热变形摄影测量相机防护方法

为了保证高精度星载天线的在轨性能,在其研制阶段需要进行热变形测量试验,试验过程中测量设备在高低温环境中的防护问题一直以来都是热变形测量研究的重点。基于热变形自动摄影测量的方式,区别于传统的真空测量环境,设计提出了一种适用于常压高低温环境的测量相机防护方法,采用相机防护罐与高透石英玻璃整体组成正压密闭防护结构,配合温度、压力传感器,通过自动调节控制系统由冷热气体设备对常压高低温环境下测量相机的温度进行控制,维持稳定的正常工作温度,保证其高精度测量环境。理论分析结果证明了该相机防护设计方法的合理性和有效性,实践结果表明提出的测量相机防护方法满足在高温100℃和低温–70℃下相机温度维持(20±10)℃的正常工作温度的能力。     

真空热环境下结构热变形试验方法研究

航天器空间结构的尺寸稳定性直接关系到航天器有效载荷和平台的在轨运行性能。为改进空间结构在轨环境下的尺寸变形测量与验证方法,开展了地面模拟在轨真空热环境下的结构热变形试验方法研究。在对国内外相关试验方法与测量系统典型案例分析的基础上,基于工业摄影测量原理提出了单相机+多摄站测量方式的试验方案,并研制了相机保护系统和相机二维运动机构,相机在真空热环境下通过运动机构的弧形导轨可以在一个弧面内二维运动进行不同角度图像拍摄,用来满足多摄站的测量需求;随后针对真空热环境下测量,分析了相机保护系统的光学窗口对测量相机标定结果的影响,通过仿真与试验验证了相机拍摄景深、圆形标志点对比度和比例因子对测量精度的影响,并提出了采集多曝光图像处理方法,从不同曝光下拍摄的圆形标志点图像中优选最佳的圆心提取和识别结果进行融合计算,来保证获取较好的对比度和亮度图像。最后结合典型试验件对提出的真空热环境下结构热变形测量方法进行了试验验证,试验结果达到0. 043 mm的测量精度,表明该方法可以有效满足未来航天器空间结构热变形的测量需要。     

影响数字摄影测量系统精度因素的分析

对影响数字摄影测量系统精度的因素进行了分析,并提出了提高测量精度的方法.系统测量实验的结果证明了所提出方法的可行性和有效性.     

大型可展开天线型面热变形近景摄影测量

为确保高精度可展开天线的在轨性能,验证设计、材料和工艺的可靠性,提出采用数字近景摄影测量技术在地面模拟环境下对可展开天线型面进行热变形测试。设计了人工测量与自动测量两种方案,主要采取了高低温环境下相机防护、耐高低温测量标志和极低膨胀长度基准尺等措施保证了大温差极端环境下的测量实施。结果表明,天线型面精度随温度的变化而变化,且三个测量循环的变化规律较为一致,均在+60℃温度节点时型面精度最差,其均方根误差(RMS)最大值达到了0.220mm(人工测量),但也满足了天线型面精度小于0.5 mm的技术设计指标要求。对于40℃和80℃的温差时,人工测量型面变形量的RMS分别为0.045 mm和0.083 mm,也分别满足了其天线型面变形量技术设计指标0.100 mm和0.150 mm的要求。同时验证了自动测量与人工测量测量结果的一致性,均能满足测量技术设计指标的要求,为高低温测量试验的自动化实现提供了一种可拓展性思路。     

重型机床基础结构件的热时效研究

重型机床基础结构件多为铸铁件和焊接件 ,均存在不同程度的残余应力 ,残余应力易使这些基础结构产生变形和裂纹。本文试图采取行之有效的工艺措施 ,有效地减小残余应力 ,提高基础几何精度的稳定性和成品率。     

基于数字摄影测量的槽式太阳能聚光器结构检测方法研究

提出了利用摄影测量技术对大型槽式太阳能聚热器支架几何量进行测量的方法。首先,建立影响截断因子的托片位置和法向量、吸热管支撑点位置和旋转轴等几何量的数学模型;其次,通过仿真确定在满足聚热效率的前提下各几何量的最大容许误差;再次,设计测量附件,并结合各几何量的最大容许误差和误差传递模型,计算测量附件的加工精度;最后,利用测量附件,通过摄影测量法计算待测几何参量,并求解误差量。将测量附件和数据分析方法应用于轻型槽式太阳能聚热器支架的几何量测量,并将结果同激光跟踪仪进行对比,得到摄影测量法的点位误差在x、y、z三个方向的标准差分别为0. 140mm、0. 083mm和0. 102mm,角度误差的标准差为0. 144°。根据摄影测量的结果对支架进行调节,结果表明:摄影测量法满足大尺寸的几何量测量高精度要求,能够为槽式太阳能支架的加工、安装及检测提供理论依据。     

光学遥感器光机结构热变形的高精度测量

空间光学遥感器光机结构在复杂的空间轨道热环境中会产生热变形,影响探测精度.为解决光学遥感器光机结构热变形测量问题,本文提出了基于数字摄影测量和光纤光栅传感的热变形组合监测方法;建立了具有热解耦功能的光纤光栅布局方法和变形测量模型算法,理论分析了光纤光栅光谱变化与应变、温度的关系,采用实验方法标定光纤光栅应变传感器和温度...     

综合误差修正方法在热变形测量装置中的应用

误差修正技术是提高测量设备精度的常用方法,但有时由于设备的误差源太多或误差不易测出,而使得误差修正不完全或无能为力.本文提出一种综合误差修正方法,其基本思想是撇开装置中每项具体误差源所引起的测量误差,而把整个测量装置看成是一个大的误差源,采用一种等价置换的方法测出这个大误差源引起的测量误差,然后在测量结果中修正.将该方法用于实验室高精度热变形测量装置中,结果表明该方法可有效提高测量装置精度和测量数据的可靠性.     

基于数字摄影原理的汽车车身三维测量技术

在汽车车型开发设计过程中,如何获得汽车车身的三维数字化信息是最重要的工作。文中讨论了一种基于数字摄影原理的三维测量技术,此测量方法精度高、速度快。     

Large field-of-view deformation measurement for transmission tower based on close-range photogrammetry

The loading capacity of transmission towers cannot be calculated accurately only by finite element analysis (FEA) method. Traditional displacement sensors and strain gauges are not suit due to larger measuring range. In this paper, a novel system based on close-range photogrammetry technology (CPT) is proposed for tracking the 3D deformation of transmission tower during loading test. Artificial markers are pasted on the deformation area before loading. The 3D coordinates of these markers are reconstructed by using CPT methods at each stage, and the coordinate systems of different stages are registered together by means of global transformation points. The whole field 3D deformation under different load level is then obtained by tracking the homonymous markers among different stages. It is helpful for further analysis of the failure mechanism and mechanical properties of steel structures. The effectiveness of the proposed system is demonstrated by retrieving a full-scaled transmission tower deformation during loading test. A feasible solution for improving the load carrying capacity of the tested transmission tower is discussed. Evaluation experiment results indicate that the proposed method could achieve accuracy of 0.1 mm/m.     

A versatile stereo photogrammetry based technique for measuring fracture mode displacements in structures

The measurement of fracture mode displacements in structures which are susceptible to cracking such as adhesive joints in composite components – is becoming increasingly important. Such measurements are essential for the understanding of the root causes for specific fracture damage types. Furthermore, they can be used to assess the remaining life span of a structure for its safe operation. An improved version of a previously devised small displacement measurement system (SDMS) is used to measure local relative displacements (LRDs) at the trailing edge of a wind turbine blade. A purpose-made automated image processing software (AIPS) allows a rapid and reliable evaluation of a multitude of subsequently taken measurements at a high-precision level. The SDMS is used to measure the LRDs at three different locations close to the trailing edge of a wind turbine rotor blade. In addition, complementary measurements obtained by linear transducers are compared with the associated LRD component obtained by the SDMS. The 3D LRD measurements showed to be in good agreement with the predictions of non-linear finite element analysis. The paper closes with a brief discussion of the proposed measurement approach and the nature of LRDs as they appear in close vicinity to trailing edge joints.     

基于摄影测量技术的板式换热器静态变形试验研究

从摄影测量所属学科门类的角度对摄影测量的概念进行描述,详细阐述摄影测量的基本原理及与经常使用的编码标志技术。通过对板式换热器结构、原理介绍,提出采用国内自主研发的XJTUSD三维光学摄影测量系统对BR1.9型板式换热器静态变形测试。测试结果得到了换热器的固定压紧板和活动压紧板的静态变形：固定压紧板的最大变形发生在1.2MPa,最大变形值为1.38mm。活动压紧板的最大变形发生在1.8MPa,最大变形值为3.29mm。     

用于三维变形测量的数字图像相关系统

针对材料力学实验中的三维变形测量,提出并实现了一种基于双目立体视觉、摄影测量术和数字图像相关法的便携式三维变形测量系统。研究了该系统涉及的双目摄像机标定,图像相关算法,三维重建,以及三维位移、应变计算等关键技术。提出了一种基于摄影测量术的摄像机标定算法,该算法采用10参数镜头畸变模型,不需要高精度标定板即可实现摄像机的高精度标定。利用最小二乘非线性优化算法实现了数字图像的高精度匹配,针对非线性优化初值难求的问题,提出了一种基于种子点的初值计算方法,为非线性优化提供了可靠的初值。最后,介绍了三维重建以及计算三维位移、三维应变的方法。实验结果表明,标定结果的重投影误差为0.03 pixel,图像匹配的误差约为0.02 pixel,静态外形及位移的测量精度为0.05%,应变的测量精度优于0.5%。与传统的测量方法相比,本文提出的系统可以更准确、全面、直观地实现对位移场、应变场的测量。     

Evaluation of thermal deformation in electronic packages

Thermal deformation in an electronic package due to thermal strain mismatch is investigated. The warpage and the in-plane deformation of the package after encapsulation is analyzed using the laminated plate theory. An exact solution for the thermal deformation of an electronic package with circular shape is derived. Theoretical results are presented on the effects of the layer geometries and material properties on the thermal deformation. Several applications of the exact solution to electronic packaging product development are illustrated. The applications include lead on chip package, encapsulated chip on board and chip on substrate.     

机械密封热变形研究进展

机械密封是旋转机械中常用的一种轴密封,受力情况复杂,工作条件非常恶劣,介质压力和弹簧力的作用使得密封端面产生机械变形,端面容易呈现局部接触,当机械密封动环以高速旋转时,端面间的接触摩擦和端面对液膜的粘切作用而产生热,引起密封端面温升和热变形.端面热变形是密封失效的主要原因之一.从密封环温度场、变形、耦合变形、优化等方面综合评述了机械密封热变形的研究现状,分析存在的问题,最后指出进一步的研究方向.     

Modified Elman network for thermal deformation compensation modeling in machine tools

Thermal deformation is one of the most significant causes of machining errors in machine tools. One effective method is to build a compensation system to offset the thermal errors. Therefore, an accurate model is the key part of the compensation system. This study proposed a modified Elman network (EN) to improve the prediction accuracy of the compensation model in machine tools. And the improved EN can be regarded as a feed-forward neural network with feedback from hidden layer and output layer as an additional set of inputs. The structure of this network determines its dynamic characteristic with memory function. On the other hand, thermal deformation of the spindle contributes the largest part of total thermal errors in precision machining. Then a precise finite element model of machine tool spindle was established. And a new method for calculating the heat transfer convection coefficient on the surface of the spindle was proposed in this paper. The improved EN was used to map the nonlinear relationship between temperature field and thermal errors of the spindle. At last, a verification experiment was implemented on a CNC center and some satisfying results were achieved.     

Integration of industrial photogrammetry and neuro-fuzzy system for measuring and modeling deformation of industrial product surfaces under external forces

Deformation of surfaces under external loadings greatly is function of physical laws. But according to the impossibility of identifying all effective factors and modeling their interactions parametrically, analytical methods do not provide good performance generally. So, it is necessary to apply practical methods by carrying out field tests and measuring deformations directly. To achieve this purpose it is required to integrate capabilities of an accurate measurement technique and a flexible modeling method. The capabilities such as: high accuracy and speed in measuring 3D coordinates of desired points, ability to perform measurement in a continuous space and no need to contact with the surface of objects at the time of measurement make close range photogrammetry a reliable tool for measuring geometric parameters of an object before and after deformation. The ability to measure geometric parameters of an object before and after deformation in one hand and following the deformation from physical laws on the other hand make neuro-fuzzy system the first choice for modeling the deformation of objects using outputs of close range photogrammetry.In this paper, a new method has been presented for measuring and modeling deformation of industrial product surfaces under external forces using close range photogrammetry (as an image-based measurement tool) and neuro-fuzzy network (as a behavior modeling tool).     

地铁隧道变形监测的数字图像处理技术研究

提出利用数字图像处理技术对地铁隧道变形进行监测的方案.通过对隧道内定点放置的目标光源进行拍摄,得到所拍摄的图像,并对图像进行平滑、锐化、腐蚀、膨胀、去噪等预处理,获取目标光源清晰轮廓,然后对图像进行二值化,边界提取,进而通过最小二乘法,拟合圆心,计算出目标光源圆心的位置变化,从而得出地铁隧道纵向的变形量.实验结果表明,该方法在地铁隧道变形检测系统中得到的隧道变形量比较精确、可靠.     

高速铣削床鞍温度场建模与热变形分析

以安阳鑫盛机床厂生产的高速CX系列立式车铣复合加工中心CX8075的移动部件床鞍为研究对象,简化了加工中心的整机模型,研究了床鞍部件的主要发热点和热力学参数,分析了床鞍的发热量,合理地选择了滚珠丝杠的滑动摩擦系数,确定了热边界条件,建立了床鞍的三维数字化模型。利用有限元法对床鞍进行加载,研究了稳态温度场的分布[1],完成了床鞍热变形的分析与计算,从而正确认识了床鞍部件的热变形,实现了高速高精密机床的优化设计和热变形分析。