An improved two-point calibration method for stereo vision with rotating cameras in large FOV

At present, binocular stereo vision is gradually being applied for 3D coordinate measurements in large fields of view (FOVs). In this study, a binocular stereo vision system with fixed and non-zooming cameras in a large FOV is constructed, in which cameras can rotate horizontally and vertically. All intrinsic parameters except the focal length of the cameras are set to default values and these focal lengths are calibrated offline in advance. Only the pitch angle and yaw angle of each camera need to be obtained during rotation. Therefore, we present a novel calibration method by using two control points and transform the imaging model of the pitch and yaw angles into a quadratic equation of the tangent value of the pitch angle so that the closed-form solutions of the pitch and yaw angles can be obtained. Computer simulation and real experiments demonstrate the effectiveness of the proposed method.     

基于单特征点的手眼系统摄像机标定

基于机器人的相对运动,提出了一种基于单特征点的手一眼系统摄像机内、外参数的标定方法。在摄像机视场中任意选择一个特征点,使机器人末端在保持姿态不变的条件下运动,相当于机器人不动但具有多个特征点。利用这些点可计算出摄像机的内参数和相对于特征点的外参数。大幅度改变机器人的姿态,可标定出特征点在机器人基坐标系下的位置,进而得到相对于机器人末端的外参数。实验结果验证了该方法的有效性。     

多目立体视觉测量系统中的快速去伪匹配法

以外极斜率匹配为基础,针对多目立体视觉测量系统的特点,提出了一种可有效解决立体图像对匹配过程中的匹配多义性问题的快速去伪匹配法。     

A possibilistic approach for designing hybrid cellular manufacturing systems

In this paper, a hybrid cellular manufacturing (HCM) system is presented in which the main sources of uncertainty, e.g. the demands of parts and unit costs are treated as fuzzy numbers in the form of possibilistic distributions. The basic concept of HCM is that high variation in demand might disturb cell efficiency, so forming cells with only those parts that have stable demand, will profit. Thus, to design stable and robust manufacturing cells, a two-phase method is proposed in which a fuzzy adaptive ranking method is first applied to identify those parts with low and non-repetitive demands (i.e. the special parts) which will then be assigned to a functional cell. Afterwards, an interactive possibilistic programming model is applied to cell formation of remaining regular parts while considering both part sequences and multiple routes. To show the capability and usefulness of the proposed method, an illustrative example is also provided. Finally, concluding remarks are reported.     

Static error budget analysis for a land-based dual-camera mobile mapping system

A mobile mapping system (MMS) is developed based on a direct sensor orientation technique that integrates GPS/inertial measurement unit (IMU) and digital cameras. This system is capable of directly mapping geospatial information without the requirement of ground control. In this article, an MMS composed of two digital single-lens reflex cameras and an Applanix POS AV-510^© is described. There are several systematic errors that need to be calibrated before achieving the goal of direct georeferencing. These are related to lens distortion, the lever-arm between the GPS and the camera's perspective center, and the boresight misalignment angles between the IMU and the camera frame. Experimental results show that the calibration field is the major error source. However, with the designed system, we can achieve a maximum three-dimensional positioning error of less than 18.27 and 7.74?cm at distances 20?m using a single camera with parallel imaging and dual-cameras with convergent imaging, respectively. The results demonstrate that the potential of high-accuracy land-based MMS applications is promising.     

一种用于外科手术导航的双目视觉简化系统

针对外科手术导航光学定位仪参数标定过程繁琐和对应点匹配歧异性大的问题,进行了双目立体视觉简化系统的研究.运用坐标变换方法一次性标定系统24个参数;选用黑白棋盘格标记物和运用相似性度量原理,简化立体匹配过程、提高立体匹配准确度.利用标定后的系统对标记物之间的距离进行测量,在距双目视觉传感单元1.5 m范围内误差小于1 mm.交叉韧带重建手术导舷模拟实验表明:该系统具有稳定,可靠,标定方法简单,匹配准确,定位精度高的特点,能够满足外科手术导航的要求.     

基于投影的二阶段空间圆线拟合算法

对空间圆线精确拟合算法进行研究．线性和非线性最小二乘法是拟合规则曲线和曲面方程的常见方法．空间圆线作为规则的二次曲线,由于没有特定的曲线方程无法直接使用线性和非线性最小二乘法来进行求解．由于空间圆线可以被看作平面和球面相交形成,圆线特征值可以通过平面和球面特征值求解．提出了基于投影二阶段拟合算法完成空间圆线拟合的方法．对空间圆线拟合原理进行了介绍,通过数据验证了算法的正确性、可行性和精确程度．使用程序进行了算法实现．与贝塞尔和B样条曲线算法精度进行了比较,表明该算法在精度方面具有优势,可用于逆向工程中提高空间拟合算法的精确度．     

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.     

基于混杂系统Q学习最优控制的信号灯控制方法

采用混杂切换系统Q学习最优控制方法实现了单交叉口信号灯优化控制.提出了应用强化学习中的Q学习进行混杂系统切换控制的方法,并将该方法应用于解决交叉口信号灯控制问题.首先建立了交叉口混杂切换系统模型,在确定信号灯控制行为集的基础上,应用Q学习算法决定最优的控制策略,进而得出交叉口信号灯最佳切换信号.采用Paramics微观交通仿真软件进行了仿真,结果验证了采用该方法实现混杂切换系统优化控制问题的可行性和有效性.     

一种改进的机器人手眼系统标定方法

针对机器人手眼系统标定中空间坐标值参考点获取的困难,提出了一种改进的不需要已知坐标值参考点的机器人手眼系统标定方法.该方法的优点是在摄像机内参数标定中考虑了径向畸变,保证了标定精度.在外参数标定中,根据机器人自身运动特性提出了一种简便求取平移矩阵的方法.     

偏心支撑框架空间子结构混合试验边界条件模拟方法

数值子结构的建模精度和子结构的边界条件模拟是子结构混合试验中的两个关键问题。为进一步研究这种新型结构试验方法对于空间框架结构的适用性,基于高强钢组合Y形偏心支撑框架模型展开研究。首先建立了一套由OpenSees, OpenFresco试验平台以及MTS加载系统组成的混合试验系统。然后分别针对2层、3层和4层3跨高强钢组合Y形偏心支撑框架,取底层带有偏心支撑的框架部分作为试验子结构,其余部分作为数值子结构在OpenSees中进行模拟。在混合试验之前,利用已有单榀试件拟静力试验结果对数值子结构的建模方法进行了数值模拟验证。最后选取El Centro波作为原始输入地震波,针对试验子结构的平动模拟和竖向荷载作用进行了一系列空间子结构混合试验。结果表明:通过数值模拟验证拟静力试验结果的方式,可以为混合试验中数值子结构的建模提供参考依据;采用双作动器水平加载来实现试验子结构的平动,可以有效考虑数值子结构对试验子结构的边界约束;竖向荷载的考虑,可以更真实的模拟试验子结构的重力二阶效应。     

A hybrid neural network method for simulating spatial variation in earthquake ground motion

Different excitations for supports should be considered for the analysis of long-span structures. The excitation of each support has time delay and spatial variation relative to other support excitations. The present study aims to propose a new method for simulating accelerograms for various distances considering spatial variation of earthquake records. The accelerograms are simulated based on response or design spectra using the learning capabilities of neural networks. In this method, the response spectrum, and the distance parameter (distance from fault rupture) are the input, and the corresponding accelerograms are the output of the network. There are three stages involved in this study. In the first stage, a replicator neural network is used as a data compressor to increase capability of the simulation. In the second stage, a radial basis function neural network is employed to generate a compressed accelerogram for a certain distance and a response spectrum. In the third stage, the compressed acceleration data is decompressed to resemble real earthquake records. Recorded accelerograms of the strong motion array in Taiwan are used to train the artificial neural network. The obtained results show the robustness of the applied method in producing spatially varying accelerograms. Finally, compatible accelerograms of the design spectrum, suggested in the Taiwan building seismic design code, are simulated for different distances with the proposed method.     

三目视觉测头在自由曲面测量中的应用

自由曲面的逆向工程是先进制造技术中的一个关键技术．开发了一种线结构光三目视觉测头，这种包括3个CCD摄像机在内的测量系统具有许多优点，避免了双目视觉中存在的匹配现象．它不但具有高效率、高精度和高可靠性的特点，而且适用于复杂自由曲面的在线测量．针对工作原理以及相关问题，对其进行了详细的讨论，其中包括系统优化、摄像机标定、采样策略、特征提取、图像匹配和数据重构．实验证明三目视觉测头在精度和可靠性方面都优于双目测头．首次研制测头的精度达到了0．02mm．     

一种立体视觉测量高精度标定新方法

提出一种实现通用摄像机标定和现场高精度立体视觉传感器标定的新方法。该方法无需预先给定初始参数,而是根据投影矩阵计算摄像机参数的初始值,结合镜头畸变的标定数学模型,实现通用摄像机标定;在立体视觉传感器三维测量模型基础上,引入目标距离约束建立结构参数标定优化目标函数,从而得到使空间距离偏差最小的最优结构参数,实现传感器现场高精度标定。实验结果表明,上述方法标定精度较高,已标定传感器空间距离测量相对误差小于0.45%。     

双目视觉系统测量精度分析

针对双目视觉系统测量精度的问题,本文提出并建立了双目视觉系统误差分析模型,分析了摄像机标定精度、镜头参数及系统结构参数对系统测量精度的影响,并结合实验证明了理论的正确性。实验表明,在标定板均匀分布于具有较大深度范围系统的整个可视区域时,增加标定图像数目能有效提高系统精度;在保证系统有效视场的前提下,增大基线距能有效的提高系统测量精度;相机光轴与基线夹角在[55o~70o]取值时,系统测量精度较高。     

一种采用单目手眼视觉的目标位置测量方法

机械臂末端安装双目视觉,会降低其在障碍环境下的可通过性。针对此问题,本文构建了一种单目手眼与激光结合的位置测量方法,先通过手眼获取光斑,利用投射位置、投射点与手眼光轴的相对位置关系构建测量方法,然后采用D-H模型构建坐标转换系统,计算目标点的位置。目标测量精度与距离负相关,适用于中短距离的位置测量。与目前常用的双目测量方法相比,本方法减少了摄像机使用个数,降低了机械臂末端测量系统的宽度,更适用于狭窄空间作业,同时也提高了机械臂的有效载荷能力。     

一种高性能低功耗的移动机器人视觉处理系统

针对传统的由图像采集卡和主控计算机构成的移动机器人视觉系统中存在的计算速度和功耗瓶颈问题,设计了一种基于数字信号处理器(DSP)和场可编程逻辑器件(FPGA)的智能图像采集卡和基于该智能图像采集卡的机器人视觉系统.该智能图像采集卡可以在完成图像采集工作的同时,通过FPGA和DSP高速处理图像数据,实时完成多种低层图像处理功能,在很大程度上减轻上位机的计算负担,使得在高性能机器人控制与传感系统中采用较低性能的上位机成为可能.实验结果表明,这种机器人视觉系统能够很好地满足移动机器人对运算速度和功耗的要求.     

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.     

A hierarchical model for characterising spatial wafer variations

Silicon wafers are commonly used materials in the semiconductor manufacturing industry. Their geometric quality directly affects the production cost and yield. Therefore, improvement in the quality of wafers is critical for meeting the current competitive market needs. Conventional summary metrics such as total thickness variation, bow and warp can neither fully reflect the local variability within each wafer nor provide useful insight for root cause diagnosis and quality improvement. The advancement of sensing technology enables two-dimensional (2D) data mapping to characterise the geometric shapes of wafers, which provides more information than summary metrics. The objective of this research is to develop a statistical model to characterise the thickness variation of wafers based on 2D data maps. Specifically, the thickness variation of wafers is decomposed into macro-scale and micro-scale variations, which are modelled as a cubic curve and a first-order intrinsic Gaussian Markov random field, respectively. The models can successfully capture both the macro-scale mean trend and the micro-scale local variation, with important engineering implications for process monitoring, fault diagnosis and run-to-run control. A practical case study from a wafer manufacturing process is performed to show the effectiveness of the proposed methodology.     

自主移动机器人视觉信息处理技术研究发展现状

视觉系统是自主移动机器人感知外界环境的主要手段之一.本文介绍了自主移动机器人视觉系统的基本组成以及不同类型的机器人视觉系统的主要特点,并结合自主移动机器人视觉系统的发展趋势,比较详细地介绍了基于 ASIC、DSP、FPGA、视觉芯片等技术的嵌入式视觉信息处理单元的主要特点及研究发展现状.本文最后提出了实现具有较强实用性的自主移动机器人视觉系统所需要解决的高实时性、通用性和适应性等若干关键问题.