线激光视觉测量机器人手眼标定方法研究

线激光视觉测量传感器与工业机器人组成三维测量系统时,法兰盘坐标系与摄像机坐标系之间变换关系求解较复杂。为解决此问题,提出一种基于固定参考点的手眼标定算法。该算法以标定球为靶标,根据标定球球心在机器人基坐标系中坐标不变原则,结合机器人运动学位置约束关系建立了矩阵变换方程,并在旋转矩阵求解中引入四元数,简化计算过程,实现机器人手眼标定。通过试验量化分析测头光平面与标定球相交位置对测量结果的影响,验证了该算法的有效性和实用性     

焊接机器人再制造中结构光传感器的标定

在基于焊接机器人的柔性再制造平台中,对零件破损部位的三维测量是获取再制造模型的关键步骤.文中提出了一种结构光传感器系统的快速标定方法,对柔性再制造线结构光三维扫描测量系统进行了标定.标定过程中首先采用平面靶标法标定出 CCD 摄像机线性模型的内外参数,然后通过靶标上的结构光条纹的像求解出光平面方程,确定结构光光平面与摄像机的位置关系.在标定出结构光测量系统的各个参数后,即可以求得零件破损部位特征点的三维坐标,从而获得破损零件的再制造模型.该方法标定过程简单,精度较高,易于实现现场标定.

Abstract：

On the flexible remanufacture platform based on welding robot, 3D ranging of the damage parts is the key step to obtain the remanufacturing data. This paper proposes a rapid calibration approach and calibrates the line structured-light 3D ranging system in the flexible remanufacture platform of the welding robot. The calibration includes the following steps: first, calibrates internal and external parameters of the camera by a planar pattern; second,solves parameters of the light plane by the structured-light strip in the image, which determine the relationship between light plane and camera, and then calculate 3D coordinate of the feature point on the damage parts to establish remanufacture model. The approach is easy, simple and accurate.     

Complete 3D measurement in reverse engineering using a multi-probe system

To meet the demand of measuring the complex prototypes completely in reverse engineering, a multi-probe measurement system integrated with a coordinate measuring machine (CMM), a structured-light sensor, a trigger probe and a rotary table is presented in this paper. The structured-light sensor is designed with optimal structure, and its model is established based on the CMM to simplify its parameters, this enables the sensor to be calibrated expediently at any condition. Three measuring modes are proposed considering the efficiency of the structured-light sensor, the high accuracy and flexibility of the trigger probe and the rotation of the table for finding proper scanning views. The structured-light sensor is usually applied to scan the profile of a part from different views, while the trigger probe is used to measure the edge and key features of the part. The data generated by different modes can be merged into a whole data body. The system possesses the function of obtaining the coordinate of nearly any point on a complicated part. Experiment studies on the accuracy of the structured-light sensor, data patch assembling and data merging show that the total accuracy of the system is ±0.033 mm.     

Enhancement of geometric accuracy of five-axis machining centers based on identification and compensation of geometric deviations

The present paper describes the enhancement of kinematic accuracy of five-axis machining centers with a tilting rotary table. Geometric deviations inherent to the five-axis machine are calibrated through the actual trajectories measured by two different settings of a ball bar in simultaneous three axis motion. Measurement using a cylindrical coordinate system is superior to measurement using a Cartesian coordinate system from the viewpoint of the number of measurements. In order to verify the effectiveness of the calibration method, the inherent geometric deviations measured on the cylindrical coordinate system were corrected through the post processing of NC data for cutting the cone-frustum.The relative displacement between the tool center point and the workpiece was detected by the ball bar. Based on the experimental results, it is confirmed that the radius, center position, and roundness of the three-dimensional circular trajectory are improved when the inherent geometric deviations are corrected.     

Study on a full field of view laser scanning system

To meet the requirement of accurate and convenient 3-D measurement for some large parts in reverse engineering, a full field of view scanning system that is mainly composed of a CCD camera, a galvanometer and a laser projector is proposed in this paper. The camera model is firstly established according to the mapping between the world coordinate system and the computer image. A planar target engraved with square patterns is adopted to calibrate the camera. Based on the rule of cross-ratio invariability, the calibration points are extracted from the square patterns and the lens distortion coefficients are simultaneously acquired. The unknown parameters in camera model are solved using these points. For obtaining the 3-D coordinate of a point in a laser plane, the orientation and position of the laser plane are computed according to the angle of the galvanometer and the intersected lines on the target. And based on the laser orientation and position, the three coordinates of a point in the laser plane can be represented by two of them. Hence, two coordinates can be directly obtained from the camera model. Experiments show that the developed system possesses good accuracy. It can identify the fine structure on a large part, also it is portable and convenient for field measurement.     

基于主动视觉的机器人辅助测量

机器人在测量领域得到了广泛的应用，文中给出了基于单目视觉的器人辅助测量，采用摄象机校准得到摄象机内、外参数，由手眼转换关系移动机器人执行器得到要求的摄象机运行，从而求出空间点在摄象机坐标系中的坐标，并由摄象机的外部参数计算得到空间被测量点在绝对坐标系中位置坐标。     

基于平差优化技术的高精度三维标定方法

为提高工业机器人、自动化校准设备等智能系统的整体精度,基于罗德里格矩阵和最小二乘法拟合建立数学模型,解决了三维直角坐标系之间转换关系的工程应用问题。采用基于冗余测量数据的平面平差优化技术和定位坐标点的间接测量方法,提升了局部坐标系建立的精度。针对坐标点接触式测量和非接触式测量的技术缺陷,提出了采用激光跟踪仪测量终端,用标定工装辅助实现间接测量的方法,能通过多点的接触式间接测量保证被测定位坐标点的精度。最后经过多次试验验证了方法的可行性。     

Autonomous form measurement on machining centers for free-form surfaces

This research aims at developing a measurement technique on machining centers for 3D free-form contours. An autonomous measuring principle is proposed and a prototype measuring device applicable to a machining center has been produced. In the measuring device, a laser displacement detector in a narrow range, which directly detects the distance from a point on the measured surface to the reference position of the detector output, is put together with the movable part of a linear encoder on the nut of a ball screw. A stepping motor controls the laser detector position to keep the output at the central value of the detector measuring range by driving the ball screw. Both the motor and the fixed part of the linear encoder are placed on the device base. The linear encoder detects the moving displacement of the screw nut, i.e. the position change of the laser detector. By installing the base on the spindle of a machining center and moving the table along a plane perpendicular to the spindle, the laser detector can automatically follow the contour of a work piece set on the table and measure its form along a scanning line, simultaneously. The displacement of a measured point relative to the reference position of the linear encoder output on the spindle side is just equal to the sum of the outputs of the two sensors, i.e. the laser detector and the linear encoder. Moreover, a simple experimental approach to identifying the sensing direction errors for an assembled measuring device is developed. The results of some experiments are also shown, which sufficiently demonstrate the effectiveness of the proposed inspection method and error identification approach.     

面向机器人激光增材制造的机器视觉系统标定算法

随着现代智能制造的快速发展,金属增材制造、绿色再制造、焊接等领域大量使用机器人等自动化装备,视觉传感是机器人智能制造的关键环节.针对上述需求设计了一套基于线结构光的视觉传感器,并对其进行标定,自主开发了用于机器人激光增材制造的机器视觉系统.该系统通过Matlab相机标定工具包实现相机的内外参数标定,利用Labview编...     

机器人单目视觉标定圆心靶标特征点几何求解

针对机器人单目视觉标定圆心靶标特征点求取问题,利用射影变化公切线不变性,建立圆心靶标的特征点几何求解模型,并进行了精确求解,该模型理论上不存在模型误差;为了检验几何求解模型的精确性和稳定性,分别对机器人单目视觉坐标系下的圆心靶标圆心点和棋盘格靶标角点进行了三维测量。实验结果表明:测量长度在300 mm内的最大相对误差小于1.5%,测量结果较精确;各点的距离平均绝对偏差均在0.2 mm左右,且无阶跃,该方法稳定。     

基于机器视觉的实体模型逆向重建系统

为了解决点激光扫描重建过程中点云稀疏、颜色纹理特征不明显的问题提出了一种基于相机图像信息与激光点云融合的三维重建方法.该方法结合线激光三角测距、相机坐标变换关系获取物体深度信息和点云数据,然后利用随机抽样一致(RANSAC)原理进行图像配准,实现对单目标实体的逆向建模.实验结果表明,该系统具有较高的可靠性和良好的精度,...     

基于工具坐标标定改进的工业机器人零点位置自整定方法

在工业机器人应用过程中更换工具时需要重新标定工具坐标,一般情况下工具坐标通过固定点约束的3点法进行标定,此方式在机器人本身零点位置不准确的情况下往往会得到一个较差的结果。基于3点法中定点约束的原理,提出一种改进的工业机器人零点位置自整定方法,对出厂标定过的六自由度串联机器人,修改其零点位置与工具坐标的标准值产生给定误差,基于空间内一个固定点的约束关系,在已知机器人连杆参数的情况下建立机器人坐标变换模型,取21组机器人关节角与笛卡尔坐标数据作为辨识条件参数,机器人工具坐标与零点位置的偏差作为未知数据,通过最小二乘迭代算法计算出工具坐标与零点位置的偏差数据。将实验对象的整定结果和给定的误差参数进行对比,整定结果基本与给定误差一致,并通过比较自整定前后示教器上的位置显示值之间的误差值,证明了校准算法的可行性。     

球头立铣刀端刃间隙磨削轨迹的算法

端刃尖点是球头立铣刀后刀面轮廓超出回转轮廓的部分,会造成切削干涉。为了有效地去除端刃尖点,文章提出一种端刃间隙磨削工艺,并设计了参数化的端刃间隙磨削轨迹算法。该算法以球头刃线中心点处切线方向为基准,在磨削坐标系下定义了砂轮磨削姿态模型和相关工艺参数,并通过矩阵变换得到工件坐标系下的砂轮磨削姿态矢量及运动轨迹坐标。通过仿真和实际加工对计算结果进行验证,证明了算法的正确性及该工艺在去除端刃尖点和减少磨削余量的有效性。     

Coordinate metrology uncertainty using parallel kinematic techniques

Dimensional metrology of manufactured objects is increasingly performed with coordinate measuring machines, where coordinates of surface points are recorded and fit to a model of the ideal surface. While coordinate metrology is often performed using machines with a serial Cartesian kinematic structure, the use of parallel kinematic machines has also been investigated. In this paper, we evaluate the uncertainty of trilateration measurements, which is the simplest form of parallel kinematic metrology for spatial coordinates. The instrument studied here is the laser ball bar, specifically designed for trilateration measurements. We use homogeneous transformation matrices to determine its length uncertainty. Monte Carlo simulation is then applied to model the coordinate uncertainty arising from propagation of the length uncertainty through the trilateration calculations. Simulation is compared to experimental results.     

基于标准球在铸件基准传递上的方法研究

通过标准球,实现三坐标测量和非接触式光学扫描测量数据的传递和验证,确定铸件基准.将标准球与铸件在同一坐标系中,使用非接触式光学扫描测量机进行扫描,根据产品三维模型进行拟合计算,得到理想的铸件尺寸状态,使标准球带有铸件坐标信息.根据标准球建立加工坐标系,通过基准目标的尺寸验证数据偏差是否满足加工要求,将理想的铸件尺寸状态...     

Accuracy test of five-axis CNC machine tool with 3D probe–ball. Part I: design and modeling

The error model of CNC machine tool describes the relationship between the individual error source and its effects on the overall position errors. A practical problem in applying this technique to five-axis machine tool is that the predicted position errors cannot be justified. This paper, the first in a set of two, presents a new measurement device, the probe–ball, which can be used to measure the overall position errors of five-axis machine tools directly. To perform the accuracy test, a three-degree-of-freedom (3D) measuring probe is installed in the main spindle and a base plate is fixed on the turntable. The kinematic chain of the five-axis machine tool is then closed through connecting the central ball on the base plate with the extension bar of the probe. To generate simultaneous axes motion under the condition of closed kinematic chain, the central ball is defined as origin of the workpiece coordinate frame and the probe is driven along a path on a spherical test surface with the central ball as center. The overall position errors are measured with the 3D measuring probe. A theoretical model is derived to explain the nature of the probe–ball error measurements.     

激光干涉仪检测光路的快速校准方法

在使用激光干涉仪时,光路校准过程比较困难,需反复调整,耗时极长,严重依赖操作者的技术水平及经验,导致检测效率大大降低。通过对雷尼绍XL-80激光干涉仪检测的机床直线轴Y轴的光路进行分析,建立被测轴的齐次坐标变换误差模型,利用机床Y轴移动距离,再借助随着光点从光靶中心移动到光靶边缘的固定距离,求解与被测轴Y轴位置无关的激光发射器偏摆和俯仰角,以及间接得到激光器和反射镜位置偏移误差和光点在坐标系间变换的距离。通过建立的误差模型求解无法直接测量的分光镜与反射镜绕各自本身垂直底座轴线的偏摆误差,调整各部件,快速准确地完成光路校准。     

集成虚拟结构光传感器的焊接机器人离线编程技术

针对传统现场示教型的焊接机器人线结构光视觉传感器的应用缺点,旨在通过离线编程技术进行解决.首先对传感器离线编程系统进行了架构设计,其次根据传感器的成像原理开发了仿真传感器的自动建模技术,并进一步讨论了针对焊接仿真对象进行特征轮廓的提取,最后介绍了如何将编程结果应用于实际的焊接特征识别,分别对复杂结构件的焊缝跟踪和焊缝起...     

单目视觉的大型零件三维测量方法

以单目视觉为基础,构建一种便携、大量程的在线测量曲面重构系统。当辅助靶标上的刚体测量头与曲面待测点垂直接触时,测头上的开关同步控制摄像机来获取靶标标志点的特征图像信息,进而由计算机进行图像处理得到各标志点的像面坐标,最后再经过坐标转换即可得到被测物体的三维坐标。通过对系统进行标定,提高了测量精度;通过摄像机的转站实现了最优视点规划分析,提高测量范围和自动化程度;另外,对系统测量不确定度进行论并提出了改进措施。     

Assembly of Hybrid Microsystems Using an Assembly System with 3D Optical Sensor

For the assembly of hybrid microsystems a high accuracy in the range of a few micrometers is required. The combination of a parallel robot with an integrated 3D vision sensor uses positioning marks on the objects for object recognition. Within the assembly process, relative positioning accuracies in the submicrometer range have been obtained. Therefore, it is necessary to use a calibration strategy for matching the coordinate system of the 3D vision sensor with the coordinate system of the robot. The construction of the system, the calibration applied and the positioning accuracy achieved by the robot will be discussed.