基于SAPSO-GA算法的高速曲轴随动数控磨床几何误差辨识方法

以某型数控曲轴磨床作为研究对象,对其结构和运动进行分析,推导出曲轴磨削时理想的砂轮轨迹方程。根据多体系统理论建立含有误差参数的模型,并推导出机床-工件和机床-刀具的运动链位置矩阵,得出机床精密加工的约束方程。对磨床的几何误差进行研究,建立几何误差模型。为快速、准确辨识出各项几何误差,提出一种混合SAPSO-GA算法。通过对比球杆仪测量补偿前后的运动轨迹,分析补偿效果。结果表明:所提方法提高了辨识准确性,通过补偿大大提高了曲轴随动磨床的加工精度。     

立式加工中心空间误差验证及补偿

为提高某立式加工中心整机加工精度,借助旋量理论建立完备立式加工中心空间误差模型,在此基础上实现机床空间误差有效补偿.以旋量理论为基础推导并建立机床刀具运动链与工件运动链运动学正解,分析机床21项几何误差原理,在考虑21项几何误差的基础上建立该立式加工中心完备空间误差模型;利用九线法完成各项几何误差辨识;基于旋量运动学正解求解机床运动学逆解后得出运动轴实际运动路径,并通过体对角线实验对比补偿前后的效果.结果表明:所提补偿方法补偿效果显著,验证了机床空间误差模型的准确性,实现了提高机床加工精度的目的.     

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。     

协作机器人关节摩擦特性辨识与补偿技术

为提高机器人的运动精度和换向过程的运动平稳性,降低换向过程中因摩擦引起的位置误差和速度波动,文章提出了一种基于改进库伦+黏性摩擦模型的补偿方法。该改进模型引入sigmoid函数克服了传统库伦+黏性摩擦模型在换向过程中的不连续问题;并采用恒速辨识方法实现了摩擦模型参数的精确辨识;在此基础上,利用前馈补偿技术实现了机器人关节摩擦特性的补偿。实验结果表明,文中提出的辨识方法能够有效的辨识出摩擦模型参数和基于模型的补偿算法明显降低了换向过程中的摩擦误差。     

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.     

工业机器人几何参数混合优化辨识与标定

为了提高串联工业机器人的绝对定位精度,文章提出了基于圆点分析法(CPA)与最小二乘法相结合的机器人几何参数混合优化辨识标定方法。首先利用CPA对机器人模型进行几何参数初辨识,然后以初辨识结果建立机器人几何误差模型,采用最小二乘法优化求解实现精辨识,再通过距离误差来验证标定效果。通过对埃夫特ER10L-C10工业机器人进行辨识标定实验研究,结果表明:采用文中方法对机器人几何参数辨识标定后其绝对定位误差的最大值、平均值和标准差明显小于理论模型和CPA辨识模型的结果,证明文中方法可以有效辨识标定机器人模型的几何参数,提高机器人的绝对定位精度。     

非球面超精密磨削误差建模与补偿研究

为提高课题组自研的超精密磨床加工精度,基于多体系统理论,运用齐次坐标变换原理,分析该超精密磨床37项几何误差来源,对非球面超精密磨削的综合误差建模。超精密磨床的多项几何误差元素已在制造阶段标定、补偿,取砂轮对刀误差和砂轮轮廓半径磨损误差作为主要面形误差来源,分别推导其对综合误差的传递函数,分析误差辨识方法,建立误差修正补偿模型,提出基于直接补偿的点补修正法。试验结果表明：建立的综合误差模型正确,根据误差辨识方法和修正补偿模型,修正误差后面形误差显著降低,有效提高面形精度。     

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。     

离心机误差对陀螺加速度计误差模型系数标定精度的影响

为了研究精密离心机自身误差对陀螺加速度计模型系数标定精度的影响,分析了离心机各个误差源,从输入比力和相对惯性空间角速率两个方面讨论了离心机误差源对加速度计参数标定的精度影响,给出了被试加速度计输入加速度和角速度的精确表达式。应用最小二乘法对误差模型参数进行辨识,且计算了在各误差源作用下对于参数辨识精度的影响程度。根据仿真结果,找出了某些离心机误差对加速度计误差系数标定的影响关系,为按照加速度计的标定精度来确定离心机的精度打下了理论基础。     

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。     

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.