Analysis, characterization and accuracy improvement of optical coordinate measurement systems for car body assembly quality control

Many car manufacturers are installing in-line car body measurement systems in order to achieve dimensional quality control of the whole production. The geometrical tolerances required by this product are narrowing increasingly; consequently, it is necessary to design these systems to calculate corrections and uncertainties as accurately as possible. This paper studies the error sources and analyzes their influence on measurement results by means of simulation and experimental tests during a nine-month study. The final goal of this work is to describe an optimization procedure for the accuracy improvement of the system. This is achieved mainly by applying a number of corrections designed to minimize the errors detected during the practical tests, and by means of algorithms to eliminate dispersions caused by a lack of stability in the positioning of the car body in the optical measurement system, or by temperature variations to reduce the final error.     

Modeling of on-line measurement for rolling the rings with blank size errors in vertical hot ring rolling process

The size errors of the ring blanks have a considerable effect on the vertical hot ring rolling process and the ring products’ dimensional precision. In this paper, the geometric relationship between the ring’s outer diameter and the measuring roll’s displacement is studied, and then, the influence of the blank size errors on this geometric relationship is analyzed. Subsequently, a modeling method of the measurement model for vertical hot ring rolling process is proposed, that is, the ring’s outer diameter can be measured indirectly through the relations of the ring’s outer diameter with respect to the measuring roll’s displacement and the ring blank’s outer diameter. Using this modeling method, the on-line measurement model of a certain type of vertical hot ring rolling mill was established, and the verification experiments were also conducted. The experiments showed that this on-line measurement model could calculate the ring’s outer diameter precisely, and the absolute errors of the formed rings were less than ±1.5 mm. The research results of this paper have general significance for the on-line measurement and process control of vertical hot ring rolling process.     

The development of a multiphase flow meter without separation based on sloped open channel dynamics

The online continuous measurement of multiphase flow is one of the most key technologies which influences the development of oil industry in future. A new type of multiphase meter system is developed based on the open channel flow. The test pipe of the meter is slightly slopped to make the flow pattern mainly stratified flow. Based on the study of oil and gas flow dynamics in the open channel test pipe, the liquid metering model and gas metering model are deduced to calculate the gas and the liquid flow rate, the water cut is measured online by the principle of differential pressure. This device can work online without the separation of the production fluid. By the lab test and field application test, the results of the metering system show that the liquid flow rate errors are within ±5%, the gas flow rate errors can be within ±5%, and the water cut absolute error is within ±2%, which can meet the demands of the field flow rate measurement.     

Error measurement and assemble error correction of a 3D-step-gauge

A new artifact called 3D-step-gauge consisting of a pyramid array and a compound, is proposed to calculate geometrical errors for machine tools. Only one point on each profile of the pyramid in the array is probed, and its center coordinate can be calculated. Then, the intervals of the pyramids can be transfered a length standard to measure errors. Considering the differences in the structural parameters and the location of the pyramids, a volumetric error measurement method of discrete points is presented. Furthermore, the location errors between the calibration state and the measurement state are studied and their influences on the accuracy of the position measurement are investigated on an actual machine tool. The 3D-step-gauge was tested on an actual machine tool and the measurement result shows quick assembly, convenient measurement, and high accuracy.     

欠观测条件下的增量Kalman滤波方法

提出欠观测条件下增量Kalman滤波的概念和定义,建立增量Kalman滤波模型及其分析方法,给出主要的计算步骤。经典的Kalman滤波方法要求量测方程有较高精度,否则在递推过程中会产生较大误差。但是量测方程通常受环境因素影响较大,而且在许多实际情况(如深空探测)中不可能对所有的使用环境逐一校准量测方程。如果某量测方程没有在某一环境条件下进行验证或校准,那么在这一条件(称为欠观测条件)下使用该量测方程往往会产生未知的系统误差,从而导致较大的Kalman滤波误差。提出的欠观测条件下增量Kalman滤波方法能够成功消除这种未知的系统误差,大大提高Kalman滤波的精度。该方法计算简单,便于工程应用。     

轮叉类零件对称度误差的检测与矫正

轮叉类零件是自行车和摩托车中的关键零件,其位置误差对使用性能影响很大。针对此类零件误差提出了检测和校正的解决方案,提高了零件的成品率,降低了生产成本。     

圆光栅角度传感器的误差补偿及参数辨识

基于正弦函数和粒子群算法提出了一种误差补偿及参数辨识方法,用于提高圆光栅角度传感器的测量精度。使用光电自准直仪和金属多面体对圆光栅角度传感器的测量误差进行了离散标定,通过对标定数据的频谱分析,发现传感器测量误差主要由几种不同频率的正弦函数信号组成,由此提出了一种基于正弦函数的圆光栅角度传感器误差补偿模型。补偿模型中包含7个待定常量,本文采用粒子群算法求解这7个待定常量以克服最小二乘法无法收敛的问题。以待定常量为粒子位置坐标,以平均误差为适值函数,建立了一种基于粒子群算法的参数辨识模型,并根据参数辨识模型求出最优的待定常量。应用补偿模型对关节臂式坐标测量机的6个圆光栅角度传感器测量误差进行了补偿,结果表明:补偿后各角度传感器的平均测量误差减小了约398～1102.5倍,大大地提高了传感器的测量精度。     

Development and application of spectacles frame parameter measurement apparatus

The measurement of the spectacles frame parameters has substantial effects on both the production and export of spectacles products. In fact, this measurement is the measurement of related three-dimensional trajectory. The working principles of the measurement apparatus developed based on capacitive grating technology are introduced in this paper. Capacitive grating technology is a precision length measurement method. Its advantages are small volume, low price, low production cost, and easy to obtain apparatus is composed of one industrial control computer, tem stability is guaranteed during the design of the circuit into account. The software is divided into lower layer and precise readings of the measured data. The measurement two microcontrollers and corresponding circuits. The syswith the practical situation of upper layer. Each layer has its industry application taken different emphasis. The causes of system errors and the method of error elimination are also analyzed. The analysis of the data obtained from experiments and the operating results of prototype apparatus both indicate that the proposed measurement apparatus has achieved outstanding competitive technical level of same kind products in international market and thus has ideal implications for mass production.     

Feasibility of using thermal response methods for nonintrusive compressed air flow measurement

Robust, low-cost nonintrusive flow meters are of interest in many industries. In particular, a reliable nonintrusive flow measurement for the diagnosis of air leaks in compressed air systems is desirable. Measurement of the air flow due to leaks in the system ensures an accurate estimation of potential cost and energy savings. This study evaluates a novel method of using thermal responses to nonintrusively measure leakage rates in compressed air lines. The method uses heat and the resulting thermal response to calculate the flow rate inside the compressed air line. Compared to the current methods for flow measurement, this method can simplify flow measurement while decreasing the sensitivity to errors when measuring flow rates. In this study, the methodology of the proposed method is explained along with the potential advantages to the design. Two approaches are evaluated: a dynamic step response and sinusoidal frequency response. Simulated tests evaluate the feasibility of the proposed methods, followed by experiments that validate the simulation results. A clear correlation between the thermal step response and the flow rate indicate viability of the proposed method in simulation. Experimental results yielded similar results, confirming the validity of the proposed method. The results of a field test in an industrial environment demonstrate the capability of the approach to other flow rate measurement techniques.     

Method of compensation for systematic errors in goniometric systems

A method based on invariants of in-plane motion of an object is developed for compensation of systematic errors of measurements in goniometric systems. Exact equations are derived for systematic errors of measurement of the object latitude with ignored fluctuating errors of measurement. Analytical expressions are also derived to calculate the standard deviation of the error in estimating systematic errors being taken into account, which allow us to impose grounded requirements to tactical and technical characteristics of goniometric systems designed for observation of various objects.     

基于双平行平面相机模型的钢板尺寸视觉测量

提出基于双平行平面相机模型的视觉测量方法,用于测量生产线上运动钢板的尺寸。该方法采用数据驱动的方式计算像点在标定平面上投影点的世界坐标;采用k近邻(k-NN)方法生成目标在标定平面上的无畸变投影图像,并建立投影图像与世界坐标系的直接关联。提出了双平行平面模型下相机光心位置标定算法,利用线结构光进行板材厚度测量;在无畸变的投影图像上利用钢板边缘间的平行和垂直性进行钢板边缘特征提取,通过边缘直线的世界坐标方程求取长宽尺寸。最后,给出了针对大尺寸钢板测量的多相机测量系统框架。提出的方法为单目视觉测量方法,相比于其他方法具有现场安装简单和标定工作量小的特点。通过图像分辨率为640×480的相机对尺寸为80mm×50mm×15mm的标准铝块进行了测量,结果显示:厚度测量误差为0.1mm,长度和宽度的误差在0.2mm以内。实际应用中测量精度远高于加工精度,能够满足产品计量的要求。     

基于改进遗传算法的等距型面轮廓参数及误差计算

等距型面轮廓曲线为非圆曲线,其参数测量和误差计算都比较困难,目前尚无统一的评价标准。本文根据圆的测量方法,采用最小包容区域法和改进的遗传算法来计算等距型面的轮廓参数及其误差,提高了等距型面轮廓曲线的测量精度,为等距型面的精确测量提供了一种新的计算方法。     

Improvement of Product Accuracy in Freeform Surface Machining

Error compensation has come to the fore as industry is demanding more accurate machines at lower cost. Most previous work has focused on the overall-error compensation of machines. However, with mass production it is often more effective to focus on product errors rather than make more accurate machines. Moreover, mass produced products are commonly designed with freeform surfaces, and errors in such products are not easy to compensate for. Accordingly, the current paper presents part-error modelling for freeform surface machining as a substitute for overall-error modelling. The proposed part-error modelling is carried out in product parts using 3D measurement systems. The proposed modelling will be very useful for constructing intelligent CAM systems, thereby increasing efficiency and product accuracy.     

螺纹参数测量中工件定位误差分析和补偿

利用齐次坐标变换方法从理论上研究了单针扫描式螺纹测量仪的工件定位误差模型,并考虑探针尖头的几何形状,建立了更加精准的曲线方程。以该曲线作为最小二乘拟合曲线,根据数学模型的特点和参数的取值范围,采用改进的单纯形-模拟退火(SMSA)算法,通过对标准件的测量,求解模型参数,补偿对应误差,减小了简单直线拟合的模型误差。基于该方法,在自主研发的测针式螺纹测量仪上进行了实验验证,结果表明,所述模型更符合实际情况,能够有效地减小工件定位误差。     

五轴机床旋转轴误差的在机测量与模糊径向基神经网络建模

考虑五轴机床中的旋转轴误差会影响加工精度和在机测量结果,本文研究了旋转轴误差的在机测量与建模方法。介绍了基于标准球和机床在机测量系统的旋转轴综合误差测量方法,采用随机Hammersely序列分组规划旋转轴的测量角位置,通过自由安放策略确定标准球初始安装位置。然后,引入模糊减法聚类和模糊C-均值聚类(Fuzzy C-means,FCM)建立旋转轴误差的径向基(Radial basis function,RBF)神经网络预测模型。最后,进行数学透明解析,从而为误差的精确解析建模提供新途径。利用曲面的在机测量实例验证了提出的旋转轴误差测量与建模方法。结果表明:利用所建模型计算的预测位置与实测位置的距离偏差平均值为9.6μm,最大值不超过15μm;利用所建模型补偿工件的在机测量结果后,其平均值由32.5μm减小到13.6μm,最大误差也由62.3μm减小到18.6μm。结果显示,提出的测量方法操作简单,自动化程度高;模糊RBF神经网络的学习速度快、适应能力强、鲁棒性好,能满足高度非线性、强耦合的旋转轴误差建模要求。     

基于彩色CCD的火焰温度检测算法研究

本文分析了彩色CCD摄像机测量机理,建立了由火焰图像求取燃烧温度场的数学模型,推导和分析了相应的三色温度测量模型,论述了图像噪声的滤除方法,分析了目前较先进的BP神经网络测温误差大的原因,并提出一种新的基于比值输入的BP神经网络法来计算温度。实验证明,该算法具有较高的计算精度和实用性。     

航空发动机空气流量测量与计算方法研究

空气流量是航空发动机重要的控制参数,利用进气道测量耙获得发动机空气流量是目前国内外常用的方法之一.本文首先对进气道测量耙系统进行了分析和研究,建立了发动机空气流量与附面层位移厚度的数学模型及空气流量的误差数学模型;然后对空气流量测量误差的主要来源进行了分析研究;最后,在某型发动机的飞行试验中运用了本文的测量与计算方法.试验结果表明:本文提出的航空发动机空气流量测量与计算方法能较准确地获得空气流量值,具有很好的工程应用前景.     

A flow rate measurement method for horizontal oil-gas-water three-phase flows based on Venturi meter,blind tee,and gamma-ray attenuation

Online horizontal oil-gas-water three-phase flow rate monitoring is essential for reliable operations during industrial production. A flow rate measurement method is developed in horizontal oil-gas-water three-phase flows by combining a blind tee, a Venturi meter, and a gamma-ray densitometer. The blind tee is installed at the test section entrance to homogenize the mixture by transforming the horizontal flow to a vertical upward flow. The Venturi meter is used for the total flow rate measurement. The dual-energy gamma-ray densitometer is used for phase holdup measurement. In the present method, blind-tee mixing effects and oil-water mixture slip behavior is essential, which were experimentally analyzed in this work. The phase inversion was found in the oil-water mixture with the increasing of the oil volume fraction. Besides, the addition of the gas reduces the oil-water slip ratio. For the range of 0–35% and 65–100% oil fraction in the oil-water liquid, the oil-water mixture can be well treated as a pseudo homogenous liquid with a slip ratio of 0.9–1.1. A three-phase flow rate model is then established for these conditions. The method was validated by horizontal oil-gas-water three-phase flows with average relative errors of 3.2% for the total flow rates, 4.3% for the gas flow rates, 11.5% for the oil flow rates, and 7.8% for the water flow rates.     

五轴数控机床万能主轴头空间误差建模研究

五轴机床万能主轴头空间误差建模的传统方法采用齐次变换矩阵(HTM)进行运算,计算过程复杂,物理意义很难理解。提出了一种主轴头空间误差的简化建模方法。综合考虑了主轴头两个旋转轴的运动误差和刀具热误差对主轴头空间精度造成的影响。优化了机床运动坐标系设置,从而降低了空间误差模型的复杂性。基于刚体运动学原理,描述了主轴头的运动误差传递关系。结合实例,推导出了主轴头空间误差的数学表达式,其建模过程简单,物理意义明确。     

Development and analysis of an automated dimension measuring microscope

A theoretical model is developed to describe the operation of a bright field, optical microscope intended to be used for making automated measurements of features as small as 0·3 μm. The measurement of gap lengths in magnetic recording heads and linewidths on integrated circuit photomasks is discussed in detail. Different measurement techniques are investigated theoretically and their perfomances in the presence of aberrations, focus errors and non-ideal transducer responses are assessed. An automated measurement technique based on image shearing is presented and compared with other measurement techniques based on bright field image scanning. It is demonstrated that the automated image shearing method is much less prone to measurement errors due to system parameters. The model was used to develop an optimized design for the measurement system and a complete instrument was built. The performance of the practical measurement system agreed well with theoretical predictions. A calibration standard and a simple but accurate calibration algorithm were also developed.