基于辅助摄像机的机器人延伸手眼标定方法

针对机器人手臂上装载的工件等对象与摄像机之间空间关系的标定问题,本文在传统机器人手眼标定的基础上提出了机器人延伸手眼标定的概念,将机器人手眼关系拓展为延伸手眼关系.该方法通过引入辅助摄像机,利用平面标定靶标以及由机器人延伸手上的矩形特征衍生出的大量标定特征点,实现了机器人延伸手眼标定.实验结果表明,该算法可有效的解决机器人延伸手眼标定问题,标定精度取决于机器人延伸手的几何尺寸精度和获得特征点的精度,文中实验结果的RMS为0.113mm.     

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BP神经网络的包装分拣机器人视觉标定算法

手眼标定确定了机器人基座坐标系和摄像机坐标系之间的非线性映射关系,在视觉伺服中起着重要作用。针对视觉伺服控制系统中的手眼标定问题,基于机器人工具箱和神经网络工具箱,在MATLAB/Simulink环境下,使用误差反向传播（BP）神经网络算法和径向基（RBF）神经网络算法进行仿真,拟合了6自由度分拣机器人和单目摄像机之间的映射关系,通过仿真结果分析了两种算法的精度。此外,在同一实验条件下使用BP神经网络与张氏法对机械臂进行手眼标定,通过在机械臂实际工作空间内抓取同一组随机取样本点进行实验,并对比随机样本点的抓取精度。仿真和实验结果表明BP神经网络在标定精度上优于RBF神经网络算法和张氏标定法,能够在实际应用中提高手眼标定的精确度,具有一定的工程意义。     

一种基于线扫描相机的手眼标定技术

提出一种以固定点变位姿的方法标定线激光扫描相机与机器人的手眼关系,该方法分为两步标定出手眼矩阵,采用直径已知的标准球作为固定点靶标,首先控制机器人以平移的方式运动至少3次,然后机器人任意位姿运动至少4次;每次运动后用机器人末端执行器上安装的线激光扫描器扫描靶球,获取靶球表面轮廓上一列点云,对点云进行空间圆拟合,进而求出靶球的球心空间坐标;最后根据约束关系可列出方程,用最小二乘法或者奇异值分解求解手眼关系。实验结果表明:该方法快捷有效计算量较小,标定精度在0. 2mm左右,可以用于线激光扫描相机与机器人现场手眼标定。     

基于主动视觉的手眼系统自标定方法

为实现非固定视点系统的标定,提出一种基于主动视觉的手眼系统自标定方法。该方法基于扩展焦点的思想,无需使用标定参照物,通过4次线性无关的平移运动、1次实旋转运动和1次虚旋转运动,即可依次实现对摄像机内参矩阵、手眼关系以及特征点目标深度的线性求解。实验结果表明:该方法可行有效,特征点选取简单,在机器人姿态不变的前提下,平面特征点和三维特征点的数据测量误差均可控制在0.40 mm以内,能够满足工业领域的精度要求,对工业生产中手眼系统的应用具有参考意义。     

线结构光视觉传感器机器人手眼关系标定

为实现对工业机器人手眼关系的标定,提出一种基于线结构光视觉传感器的手眼关系标定方法。该方法在标定时,将一个平面靶标作为参考物固定在工业机器人工作空间内,控制工业机器人末端运动以带动线结构光视觉传感器作多组变位姿运动,获取在不同位姿状态下的平面靶标图像并对其进行图像处理。通过对图像上固定特征点的测量,以及建立线结构光视觉传感器模型和手眼关系模型实现对线结构光内参数和手眼关系的标定。用棋盘格标定板进行测量实验验证,实验结果表明该方法准确度为0.036 mm,即优于40μm,可用于工业机器人的测量应用。     

基于手眼系统的视觉定位研究

针对自动化产品装配中的视觉定位问题,搭建一套基于手眼(eye-in-hand)系统的机器视觉装配实验平台。在Halcon软件平台上运用张正友标定法对相机内参数和外参数进行标定,并利用手眼关系方程CX=XD求解出机器人的手眼关系以完成手眼系统标定的过程,最终将手眼系统标定结果应用于视觉装配平面的目标点定位。其中以机器人定位到的目标点坐标为理想位置坐标,对视觉定位与机器人定位得到的目标点位置进行比较分析,验证该手眼系统视觉定位的准确性并对视觉系统进行不确定度评定,实验重复性良好。实验结果表明,用此方法得到的手眼系统视觉定位精度能达到0.6 mm,满足机器视觉生产线上产品装配的需求。     

基于相位测量的摄像机标定方法

提出一种新的摄像机标定方法,该方法基于2D共面参照物摄像机标定方法和相移技术.首先由摄像机记录已知相位分布的平面,通过相移计算出相位分布.对任意标定平面,两个正交相位分布与平面坐标的对应关系已知,由此可以建立像素坐标与2D平面坐标的一一对应关系.将该已知相位分布的平面在空间中放置不同的位置,分别完成上述测量,即可根据2D共面参照物摄像机标定方法完成摄像机的高精度标定.该方法避开了复杂的标定特征点提取,大大增加了2D标定数据量,提高了标定精度.实验和计算机模拟表明,该方法简单、可靠和精度高.     

机器人激光扫描式焊缝跟踪测量系统研究

提出了机器人激光扫描式焊缝跟踪系统参数的标定方法和基于数字图像处理的焊缝特征点识别方法.采用中值滤波、自适应阈值分割和孤点滤波法等对激光图像进行预处理,以数字形态学方法获得焊缝特征点坐标;然后以一组平行线为靶标,获得激光平面上无穷远处一点在摄像机中的投影,实现结构光参数的标定;最后以多个机器人位姿对固定目标点进行检测,求解出机器人的手眼矩阵.整个系统标定过程简单,精度可靠,可用于空间曲面的U型焊缝检测.     

采用点云切片技术的喷漆机器人轨迹生成

提出了一种直接生成喷漆机器人运行轨迹的方法.该方法首先扫描待喷涂工件的表面以获取工件的点云数据信息,然后对点云数据进行切片处理,估算采样点的法矢量,最后采样点沿其法矢量偏置喷枪到工件的距离,得到喷漆机器人的喷枪轨迹.该方法将点云切片技术运用到喷漆机器人的轨迹规划,能准确地控制喷枪的运行位置、方向以及喷枪与喷涂工件表面之间的距离,提高了喷涂质量和效率.     

Shock loading response of sandwich panels with 3-D woven E-glass composite skins and stitched foam core

Sandwich composite are used in numerous structural applications, with demonstrated weight savings over conventional metals and solid composite materials. The increasing use of sandwich composites in defense structures, particularly those which may be exposed to shock loading, demands for a thorough understanding of their response to suc highly transient loadings. In order to fully utilize their potential in such extreme conditions, design optimization of the skin and core materials are desirable. The present study is performed for a novel type of sandwich material, TRANSONITE^® made by pultrusion of 3-D woven 3WEAVE^® E-glass fiber composites skin preforms integrally stitched to polyisocyanurate TRYMER^TM 200L foam core. The effect of core stitching density on the transient response of three simply supported sandwich panels loaded in a shock tube is experimentally studied in this work. The experimental program is focused on recording dynamic transient response by high-speed camera and post-mortem evaluation of imparted damage. The obtained experimental results reveal new important features of the transient deformation, damage initiation and progression and final failure of sandwich composites with unstitched and stitched foam cores. The theoretical study includes full 3-D dynamic transient analysis of displacement, strain and stress fields under experimentally recorded surface shock pressure, performed with the use of 3-D MOSAIC analysis approach. The obtained theoretical and experimental results for the transient central deflections in unstitched and two stitched foam core sandwiches are mutually compared. The comparison results reveal large discrepancies in the case of unstitched sandwich, much smaller discrepancies in the case of intermediate stitching density, and excellent agreement between theoretical and experimental results for the sandwich with the highest stitching density. The general conclusion is that further comprehensive experimental and theoretical studies are required in order to get a thorough understanding of a very complex behavior of composite sandwiches under shock wave loading.     

多场景下基于快速相机标定的柱面图像拼接方法

针对目前利用相机标定参数进行图像拼接的方法存在受场景限制大、标定过程复杂而耗时长的问题,提出一种多场景下基于快速相机标定的柱面图像拼接方法。首先,利用棋盘格标定板角点特征提取精度高的特点,使其分别位于两两邻接图像的重叠视场中,对该图像序列依次进行角点提取、精确化和匹配等预处理,以准确快速求解出待拼接图像间的配准参数;然后利用标定得到的配准参数快速拼接图像,通过柱面投影以保持图像的视觉一致性,并采用多频段融合以保留图像的细节信息;最后,将整个系统搭建在低功耗嵌入式平台,实现可在多场景下完成快速标定及基于标定参数的拼接过程。实验结果表明,该文方法在室内及隧道等场景下可准确快速完成相机标定,图像拼接过程耗时短,同时可保证较高的拼接精度和较好的成像效果,具有较强的鲁棒性。     

三维缝合复合材料研究进展

三维缝合复合材料是指使用缝合的方式在厚度方向上将织物连接成三维结构,再通过树脂传递模塑等工艺浸渍固化缝合后得到的三维织物。介绍了宏细观角度下三维缝合复合材料的拉伸、弯曲、层间剪切及冲击后压缩等力学性能的主要研究成果,并对其湿热、机械连接性能进行探讨,总结了三维缝合复合材料目前的应用现状,对三维缝合复合材料的发展研究方向进行了展望。     

缝合复合材料的应用与力学性能

从缝合复合材料的应用、力学性能等方面对缝合复合材料技术及其发展状况进行了比较全面的阐述。缝合复合材料在结构整体性以及高层间性能等方面具有明显的优势,因此有其应用价值与前景。在选用缝合时,应根据所用层板的铺层顺序及其使用的环境条件,同时还应兼顾缝合对铺层面内力学性能的影响,决定是否使用缝合结构。     

Pose estimation for autonomous grasping with a robotic arm system

A robust and accurate method for estimating the 3-D pose of a planar rigid object is presented. This article demonstrates that 3-D pose estimation becomes feasible by using the 2-D tracking points on an object of scale-invariant feature transform (SIFT) and 3-D point cloud detected by stereo vision on an object, assuming that a 3-D geometric model of an object is known a priori. The roll and pitch angles of an object are estimated by the normal vector of approximate plane of 3-D point cloud on an object and the yaw angle is estimated by 2-D tracking point on an object of SIFT. Accurate object detection and localization in the camera coordinate system is crucial for grasping. In the motion planning, the bidirectional rapidly exploring random tree algorithm is used to search for a valid path for efficient grasping. Our robot arm can robustly and autonomously grasp a randomly rotative rigid object detected by SIFT in 3-D space. We have realized a grasping scenario with a dexterous arm (ADAM) such that an object in front of ADAM can be grasped. This demonstration shows how the proposed components build a dexterous and robust system integrating object detection, pose estimation, and motion planning.     

缝纫泡沫夹芯复合材料的刚度预测与试验验证

基于材料细观结构,建立了缝纫泡沫夹芯复合材料的刚度预测模型,并进行了刚度性能的相关试验验证。其中,对缝纫复合材料层合面板部分,考虑了缝纫角对单胞尺寸和富脂区大小的影响,以及缝纫前后层合面板厚度的变化对复合材料面板纤维体积含量的影响,采用改进的纤维弯曲模型计算了缝纫复合材料层合面板的刚度;对缝纫增强的泡沫夹芯部分,把缝线树脂柱看作是泡沫基体中的增强相,将其简化为特殊的单向增强复合材料,提出了用串并联组合模型来预测其刚度。试验测试了缝纫泡沫夹芯复合材料板试件的刚度。应用本文模型对缝纫层合面板和缝纫泡沫夹芯复合材料板的刚度进行预测,结果均与试验结果吻合较好。采用理论模型系统研究了缝纫参数和结构参数对缝纫泡沫夹芯复合材料刚度的影响。     

Fracture Toughness (Mode-I) of Para-Aramid/Phenolic Nano Preform Composites

The mode-I interlaminar toughness properties of nanostitched para-aramid/phenolic multiwall carbon nanotube composites were studied. The toughness strength of the stitched and stitched/nano composites demonstrated 40 fold and 38 fold (beam theory) increases compared to the base composites, respectively. It was found that stitching yarn type, especially prepreg para-aramid stitching yarn, was effective. On the other hand, the initiation and propagation of the G_IC values for stitched and stitched/nano composites were considerably deviated due to strengthening mechanism of the para-aramid stitch yarn in the transverse direction of the composite. The fracture toughness resistance to arrest crack propagation in the stitched/nano composite was mainly due to through-the-thickness stitching fiber bridging and pull-out, and was also due to warp and weft directional fiber bridging and multiwall carbon nanotubes. The results demonstrated that mainly stitching and some extent the nanotubes arrested the crack growth. Therefore, the stitched/nano and especially stitched para-aramid/phenolic composites showed a better damage resistance performance.     

Aspects of the stitch formation process on the quality of sewn multi-textile-preforms

Stitching technologies are considered to be one of the key technologies for automated manufacturing of complex textile preforms which are used for liquid composite moulding of fibre reinforced plastic parts [Proceedings of Sixth International Conference on Automated Composites (1999)]. The sewing or stitching process is applied for different purposes during the production of dry fibrous reinforcements as well as for structural aims in the composite component (through-the-thickness reinforcement), thus, the requirements on the stitch itself are wide spread [Complex Multi-textile Preforms – The Potential of Sewing. 90(4) (2000) 43; Stress Conc Compos Sci Technol, 59 (1999) 2125; Tech Textiles 43 (2000) 120; Compos Part A 31 (2000) 571; D 82 Dissertation RWTH Aaachen (1999)]. A detailed prediction of properties of the stitched reinforcements requires an understanding of the stitch formation process and the interaction between textile reinforcements, the stacking sequence thereof, the stitching process parameters and sewing thread properties.     

Characterization of 3D morphology and microcracks in composites reinforced by multi-axial multi-ply stitched preforms

The micro-structure of polymer matrix composites reinforced by multi-axial multi-ply stitched carbon preforms and manufactured by liquid resin infusion is analyzed. The stitching induces deviations in fibre placement and creates openings which become resin-rich regions after the resin infusion. Characterization of the size and shape of the resin-rich regions of composites with different stitching yarn size and tightness and various stacking sequences has been performed by 2D metallographic micrography and X-ray microtomography. The resin-rich region volume was estimated at roughly 3.0 ± 0.5% of the material volume. The resin-rich regions constitute about 9% of the resin in the entire composite, whose fibre volume fraction is close to 65%. X-ray microtomography was successfully used to characterize the 3D microcracks created by hygrothermal fatigue.