基于对偶四元数的机器人手眼标定算法研究

针对机器人手眼视觉系统中的手眼标定问题,对机械手末端执行器与摄像机之间的手眼转换关系进行了研究。对手眼标定问题中求解齐次矩阵的方法进行了归纳,建立了完整的基于运动位姿的视觉模型;利用改进对偶四元数方法分别求解了手眼齐次变换矩阵中的旋转矩阵和平移向量;为保证获得的平移向量是最优解,在求解平移向量过程中引入了无穷范数最小化,通过迭代求取了局部最优解的值;基于所考虑的求解最优,利用Matlab对平移向量算法进行了仿真研究,并将该算法标定结果与线性解耦估计算法和传统对偶四元数算法进行了比较。研究结果表明:该算法在标定精度、对噪声的鲁棒性、对运动位姿个数的敏感性和稳定性方面均优于其他两种算法,能满足手眼标定的精度要求。     

车载LiDAR-IMU外参联合标定算法

为提高LIO-SAM算法的定位精度,本文从LiDAR-IMU外参标定方面开展研究,针对现有的传感器标定算法在车载条件下标定精度低的缺点,提出一种新的车载传感器联合标定算法。针对车载条件下自由度低导致俯仰、横滚方向约束建立不充分的问题,利用车辆的大范围运动轨迹消除平移参数影响,使用正态分布变换(NDT)和迭代最近点(ICP)的点云匹配算法快速得到旋转参数初值,提高俯仰角和横滚角的标定精度。针对粗标定过程中激光里程计存在漂移以及没有标定平移外参的问题,对基于点云优化的全参数标定方案进行改进,利用转弯区域构建对平移外参的约束,结合统计误差平均效应和位移约束构建新的目标函数,迭代优化后得到全参数标定结果。实验结果表明,加入了外参标定模块的LIO-SAM算法的定位精度提升了1.74%～5.92%。     

三维激光雷达-相机间外参的高效标定方法

在自动驾驶、移动机器人等领域,激光雷达与相机是常用的传感器,融合这两者的信息首先应该标定两者间的外参。本文在考虑平面移动机器人运动特点的基础上提出两阶段外参标定方法,在尽可能少的人为干预下实现快速标定。第一阶段,在机器人运动过程中同时估算激光里程计和视觉里程计,提取平移、旋转两种运动信息以修改的Kabsch算法初步估计外参中的旋转矩阵;第二阶段,以箱体三面相交组成的三面体作为标识物,优化点云中三面体边的投影点和图像中对应三面体边的距离,从而得到精确的外参。此两阶段方法效率高、无需专业设备,在少量人工干预下即可实现外参标定。最后,实验结果表明,在3个坐标轴上的平均误差仅为3.67、1.11、0.78 mm,在典型移动计算平台上相应的平均标定时间仅需约635 ms。     

单目相机-IMU-机械臂的空间联合标定方法

将单目相机和惯性测量单元(IMU)固定在机械臂末端,可以有效地协助机械臂进行运动估计和场景感知。单目相机、IMU和机械臂之间可靠、准确的标定是实现随动感知的前提。但是,传统的标定方法存在耦合误差大、标定一致性差和6自由度激励不充分的问题。为此,本文提出了一种新颖的单目相机-IMU-机械臂的空间联合标定模型,该模型能够将旋转分量的误差和平移分量的误差完全解耦。此外,创新性地设计了一种螺旋式运动轨迹来标定感知模块,采用这种运动轨迹能够避免6自由度激励不充分和一致性差等问题。在实验环节,本研究搭建了单目相机-IMU-机械臂空间联合标定平台,计算得到三轴姿态角和平移分量的均方根误差分别小于0.7°和7 mm,证明了所提标定方法的有效性。     

基于二阶锥规划无标定参照物的手眼标定

为了克服传统机器人手眼标定方法求解手眼关系及机器人坐标系与世界坐标系方位关系对标定参照物的依赖,提出一种基于二阶锥规划的无标定参照物手眼标定改进方法,并搭建相关实验系统进行验证。首先,利用运动恢复结构算法解算定义在一个尺度因子基础上的相机运动矩阵;然后,引入对偶四元数理论参数化标定方程中的旋转矩阵和平移向量;最后,通过二阶锥规划方法同时求解相机运动矩阵尺度因子、手眼关系及机器人坐标系与世界坐标系方位关系的最优解。仿真和实测结果表明,在没有标定参照物作为测量基准的情况下,标定结果中旋转参数相对误差为3.998%,平移参数相对误差为0.117%。与其他标定方法相比,该方法提高了无标定参照物模式下机器人手眼标定精度,扩展了手眼标定方法的应用范围。     

随钻姿态测量重力加速度自适应提取算法

为解决旋转导向钻井过程中由于钻具的高速旋转、剧烈振动和冲击给随钻姿态测量带来巨大干扰的问题,基于互补滤波框架提出了一种钻具重力加速度提取算法。首先通过余弦矩阵微分方程得到基于陀螺仪的重力加速度的递推方程,然后利用陀螺仪和加速度计在频率上互补的特性,在互补滤波框架下融合得到钻具重力加速度;同时,为了提高系统鲁棒性,利用非重力加速度和钻具旋转速度作为模糊算法输入,通过模糊算法动态调整互补滤波参数;最后设计了振动和旋转实验验证了算法的有效性。实验结果表明,使用本文算法提取重力加速度后姿态估计精度得到明显提升,本文算法相比于基于Kalman滤波框架的重力加速度提取算法在PC机测试环境下单次运算时间减少31.9%。     

高鲁棒性两阶段激光雷达-惯性测量单元外参在线标定算法

针对车辆在近似平面上运动时,退化的传感器数据难以标定外参的问题,提出了一种高鲁棒性两阶段激光雷达-惯性测量单元(LiDAR-IMU)外参在线标定算法。标定算法包括剔除外点的解析解初值计算和非线性滑窗在线迭代优化两个阶段。第一阶段剔除预数据集中的外点,以滑动窗口的形式多次求解只包含旋转分量的手眼标定模型,并改进解析解筛选的条件,求解出多解加权旋转外参的SVD解析解。第二阶段最小化包含外参的残差函数,以旋转解析解为初值滑动窗口迭代优化六自由度外参,使外参快速收敛,并在退化运动和错误历史约束过大时固定外参,避免外参退化。与原始算法对比,该算法对退化的传感器数据具有鲁棒性,可在无外参初值的情况下实现精准鲁棒地在线标定外参。     

基于共面直线迭代加权最小二乘的相机位姿估计

针对相机内参数已标定和未标定情况下的相机位姿求解,提出了基于共面直线迭代加权最小二乘的相机位姿估计算法。推导了关于相机焦距和位姿参数的线性方程,通过4条以上共面直线实现了相机位姿参数的线性解算;对参数线性解进行迭代加权最小二乘优化,得到更高精度的参数估计值和直线权值;最后,利用直线权值和欧式变换的保距性实现相机焦距的解算,得到了相机焦距和位姿参数的估计值。仿真实验表明:提出的算法在相机已标定,直线数为20,像点噪声方差为5pixel的情况下,角度误差小于0.2°,相对平移向量误差小于0.5%,耗时大约为1ms。真实数据实验表明,提出的算法可以获得与棋盘标定结果相近的精度。与现有算法相比,提出的算法抗噪性更好,精度更高,能够实现基于单幅图像的未标定相机的位姿估计。     

面向机器人抓取的双目视觉系统标定与目标位姿估计算法

在双目视觉抓取系统中,首要任务是解决相机标定以及目标位姿估计问题。针对工业应用场景,文中提出了一种基于灭点一致性约束的相机标定算法,并利用目标的双目图像立体匹配结果,通过改进迭代最近点算法实现目标位姿估计。实验结果表明:该系统能够有效地估计目标位姿,目标位姿估计的平移与角度误差均能满足抓取需求。     

基于三轴加速度计的多维力传感器静态自校正

提出了一种多维力传感器的静态自校正方法.将三轴加速度计静态应用,可以测得其敏感轴与重力加速度的相对夹角.将多维力传感器中集成三轴加速度计,在校正过程中,旋转施加着标准砝码的多维力传感器,测量力传感器的输出,同时通过三轴加速度计测量力传感器的旋转角度姿态,计算得到砝码重力施加在传感器E的力向量,最终自动地得到多维力传感器的校止矩阵.实验结果表明,该方法显著地提高了校正效率,但与通常的标定台校正方法相比,较正精度略低.     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

ANGULAR DISTORTION ALLOWABLE VALUE AND ASSESS METHOD OF WELD ON COKE TOWER

A graph as the new engineering method for estimate the safety of bulging deformation of coke tower is proposed. Through stresses analysis of circumferential weld of coke tower and comparing the stresses produced by pressure with heat stress of steady state, residual stress, bending stress produced by both itself weight and wind loads, it showed that the stresses produced by pressure on the angle distortion are the main factor of equivalent stress of the combined stress. After comparing four kinds of stress controlling conditions, the relation to stress with depth of angular distortion, grade of curvature of angular distortion and half of region of angular distortion has been inferred. Graph of deformation allowable value of coke tower for different condition by angular distortion and half of region of angular distortion has been plotted. The five steps for its engineering use have been explained. The lighter the grade of curvature is, the larger of bulge allowance, may be, and the bigger of depth of angular distortion may pose too. For the coke tower with a popular structure of Dg 5 400 mm×28 mm, the result by graph is nearly more than the result of two formulas formed by other research, the error is less than 7.0%. But, the graph can be easily applied to different size of angular distortion.