基于Solidworks Simulation的三坐标测量仪动态误差分析

采用三坐标测量仪进行高速测量时,由于受附加惯性力及自身重力的影响,机体会变形,从而导致动态误差。对三坐标测量机的动态误差进行理论分析;利用Solidworks Simulation有限元分析方法对移动桥进行受力变形分析;在z轴静止状态下,推导出滑架沿y轴方向加速(减速)和匀速的运动状态下动态误差补偿模型。仿真结果表明:各运动状态下的动态误差有效降低,为提高三坐标测量机的测量精度奠定基础。     

蛇形空间机械臂单个2-DOF关节的运动学标定

绳索驱动的分段式蛇形空间机械臂通常具有相同结构的模块化关节,能够在狭小空间中灵巧操作,其精度是制约机器人发展的主要因素。为了提高蛇形空间机械臂的位置精度,指导蛇形空间机械臂的精度设计,以单个2-DOF关节为对象,提出一种正则化的运动学标定方法。首先,对具有多重映射关系的2-DOF关节的运动学进行分析,通过矩阵全微分理论建立包含所有几何误差参数的误差模型。然后,对2-DOF关节各部件的所有误差源进行灵敏度分析,依据3σ原则和理想的位置精度设计指标指导各部件的公差设计。最后,考虑所有的制造和装配误差,采用正则化方法对2-DOF关节进行误差辨识,用于补偿控制器中的名义运动学模型。结果表明,经过修正后的运动学模型的位置精度提高了50%,验证了运动学标定的有效性。     

水平移动式三坐标测量机空间误差检测与补偿

以水平移动式三坐标测量机为例,为了提高其空间精度而准确地实现测量机误差修正,设计了空间误差检测方案,并采用专用检具实测和间接计算了三坐标测量机21项几何误差中的18项,通过了误差补偿效果检验,验证了此方法是可行的.     

六自由度工业机器人本体标定实验的研究

目前六自由度工业机器人普遍具重复定位精度较高,但绝对定位精度较低的特性,所以为了提高离线编程的精度,需要通过运动学建模、实际测量、参数辨识、误差补偿四步进行机器人本体标定。文中在概括总结现有的工业机器人本体标定技术的基础上,运用MATLAB进行运动学仿真建模,Leica AT960绝对激光跟踪仪系统进行实际测量,SA软件实现参数辨识,外部控制器进行关节补偿,完成本体标定实验。并在此基础上,按照GB/T12642-2013进行标定前后机器人位姿特性检测,通过Robot Check软件处理检测数据,对比前后结果,验证了本体标定实验。     

基于多体系统理论的数控机床加工精度几何误差预测模型

针对多轴联动数控机床加工精度误差补偿问题,从分析数控机床误差产生机制和建立精度误差补偿模型的角度,提出基于多体系统理论的数控机床加工精度几何误差预测模型。分析B-A摆头五轴龙门数控机床的拓扑结构关系、低序体阵列、各典型体坐标变换,推导出B-A摆头五轴龙门数控机床的精度几何误差预测函数模型。采用平动轴十二线法误差参数辨识算法,计算出B-A摆头五轴数控机床21项空间几何误差,为精度几何误差预测函数提供有效的误差参数。该精度误差参数建模方法,对不同结构和运动关系的数控机床具有通用性,为后续数控机床误差动态实时补偿提高切削加工精度提供了理论基础。     

基于作业轨迹约束的机械臂多闭环标定方法

为了解决机械臂标定方法成本高、效率低的问题,对低成本的机械臂实时标定方法进行研究。选择低成本的双目相机为测量设备,基于微分变换理论阐述连杆参数误差辨识模型的建立方法;以作业轨迹和靶标可视性作为约束条件,采用逆运动学算法生成测量构型库;在此基础上通过DETMAX优化算法挑选出合适的构型用于建立辨识模型,并提出一种矩阵平衡方法改善模型性态水平;与此同时,还采用K-means聚类算法将所选构型进行划分,以此作为多组中间姿态输入至控制系统生成若干条平滑的作业-标定轨迹;最后,仿真验证了新方法在不同强度测量噪声下的连杆参数误差辨识精度。结果表明：矩阵平衡法将辨识模型观测指数由10.6提升至6.2×104,同时将其条件数由1.2×103降低至37.8,显著改善了模型性态水平;良态辨识模型使得绝大部分连杆参数误差辨识结果不易受测量噪声影响;距离测量噪声标准差由0.1/3 mm提高至1/3 mm时,DH误差平均辨识偏差仅由1.1%增大至1.4%。因此新方法能够满足机械臂低成本、实时、高精度的标定要求。     

三坐标测量机工作台面的检定及补偿

三坐标测量机广泛用于机械零件的检测,它的精度直接影响着被测工件的精度.文章利用千分表和四等量块对光电非接触三坐标测量机工作台面上的20个点进行了检定,实验结果显示工作台面与XOY移动平面的平行度超出了误差范围.作者采用误差补偿的方法,先设定补偿平面上的一点,再求出通过该点分别与XOZ和YOZ平面相平行的直线与XOY平面的夹角,根据设定点及两个夹角确定补偿平面,最后求出补偿后的工作台面与XOY移动平面的平行度在误差范围之内,从而使工作台满足设计要求.因而证明了误差补偿是一种有效的提高机器精度的方法.     

基于三坐标测量机的非圆齿轮误差测量

为了提高非圆齿轮的测量精度和效率,提出应用三坐标测量机进行测量的思想。从制造工艺上根据非圆齿轮有别于圆齿轮的特点,提出适用于非圆齿轮的误差项目。通过类比圆柱齿轮精度指标公差的计算方法,找到非圆齿轮精度指标公差的计算方法。选取合适的测头、对测量路径进行规划、采用三坐标测量机实现对非圆齿轮的逐齿扫描测量,以获得非圆齿轮的齿廓数据值。在此基础上,对数据值进行曲线拟合和计算,从而得出非圆齿轮的误差。     

基于预标定基坐标系及MIEKF算法的工业机器人标定方法

为了提高工业机器人的绝对定位精度和标定效率，提出一种基于预标定基坐标系及改进迭代扩展卡尔曼滤波(MIEKF)算法的运动学标定方法。该方法的优点在于用采集的位置数据进行基坐标系和工具坐标系预标定，节省两者拟合的时间。在建立位置误差模型时利用相关系数和复共线性分析去除模型的冗余参数。用MIEKF算法辨识模型的几何参数误差。通过实验对比验证，机器人经补偿后的绝对定位精度提高了88.07%。     

斜交非球型3R手腕全参数误差建模与标定实验研究

根据连续3R斜交非球型手腕的结构特征和工作原理,以D-H参数模型为理论依据,建立该手腕的运动学模型和全参数误差辨识模型,并用美国FARO公司生产的Xi型三维激光跟踪仪对手腕几何参数进行标定试验。经标定补偿后,连续3R斜交非球型手腕单轴方向定位精度可达到0.09mm,空间位置定位精度可达到0.104mm,完全可以满足喷涂机器人的工作精度要求。     

ADAMS环境下并联坐标测量机运动分析与仿真

并联机构的运动学分析即是求解并联机构的输入与输出构件的位移、速度、加速度之间的关系。文章以基于Stewart平台的六自由度并联机构坐标测量机为研究对象,在ADAMS软件环境下建立了六自由度并联坐标测量机的虚拟样机模型,然后基于虚拟样机对所研究的并联坐标测量机进行了运动学仿真。通过软件仿真,可以对并联坐标测量机各种运动性能产生直观的了解,从而为并联坐标测量机的设计与开发提供软件验证方法,为建立物理样机打下坚实的基础。同时利用虚拟样机技术还可以大大简化并联坐标测量机的运动学逆解和正解,为进一步对并联坐标测量机的系统优化创造了有利条件。     

基于光学坐标测量机的STEWART机构标定研究

为提高大型Stewart机构的定位精度,建立了误差模型并提出了基于光学坐标测量机的标定方法.仿真和试验研究表明,本方法姿态测量过程简便,算法的收敛速度快,系统的定位精度明显提高,为Stewart机构的标定提供了一种解决方案.     

A new calibration method for parallel kinematics machine tools using orientation constraint

This paper considers the problem of improving the accuracy of parallel kinematics machine tools through a low-cost and effective calibration method. A novel orientation constraint of keeping two attitude angles of the end-effector constant is presented to derive the calibration algorithm with special insight on the effect of using various combinations of two angles. The orientation constraint of the selected combination is realized physically through leveling a commercial biaxial inclinometer installed on the end-effector. Benefits of the proposed method include exempting the needs for precise pose (position and orientation) measurement and for mechanical fixtures, as well as rendering the independence of the measuring range and angular positioning accuracy of the inclinometer. Simulation based on the geometry of the Stewart platform of XJ-HEXA shows the position and orientation accuracy can reach 0.1 mm and 0.01° after calibration, when using an inclinometer with the repeatability of 0.001° and measuring the leg lengths with the precision of 0.002 mm at 80 configurations. Experiments on XJ-HEXA further verify the effectiveness of the proposed method.     

平行双关节坐标测量机运动学分析及其仿真研究

平行双关节坐标测量机是介于传统三坐标和关节臂式柔性三坐标测量机之间的新型三坐标测量机。对平行双关节坐标测量机进行运动学分析是对其进行研究的基础,也是研究其误差模型的前提。根据D-H法建立平行双关节坐标测量机的运动学模型,并将Mtalab的M函数编程与SimMechanics进行联合仿真。通过仿真实验验证了运动学模型的正确性,为以后的理论研究提供了参考。     

基于机器视觉的UVW定位系统

面向工业装备对高性能运动平台的需求,开发一套基于机器视觉的UVW定位系统。提出一种基于机器学习的视觉系统标定方法,利用平台运动学分析得到的平台坐标与图像坐标的方程,建立UVW平台的逆运动学图像求解关系,用于求解目标坐标的控制量。完成了定位系统的机器学习视觉标定和双目视觉定位控制实验,结果表明:设计的UVW平台视觉标定方法简单高效,运动平台具有较高的对位精度,可以满足工业应用需求。     

一种并联平台位姿的测量方法

提出了一种新型的基于超声波测距原理的并联平台位姿高精度测量方法，以Stewart型平台为例，介绍了通过三角形法实现运动平台三维定位及运动学建模的方法，并给出了基于测量模型的平台位姿的表达式。     

Stewart型并联机床伸缩杆伸长量误差在线测量

标定作为提高Stewart型并联机床静态精度的有效方法，包括建模、测量、参数识别和补偿等环节。其中伸缩杆伸长量误差的测量准确性直接影响标定效果。本文提出间接方法准确测量其值。首先选择激光跟踪系统精确测量并联机床不同位姿对应的伸缩杆绝对伸长量，再辅以符号运算，最终达到测量机床伸缩杆伸长量误差的目的。     

Five-axis milling machine tool kinematic chain design and analysis

Five-axis CNC machining centers have become quite common today. The kinematics of most of the machines are based on a rectangular Cartesian coordinate system. This paper classifies the possible conceptual designs and actual existing implementations based on the theoretically possible combinations of the degrees of freedom. Some useful quantitative parameters, such as the workspace utilization factor, machine tool space efficiency, orientation space index and orientation angle index are defined. The advantages and disadvantages of each concept are analyzed. Criteria for selection and design of a machine configuration are given. New concepts based on the Stewart platform have been introduced recently in industry and are also briefly discussed.     

A systematic optimization approach for the calibration of parallel kinematics machine tools by a laser tracker

Parallel kinematics machine has attracted attention as machine tools because of the outstanding features of high dynamics and high stiffness. Although various calibration methods for parallel kinematics machine have been studied, the influence of inaccurate motion of joints is rarely considered in these studies. This paper presents a high-accuracy and high-effective approach for calibration of parallel kinematics machine. In the approach, a differential error model, an optimized model and a statistical method are combined, and the errors of parallel kinematics machine due to inaccurate motion of joints can be reduced by this approach. Specifically, the workspace is symmetrically divided into four subspaces, and a measurement method is suggested by a laser tracker to require the actual pose of the platform in these subspaces. An optimized model is proposed to solve the kinematic parameters in symmetrical subspaces, and then arithmetical mean method is proposed to calculate the final kinematic parameter. In order to achieve the global optimum quickly and precisely, the initial value of the optimal parameter is directly solved based on the differential error model. The proposed approach has been realized on the developed 5-DOF hexapod machine tool, and the experiment result proves that the presented method is very effective and accurate for the calibration of the hexapod machine tool.     

Kinematical calibration of a hybrid machine tool with Regularization method

The hybrid machine tools, combining the advantages of serial and parallel type machine tools, provide more and more application opportunities for less-freedom parallel mechanism. Accuracy performance is still an important index of hybrid machine tool for industry application. In this study, configuration of a 3-P(4R)S-XY hybrid machine tool is first introduced. The 3-P(4R)S parallel mechanism can be simplified to a 3-PRS mechanism on kinematical calibration. Based on that, error model and error kinematics are derived to introduce all possible manufacturing and assembling errors into calibration. Then, identification matrix is derived by differentiating kinematical equations. Combining the advantages of calibration schemes based on both inverse and forward kinematics model, a new measurement scheme is put forward, in which not all freedoms of motions needs to be measured and error identification could be efficiently accomplished in one time measurement. In order to solve the ill-posed problem in error identification, practical Regularization methods are adopted. Finally, the kinematical calibration experiment of the prototype machine tool is performed with a combined measuring tool. The results of RTCP accuracy test reveal that the positioning accuracy is less than 0.05 mm in the 30° cone workspace. Calibration experiments for the prototype verify feasibility and effectivity of the more precise kinematical error model, the low-cost measurement scheme, and the error identification solution with Regularization method.