Algorithm for Detecting Volumetric Geometric Accuracy of NC Machine Tool by Laser Tracker

Quick and accurate detecting the error of NC machine tool and performing the error compensation are important to improve the machining accuracy of NC machine tool. Currently, there are many methods for detecting the geometric accuracy of NC machine tool. However, these methods have deficiencies in detection efficiency and accuracy as well as in versatility. In the paper, a method with laser tracker based on the multi-station and time-sharing measurement principle is proposed, and this method can rapidly and accurately detect the geometric accuracy of NC machine tool. The machine tool is controlled to move in the preset path in a 3D space or 2D plane, and a laser tracker is used to measure the same motion trajectory of the machine tool successively at different base stations. The original algorithm for multi-station and time-sharing measurement is improved. The space coordinates of the measuring point obtained by the laser tracker are taken as parameter values, and the initial position of each base point can be determined. The redundant equation concerning the base point calibration can be established by the distance information of the laser tracker, and the position of each base point is further determined by solving the equation with least squares method, then the space coordinates of each measuring point can be calibrated. The singular matrix does not occur in calculation with the improved algorithm, which overcomes the limitations of the original algorithm, that the motion trajectory of machine tool is in a 3D space and there exits height difference between the base stations. Adopting the improved algorithm can expand the application of multi-station and time-sharing measurement, and can meet the quick and accurate detecting requirements for different types of NC machine tool.

Comparison of GUF and Monte Carlo methods to evaluate task-specific uncertainty in laser tracker measurement

Measurement uncertainty plays an important role in laser tracking measurement analyses. In the present work, the guides to the expression of uncertainty in measurement(GUM) uncertainty framework(GUF) and its supplement, the Monte Carlo method, were used to estimate the uncertainty of task-specific laser tracker measurements. First, the sources of error in laser tracker measurement were analyzed in detail, including instruments, measuring network fusion, measurement strategies, measurement process factors(such as the operator), measurement environment, and task-specific data processing. Second, the GUM and Monte Carlo methods and their application to laser tracker measurement were presented. Finally, a case study involving the uncertainty estimation of a cylindricity measurement process using the GUF and Monte Carlo methods was illustrated. The expanded uncertainty results(at 95% confidence levels) obtained with the Monte Carlo method are 0.069 mm(least-squares criterion) and 0.062 mm(minimum zone criterion), respectively, while with the GUM uncertainty framework, none but the result of least-squares criterion can be got, which is 0.071 mm. Thus, the GUM uncertainty framework slightly underestimates the overall uncertainty by 10%. The results demonstrate that the two methods have different characteristics in task-specific uncertainty evaluations of laser tracker measurements. The results indicate that the Monte Carlo method is a practical tool for applying the principle of propagation of distributions and does not depend on the assumptions and limitations required by the law of propagation of uncertainties(GUF). These features of the Monte Carlo method reduce the risk of an unreliable measurement of uncertainty estimation, particularly in cases of complicated measurement models, without the need to evaluate partial derivatives. In addition, the impact of sampling strategy and evaluation method on the uncertainty of the measurement results can also be taken into account with Monte Carlo method, which plays a guiding role in measurement planning.

Research on volumetric error compensation for NC machine tool based on laser tracker measurement

Error compensation is an effective method to improve the accuracy of NC machine tool.The compensation results are greatly affected by the error modeling and error measurement,so how to establish an accurate error model and accurately detect the geometric errors of machine tool are particularly important.In the paper,the volumetric error model of a multi-axis NC machine tool is established based on the multi-body system theory.The relative position deviations between the rotary axis and linear axis of the machine tool are considered in the modeling.To achieve quick and accurate detection,a laser tracker is based on the multi-station and time-sharing measurement principle to detect the geometric errors of machine tool,and each error of linear axis and rotary axis can be identified by this method.With the error model,error compensation can be carried out by modifying the machining process(G code),and the machining accuracy can be improved with the new G code.Experiment results show that the motion errors of a milling machine are significantly reduced after compensation,which verifies the effectiveness of compensation method.

应用激光跟踪仪和单目视觉检测三维水模体定位精度方法研究

针对三维水模体检测方法较少、检测过程复杂等问题,提出基于激光跟踪仪和单目视觉的三维水模体定位精度检测方法。激光跟踪仪三维水模体定位精度检测对比实验验证三维水模体在有水和无水的情况下定位精度一致。单目视觉三维水模体定位精度检测实验结果表明:X轴、Y轴、Z轴和空间对角线的定位误差均在0.050 mm以内,重复性分别为0.030 mm,0.064 mm,0.056 mm,0.140 mm,X轴和Y轴的垂直度为0.800 mm,Y轴和Z轴的垂直度为0.761 mm,X轴和Z轴的垂直度为0.503 mm,与激光跟踪仪的测量精度在一个量级。最后,经不确定度分析得到相邻点距离测量误差的标准差为0.0187 mm,满足检测要求。两种方法都能实现非接触测量,简化冗杂的检测过程,可满足医院对医用直线加速器的日常检测需求。

一种工具坐标系标定与公共点结合的机器人与激光跟踪仪坐标转换方法

机器人标定需要实现测量坐标系与机器人坐标系的配准关联,得到两者之间的转换关系。为克服传统基于轴线矢量坐标系转换方法操作复杂、拟合精度不高等缺点,提出一种工具坐标系标定与公共点转换相结合的解算方法。首先基于距离约束标定出光学靶标球中心相对于末端法兰坐标系的位置参数,而后通过重心化配置降低测量误差对坐标转换的影响,最后基于公共点转换采用三维七参数模型求解坐标转换齐次矩阵。实验结果表明,相比于基于轴线矢量坐标系转换的传统拟合方法,该方法的点位综合MAE减小35.44%,坐标转换精度更高,且操作方法简单,适合工业现场使用。

基于直线轨迹的激光跟踪仪测量精度测试方法

激光跟踪仪测量技术广泛应用于装配、制造等多个领域。为研究激光跟踪仪测量精度,研制了一套以光栅尺采集值为参考,通过多轴运动控制器实现电机运动控制、光栅尺采集、激光跟踪仪测量三者同步触发的坐标测量精度测试系统。对系统重复定位精度与激光跟踪仪同步触发坐标测量精度分别进行了试验。结果表明,系统重复定位误差在[–4.0μm,4.0μm]之间。3台不同型号激光跟踪仪在切向方向上与目标反射镜的距离为[2.7 m,3.4 m]时,其坐标测量误差随速度变化分布在[–23μm,988μm]之间。激光跟踪仪在径向方向上与目标反射镜的距离为[1.5 m,3.8 m]时,其坐标测量误差随速度变化分布在[5μm,915μm]之间。

复合式机器人接触式测量站位规划方法

在航空各部件的大空间测量中,针对人工测量工作强度大、检测精度不稳定、检测效率低等问题,提出基于全向移动复合式机器人的接触式测量机器人站位规划方法。首先进行机器人D-H参数建立以及关节转角求解,构建测量可达性约束模型,分析工具末端对机器人工作空间以及T-Mac与激光跟踪仪之间激光可达性的影响;然后针对最大工作限位和关节转角限位约束对大部件轴向以及径向进行机器人站位规划算法流程开发,保证测量特征点处于机器人工作限位内;最后基于AnyCAD几何引擎在三维虚拟环境中进行CAD模型测量特征点提取、站位规划、测量仿真。通过实例仿真试验对规划结果进行验证及评价,证明了站位规划算法可保证全部测量点的机器人可达性与激光可达性。

HL-3装置测量基准网的建立及部件定位测量

根据HL-3装置总装集成设计安装精度的要求,需要建立一个高精度的测量基准网,在总装过程中采用激光跟踪仪等先进测量设备对安装部件的空间位置进行测量。建立的基准网实现了网内基准点空间坐标最大不确定度为0.133mm。特别在对真空室、临时第一壁/限制器等部件的安装中,进行定位测量和数据反馈,然后再进行安装调整,实现了真空室∅1.84mm的同轴度精度,满足同轴度≤∅3mm的要求;标高偏差为-0.08~+0.136mm,满足标高偏差≤±1mm的要求。临时第一壁/限制器安装最大偏差值为+1.9351mm,最小偏差值为-1.8337mm,均满足各模块表面位置误差不超过±2mm的技术要求。测量基准网的建立以及安装过程中对部件高精度的定位测量,保证了HL-3装置高质量的建造。

基于激光跟踪仪的机器人末端负载重力辨识与在线补偿方法

为准确测量工业机器人在飞机装配中的真实装配受力,提出了一种基于激光跟踪仪的机器人末端负载重力辨识与在线补偿方法。借助激光跟踪仪等外部测量设备,建立了机器人系统的全局运动学模型,实现机器人末端位姿的精准获取。利用卡尔曼滤波处理力传感器信号,以获取更加准确平稳的外部力信息。基于最小二乘法建立了末端负载重力分量与位姿的映射关系,其中,考虑了力传感器的零点偏移与机器人安装偏差带来的影响。最后开展了机器人负载重力在线补偿试验,试验结果表明,该方法具有良好的效果。

无需公共点的高精度激光跟踪仪自标定方法

多台激光跟踪仪组成的测量系统能够得到高精度的坐标观测值,在加速器准直工程领域应用十分广泛。该系统需要自标定仪器中心的距离,目前基于球面拟合的自标定方法虽然测量效率较高,但是其精度有限。为了提高其精度,分析基于拟合的自标定方法精度较低的主要原因,提出了基于三角形结构的自标定方法,定量对比了新方法和基于球心拟合方法的精度。新方法建立非线性误差模型进行参数迭代求解,能够应用于激光跟踪仪的三维自标定。通过模拟仿真和实测实验,证明了该方法比基于球心拟合的自标定方法在精度上有了大幅度提升。文中算法无需增加额外设备,改进了原先基于球心拟合方法并提高其自标定精度,具有一定的工程应用价值。

高速磁浮轨道(梁)安装测控平面控制网测量技术实验研究

首先提出高速磁浮轨道(梁)安装测控平面控制网的精度要求,然后建立了小范围的CFⅢ平面控制测量实验网,在实验网中分别进行了基于高精度智能型全站仪和激光跟踪仪的观测实验,并对观测数据进行了处理与分析,以验证用这2种仪器及其对应的测量方法建立高速磁浮轨道安装测控平面控制网的精度及其可行性。实验结果表明,利用激光跟踪仪进行高速磁浮轨道(梁)安装测控平面控制网测量是可行的,且能够满足平差后方向改正数≤±1.5″、距离改正数≤±1 mm、相邻点的相对点位中误差≤±0.5 mm的精度要求。

激光跟踪仪双点靶球座的加工工艺

双点靶球座是激光跟踪仪的常用附件,具有较高的尺寸及形位精度要求,大外圆圆弧与小轴连接处薄弱,加工变形较难控制。对此,提出激光跟踪仪双点靶球座的加工工艺。介绍了具体工艺流程,进行了实测精度对比,确认采用所提出的加工工艺,激光跟踪仪双点靶球座的精度达到外购件水平,可以取代外购件。

激光跟踪仪在大型钢结构安装测量中的应用∗

详细介绍了激光跟踪仪在大型钢结构安装测量中的应用,主要包括制定技术路线、三维安装控制网的布设、测量和平差、设备安装测量等。试验表明,在120 m测量范围内,激光跟踪仪能够满足0.5 mm的平面度和直线度安装要求。

激光跟踪仪CFIII三维控制网数据采集软件研制

根据激光跟踪仪自身特点和实际工程应用需要,设计开发了一款激光跟踪仪CFIII三维控制网数据采集软件,该软件主要为高速磁浮、火箭撬滑轨测设一类具有特殊精度要求的测量工作提供外业数据采集服务。本文首先按照软件开发的一般流程进行需求分析和功能设计,并以此为基础对激光跟踪仪控制网测量等相关功能算法进行研究,然后对其中一些关键的功能算法进行阐述,再对各项子功能进行编码实现。最后,本文设计了一系列测量对比分析和仿真计算实验对软件各项功能进行可靠性验证,实验结果表明,本文研制的软件运行正常,测量结果正确、可靠。

移动操作机器人运动控制与误差分析实验研究

针对汽车零部件装配线的物料分拣及供给问题,设计并组装了一台移动操作机器人用于实现智能化自动送料。以此移动操作平台为对象,建立了其运动学模型,并以此为依据提出了运动控制策略,分析了输入脉冲与机器人速度及转弯半径之间的关系。利用激光跟踪仪对机器人直线和圆周运动的轨迹进行标定,获取了轨迹误差随速度的变化规律。研究结果表明,通过控制电机的输入脉冲,提出的运动控制策略可以满足在不同场景要求下的移动机器人定位和运行。机器人直线速度与输入脉冲成正比,转向速度与输入脉冲差成正比,转弯半径与输入脉冲和成正比。由轨迹误差与速度的关系,得到机器人的最佳速度为(0.2~0.3)m/s,当运送小型零部件且需要提高运行效率时,可控制直线速度在(0.5~0.7)m/s,为分析运动性能提供了一种解决方法。

激光跟踪仪测量系统主动靶球装置设计及测试

针对目前激光跟踪仪测量工作中靶球容易断光、需要人工引导激光的问题,课题组设计出了一种能够自动对光的主动激光靶球(spherically mounted retroreflector,SMR)装置。基于STM32系列单片机实现了控制电路的设计,通过实时检测跟踪仪的转角以及靶球自身的自转角度,能够准确计算出靶球收光口与跟踪仪出射激光之间的偏角,进而控制步进电机带动靶球作相应的旋转实现对光;将主动靶球装置安装在4足机器人上进行了性能测试。研究结果表明使用该主动靶球装置可以有效减少激光跟踪仪断光次数,提高了跟踪仪在机器人在线检测等领域的测量效率,具有良好的实用性。

面向起重机现场的激光跟踪测量不确定度分析与应用

本文在起重机械制造测量过程内引入激光跟踪仪测量技术,对其测量基本原理进行简要分析,提出了利用激光跟踪仪测量主梁上拱度的方法。通过理论计算得到在40 m测距处,单台激光跟踪仪进行不转站的单点测量扩展不确定度约为0.294 mm,并测量了激光跟踪仪单点重复测量精度和不同测距情况下单点最大偏移距离,在精确和快速测量模式下,单点的最大偏移距离均在0.05 mm内,在40 m测量距离内5个不同测站的激光跟踪仪的测量精度也均满足实际需求。最后对1台起重机主梁上拱度进行测量并与传统方法对比,两者测量结果均值相近,激光跟踪仪测量结果重复性表现更优。

辊系交叉测量与调整的生产应用

热轧线轧机长期高负荷生产状态下,轧机牌坊窗口与辊座精度把控不足导致的缺陷逐步放大,出现因辊系交叉偶发板形失控现象,其典型特征为以换辊作为出现或消除标志。本文对柳钢1450 mm热轧生产线轧机出现辊系交叉的现象进行描述与分析,通过激光跟踪仪测量轧机牌坊窗口并结合测量数据,调整牌坊衬板尺寸、辊座衬板尺寸达到减小辊系轴线交叉角度,进而改善轧机窜动、板形、轧制力差等异常现象,提高轧机设备与板形稳定性。

基于激光跟踪仪的俯仰角度测量方法研究

针对现有俯仰角度测量技术抗干扰能力弱、适应场景单一的问题,提出了基于激光跟踪仪的俯仰角度两种测量方法。一是通过测量点拟合圆的圆心角计算俯仰角,二是通过测量点构成直线之间的夹角计算俯仰角。结果表明:方法2的测量效果优于方法1,其非线性误差为0.051%,迟滞误差为0.019%,重复性误差为0.027%,总误差为0.061%。

基于激光跟踪仪的三维坐标转换方法

为了进一步提高工程测量三维坐标转换精度,本文开展了基于激光跟踪仪的三维坐标转换方法研究。首先,介绍了徕卡AT960激光跟踪仪的原理和测量精度;其次,推导了目前常用的大旋转角非线性13和7参数转换模型;最后,设计实测实验进行精度验证。实验步骤如下:利用徕卡AT960激光跟踪仪采集不同测站下的公共点三维坐标信息,然后利用非线性13参数和7参数模型将各个公共点坐标归算到统一坐标系下,对归算后的坐标进行精度分析。结果表明:非线性13和7参数转换模型的单位权中误差分别为9.79μm和9.54μm,整体精度基本一致,说明基于激光跟踪仪的三维坐标转换精度可以达到微米量级。