块匹配与光流技术在微结构动态特性检测中的应用

在微结构动态特性的检测中引入块匹配技术和光流技术.结合微结构的运动特性,分别提出了基于块匹配技术和基于光流技术的两种微结构二维运动估计算法.利用这两种二维运动估计算法对平面微谐振器做动态特性分析,均取得了较好的测量结果.对这两种二维运动估计算法在微谐振器动态特性中的测量应用做比较,结果表明:块匹配算法适合简单的平移运动测量,计算量小,但它要求被测器件在结构上有较为特殊或显著的运动特征区域;光流算法通过分析单个像素的灰度分布特性来测量被测器件的运动特性.与块匹配法相比,它并不要求被测器件有较为特殊的运动特征结构.由于光流法以单个像素为计算单位,且其中包含有较多的差分计算,计算过程较为复杂,因此测量分析所需的时间长.     

基于分形小波变换的MEMS动态模糊图像亚像素检测技术

基于机器微视觉的微机电系统（MEMS）动态测试系统,提出了一种分形小波变换亚像素检测技术提取MEMS运动轨迹算法.该算法结合电耦合器件（CCD）成像机理,利用图像的分形参数进行随机分形插值对图像边缘进行重建,通过小波变换实现重建后图像亚像素精度的边缘检测.在连续光照明条件下,对MEMS平面微运动模糊图像进行检测处理,提取和分析了MEMS运动轨迹.将该方法和在频闪条件下测得的MEMS器件的平面微运动幅值的结果进行了比对分析和讨论.由实验结果可以看出,本方法有较高的测量精度,其测量绝对误差小于0.02像素.     

微结构运动特性表征中的全场三维重建方法

微机电系统(MEMS)测试的主要目的是为工程开发中的设计和模拟过程提供数据反馈,其中一个重要方面就是MEMS器件运动特性的高速可视化。基于计算机控制的频闪干涉测试系统,文中提出了一种时间轴和空间轴双向解包裹的干涉条纹分析方法,实现了MEMS器件离面运动参数的精确测量,并与微结构平面结构图像模板相结合,可以进行MEMS器件全视场运动的分析,达到了纳米级分辨力。     

基于光流技术MEMS平面微运动特性的测量

实现MEMS动态测试技术中平面微运动特性的测量，关键是记录MEMS运动过程中的瞬间运动状态，并恢复MEMS面内的运动历程．为此，介绍了光流技术，并提出利用邻域优化法进行微结构运动的光流计算．组建了基于频闪成像的MEMS平面运动测试系统，通过该系统获得MEMS谐振器周期运动不同相位下的清晰图像序列．利用邻域优化计算该图像序列的光流，选取合适的邻域大小和阈值，得到了MEMS谐振器在特定驱动频率下的运动幅度-相位图及其拟合曲线，从而获得微谐振器在此驱动频率下的运动幅度值为2．12μm．实验结果表明，该方法是准确有效的．     

基于模糊图像合成技术的MEMS平面微运动测试技术

随着微电子机械系统(MEMS)研究的深入和产业化的需求，捡测技术在其中的重要性越来越大．基于机器微视觉的MEMS动态测试系统．利用模糊图像合成技术对MEMS的平面微运动特性参数进行提取和分析．利用图像处理方法对MEMS谐振器做扫频和扫压测量，获得了MEMS器件的平面微运动特性，并对测量结果进行了分析和讨论．由实验结果可以看出，这种方法有较高的测量精度，测量重复性误差为100nm．     

利用Linnik显微干涉技术测量微结构动态特性

为了实现微结构的离面运动、幅频特性和谐振频率等动态参数的测量,设计开发了微结构动态测试系统,采用Linnik显微干涉结构,具有放大倍率高和工作距离长的特点.首先,系统利用频闪成像技术、五步相移方法和分割线去包裹算法测量微结构离面运动,然后,再通过扫频技术得到微结构的幅频特性和谐振频率.利用该测试系统对硅微悬臂梁的离面振动和幅频特性进行了测试,实验结果表明:硅微悬臂梁的谐振频率为13.03kHz,离面振动测量重复性误差小于10nm.系统具有较好的测量可重复性和较高的测量精度,能满足微结构动态特性测量对测试系统的性能要求.     

频闪干涉仪在微机电系统动态表征中的应用

微机电系统(MEMS)测试的主要目的是为工程开发中的设计和模拟过程提供数据反馈，其中一个重要方面就是MEMS器件动态特性的高速可视化．介绍了一种基于计算机控制的频闪干涉测试系统，用来测量可动MEMS器件的离面运动，实现了纳米级分辨力，该系统采用改进的相移干涉算法，使用一个大功率激光二极管(LD)作为频闪照明的光源，可以实现1MHz范围内大幅值(十几微米)的微运动测量，这种高离面灵敏度的测量方法特别适合进行微机械(光学)元件的动态特性测量．通过研究一个多晶硅微谐振器的动态特性说明了系统的强大功能。     

基于亚像素综合定位匹配算法的MEMS平面运动测量

动态测试对MEMS的设计、制造和可靠性具有非常重要的意义．提出了快速高精度的综合亚像素定位匹配算法,应用于MEMS平面运动测量．该综合算法把标准化协方差相关法、亚像素步长相关法、曲面拟合法、序惯相似性检测算法和单纯形法有机结合,综合运用各算法的优点,达到了提高亚像素定位速度和精度的目的．通过位移测量实验和对硅微陀螺仪质量块面内振动及谐振频率的测量,验证了该综合算法的可行性和有效性．     

飞秒激光微精细加工技术与MEMS动态测试技术

本文阐述了飞秒激光微精细加工技术的原理特点,在微机械和微光学中的应用,及其在加工研究中取得的一些进展;提出一种基于计算机视觉、显微干涉及激光多普勒的 MEMS 的动态测试技术,实现 MEMS 器件平面运动幅度的快速测量、平面和离面运动的测量和离面运动的瞬态测量。     

基于平面环形微腔结构的超高灵敏度位移传感器的研究

以平面环形微腔结构为核心器件,基于量子力学的隧道效应和“参量振荡不稳定”效应,结合理论计算及ANSYS和Beamprop仿真,设计出基于环形微腔结构的超高灵敏度位移传感器,特别是在1．55μm的谐振波下,对所设计的位移传感器进行了ANSYS力学仿真、Beamprop传输特性仿真以及输出特性数值模拟,论证了位移传感器的可行性,并为以后的实验奠定了基础。     

Optimal re-referencing rate for in-plane dynamic speckle interferometry

We investigate experimentally the optimal rate at which the reference speckle pattern should be updated when dynamic speckle interferometry is used to measure transient in-plane displacement fields. Images are captured with a high-speed camera and phase shifting and phase unwrapping are done temporally. For a wide range of in-plane velocities, up to a maximum of 40% of the Nyquist limit, the random errors in the calculated displacement field are minimized by updating the reference speckle pattern after a speckle displacement of 1/10 of the pixel spacing. The technique is applied to measurements of microscale deformation fields within an adhesive joint in a carbon-fiber epoxy composite.     

动物骨折治疗用金属骨板局部增量成形新工艺

目的目前动物骨折常用的锁定骨板内固定技术(Point-contact Reconstruction Compress Locking, PRCL)需要采用多个工具配合手动完成骨板成形,针对该过程中精度不可控、效率低等问题,提出一种弯扭复合成形模具,发展一种局部增量成形金属骨板的方法。方法 PRCL骨板固定治疗中,为了贴合受伤骨骼,治疗前骨板需经过面内弯曲、弯曲以及扭转3类变形。通过调整弯扭复合成形模具的空间位置及模具不同组成部分的相对位置,实现不同区域内不同变形量的面内弯曲、弯曲或扭转。应用数值方法分析验证弯扭复合成形模具及成形方法的适用性,基于DEFORM软件建立工业纯钛TA2骨板局部增量成形过程有限元模型,分析具有两个成形区的TA2骨板局部增量成形特征。结果塑性变形仅发生在复合模具附近,对已变形区无影响,会引起未成形区的刚性位移;骨板长度方向受力小于其宽度和厚度方向受力,面内弯曲需要较大的成形载荷。结论所发展的模具和方法可实现预期的骨板成形,也适用于其他PRCL金属骨板的成形。     

Digital speckle-pattern interferometry: fringe retrieval for large in-plane deformations with digital speckle photography

The compensation of large in-plane motions in digital speckle-pattern interferometry (DSPI) with the use of digital speckle photography (DSP) is demonstrated. Ordinary recordings of DSPI are recombined and analyzed with DSP. The DSP result is used to compensate for the bulk speckle motion prior to calculation of the phase map. This results in a high fringe contrast even for deformations of several speckle diameters. In addition, for the case of an in-plane deformation, it is shown that the absolute phase change in each pixel may be unwrapped by use of the DSP result as an initial guess. The principles of this method and experiments showing the in-plane rotation of a plate and the encounter of two rounded plates are presented.     

Determination of three-dimensional displacement using two-dimensional digital image correlation

A novel method that uses a two-dimensional (2D) digital image correlation (DIC) based on a single CCD camera to measure three-dimensional (3D) displacement and deformation is proposed. Rigid-body displacement in 3D space consists of both in-plane and out-of-plane components. The presence of an in-plane displacement component results in a shift of the center of the image displacement vector, while the slope of the image displacement vector is related to the out-of-plane displacement component. Global DIC is employed to determine the displaced position of each point on an object based on a linear distribution characteristic of the displacement vector. Speckle images with deformation introduced by 3D displacement are generated to demonstrate the feasibility of the proposed method. In the 3D rigid-body displacement, both in-plane and out-of-plane displacement components are separated by determining the intercept and slope of the image displacement vector. In the 3D deformation, a zero order displacement (pure rigid-body displacement) mode is assumed in a small subset of pixels. Simulated and experimental results demonstrate that both in-plane and out-of-plane displacements can be accurately retrieved using the proposed method.     

Uneven intensity change correction of speckle images using morphological Top-Hat transform in digital image correlation

By comparing two digital speckle images recorded before and after deformation, two-dimensional digital image correlation (DIC) method can accurately determine the in-plane displacement fields and strain fields. In a practical measurement, however, the variance of light source intensity, location and direction will cause the random uneven intensity change of the random speckle images and will lead to the obvious measurement error. Numerical simulation experiment is first carried out to analyse the influence of the recorded speckle images undergoing uneven light variation on DIC measurement accuracy. Then, a correction method for speckle images with uneven intensity change is proposed based on morphological Top-Hat transform. In addition, quantitative measurements of both in-plane rotation of a rigid body and three-point bending beam are investigated experimentally by DIC to verify the feasibility of the correction method. Experimental results show that the measurement accuracy of DIC is improved dramatically after the procedure of uneven light variation correction.     

Total Lagrangian formulation for the large displacement analysis of rectangular plates

In this paper, a method for the non-linear dynamic analysis of rectangular plates that undergo large rigid body motions and small elastic deformations is presented. The large rigid body displacement of the plate is defined by the translation and rotation of a selected plate reference. The small elastic deformation of the midplane is defined in the plate co-ordinate system using the assumptions of the classical theories of plates. Non-linear terms that represent the dynamic coupling between the rigid body displacement and the elastic deformation are presented in a closed form in terms of a set of time-invariant scalars and matrices that depend on the assumed displacement field of the plate. In this paper, the case of simple two-parameter screw displacement, where the rigid body translation and rotation of the plate reference are, respectively, along and about an axis fixed in space, is first considered. The non-linear dynamic equations that govern the most general and arbitrary motion of the plate are also presented and both lumped and consistent mass formulations are discussed. The non-linear dynamic formulation presented in this paper can be used to develop a total Lagrangian finite element formulation for plates in multibody systems consisting of interconnected structural elements.     

Quantitative Error Assessment in Pattern Matching: Effects of Intensity Pattern Noise, Interpolation, Strain and Image Contrast on Motion Measurements

Abstract: Basic concepts in probability are employed to develop analytic formulae for both the expectation (bias) and variance for image motions obtained during subset‐based pattern matching. Specifically, the expectation and variance in image motions in the presence of uncorrelated Gaussian intensity noise for each pixel location are obtained by optimising a least squares intensity matching metric. Results for both 1D and 2D image analyses clearly quantify both the bias and the covariance matrix for image motion estimates as a function of: (a) interpolation method, (b) sub‐pixel motion, (c) intensity noise, (d) contrast, (e) level of uniaxial normal strain and (f) subset size. For 1D translations, excellent agreement is demonstrated between simulations, theoretical predictions and experimental measurements. The level of agreement confirms that the analytical formulae can be used to provide a priori estimates for the ‘quality’ of local, subset‐based measurements achievable with a given pattern. For 1D strain with linear interpolation, theoretical predictions are provided for the expectation and co‐variance matrix for the local displacement and strain parameters. For 2D translations with bi‐linear interpolation, theoretical predictions are provided for both the expectation and the co‐variance matrix for both displacement components. Theoretical results in both cases show that the expectations for the local parameters are biased and a function of: (a) the interpolation difference between the translated and reference images, (b) magnitude of white noise, (c) decimal part of the motion and (d) intensity pattern gradients. For 1D strain, the biases and the covariance matrix for both parameters are directly affected by the strain parameter p₁ as the deformed image is stretched by (1 + p₁). For 2D rigid body motion case, the covariance matrix for measured motions is shown to have coupling between the motions, demonstrating that the directions of maximum and minimum variability do not generally coincide with the x and y directions.     

Simple method for simultaneously measuring the magnitude and direction of 2D in-plane displacement in white-light speckle photography

A simple method for simultaneously measuring the magnitude and direction (or argument) of a 2D in-plane displacement vector is presented. The theoretical mechanism for extracting the desired displacement signal from random noises produced by the nonoverlapping area of the recorded specklegrams of the test specimen surface is derived in detail. This procedure is realized by establishing a 1D displacement model in a white-light speckle photographic system using discrete Fourier transform shifting theorem. Results of the computer simulation and experiment show that the present method exhibits advantages such as convenient displacement direction determination, better robustness and wider measurement range than those of the traditional fringe analysis-based method. These characteristics make the proposed method a potential approach in practical applications.     

基于非刚性运动分析理论的心脏运动估计

针对心脏的运动分析问题,本文提出一种采用非刚性运动分析理论,根据X射线冠状动脉造影图像序列中血管的形态变化分析心脏三维运动的算法.该方法根据已经被临床实验证实的有关心脏运动的先验知识,将复杂的心脏运动分解为整体运动和局部运动,按照从整体到局部、从粗糙到精细的顺序定量估计各运动组成部分的参数.实验结果表明,该算法可以得到心动周期中心脏运动的全面量化描述.     

In-plane impact behavior of honeycomb structures filled with linearly arranged inclusions

Honeycomb structures filled with linearly arranged inclusions were analyzed with a finite element method (FEM) to study how the arrangement of rigid inclusions affects the in-plane impact behavior of honeycomb structures. Each model was divided into several cell regions by inclusion lines. The analysis revealed the effect of inclusion lines on the mean stress of the cell region, maximum displacement of the cell region, and the order of deformed cell regions. Maximum displacement of the cell region was proportional to the width of the cell region, and mean stress of the cell region decreased as the width of the cell region increased. Approximate equations for the maximum displacement and mean stress of the cell region were derived. The approximations accounted for the deformation process of the honeycomb models with inclusion lines and revealed the dependence of the order of the deformed cell region on the mean stress of the regions. The validity of the approximate equations was confirmed by comparing them with experimental results. It was found that the approximate equations enabled us to design the in-plane impact behavior of honeycomb structures filled with linearly arranged inclusions.