位置度误差的测量

位置度是用以控制被测要素的位置要求，是零件上被测的点、线、面的实际位置偏离理想位置的程度。在实际测量中，位置度误差的测量是一项较为复杂的工作。它不能通过直接测量得到，而是要按基准合理地定位被测零件，并且根据孔组对基准的定位尺寸，测量值需要经过正确的计算，最后才能得出真正的位置度误差。位置度多用以控制孔的轴线的位置变动，因此，文章以图文并茂的形式，以线位置度为主体，给出了不同条件下其位置度误差的测量与计算方法。     

零件的立体视觉测量和三维重建研究

本文采用立体视觉测量并结合三维重建的方法,解决了零件的非接触测量问题。首先,分析了立体视觉测量系统的组成结构,利用左、右2个摄像机分别采集零件信息,进而根据二者间的空间关系计算视差数据。其次,采用均值滤波方法去除零件图像噪声,为立体匹配创造条件,进而根据立体图像对二者间的极线关系求取视差。选择Bowyer算法对视差图像进行剖分和三维重建。试验结果表明,本文建立的方法可有效完成航空发动机的叶片零件测量,进而实现生动逼真的三维重建。     

孔轴心线对平面垂直度专用量仪

我们设计、制造了如图所示的测量孔轴心线相对于平面的垂直度专用量仪。它利用检测跳动量的原理进行测量,可用于测量例如汽缸体一类的零件。测量时,将被测汽缸体孔套在弹性三爪9的外面,将H面贴住定位块4的基面,并使测量杆上的球形触头1与被测孔壁接触,汽缸体转动一周,从指示表7上即可读出     

高精度零件热变形量测量系统

设计了一种高精度测量零件受热变形量的实验装置.用恒温箱控制温度变化及保持温度稳定,利用电感测头对测量进行定位;同时,利用双频激光干涉仪对电感测头间距离进行精确测量,测头间的距离就是零件的受热变形量.理论分析和实验结果表明,这一系统具有较高的温度控制精度和测量精度.利用该系统对直径为50 mm的圆柱类零件在稳态均匀温度场中相同温度变化下的直径热变形量进行了5次重复性测量,其重复性误差为0.5μm.     

超长尺寸检测方法研究

讨论了超长尺寸因测量时基准与被测要素因为位置和条件的限制无法直接检测到的零件在三坐标测量机上灵活地通过间接的方法来完成测量,所谓间接测量是指基准的转换和被测要素的延伸。还有坐标的旋转、偏置、平移坐标系。同时、利用三坐标测量机先进的软件处理功能和计算来进行数据处理得到准确的测量结果。     

孔组位置度测量中测量基准的误差传播及优化

许多精密仪器仪表零件上分布有相互位置关系的一组孔,如图1所示。手表主夹板就是集中孔组、位置精度要求高的典型零件,其上孔组的位置度测量是生产中的重要环节。目前,国内各表厂均用直角坐标系统的坐标显微镜或工具显微镜来测量其坐标位置误差,然后换算成位置度误差。测量时,通常选取两个孔作为定位基准孔,即定心孔和定向孔,这样就在测量系统中形成测量基准坐标系,使被测夹板定位。由于在实际加工中,夹板孔组中各孔包括定位孔本身的位置,不可避免地产生坐标误差,而作为定位孔的误差就会传播到各被测     

阀套零件周向台阶槽的尺寸测量

在测量阀套零件周向台阶槽的台阶面距内孔中心距离时,因它的设计基准为孔中心线,被测台阶面与设计基准处于立体空间内且被测台阶面位于阀套壁内,常规测量量具和测量方法无法直接测量。笔者通过设计专用测量工装,巧妙解决了阀套零件台阶槽的台阶面的测量难题,成功实现了空间尺寸的精确测量,对类似零件测量有一定的参考意义。     

喷嘴内螺纹对锥凸台跳动的测具

本文介绍的测具可在生产条件下测量喷嘴内螺纹对锥凸台的跳动。图示测具由千分表1、本体2、测棒3和导向套筒4组成。导向套筒4的一端外螺纹用作被测零件5的定位表面,另一端装在本体2     

基于恒力定位支座的微小薄壁零件盲孔测试技术

本文介绍了一种恒力定位支座,与测微仪配合使用,可实现薄壁零件深度尺寸的快速测量,达到提升测试技术,提高检测效率的效果。这套恒力定位支座也可在其它测量中得到应用。     

用于非接触测量的光学传感器

本文介绍了一种用于批量零件进行公差带测量的传感器．由一个双光束投射系统将具有互补色的光带投射到被测零件表面，通过显微系统接收后，由视场中光带的颜色即可判定该被测零件是否合格，并可判定被测件尺寸的超差方向。由于该传感器采用的是光学非接触测量法，所以适用于橡胶、塑料以及软金属的测量．     

采用VC++与OpenGL的三维场景编辑系统的研究与设计

三维场景和模型编辑是开发可视化系统时一项必不可少的工作.介绍了基于Visual C++及OpenGL的三维场景编辑系统的构建,研究和设计了外部模型导入,场景编辑控制,渲染输出等功能.重点阐述了系统的总体设计,功能模块及其实现过程中的关键技术,并列举了主要功能模块的关键代码.     

A rapid shape acquisition method by integrating user touching input

The easiness of creating three-dimensional (3D) models from physical objects is one of the core challenges that remain to be addressed in reverse engineering. In this paper, a touch-based 3D shape acquisition method is presented that is easy and intuitive to use. Based on the method, a user can easily interact with both real and virtual objects and directly generate feature-based CAD models. The key technical challenges associated with developing the related hardware and software systems are discussed. By using widely available consumer electronic devices, a low-cost prototype system is designed and built. Based on the designed system, a novel 3D coordinate computation method is developed to obtain the touching point positions. Related challenges on using such a system in generating 3D models are also discussed. Multiple examples are presented to illustrate the effectiveness and efficiency of the developed method.     

Non-destructive testing of industrial structures with the use of multi-camera Digital Image Correlation method

Although Digital Image Correlation (DIC) provides capabilities of scaling a field-of-view (FOV), dimensions of some industrial installations in many cases are too big to be measured with DIC based on a single camera pair. In this paper we present two strategies of spatial stitching of data obtained with multi-camera DIC systems that can be used for engineering failure analysis, namely strategy for the case when there are overlapping FOVs of 3D DIC setups and strategy for the case when 3D DIC setups are distributed and not necessarily have overlapping FOVs. Data obtained with the presented methodologies can be used to verify or update FEM models of the investigated objects. Two practical applications of the multi-camera DIC system are described in order to show its feasibility in engineering failure analysis.     

Data input model for virtual reality-aided facility layout

An approach to automatically extract three dimensional (3D) models (that is, geometries and topologies) of physical objects in a facility is described. The rationale for this work is its repeated use in efficiently developing databases of 3D objects for applying virtual reality (VR) tools in detailed layout decision support. Obtaining 3D object models can be a challenging task. Sometimes they are available, for example, in a Computer-Aided Design (CAD) database and these can be readily imported into a VR database. But on many occasions one is not so fortunate and these object models have to be created in correlation to an existing or proposed facility, which can be an extremely tedious and time consuming task. A time efficient and economical alternative is to use video camera images, but quickly and accurately capturing the depth information from 2D camera images has so far remained elusive because the existing methodologies are too general purpose and operate at a lower level of abstraction, namely digitized images. We have developed a method for directly inputting 3D objects into VR-aided facility layout models, by integrating the strengths of previously tried and tested technological components: (i) camera calibration; (ii) image processing; (iii) stereo vision; and (iv) Delaunay triangulation. The techniques described here are embedded in a prototype architecture and toolkit called MIRRORS (Methodology for Inputting Raw Recordings into 3D Object Renderings for Stereo). The primary contribution of this paper is that it has been able to design an integrated system to build 3D object models from 2D images. The MIRRORS system has been primarily designed for objects without free-form surfaces and whose shape can be recovered from a relatively nondense set of points.     

Fast acquisition system for digital holograms and image processing for three-dimensional display with data manipulation

A three-dimensional (3D) digital holographic display system with image processing is presented. By use of phase-shifting digital holography, we obtain the complex amplitude of a 3D object at a recording plane. Image processing techniques are introduced to improve the quality of the reconstructed 3D object or manipulate 3D objects for elimination and addition of information by modifying the complex amplitude. The results show that the information processing is effective in such manipulations of 3D objects. We also show a fast recording system of 3D objects based on phase-shifting digital holography for display with image processing. The acquisition of 3D object information at 500 Hz is demonstrated experimentally.     

掩埋物体的小掠角散射声场与回波信混比

探测掩埋物体的水声系统,通常是在一定距离之外以小掠角声波扫描海底的方式工作,现有的射线声学模型已不能进行系统性能预报。采用波数积分模型和等效源建模方法,将声波在介质中的传播和掩埋物体的散射场计算融为一体,可以高精度地进行各种形状物体、不同声波束和任意掩埋状态下的三维散射场计算。利用开发的声场模型,计算出了典型球壳的等效目标强度和信号混响比随频率、掠射角及掩埋深度的关系曲线。在此基础上,提出一种基于时反聚焦发射、水下移动平台接收的双基地探测设想,并采用开发的声场模型验证了其正确性。     

Real-time three-dimensional object recognition with multiple perspectives imaging

A novel system for recognizing three-dimensional (3D) objects by use of multiple perspectives imaging is proposed. A 3D object under incoherent illumination is projected into an array of two-dimensional (2D) elemental images by use of a microlens array. Each elemental 2D image corresponds to a different perspective of the 3D object. Multiple perspectives imaging based on integral photography has been used for 3D display. In this way, the whole set of 2D elemental images records 3D information about the input object. After an optical incoherent-to-coherent conversion, an optical processor is employed to perform the correlation between the input and the reference 3D objects. Use of micro-optics allows us to process the 3D information in real time and with a compact optical system. To the best of our knowledge this 3D processor is the first to apply the principle of integral photography to 3D image recognition. We present experimental results obtained with both a digital and an optical implementation of the system. We also show that the system can recognize a slightly out-of-plane rotated 3D object.     

Three-dimensional object feature extraction and classification with computational holographic imaging

We address three-dimensional (3D) object classification with computational holographic imaging. A 3D object can be reconstructed at different planes by use of a single hologram. We apply principal component and Fisher linear discriminant analyses based on Gabor-wavelet feature vectors to classify 3D objects measured by digital interferometry. Experimental and simulation results are presented for regional filtering concentrated at specific positions and for overall grid filtering. The proposed technique substantially reduces the dimensionality of the 3D classification problem. To the best of our knowledge, this is the first report on the use of the proposed technique for 3D object classification.     

基于反求工程的计算机变形动画技术

提出采用反求工程的原理构造三维物体模型库,然后对两个三维物体进行自适应重采样的方法来建立两个物体顶点之间的关系,实现了两个三维物体之间的变形动画。然后对MDT3．0进行二次开发实现了两个三维物体之间的计算机辅助变形动画系统。     

Three-dimensional shape measurement using improved binary spatio-temporal encoded illumination and voting algorithm

Some regions of objects will be measured incorrectly or cannot be measured in optical three-dimensional (3D) measurement system based on coded structured light, due to occlusion, shadow, transfer function of measurement system, and noise. To obtain 3D data as much as possible and as correctly as possible, we proposed a method using improved binary spatio-temporal encoded illumination and voting algorithm. Firstly, the binary spatio-temporal encoded (BSE) pattern is improved with a redundancy encoding method. One code is assigned to two adjacent sections and distinguished with their temporal coordinates. The redundancy encoding method provides more cues for code correcting and retrieving. Secondly, symbols are estimated according to four coding cues--code redundancy, continuity of stripes, intensity variation in temporal direction, and neighbor symbols in sequence. Finally, a voting algorithm is adopted to obtain final symbols. A plaster model of a human head was measured to validate the method. The experimental results reveal that more valid points can be obtained and the reliability of the decoding results is improved.