An image mosaic technique with non-overlapping regions based on microscopic vision in precision assembly

Microscopic vision has been widely applied in precision assembly.To achieve sufficiently high resolution in measurements for precision assembly when the sizes of the parts involved exceed the field of view of the vision system,an image mosaic technique must be used.In this paper,a method for constructing an image mosaic with non-overlapping areas with enhanced efficiency is proposed.First,an image mosaic model for the part is created using a geometric model of the measurement system installed on a X-Y-Z precision stages with high repeatability,and a path for image acquisition is established.Second,images are captured along the same path for a specified calibration plate,and an entire image is formed based on the given model.The measurement results obtained from the specified calibration plate are utilized to identify mosaic errors and apply compensation for the part requiring measurement.Experimental results show that the maximum error is less than 4μm for a camera with pixel equivalent 2.46μm,thereby demonstrating the accuracy of the proposed method.This image mosaic technique with non-overlapping regions can simplify image acquisition and reduce the workload involved in constructing an image mosaic.

In-situ strain measurement and error analysis of arc welding with 2D digital image correlation

The deformation and residual stress generated by the welding process can seriously affect the use of components.As a result,it is very important to understand the evolution of stress and strain during the welding process.The strain measurement method based on digital image correlation(DIC)is an excellent method to detect welding strain and residual stress.The out-of-plane translation and out-of-plane rotation introduce errors to the two-dimensional DIC.In this paper,the causes of errors are analyzed theoretically,and the formulas of errors caused by the out-of-plane displacement and the out-of-plane rotation are derived.The out-of-plane translation experiment and the out-of-plane rotation experiment were carried out to verify the theory,and the experimental results are consistent with the theoretical analysis results.The error caused by the out-of-plane translation can be reduced by increasing the object distance;the error caused by the out-of-plane rotation is greatly affected by the rotation angle.

Precise Measurement of Moving Object by Moiré-Based Image Processing Technique

Moiré images that are generally termed as moiré fringes have been generated due to the interference of two repetitive gratings. These patterns can be applied to many uses in metrology such as the measurements of surface profilometry of aerofoil, stress-strain effects, thermal deformation and so on. Moreover, 3D surface reconstruction as well as movement characterization of linearly and rotary moving objects can be visualized and identified by the moiré imaging technique. Recently it is approached as an emerging tool in the fields of biotechnology-particularly in biomechanics, nanotechnology, broadband communication and optoelectronics as well. Conventional Moiré interferometry evaluates the interference of two light waves being reflected on a reference surface and the object to be profiled. However, satisfactions in the requirements for the current significant issues in obtaining accurate measurements regarding the information of the movements as well as the dimensional deformations of objects dealing with the online inspection in micro-level and nano-level are still challenging. Particularly, for the demand of the present real-time auto-inspection of different precise information of movements objects statistically and dynamically. In that case single light wave system makes the moiré sensing system easier and applicable in real-time imaging. Furthermore, avoiding the employment of expensive conventional imaging facilities in 3-D measurement in mechanical as well as bio-mechanical systems has become a critical problem to be tackled. Therefore, research has been conducted focusing on the objective of developing a simple but precise measuring tool based on a single wave moiré imaging technique for multidimensional motion sensing by employing simple image processing approaches. An experimental set-up with a small CMOS camera has been developed capable of measuring the motion of an object by using a simply ink-printed straight optical grating lines attached to the moving objects. Several model experiments have been conducted for getting the information of movements of an object by adopting several mouse click options only on the moiré image visible at the computer screen. After getting information of the moiré image by the proposed technique, the movements of the object have been accurately identified. The system has been found simple and faster compared to the other conventional methods as well.

A novel wide-range precision instrument for measuring three-dimensional surface topography

We developed a measuring instrument that had wide range, high precision, small measuring touch force. The instrument for three-dimensional (3D) surface topography measurement was composed of a high precision displacement sensor based on the Michelson interference principle, a 3D platform based on vertical scanning, a measuring and control circuit, and an industrial control computer. It was a closed loop control system, which changed the traditional moving stylus scanning style into a moving platform scanning style. When the workpiece was measured, the lever of the displacement sensor returned to the balanced position in every sample interval according to the zero offset of the displacement sensor. The non-linear error caused by the rotation of the lever was, therefore, very small even if the measuring range was wide. The instrument can measure the roughness and the profile size of a curved surface.

基于矢量衍射理论的光栅干涉仪位移测量误差研究

光栅干涉仪位移测量系统作为测量领域中最精密的测量仪器之一,由于在测量过程中光栅的姿态位置无法保证完美装配,使得光栅的光栅矢量方向与运动矢量方向之间出现偏差,导致位移测量结果出现周期性非线性误差。文中针对在光栅干涉仪位移测量过程中出现的光栅与位移台以及读数头之间的姿态位置误差进行分析,通过分别建立位移坐标系及光栅坐标系,参考惯性导航领域中飞行器姿态表示方法,利用一维光栅的横滚、俯仰和偏航角共同描述一维光栅相对于位移台的装配状态。通过基于矢量衍射理论分析光栅干涉仪位移测量时三个维度的角度偏差量,对可能产生的位移测量误差进行了分析说明。基于广义一维光栅方程,探究出了一个更为普遍的结论,为后续装置的改进提供理论依据,以提高系统的测量精度。

基于遥测姿态变换的外测数据跟踪部位修正方法

外测数据跟踪部位修正对于飞行器飞行试验的高精度轨迹参数获取有着重要意义.提出一种基于飞行器遥测姿态数据和粗略轨迹参数的跟踪部位修正新方法,利用遥测姿态数据确定惯导平台中心与跟踪部位轨迹参数的变换关系,进而由粗略轨迹参数推算惯导平台中心与跟踪部位测距、径向速度、方位角和俯仰角的差异值,实现跟踪部位修正量的准确计算.采用误差传播法对粗略轨迹误差影响下的跟踪部位修正精度进行理论分析,验证了该修正方法在实际应用中的有效性.进一步通过仿真实验和实装实验检验了修正精度.结果表明跟踪部位修正量的计算误差远小于外测系统的精度指标要求,有重要的实际应用价值.

基于机器视觉技术的高精度光学仪器表面动态变形测量研究

伴随着光学仪器精度的逐渐提高,其表面动态变形事件发生频率也呈现急剧增加的趋势,是影响与制约光学仪器发展与应用的主要因素之一。为了满足光学仪器的应用需求,提出基于机器视觉技术的高精度光学仪器表面动态变形测量方法。采用机器视觉设备获取高精度光学仪器表面图像,对表面图像进行灰度化处理、去噪处理与增强处理,以此为基础,应用SURF特征检测算法提取表面图像的特征点,通过FLANN算法匹配相邻图像的特征点,利用Delaunay三角化在表面图像区域形成三角网格,进一步计算表面图像特征点的位移与应变,从而实现高精度光学仪器表面动态变形的测量。实验数据显示:在横坐标为1μm时,应用提出方法获得的表面动态变形位移纵坐标为1.8μm,与实际位移基本保持一致,在实验组别为6时,应用提出方法获得的光学仪器表面动态变形应变数值为3μm,与实际应变数值保持一致,充分证实了提出方法具备较好的应用性能。

三坐标测量机在精密加工中的误差补偿研究

三坐标测量精度对精密加工过程的质量控制有直接影响,研究三坐标测量误差模型与补偿方法,实现高精度测量对提升精密加工质量意义重大。分析了三坐标测量机的误差来源及分类,重点研究误差建模识别与补偿核心技术,并阐述误差补偿技术在航空航天、半导体集成电路、精密模具等领域中的实际应用情况。研究表明,当前的误差补偿技术可以有效提高三坐标测量机的重复性、重现性和绝对精度,为精密加工提供高效的质量检验与动态控制保障。

ZC1蜗杆齿廓测量测头对准误差修正

测头对准误差对齿轮测量中心ZC蜗杆齿廓偏差测量结果的影响较大,需要建立测头对准误差修正方法。基于ZC1蜗杆齿面方程,建立了蜗杆轴向齿廓测量误差模型,修正得到轴截面上齿廓测量点的轴向坐标,再依据精度标准评定得到蜗杆齿廓偏差,并分析了蜗杆的不同头数、模数和分度圆直径对蜗杆轴向齿廓测量误差的影响规律。在齿轮测量中心上开展了蜗杆轴截面齿廓测量实验,测头对准误差对齿廓形状偏差的影响较小;测头对准误差修正前后齿廓测量总偏差的最大差异由1.2μm降为0.2μm;齿廓形状测量偏差的最大差异由0.5μm降为0.3μm;齿廓倾斜测量偏差的最大差异由2.5μm降为0.4μm。该方法可有效减小齿轮测量中心测头对准误差对蜗杆轴截面齿廓偏差测量的影响。

精密加速度计组件自动装配及焊接系统

悬丝摆式加速度计广泛应用于航空、航天、惯性导航等领域,其装配质量对加速度测量精度有很大的影响,其关键组件的装配涉及位置和姿态的调整,同时悬丝在装配中需要控制张紧力并完成焊接。针对悬丝摆式加速度计组件的精密装配,研发了集成力、温度传感器和机器视觉的精密装配及焊接系统。采用相机配合转台实现待装配零件视觉测量,完成零件特征点的识别定位;利用精密滑台和转台调整待装配零件位姿;直线电机运动结合力反馈实现装配过程中零件间隙调整以及张紧力控制;开发专用焊接单元,实现在紧凑空间内对微小器件的自动温控焊接。试验结果表明,该系统能够完成加速度计组件自动装配及焊接,装配结果满足技术指标要求,焊点无虚焊,摆组件内边缘相对于磁钢边缘间隙偏差小于10μm,悬丝中心相对于加速度计底座地面位置精度优于20μm,悬丝张紧力偏差控制在±5 mN之内,能够达到产品装配质量要求。

基于热图像的GWOA-BiLSTM机床主轴热误差预测

热误差是影响高精密数控机床加工精度的重要因素。为了提高机床加工精度和性能,减少机床运行中产生的热误差,文章提出一种基于热图像的灰狼优化算法(grey wolf optimization algorithm,GWOA)和双向长短期记忆神经网络(bidirectional long short-term memory,BiLSTM)混合的热误差预测模型。首先,采用热成像仪获取机床主轴区域的温度场信息;其次,利用DBSCAN聚类(density-based spatial clustering of applications with noise)算法和相关系数法筛选出温度敏感点;然后,通过模拟灰狼群体捕食行为,在参数空间中进行搜索以找到BiLSTM所需的最优参数;最后,使用获得的机床温度敏感点和热位移数据进行热误差预测,并在试验机床上进行验证。实验结果表明,使用GWOA优化BiLSTM神经网络的预测模型相比BiLSTM神经网络预测模型的均方根误差(root mean square error,RMSE)和平均绝对误差(mean absolute error,MAE)分别减小了约0.5180、0.3823μm,决定系数R^(2)提升了0.0578。与BiLSTM神经网络模型相比,利用GWOA优化后的模型具有更加优良的预测性能。

基于多波长干涉的瞬态轮廓检测Mirau显微镜

针对单波长Mirau干涉显微镜存在测量范围小和2π模糊等问题,提出了多波长Mirau偏振干涉显微镜,以实现微观轮廓的大动态范围测量的和表面粗糙度等显微结构的瞬态检测。系统利用R、G、B三个单色LED光源实现多波长干涉;利用彩色偏振相机获取瞬态相移干涉条纹图,降低实时瞬态检测中复杂的环境扰动影响;利用线栅偏振片调节条纹对比度,满足不同被测对象的反射率检测要求。为验证系统方案的可行性,经过系统误差补偿校准后测量标称值为1.9939μm的标准微米台阶,结果与标称值的偏差约为5.4 nm。利用该方法与Wyko干涉仪对金刚石车削凸面反射镜表面微观轮廓和表面粗糙度进行测量,表面粗糙度测量结果均方根值偏差为3.7 nm,验证了该系统可实现高精度的大动态范围测量。

磁共振IDEAL-IQ序列测量肝脏脂肪含量的可行性研究

目的 探究IDEAL-IQ序列测量肝脏脂肪含量的准确性,以及影响测量准确性的因素。方法 利用GE DISCOVERY MR750 3.0T的单通道头线圈、八通道头线圈以及八通道腹部线圈,对配置的不同浓度的水脂混合溶液模体进行高参数扫描。在GE AW4.6工作站上进行多次脂肪含量测量,并对测量数值进行线性回归分析,讨论测量值与已知配置值的相关性,分析配置水脂混合模体在不同线圈中测量的准确性。结果 对于已知浓度的水脂混合溶液模型,IDEAL-IQ序列在三个线圈测量数据的一元线性回归讨论中,三个回归模型的P<0.0001,测量模型均在α=0.0001的水平上显著性明显,拟合较好,置信度达到99.99%。不同线圈在同参数扫描的情况下,由于信噪比不同,在图像中出现明显噪点,在使用小ROI测量时,会使得同一层面测量结果出现较大偏差。结论 IDEAL-IQ序列运用于脂肪含量的定量测量是可行可靠的,并且精准性较高。但扫描图像的质量对于测量稳定性以及准确性有影响,图像噪声越大则测量结果越不稳定,测量值的偏差越大。在临床扫描条件下,临床医师的测量应该采用适当ROI多点测量取平均值的方式进行肝脏脂肪含量的测量,同时还应该避开肝脏扫描层中的初始层及末端层。如果选取区域落于初始层及末端层,则可能会导致脂肪含量的过估计。

距离和雾对红外测温精度影响的补偿研究

为提高在线式红外热像仪在大雾天气下的测温精度,研究了距离、相对湿度和雾对红外热像仪测温精度的影响。采用二次开发的热红外故障数据采集系统,搭建实验平台,分别进行单因素和多因素干扰下的测温实验。得到距离-误差温度的分段多项式拟合关系;基于暗通道先验理论,实现对雾的定量描述,得到透射率-误差温度的指数函数拟合关系;以代数和的方式,提出一种误差补偿模型来补偿距离和雾共同作用产生的测量误差。实验结果表明,该模型能显著提高热像仪测温精度,对在线式红外热像仪在大雾环境下进行长时间精确温度数据的采集与存储,构建设备故障数据特征库具有重要意义。

基于标准电容器的高压信号精密测量系统设计

电子式电压互感器的误差稳定性较差,需要在不停电的条件下进行误差检测。检测中的关键在于一次高压信号的在线测量。针对这一需求,设计了1种基于标准电容器的高压信号精密测量系统。相比于标准电压互感器,标准电容器无铁芯和电感单元,并且作为高压信号的传感主体,可安全地通过机械升降的方式带电接入一次导体。此外,为实现电压信号的精密测量,设计了1种带T型网络的改进模拟积分电路和高精度信号采样电路。校准试验结果表明,所设计的高压信号精密测量系统测量准确度满足0.05级的要求。该系统可作为标准电压互感器,用于电子式电压互感器测量误差的带电检测。

三坐标测量机辅助工装检测误差补偿策略研究

随着先进制造技术的迅猛发展,对零件精度的要求也在不断提升,而误差检测的准确性是确保零件精度的重要前提。在三坐标测量机的工作过程中,运动轴的几何误差会显著影响检测结果。为提高检测精度和效率,设计了一款用于三坐标测量机的辅助工装,并通过对主要运动方向进行微调,实现对工件检测误差的精准补偿。以齿轮误差检测为例,根据检测系统的拓扑结构,可以推导出Houston较低序号物体阵列,建立含工装和齿轮的几何误差传递模型。研究结果为检测误差补偿提供了理论依据,也为其他多轴运动的误差传递模型提供了参考。

高分辨率光纤法珀传感器解调系统设计

光纤法珀传感器的腔长测量精度取决于解调系统的分辨率,现有的解调系统的分辨率多大于10 nm,难以实现10 nm以内腔长变化的测量。针对该问题,提出了以7 450像元数的线阵图像传感器为基础搭建解调系统,通过硬件设计与软件算法提高特征信号质量,完成腔长数据提取,实现了一种高分辨率光纤法珀传感器解调系统。实验结果表明,该系统在0~20μm的腔长测量范围内,实现了2.7 nm的光学分辨率,精度达到0.013 5%FS。

精密减速器摆线轮制造误差的数字化测量

摆线轮的制造误差是影响精密减速器传动精度的重要因素。基于使用一维测头的齿轮测量中心提出了一种精密减速器摆线轮制造误差的数字化测量方法,该方法能够快速而精确的实现摆线轮制造误差的测量。通过建立摆线轮的理论齿廓模型和误差测量模型,计算得到了测头的理论运动轨迹。根据精密测量原理,通过采取实际齿廓的NURBS拟合以及实际齿廓与理论齿廓的最佳匹配处理,构建了摆线轮制造误差精确计算过程及制造误差处理的数学模型,通过采用优化迭代算法求解得到了摆线轮的实际制造误差。在国产JB45型齿轮测量中心上对摆线轮的实际齿廓进行了实际检测,验证了该方法的准确性和有效性。

公路隧道施工水平位移及收敛量测精度确定方法与衡量方法探讨

隧道施工监控量测是隧道工程专业与测绘工程专业的交叉领域,在精度要求方面,隧道专业和测绘专业的规范标准中都有相关的条文说明,但不同规范标准之间存在侧重和差异,这给使用者在参考时造成一定的困扰。为了明确公路隧道施工监控量测水平位移监测精度要求,通过分析现行的国家标准、行业标准中的相关规定,结合多本现行规范中关于精度要求的说明,给出一种以确定允许变形量→确定衡量标准(中误差)→确定最大允许误差(中误差限差)为思路的精度确定方法,和计算实测数据中误差→对比计算中误差与中误差限差→判断数据可信度的精度衡量方法,并通过实测数据论证其合理性。结果表明,文中提出的精度确定方法、精度衡量方法及仪器选用能满足公路隧道水平位移监测或收敛监测的工作需求。

基于改进GWO-GRNN的管道焊缝三维重构测量

为提高双目相机不同位姿下焊缝的三维重构测量精度,提出一种基于立体视觉图像误差补偿的管道焊缝三维重构测量方法。采用改进灰狼算法(IGWO)优化广义回归神经网络(GRNN)补偿焊缝三维重构图像点的坐标误差。采用混沌映射、非线性收敛因子和最优记忆保存思想对GWO算法进行改进,通过8个标准测试函数进行仿真验证;利用优化后的GRNN模型对图像点坐标误差进行预测和补偿,计算三维坐标重构出焊缝点云,三维测量焊缝的焊宽、余高和长度。试验结果表明:该模型在双目相机不同的位姿状态下都能较准确地实现焊缝的三维重构,焊缝的三维测量相对误差在0.9%以内。