态定位.     

Semi-Direct Visual Odometry and Mapping System with RGB-D Camera

In this paper a semi-direct visual odometry and mapping system is proposed with a RGB-D camera, which combines the merits of both feature based and direct based methods. The presented system directly estimates the camera motion of two consecutive RGB-D frames by minimizing the photometric error. To permit outliers and noise, a robust sensor model built upon the t-distribution and an error function mixing depth and photometric errors are used to enhance the accuracy and robustness. Local graph optimization based on key frames is used to reduce the accumulative error and refine the local map. The loop closure detection method, which combines the appearance similarity method and spatial location constraints method, increases the speed of detection. Experimental results demonstrate that the proposed approach achieves higher accuracy on the motion estimation and environment reconstruction compared to the other state-of-the-art methods. Moreover, the proposed approach works in real-time on a laptop without a GPU, which makes it attractive for robots equipped with limited computational resources.     

基于交比不变量的摄像机标定方法

为了解决摄像机标定的菲线性优化过程中解的不稳定性问题,针对具有镜头径向畸变的摄像机模型,提出了一种实用的摄像机线性标定方法.该方法利用透视投影的交比不变性原理标定镜头的畸变系数,基于摄像机成像的单应性矩阵及内部参数的基本约束,线性标定出其他摄像机参数.实验结果表明,该方法标定模板制作简单,速度快,具有一定的鲁棒性,可以满足工业机器视觉的精度要求.     

基于单摄像机手眼系统的距离测量标定方法

距离信息的获取在机器人技术中是非常重要的。提出了一种适于机器人手眼系统进行双目测距的简单的测量标定方法。这种方法通过控制深度方向上的一次移动，即可得到某些参数的标定解，从而克服了一些标定系统技术上的难点．通过实验验证，本方法可以达到小于１２％的测量精度．可以用于机器人的视觉粗定位和三维避平障等实际应用．     

New method for camera pose estimation based on line correspondence

The key technology of the measuring method of pose shaking of unstable platform based on CCD lies in the camera pose estimation.A new method for camera pose estimation based on line correspondence is put forward in this paper.First,two appropriate lines are selected in the space to establish a local coordinate system,the remaining lines form three-line sets with these two lines respectively and then the angle depth of the lines of the local coordinate system can be obtained by using the linearity of interpretation plane;then the invariance of included angle between spatial coordinate system and camera coordinate system during rigid transformation is used to establish a constraint equation set of angle depth of three lines similar to traditional P3P,and the corresponding angle depth of the third line in the set can be obtained linearly by variable substitution;finally,the rotation matrix can be expressed with quaternion and the pose parameters of camera in the space can be calculated by singular value decomposition(SVD).The static experiment and dynamic experiment verify the accuracy and stability of the algorithm and that the camera pose shocking is within 1°and the 3σ error is superior to 0.3′.The method in this paper can be directly used in the micro-vibration measurement of experimental platform and robot navigation and other fields and is of important theoretical significance and engineering application prospect.     

基于激光条带追踪的桥梁振动非接触测量方法

针对基于计算机视觉的结构位移测量方法存在对靶点要求高及光照依赖性强的问题,提出了一种通过竖直投射激光条带于桥梁结构表面,追踪光带中心以分析桥梁振动的新方法。通过大功率线激光器投射激光线至梁底面或顶面,倾斜拍摄激光线连续影像,利用改进灰度重心法亚像素追踪激光条带中心线位置在图像上的改变,几何换算得到桥梁振动位移时程曲线,进而可分析获得桥梁结构的动力参数。在室内实验条件下对简支梁模型桥进行了锤击强迫振动试验,以SONY 4K摄像机作为影像采集设备,LVDT位移传感器和加速度传感器作为传统数据采集设备进行了同步数据采集实验。分析结果表明,动位移测量结果以LVDT采集数据为参考,SONY摄像机所得结果相对误差极值为3.17%。模态分析结果以加速度传感器为基准来比较,摄像机对前二阶频率识别的相对误差极值为1.81%,表明动位移测量与低阶模态参数识别都取得了理想的效果,不同于加速度传感器所得模态振型空间精度受限于传感器数量,本文方法所得模态振型空间精度可达像素级,且几乎无环境光照改变干扰实验结果的困扰。该方法为非接触测量以识别桥梁自振特性提供了一条经济高效的新思路。     

基于数码相机的土三轴试样变形的数字图像测量

将数码相机用于土三轴试样变形的图像采集，提出了一种基于数码相机的土三轴试样变形的数字图像测量方法．通过与常规土三轴试验测量结果对比，说明了该方法的可行性和优越性，它不仅可以克服常规三轴试验方法中存在的诸多缺陷，而且具有较高的测量精度，是一种简单、有效且有广阔发展前景的测量方法．     

Vision algorithms for fixed-wing unmanned aerial vehicle landing system

Autonomous landing has become a core technology of unmanned aerial vehicle (UAV) guidance, navigation and control system in recent years. As a novel autonomous landing approach, computer vision has been studied and applied in rotary-wing UAV landing successfully. This paper aims to fixed-wing UAV and focus on two problems: how to find runway only depending on airborne front-looking camera and how to align UAV with the designated landing runway. The paper can be divided into two parts to solve above two problems respectively. In the first part, the paper firstly presents an algorithm of region of interest (ROI) detection, which is based on spectral residual saliency map, and then an algorithm of feature vector extraction based on sparse coding and spatial pyramid matching (SPM) is proposed, finally, ROI including designated landing runway is recognized by a linear support vector machine. In the second part, the paper presents an approach of relative position and pose estimation between UAV and landing runway. Estimation algorithm firstly selects five feature points on the runway surface, and then establishes a new earth-fixed reference frame, finally uses orthogonal iteration to estimate landing parameters including three parameters of distance, height and offset, and three pose parameters of roll, yaw, pitch. The experimental results verify the effectiveness of the algorithms proposed in this paper.     

基于三维测量的奶牛体型性状指标的数据采集

采用立体视觉的三维测量方法重建奶牛的三维模型,实现了对奶牛的体型性状指标测量,首先通过立体标靶进行摄像头的标定,然后利用SIFT（scale invariant feature transform）尺度不变特征点匹配算法对图像进行特征点提取与匹配,最后通过投影矩阵计算匹配特征点的三维坐标;针对双目视觉中摄像头视角范围受限问题,提出通过在相邻视点的公共区域设置标记点,根据标记点计算不同坐标系的转换关系,将各局部特征点转换到统一坐标系下,从而实现不同视点下各局部区域的三维拼接.实验表明,采用该方法重建的奶牛模型较理想,测量精度和测量效率满足评定要求,能够取代手工测量.     

Simplified Method for Joint Calibration of 3D Ladar and Monocular Camera

To address the problem of data fusion between monocular camera image with 3D data from laser detection and ranging (LADAR) sensor, this paper proposes a novel simplified scheme based on the planar feature method, which can meet the accuracy requirements of the joint calibration with fewer checkerboard calibration plate (CP) positions than traditional methods. First, a mathematical model of the joint calibration is established to obtain the calibration parameters. Secondly, the selection of positions and orientations of the CP are introduced and the corresponding influence to the calibration is analyzed. Then, the calibration result is optimized by using a nonlinear Levenberg-Marquardt (LM) optimization approach, and the distance residual method is utilized to estimate the accuracy. Finally, experimental results conclude that the minimum number of positions required to meet the joint calibration accuracy in the proposed method is 5, which is less than 12 in traditional methods.     

基于图像处理的食品细菌自动检测方法

介绍了一种基于显微图像识别的食品中细菌快速检测系统。分析了细菌图像特征,给出了提取细菌特征的方法,经实际检验,该方法可以有效识别食品中的细菌,同时可以很好地去除噪声的影响。文中方法都经过实际检验并给出了实际效果图。     

Multi-perspective digital image correlation method using a single color camera

A novel 3 D digital image correlation(DIC) system based on a single three charge-couple device(3 CCD) color camera is proposed in this paper. Images from three different perspectives are captured by a 3 CCD camera using a reflective-based pseudo-vision system. These images are then separated by the different CCD channels, and the correlation algorithm for the multi-camera DIC system is adopted to evaluate the images. Compared to the conventional multi-camera DIC system, the proposed system is much more compact. In addition, the proposed system has no loss of spatial resolution, compares to the traditional single camera DIC system. The complex surface measurement ability and the measurement accuracy is significantly improved through the use of the multi-camera DIC algorithm. The principle of the proposed system is described in detail as well as the experimental setup. A series of validation tests are performed, and the results are verified with the commercial 3 D-DIC system.     

基于移动最小二乘曲面的多视三维点云数据ICP对齐方法

多视数据最近迭代点(ICP)对齐广泛应用于反求工程及特征识别中,为了提高对齐精度以及稳定性,提出了一种基于移动最小二乘(MLS)曲面的ICP多视数据对齐方法.该方法的主要思想是直接利用MLS曲面表示原始曲面模型,将其他视角数据ICP对齐到该MLS曲面,其优点是无需对测量数据进行额外的去噪处理与数据分割,即可实现多视点云数据的精确对齐.实验结果表明,该方法能得到更加精确稳定的对齐结果.     

Non-Metric CCD Camera Calibration Algorithm in a Digital Photogrammetry System

Camera calibration is a critical process in photogrammetry and a necessary step to acquire 3D information from a 2D image. In this paper, a flexible approach for CCD camera calibration using 2D direct linear transformation （DLT） and bundle adjustment is proposed. The proposed approach assumes that the camera interior orientation elements are known, and addresses a new closed form solution in planar object space based on homogenous coordinate representation and matrix factorization. Homogeneous coordinate representation offers a direct matrix correspondence between the parameters of the 2D DLT and the collinearity equation. The matrix factorization starts by recovering the elements of the rotation matrix and then solving for the camera position with the collinearity equation. Camera calibration with high precision is addressed by bundle adjustment using the initial values of the camera orientation elements. The results show that the calibration precision of principal point and focal length is about 0.2 and 0.3 pixels respectivelv, which can meet the requirements of close-range photogrammetry with high accuracy.     

基于全景视觉技术的旋翼共锥度测量系统的设计及实现

在深入分析以往旋翼桨叶共锥度测量手段的基础上,提出了一种基于全景视觉技术的旋翼共锥度测量的新方法。由全景图像球面还原算法原理,推导出了一组用于计算桨叶锥度差的逆投影公式。利用同步电路控制摄像机拍摄实现了对目标桨叶的实时提取,并对全景图像的解算方法进行了相应研究。应用脉冲耦合神经网络(PCNN)对全景图像进行初次分割,重点介绍了在此基础上结合区域标记法对桨叶图像进行特征提取的过程并取得了很好的识别率。实验结果表明,该测量方法对于桨叶锥度差的计算具有较高的精度,可以应用于未来的实际生产过程。     

确定板材塑性本构产参数的神经网络方法研究

在分析传统单向拉伸实验的缺点的基础上,提出了一种应用神经网络、有限元模拟和实验相结合的板材塑性参数的识别模型。采用了具有双向应力 板料拉伸试件,利用BP的神经网络实现试件拉伸变形过程中载荷,位移曲线与材料性能参数之间的映射关系,从而可以得到双向应力状态和大变形条件下的材料参数。研究中对08Al、LY12M两种材料进行了实验验证。