基于双目相机的光栅立体印刷图像合成

目的研究一种基于双目相机的光栅立体图像合成方法。方法首先用双目相机采集场景中2个观察角度的二维平面图像数据。基于双目立体视觉理论,采用一种鲁棒性较强的基于区域分割的图像匹配方法,得到精度较高的深度图。然后分析序列视差图像的成像模型,建立一种基于双目图像对生成序列视差图像的方法,得到连续角度等间隔的序列图像。最后基于柱镜光栅的光学特性形成的立体印刷图像编码规则,对序列视差图像进行纵向条纹抽样分割,等间隔的抽取每幅序列视差图像中的对应列实现光栅立体图像的合成。结果验证了该光栅立体图像合成方法的有效性。结论基于双目相机的光栅立体合成方法,可以使立体印刷产品实现个性化、便捷化的即时输出。     

Research on the application of single camera stereo vision sensor in three-dimensional point measurement

A single camera stereo vision sensor model based on planar mirror imaging is proposed for measuring a three-dimensional point. The model consists of a CCD camera and a planar mirror. Using planar mirror reflections of a scene, a picture with parallax is obtained by shooting the target object and its virtual image. This is equivalent to shooting the target object from different angles with the camera and the virtual camera in the planar mirror, so it has the function of binocular stereo vision. In addition, the measurement theory of the three-dimensional point is discussed. The mathematical model of a single camera stereo vision sensor is established, the intrinsic and extrinsic parameters are calibrated, and the corresponding experiment has been done. The experimental results show that the measuring method is convenient and effective; it also has the advantages of simple structure, convenient adjustment, and is especially suitable for short-distance measurement with high precision.     

车、路的相互作用下沥青路面动力学特性分析

文中采用二自由度四分之一汽车悬架模型模拟汽车系统,依据弹性层状体系理论,建立路面结构的三维有限元分析模型,考虑车路相互作用,采用ANSYS有限元分析软件对移动车辆荷载作用下路面各结构层中的位移、应力、应变进行了模拟。计算分析了行车速度、悬架刚度、悬架阻尼、轮胎刚度和轮胎阻尼五个参数对路面动力响应的影响。结果表明：沥青面层处于三向受压状态,层内切应力是引起其破坏的主要原因;最大水平拉应力和最大横向拉应力均发生在路面结构的基层和底基层结合处;车速对路面动态响应的影响规律很复杂,应考虑车辆模型和路面不平整度,并划分速度区间加以探讨;路面动态响应随轮胎刚度、悬架刚度和悬架阻尼的增大而减小。上述结论对于深入分析路面结构动力响应与疲劳损坏以及研究车辆与路面相互作用的机理有重要价值。     

基于红外热图像的沥青路面温度离析区域检测方法

提出一种基于红外热图像的沥青路面温度离析区域检测方法。将红外热图像中沥青路面的温度和改进后的灰度图像边缘分割模型相结合,建立了沥青路面温度离析区域的检测模型,利用对偶法对模型中的参数进行求解,将BP神经网络优化和最小二乘拟合相结合,确立了红外热图像中沥青路面温度和模型中灰度之间的关系,实现了沥青路面温度离析区域的检测。最后通过仿真实验验证了提出方法的可行性,为道路工程建设以及科研等领域的红外热图像的处理提供了理论依据。     

一种双目立体视觉系统的校准方法

基于双目立体视觉系统的图像分析以及人工神经网络的三维空间建模算法,设计了一种针对双目立体视觉相机的校准方法,并可应用于运动目标点的轨迹追踪。将均匀分布目标点的校准平面放置在有效视野内的不同位置,通过双目立体视觉系统来捕获处于不同位置的校准平面图像。在图像处理之后,使用校准点中心的二维坐标作为人工神经网络训练的输入样本集,通过建立人工神经网络模型结构,实现目标点二维平面坐标到三维空间坐标的映射关系。采用这种具有通用性的方法,可以有效修正系统中存在的失真因子,获得目标三维位置信息,而无需进行复杂的相机校准操作。实验表明,提出的方案具有良好的可行性和鲁棒性。     

远程测量系统中被测零件的重建

坐标测量机（CMM）与测量者分离进行远程测量时,掌握被测零件的位置与形状信息具有重要意义。提出一种对被测零件进行三维重建和定位的方法,根据双目视觉原理,利用从测量现场获取被测零件的图像及机械零件的规则性较强采用体积表示方法进行被测零件的三维重建,详细阐述了准确识别组成被测零件基本几何体的方法,展示了应用该系统三维重建和定位示例。     

Depth-based computational photography

A depth-based computational photography model is proposed for all-in-focus image capture. A decomposition function, a defocus matrix, and a depth matrix are introduced to construct the photography model. The original image acquired from a camera can be decomposed into several sub-images on the basis of depth information. The defocus matrix can be deduced from the depth matrix according to the sensor defocus geometry for a thin lens model. And the depth matrix is reconstructed using the axial binocular stereo vision algorithm. This photography model adopts an energy functional minimization method to acquire the sharpest image pieces separately. The implementation of the photography method is described in detail. Experimental results for an actual scene demonstrate that our model is effective.     

Optical positioning technology of an assisted puncture robot based on binocular vision

Percutaneous image-guided interventions are increasing in number in clinical practice because they are minimally invasive. Needle positioning placement is crucial and highly dependent on the physician's skills and experience, it is often the longest part of the intervention. Medical robotics and computer-assisted surgery are hotspots in the field of robotics and medicine, changing the essence of traditional surgery using a combination of robotic, image processing, and computer technologies. The present paper aimed to study the auxiliary puncture procedure using a robot based on optical positioning technology that can be used to mark points in puncturing operation. Binocular camera is used for image acquisition, and Zhang's calibration method is used to establish the binocular camera model. In addition, the circular markers are identified by the least square method detection circle, and the coordinate information of the markers in three-dimensional space is solved by using the visual depth information of binocular phases. This paper studies the verification of the three-dimensional bone model of the human body, which lays a foundation for the application of the assistant puncture robot.     

Super deep 3D images from a 3D omnifocus video camera

When using stereographic image pairs to create three-dimensional (3D) images, a deep depth of field in the original scene enhances the depth perception in the 3D image. The omnifocus video camera has no depth of field limitations and produces images that are in focus throughout. By installing an attachment on the omnifocus video camera, real-time super deep stereoscopic pairs of video images were obtained. The deeper depth of field creates a larger perspective image shift, which makes greater demands on the binocular fusion of human vision. A means of reducing the perspective shift without harming the depth of field was found.     

基于激光和机器视觉的微量液体容量计量方法

针对玻璃量器的液体容量计量,提出一种基于激光和机器视觉技术的液位测量方法。建立了标准玻璃量器液位高度和容量对应关系的容积表,通过测量得到液位高度就能得到对应的液体体积值;采用数字图像处理等技术,使用高精度摄像头和图像处理软件,提取特征元素,实现玻璃量器中液体体积的高精度测量。设计了和静力衡量法的比对试验进行方法验证,对于100mL的玻璃量器,测量装置引用误差优于0.2%,拟合算法的扩展不确定度为0.137%(k=2),测量重复性为0.08%。     

复杂光照环境下空间目标相对位姿测量方法研究

为解决空间复杂光照环境下可见光相机获取的图像照度不一、信息失真、特征不完整导致的目标 航天器相对位姿求解困难的问题,提出了一种基于图像增强和弧段特征的双目视觉相对位姿测量方法。首先通 过基于带色彩保留的多尺度Retinex（Multi?scale Retinex with Chromaticity Preservation, MSRCP）自适应图像预处理 方法提升空间暗弱光、局部强曝光环境下的图像质量;然后利用基于边缘弧支撑线段的椭圆检测算法提取目标 航天器表面星箭对接环的弧段特征,并拟合得到椭圆轮廓;最后利用双目相机搭建了空间相对位姿测量物理仿 真实验平台,建立双目空间椭圆锥测量模型解算目标的六自由度相对位姿,实现了近距离正常光照和暗弱光照 场景下目标航天器相对位姿求解。实验结果显示：在正常光照场景下,相对位置平均误差优于20 mm,相对姿 态平均误差优于0. 3°;在暗弱光照场景下,相对位置平均误差优于30 mm,相对姿态平均误差优于1°。研究成 果为近距离空间交会对接等在轨服务任务中的目标识别与测量提供了参考,具有技术借鉴价值。     

Binocular self-calibration performed via adaptive genetic algorithm based on laser line imaging

Abstract

An accurate technique to perform binocular self-calibration by means of an adaptive genetic algorithm based on a laser line is presented. In this calibration, the genetic algorithm computes the vision parameters through simulated binary crossover (SBX). To carry it out, the genetic algorithm constructs an objective function from the binocular geometry of the laser line projection. Then, the SBX minimizes the objective function via chromosomes recombination. In this algorithm, the adaptive procedure determines the search space via line position to obtain the minimum convergence. Thus, the chromosomes of vision parameters provide the minimization. The approach of the proposed adaptive genetic algorithm is to calibrate and recalibrate the binocular setup without references and physical measurements. This procedure leads to improve the traditional genetic algorithms, which calibrate the vision parameters by means of references and an unknown search space. It is because the proposed adaptive algorithm avoids errors produced by the missing of references. Additionally, the three-dimensional vision is carried out based on the laser line position and vision parameters. The contribution of the proposed algorithm is corroborated by an evaluation of accuracy of binocular calibration, which is performed via traditional genetic algorithms.     

Dynamic response of top-down cracked asphalt concrete pavement under a half-sinusoidal impact load

A 3D finite element analysis model of cracked asphalt pavement is established by the FEM software ABAQUS. Based on dynamics mechanics, fracture mechanics and finite element theory, this paper studies the influence of various vehicle speeds, crack location, crack depth, damping ratio etc. on the dynamic response. The results show that the surface deflection, the maximum tensile strain at the bottom of the asphalt layer, and the maximum shear stress of the asphalt layer decreased with the increase in vehicle velocity when there is no crack in the pavement. No matter where the transverse position of the crack is the stress intensity factors increase with the increase in crack depth and decrease exponentially with the increase in longitudinal distance between the vehicle center and the crack. In the case of the crack locating in the center of wheel clearance, the surface deflection increases with the crack depth increasing. But if the crack is at the edge of the wheel track, there will be a critical vehicle velocity where the surface deflection is smaller than the asphalt pavement without crack if the vehicle velocity is above it. The maximum tensile strain at the bottom of the asphalt layer and the maximum shear stress of the asphalt layer are also smaller than the asphalt pavement without crack. The maximum tensile strain and the maximum shear stress decrease with the damping ratio increasing. So the increase in damping ratio can help to alleviate the propagation of cracks.     

Finite element modelling of field compaction of hot mix asphalt. Part II: Applications

A constitutive model is developed and implemented in the finite element system three-dimensional computer-aided pavement analysis for the simulation of hot mix asphalt field compaction. The details of this model are presented in a companion paper (Masad et al., Finite element modelling of field compaction of hot mix asphalt. Part I: Theory, International Journal of Pavement Engineering, Accepted, 2014). This model is based on nonlinear viscoelasticity theory and can accommodate large deformations that occur during the compaction process. The model was used to study the influence of frequency and amplitude of vibratory compaction rollers on the level of compaction. In addition, it was used to analyse the influence of various methods for compacting longitudinal joints on the percent air voids near these joints. The model was used to simulate the compaction of asphalt pavements with different structures and compacted using various equipment and patterns. The finite element results of the level of compaction and percent air voids were in reasonable agreement with the measurements. The model offers the opportunity to simulate and predict the compaction of asphalt mixtures under various rolling patterns and for different pavement structures.     

基于非线性模型的沥青路面动力响应研究

根据路基变形的非线性及沥青路面具有明显粘弹性的特点,将沥青路面简化为非线性粘弹性地基上的粘弹性无限长梁,建立了移动载荷作用下非线性粘弹性梁系统动力响应数学模型。利用Adomian分解法和小波变换法得到求解稳态响应解析解的新方法。通过实际道路参数对沥青路面动力响应进行了数值仿真,研究了车速、车辆轴载、路面材料及温度对沥青路面动力响应的影响规律。结果表明该文提出的计算方法简便、快捷,是求解该类非线性动力响应问题的一种有效方法;非线性模型更能准确地反映重载及超载时沥青路面实际结构受力状态。     

基于点云三维重构的配合面装配间隙分析方法研究

在大型航空复合材料零部件装配过程中难免出现装配对接间隙,由于间隙较小,当构件固定之后内部间隙不可达,难以测量。因此,为了克服这一难题,完成装配体小间隙的测量,本文提出了利用逆向重建和虚拟装配的方式进行装配间隙测量的方案。本文基于大型航空复合材料零部件测量的背景,结合双目视觉测量原理,采用视觉与激光相结合的测量方式,研究从点云获取至装配仿真模型的逆向重建技术,在CATIA的虚拟环境下完成装配间隙的测量。     

Calibration modeling for mobile vision based laser imaging and approximation networks

A mobile calibration technique for three-dimensional vision is presented. In this technique, the parameters of mobile vision are computed automatically by approximation networks and image processing of a laser line. Also, the three-dimensional vision is performed by the networks. The proposed vision system provides online geometric modifications from the initial configuration. Here, an online re-calibration is performed via network data to determine the setup modifications. Thus, vision limitations caused by the geometric modifications are overcome. The network is built based on the behavior of the laser line and the camera position. In this manner, the network provides the data for the automatic re-calibration. This system avoids calibrated references and external procedures for re-calibration. Therefore, the calibration model improves the accuracy and performance of the mobile vision. It is because the external data are not passed to the procedure of the three-dimensional vision. This kind of modeling represents a contribution for calibration of mobile vision. To elucidate this contribution an evaluation is carried out based on the calibration via perspective projection model. The time processing is also described.     

Hierarchical asphalt pavement deterioration model for climate impact studies

Quantification of the impacts of projected climate change on road pavement performance is possible using predictive models that correctly consider key causal factors of pavement deterioration. These factors include climate, traffic, properties of materials and the design of pavements. This paper presents a new model developed to predict rutting in asphalt surfacing. In addition to the key causal factors of road deterioration, the developed model takes into account several sources of uncertainties, particularly those inherent in future climate change predictions and model input parameters. The asphalt surfacing rut depth progression model was developed from a hierarchical road network data structure using a Bayesian regression approach resulting in a model for each surfacing group. The model was applied within a Monte Carlo simulation framework to derive probabilistic outputs of pavement rut depth progression and maintenance costs under the pre-determined future climate scenarios. This model is useful for application at both the network and project levels to develop road management strategies and policies.     

服务机器人新型双目视觉系统及结构参数标定的研究

构建了一种新型的满足服务机器人视觉任务需要的双目视觉系统,该系统是由一个云台(Pan/Tilt/Zoom,PTZ)摄像机和一个手眼系统组成的变基线双目配置,具有更大的视觉空间和灵活性。对该双目配置下实现目标定位的关键参数——双目结构参数的实时自标定方法进行了研究,提出了将大部分繁琐的坐标变换关系转移到离线环节标定的离线/在线二步标定算法。仿真实验表明,此方法可有效降低在线处理时对图像匹配点的数目要求,同时该双目系统对图像噪声和机械运动误差具有一定鲁棒性。     

基于感兴趣区域的彩色三维物体快速喷绘方法

目的 针对目前三维空间喷绘效率低及个性化不足问题,提出一种基于感兴趣区域再分割的三维物体快速喷绘方法.方法 首先利用感兴趣区域算法提取出彩色图像中最显著部分,再通过一种新灰度图再分割算法进行二次图像处理,得到具有不同显著性区域等级的图像,将带有区域分级图像和原图像进行合并,得到具有区域分级的彩色图像.然后通过三维纹理映射方法,将后得到的彩色图像映射到目标三维模型,三维模型的表面就带上所需的纹理信息.再利用一种新的多喷头控制技术,合理地安排不同的喷头处理不同的区域.最终通过信号传输,将打印文件传输到机械臂,机械臂进行工作喷绘.结果 该三维喷绘方法对半径为100 mm球体的工作总时间为100.34 s,具有较高的工作效率.结论 相较于传统的三维喷绘,基于传统的感兴趣区域的喷绘所提出的基于感兴趣区域再分割算法,在保证喷绘精度的前提下显著提高了喷绘效率,在性能指标上总体优于传统的感兴趣算法.