3自由度并联坐标测量机运动学参数标定与计算机仿真

首先对3自由度并联坐标测量机的组成结构及工作原理进行了介绍,然后针对该坐标测量机的运动特点,提出了一种基于逐次逼近算法的运动学参数标定方法,并利用该方法对所研究的并联坐标测量机的22个主要运动学参数进行了辨识,最后通过计算机仿真,对辨识结果进行了验证,从而为提高该坐标测量机的测量精度奠定了理论基础。     

Full-pose calibration of a robot manipulator using a coordinate-measuring machine

The work reported in this article addresses the kinematic calibration of a robot manipulator using a coordinate measuring machine (CMM) which is able to obtain the full pose of the end-effector. A kinematic model is developed for the manipulator, its relationship to the world coordinate frame and the tool. The derivation of the tool pose from experimental measurements is discussed, as is the identification methodology. A complete simulation of the experiment is performed, allowing the observation strategy to be defined. The experimental work is described together with the parameter identification and accuracy verification. The principal conclusion is that the method is able to calibrate the robot successfully, with a resulting accuracy approaching that of its repeatability.     

三自由度并联机构坐标测量机误差建模与仿真

给出了三自由度并联机构坐标测量的运动反解模型,依据矩阵全微分理论,导出测头位姿态差与各运动副位置误差及调节器运动误差之间的相互关系,建立了新型坐标测量机的误差模型。通过计算机仿真,讨论了机构参数误差对测量结果的影响,为实际误差的补偿写控制奠定了理论基础。     

Robot calibration using an automatic theodolite

The Vision Based Automatic Theodolite (VBAT) is an automatic partial pose measurement system for robot calibration. It uses low resolution rotation stages and resolution enhancement from a vision system to determine the line-of-sight to a spherical illuminated target. Automatic tracking, focusing, and centring provide the calibration system with speed, reliability, and repeatability. A kinematic model of the VBAT is described which includes both the mechanical parts of the system and the optics, using a modified Denavit-Hartenberg approach. All parameters in the VBAT model are identified and embedded into the system controller producing an instrument of 2 arc second accuracy. The system is then used in a conventional manner to calibrate a six degree of freedom PUMA robot, and the results compared to another calibration of the same arm by a coordinate measuring machine with repeatability and accuracy of 0.02 mm. The calibration using the VBAT enhances the accuracy of the PUMA to within 0.2 mm of that produced by the CMM calibration, compared to an accuracy of 14 mm prior to calibration.     

Ball array calibration on a coordinate measuring machine using a gage block

The distances between the balls of a ball array used in machine geometry calibration have to be very accurate. These distances can be calibrated using a laser measurement system, which requires specially designed optical devices and measuring probes. In this paper, a new and economical alternative method for calibrating the ball array is described. A single gage block is used for measuring the standard distance at the starting position. Then, the exact distances between the balls can be obtained by using the coordinate measuring machine (CMM) probe motion. This method does not depend on the accuracy of the CMM. Also, this method does not require expensive instruments or devices, but a CMM and a gage block. A simple “parallel-plane” bracket, mounted on to the measuring end of a CMM probe, is used to determine the centers of the balls automatically and accurately.     

六自由度并联坐标测量机运动模型及其虚拟原型研究

介绍了基于Stewart平台机构的六自由度并联坐标测量机的结构、特点及工作原理，建立了运动学模型，并在Windows XP环境下，通过Visual C＋＋6．0调用OpenGL图形库中的图形函数，对该坐标测量机的虚拟样机进行了三维建模与仿真。     

基于三坐标测量机的球面5R并联机构运动学标定研究

基于D-H参数建立了包含球面5R并联机构全部结构参数的标定用位置反解模型。建立了该机构位置和姿态运动学标定模型,结合实际样机进一步得到了标定简化模型,简化了参数辨识与补偿计算过程。通过三坐标测量机确定了球面机构的近似球心,并以此为原点建立了测量坐标系,从而实现了测量参考系与运动参考系的统一,便于末端执行器位姿的测量。通过标定实验,验证了该方法能够提高球面并联机构的绝对精度。     

石油管螺纹量规校准控制程序研究

以石油管螺纹量规校准控制程序为研究对象,PMM 12106三坐标测量机作为参考,重点分析了控制程序中的测量参数控制程序和测量路线控制程序.并通过实验的方式对测量位置、测头移动速度、探测速度、逼近距离和测量路线进行了论证,达到控制程序最佳效果的实现,进而保证校准数据的准确性与可靠性.     

基于改进遗传算法实现柔性三坐标测量机参数标定

针对柔性三坐标测量机测量精度低的弊端,提出了误差修正和参数标定的方法.应用Denavit-Hartenberg( DH)法建立了柔性三坐标测量系统的运动学模型和误差模型,考虑系统结构参数标定问题,提出了一种基于优化最小二乘法的改进遗传算法.首先,在最小二乘法中引入变化因子来衡量收敛速度;其次,当该因子趋于稳定时,将产生...     

高斯-牛顿法在关节式柔性三坐标测量机参数辨识中的应用

介绍了一种自行设计的六自由度关节式柔性三坐标测量机,并对该测量机的结构参数进行辨识,提出了一种基于空间两点距离的标定方法。该方法使用API激光跟踪仪作为基准,利用非线性最小二乘中的高斯—牛顿法,求解测量机测量方程的参数值。实验结果表明,该方法能够有效提高测量机的整体精度。     

Modelling,kinematic parameter identification and sensitivity analysis of a Laser Tracker having the beam source in the rotating head

This paper presents a new kinematic model, a parameter identification procedure and a sensitivity analysis of a laser tracker having the beam source in the rotating head. This model obtains the kinematic parameters by the coordinate transformation between successive reference systems following the Denavit–Hartenberg method. One of the disadvantages of laser tracker systems is that the end-user cannot know when the laser tracker is working in a suitable way or when it needs an error correction. The ASME B89.4.19 Standard provides some ranging tests to evaluate the laser tracker performance but these tests take a lot of time and require specialized equipment. Another problem is that the end-user cannot apply the manufacturer’s model because he cannot measure physical errors. In this paper, first the laser tracker kinematic model has been developed and validated with a generator of synthetic measurements using different meshes with synthetic reflector coordinates and known error parameters. Second, the laser tracker has been calibrated with experimental data using the measurements obtained by a coordinate measuring machine as nominal values for different strategies, increasing considerably the laser tracker accuracy. Finally, a sensitivity analysis of the length measurement system tests is presented to recommend the more suitable positions to perform the calibration procedure.     

零件轮廓测量机安全监测系统的设计

为适应现代先进制造业质量检测自动化的需要,研究开发能够在线非接触、高精度自动检测的智能三坐标测量机已经成为制造业发展的必然趋势,其中机器视觉检测技术的应用为实现复杂自由曲面的自动化检测提供了技术支持。介绍了零件轮廓测量机的工作原理,分析了回转工作台和偏心调整机构在回转体零件测量系统中的作用。采用合理的图像处理技术,完成了包括测量工位上异常物体的检测、工件类型识别和工件位置检测等功能在内的图像识别系统的设计。     

Uncertainty analysis of a laser calibration system for evaluating the positioning accuracy of a numerically controlled axis of coordinate measuring machines and machine tools

This paper presents an uncertainty analysis of a Positional Error Calibrator based on a laser interferometer system. This laser calibration system is capable of evaluating the positioning accuracy of a numerically controlled axis of machine tools and coordinate measuring machines (CMM) under dynamic conditions. In order to assess the measurement uncertainty of this calibrator, an analysis of the uncertainty components that make up the uncertainty budget of this calibrator has been carried out. These uncertainty components can be classified into three categories as follows: (1) uncertainties intrinsic to the laser system; (2) uncertainties due to environmental effects; (3) measuring uncertainties due to the installation. The procedure for evaluating the uncertainty of this calibrator follows GUM (“Guide to the Expression of Uncertainty in Measurement”). This uncertainty analysis was carried out when this calibrator was used to assess the positional errors of the “X” axis of a moving bridge type CMM.     

并联六坐标测量机测量模型的研究

建立和求解并联坐标测量机的测量模型是并联机构位置分析的正解问题，是其工作空间、控制算法和测量精度等研究的基础，为降低建立和求解测量模型的难度，设计了演化Stewart平台型的并联六坐标测量机，介绍了其特点，建立了推导测量模型的坐标系，按空间并联机构理论，采用等效机构法获得了测量模型的解析解，利用Matlab语言编制程序求解测量模型，得到了不同初始条件下测量模型的数值解，通过位置反解检验仿真结果，证明了测量模型的正确性。     

On the calibration of surface plates

Calibration of large surface plates could be performed using different measuring systems. In this investigation an autocollimator system, a laser system and a coordinate measuring machine have been investigated. A comparison among these methods of calibration has been carried out. An Elcomat 3000 autocollimator of resolution 0.05 arcsecond, an Agilent 5529A laser interferometer system of resolution 0.05 arcsecond and a Prismo/Zeiss Computerized Numerically Controlled Coordinate Measuring Machine (CNC–CMM) respectively are used. Large reflecting mirror, angular retro reflector and sensitive probe are used with autocollimator, laser systems and CNC–CMM respectively to identify heights at each position on the tested surface plate. Repeated results from the different methods are carried out and presented in the paper. Uncertainties associated with the measurement results of each method have been estimated using the GUM procedures and given in the paper. The paper discusses the difficults and ease as well as accuracies associated with each method.     

Improving the kinematic calibration of a coordinate measuring arm using configuration analysis

Portable coordinate measuring arms (CMA) represent a special class of coordinate measuring machines providing high accuracy combined with high flexibility. To obtain high accurate and reliable 3D coordinates, the kinematic model has to represent precisely the mechanical construction of the CMA. Thus, a reliable and accurate calibration is essential to preserve the CMA's accuracy. However, due to its redundant characteristics, estimating the kinematic parameters has to deal with linear dependencies and, therefore, with rank deficiencies. A profound statistical analysis of the existing calibration approaches has not yet been performed. For this reason, this paper introduces an innovative and replicable least-squares calibration approach based on the general case of adjustment (Gauß–Helmert model). This rigorous optimization procedure integrates the original observations and enables a statistical evaluation of the estimated parameters as well as of each observation, based on the configuration analysis. The applicability of the approach is proofed using simulated and real measuring data. Thanks to the configuration analysis and supported by experimental results, it is shown that an accurate solution of the calibration can be obtained using measurements only located in a small part of the workspace.     

A new technique for directly measuring the position errors of a 3-axis machine. Part 2: application

To expand the measurement range of the method introduced in part 1 of this paper series, a pyramid array artifact is proposed and calibrated on a CMM. In the calibration procedure, the distance between the pyramids is presented by data from three groups. Then in the measurement procedure, the position changes are calculated from both calibration and measurement data. In addition, the error induced by manufacture can be reduced or erased in these two procedures. After calibration by a high-accuracy CMM or machine tools, the developed device can also have the same accuracy as these tools. The developed device has been tested using an actual machine tool. The measurement results of the proposed device were checked by other high-accuracy measuring systems, and the comparison showed good agreement.     

3-PSS并联机构正解及其在坐标测量机中的应用

针对传统坐标测量机和关节臂测量机存在的技术局限,基于3-PSS并联机构原理,提出了只需一只长光栅、一条精密导轨即可实现三维空间精密测量的坐标测量机,并研究了测量系统的测量模型、测量误差模型及并联机构误差平均效应.根据并联机构基本理论建立了测量机的六杆测量模型,在此基础上进行了杆长制造、装配误差和光栅读数误差的理论分析.然后,从理论上展示和说明了并联机构存在误差平均效应的数学本质和依据.最后,介绍了样机的设计及制造,并给出初步的实验结果.在没有进行误差修正和系统标定的前提下,该样机在X,Y,Z3个坐标方向上的测量误差分别为0.029 mm,0.045 mm和0.058 mm.得到的结果可指导新样机的优化设计.     

Efficient inspection planning for coordinate measuring machines

The coordinate measuring machine (CMM) has been recognized as a powerful tool for dimensional and geometric tolerance inspection in the manufacturing industry. The power of the CMM depends heavily on an efficient inspection plan that measures a part in minimal time. This paper proposes CMM inspection planning that can minimize the number of part setups and probe orientations and the inspection feature sequence. In our planning, a greedy heuristic method is adopted to obtain the minimal number of part setups and probe changes. Meanwhile, a continuous Hopfield neural network is developed to solve the inspection feature-sequencing problem. The proposed method was successfully implemented and tested using a machine spindle cover part. The results show that the proposed method can achieve excellent performance compared to the other methods.     

基于人工布点规划的测量数据模型重建

虽然基于各种物理原理的坐标测量设备发展很快 ,测量方法朝着自动化方向发展 ,但目前机械点触发式的坐标测量机在许多情况下仍有大量应用。本文根据点触发式坐标测量机的特点 ,首先提出了坐标数据测量的布点规划原则 ,包括考虑被测物体的对称性、分区测量的规划以及测量数据的充分性和必要性原则。在此基础上 ,给出了基于人工规划的测量数据模型重建方法。应用实例中给出了对摩托车整车外形数据的采集及 CAD模型重建