Evaluation of circularity from coordinate and form data using computational geometric techniques

Data for evaluating circularity error can be obtained from coordinate measuring machines or form measuring instruments. In this article, appropriate methods based on computational geometric techniques have been developed to deal with coordinate measurement data and form data. The computational geometric concepts of convex hulls are used, and a new heuristic algorithm is suggested to arrive at the inner hull. Equi-Distant (Voronoi) and newly proposed Equi-Angular diagrams are employed for establishing the assessment features under different conditions. The algorithms developed in this article are implemented and validated with the simulated data and the data available in the literature.     

Determination and mapping of measurement and design coordinate systems using computational geometric techniques

Automotive industry is one of the most prospective manufacturing industries in the present world. In order to keep up with the challenges of competitors, the automobile industries are taking necessary steps to satisfy the customers by supplying products of good quality at lower cost. The machine vision inspection systems play an important role in quality control with their accurate dimensional measurement capability. The data obtained from these systems have to be analyzed using appropriate algorithms. In the present work, algorithms based on computational geometric techniques have been developed, to set up the coordinate system for the data obtained from the laser vision system for subframe and lower arm assembly of automobile front chassis module. The concept of a convex hull and a modified Voronoi diagram are utilized for establishing the coordinate system for measurement data. The design coordinate system is determined using the Voronoi diagrams. The measurement and design coordinate systems are mapped using 3D transformations. The results obtained for the sample data are also presented in this paper.     

New evaluation methods for conceptual design selection using computational intelligence techniques

The conceptual design selection, which aims at choosing the best or most desirable design scheme among several candidates for the subsequent detailed design stage, oftentimes requires a set of tools to conduct design evaluation. Using computational intelligence techniques, such as fuzzy logic, neural network, genetic algorithm, and physical programming, several design evaluation methods are put forth in this paper to realize the conceptual design selection under different scenarios. Depending on whether an evaluation criterion can be quantified or not, the linear physical programming (LPP) model and the RAOGA-based fuzzy neural network (FNN) model can be utilized to evaluate design alternatives in conceptual design stage. Furthermore, on the basis of Vanegas and Labib’s work, a multi-level conceptual design evaluation model based on the new fuzzy weighted average (NFWA) and the fuzzy compromise decision-making method is developed to solve the design evaluation problem consisting of many hierarchical criteria. The effectiveness of the proposed methods is demonstrated via several illustrative examples.     

Solar panel modelling through computational intelligence techniques

The efficiency of a solar panel depends on several factors. In particular, the ability to operate in the Maximum Power Point (MPP) condition is required in order to optimize the energy production. The ability to identify and reach the MPP condition is therefore critical to an efficient conversion of the photovoltaic energy. Several techniques to tackle this problem are reported in literature. They differ for the input variables used to compute the MPP as well as the structure of the controller that makes use of the prediction. We focus only on the prediction of the MPP which is related only to the former aspect. In this paper, several computational intelligence paradigms (namely, Fuzzy C-Means, Radial Basis Function Networks, k-Nearest Neighbor, and Feed-forward Neural Networks) are challenged in the task of identifying the MPP power from the working condition directly measurable from the solar panel, such as the voltage, V, the current, I, and the temperature, T, of the panel.     

A study on reliability centered maintenance planning of a standard electric motor unit subsystem using computational techniques

The design and manufacture of urban transportation applications has been necessarily complicated in order to improve its safety. Urban transportation systems have complex structures that consist of various electric, electronic, and mechanical components, and the maintenance costs generally take up approximately 60% of the total operational costs. Therefore, it is essential to establish a maintenance plan that takes into account both safety and cost. In considering safety and cost limitations, this research introduces an advanced reliability centered maintenance (RCM) planning method using computational techniques, and applies the method to a standard electric motor unit (EMU) subsystem. First, this research devises a maintenance cost function that can reflect the current operating conditions, and maintenance characteristics, of components by generating essential cost factors. Second, a reliability growth analysis (RGA) is performed, using the Army Material Systems Analysis Activity (AMSAA) model, to estimate reliability indexes such as failure rate, and mean time between failures (MTBF), of a standard EMU subsystem, and each individual component Third, two optimization processes are performed to ascertain the optimal maintenance reliability of each component in the standard EMU subsystem. Finally, this research presents the maintenance time of each component based on the optimal maintenance reliability provided by optimization processesand reliability indexes provided by the RGA method. This paper was recommended for publication in revised form by Associate Editor Dae-Eun Kim Myung-Won Suh is a professor of Mechanical Engineering. During 1986–1988, he worked for Ford motor company as researcher. During 1989–1995, he worked in the technical center of KIA motors. He earned a BS degree in Mechanical Engineering from Seoul National University and an MS degree in Mechanical Engineering from KAIST, South Korea. He obtained his Doctorate at the University of Michigan, USA, in 1989. His research areas include structure and system optimization, advanced safety vehicle and reliability analysis & optimization. Chul-Ho Bae is a PhD candidate at Sungkyunkwan University in Suwon, South Korea. He ac-complished fellowship work as researcher at Mississippi State University, USA, in 2003 and 2005. He worked in Institute of Advanced Machinery and Technology (IMAT) as a Research Assistant in 2004. He was a part time Lecturer in computer aided Mechanical Engineering of Ansan College of Technology, Suwon Science College, and Osan College during 2004–2005. He took a BS Degree in Mechanical Design and an MS Degree in Mechanical Engineering from the Sungkyunkwan University. His research interests include computer aided engineering, reliability engineering, and optimization.     

应用 Excel - VBA 编制检验报告

基于Excel-VBA设计了报告编制工具“Shortcut”,阐述了工具的结构和代码编写方式,并将Excel-VBA编制方式同常规编制方式进行了比较。结果表明Excel -VBA编制方式编制效果更好,编制效率更高,完全适用于检验报告的编制。     

Super-resolution microscopy using normal flow decoding and geometric constraints

Prior knowledge about the observed scene provides the key to restoration of frequencies beyond the bandpass of an imaging system (super-resolution). In conjunction with microscopy two super-resolution mechanisms have been mainly reported: analytic continuation of the frequency spectrum, and constrained image deconvolution. This paper describes an alternative approach to super-resolution. Prior knowledge is imposed through geometric and dynamic models of the scene. We illustrate our concept based on the stereo reconstruction of a micropipette moving in close proximity to a stationary target object. Information about the shape and the movement of the pipette is incorporated into the reconstruction algorithm. The algorithm was tested in a microrobot environment, where the pipette tip was tracked at sub-Rayleigh distances to the target. Based on the tracking results, a machine vision module controlled the manipulation of microscopic objects, e.g. latex beads or diamond mono-crystals. In the theoretical part of this paper we prove that knowledge of the form 'the pipette has moved between two consecutive frames of the movie' must result in a twofold increase in resolution. We used the normal flow of an image sequence to decode positional measures from motion evidence. In practice, super-resolution factors between 3 and 5 were obtained. The additional gain originates from the geometric constraints that were imposed upon the stereo reconstruction of the pipette axis.     

A reconstruction method using geometric subdivision and NURBS interpolation

Subdivision surfaces (SubD, NURSS) construction is a popular method to present and animate sculpture shapes for entertainment, and this is preferred due to advantage of polygon mesh. But subdivision surfaces have limited familiarity and portability in modern CAD, unlike NURBS-based entities. NURBS-based sculpting using dense point cloud data obtained through geometric subdivision has been so far a less discussed topic. The current work discusses the new methodology of using geometric subdivision and NURBS interpolation with an aim to add a new dimension to reverse engineering. This has distinct advantages like accurate shape building using scanned data, manufacturing ability of complex shapes, faster and accurate shape representation with high quality surfaces, model portability, and a better control on object shape and better patch-planning. Major milestones of the work are bridging the geometric subdivision and NURBS reconstruction on subdivided data, NURBS patch and topology planning (straight and PDPA scan), construction of trimmed NURBS surfaces and, finally, writing IGES of resultant patches. The work is a high-level automation solution for complex constructions. It is applied on human head-scan data and results are displayed.     

基圆旋转法铣削渐开线型腔

对涡旋式压缩机关键零件涡旋盘的渐开线型腔加工提出了基圆旋转法 ,并对其加工精度从编程方法和机床运动方面进行了分析 ,说明基圆旋转法是能保证加工精度的方法之一。     

基于有序Hough变换的快速圆检测算法

针对随机Hough变换（RHT）及其改进算法在同一圆边缘点随机抽样时命中率低且投票处理过程复杂,提出了基于有序搜索的广义Hough变换快速圆检测算法（SQHT）。该算法利用圆的几何性质和梯度方向信息来有序搜索圆边缘点集,将Hough变换的基于投票判定基元参数转变为有效确定基元三点的讨论。执行算法时,首先顺序搜寻第一边缘点并根据邻域边缘点集或图像灰度值计算其梯度值;接着在第一点所在行匹配与其梯度信息相符的第二点,根据前两点信息在第一点所在列匹配第三点;最后按照RHT算法流程确定有效基元参数,从而避免了随机抽样带来的时间不确定性。该算法具有计算速度快,检测时间可控,适用范围广泛,抗干扰性强等特点。相比于RHT算法,提出的算法在单目标圆检测情况下检测效率提高了2倍,在多目标圆（5个及以上）且有非目标边缘点情况下检测效率提高了5倍,在多圆检测方面能有效弥补了Hough变换算法的不足。     

Modeling of eddy current sensor using geometric and electromagnetic data

In this paper a new modeling method for an eddy current sensor is presented using geometric and electromagnetic data of a sensor and a measuring target It can predict not only sensor output but also medium behavior related to sensor output The geometric data of a sensor coil and the eddy current generated on a measuring target are simplified to an array of circular loops. And to perform computations of the network circuit between sensor coil loops and eddy current loops using the geometric and electromagnetic data in order to consider all possible interactions, the equivalent network circuit of eddy current sensor’s behavior has been drawn. Because the sensor’s initial value, medium behavior, and final value can be shown quantitatively by the proposed modeling method as the geometric and electromagnetic data varies, it can precisely predict the sensor output depending on the measuring goal and application field. Thus the model can be utilized to improve accuracy, eliminate the need for calibration before use, and produce the best design for any given purpose.     

利用几何特征和时序注意递归网络的动作识别

为提高基于人体骨架(Skeleton-based)的动作识别准确度,提出一种利用骨架几何特征与时序注意递归网络的动作识别方法。首先,利用旋转矩阵的向量化形式描述身体部件对之间的相对几何关系,并与关节坐标、关节距离两种特征融合后作为骨架的特征表示;然后,提出一种时序注意方法,通过与之前帧加权平均对比来判定当前帧包含的有价值的信息量,采用一个多层感知机实现权值的生成;最后,将骨架的特征表示乘以对应权值后输入一个LSTM网络进行动作识别。在MSR-Action3D和UWA3D Multiview Activity II数据集上该方法分别取得了96.93%和80.50%的识别结果。实验结果表明该方法能对人体动作进行有效地识别且对视角变化具有较高的适应性。     

Nonrigid geometric metrology using generalized numerical inspection fixtures

Freeform surfaces have become an integral part of the automobile and aerospace industries. The parts with a very thin wall in proportion to their size are referred to as nonrigid (or flexible) parts. Generally, for the geometric inspection of such flexible parts, special inspection fixtures, in combination with coordinate measuring systems (CMM), are used because these parts may have different shapes in a free state from the design model due to dimensional and geometric variations, gravity loads and residual strains. A general procedure to eliminate the use of inspection fixtures will be developed. Presented methodology is based on the fact that the interpoint geodesic distance between any two points of a shape remains unchangeable during isometric deformation. This study elaborates on the theory and general methods for the metrology of nonrigid parts. We will merge existing technologies in metric and computational geometry, statistics, and finite element method to develop a general approach to the geometrical inspection of nonrigid parts.     

利用圆心不对称投影精确标定工业相机

工业相机常采用基于圆形控制点的方法进行标定,但该方法存在不对称投影问题,极易产生标定误差。为了避免引入不对称投影误差并能以迭代方式修正这一误差,本文提出了一种利用圆心不对称投影所蕴含信息的相机标定方法。首先,推导了平面模板上的圆形控制点投影成为椭圆之后的理论坐标;然后,提取每一幅标定板图像中实际椭圆的中心坐标,通过最小二乘算法求得该幅图像对应的精确投影变换矩阵;最后,利用所有的投影变换矩阵求出相机内参数。实验结果表明:采用本文提出的标定方法,标定结果的重投影误差降到了1/50pixel。该方法可一次完成标定,计算简单,标定精度高,适用于工业相机的标定。     

光学掩模实现几何超分辨成像的仿真

将基于实际CCD模型的频谱编码方法引入光电成像系统,以克服CCD对空间分辨率的限制,实现几何超分辨成像。介绍了光学掩模实现几何超分辨成像的工作原理,基于实际的CCD模型在4f成像系统的频谱面上放置光学编码掩模来提高图像分辨率。对该成像系统模型进行了数学分析,从理论上证明了这种基于实际CCD模型的频谱编码方法的有效性。根据建立的理论完成了基于一维光学编码掩模方法的仿真实验。仿真结果表明:提出的方法能实现几何超分辨成像,解决了光电成像系统中因CCD欠采样造成的物频谱混叠和因像素尺寸非零而造成的低通效应问题。与传统的超分辨方法相比,该方法的系统结构简单、易实现。     

In vitro and in silico (IVIS) flow characterization in an idealized human airway geometry using laser Doppler anemometry and computational fluid dynamics techniques

The air flow in idealized human airway geometry was studied using computational and experimental methods. A computational fluid dynamics model developed to determine the air flow characteristics in airways was validated by comparison of the experimental velocity profiles obtained with laser Doppler anemometric measurements with numerical data. A good correlation was found between the values obtained with the two methods. Both the measurements and the calculations showed the flow to be laminar in the trachea region of the airway model, but it is affected by the airway geometry in subsequent airways.     

The relationship between the minimum zone circle and the maximum inscribed circle and the minimum circumscribed circle

Following the minimum zone criterion set forth in the current ANSI and ISO standards, evaluation of roundness error is formulated as a non-differentiable unconstrained optimization problem and hard to handle. The maximum inscribed circle and minimum circumscribed circle are all easily solved by iterative comparisons, so the relationship between the minimum zone circle and maximum inscribed circle, minimum circumscribed circle is proposed to solve efficiently the minimum zone problem. Based on the known minimum zone circle, the maximum inscribed circle and minimum circumscribed circle can be easily determined. The relationship is implemented and validated with the data available in the literature.     

Advances in experimental mechanics by the synergetic combination of full-field measurement techniques and computational tools

The continuous improvement of full-field measurement techniques has fostered the development of mechanical testing procedures of increasing complexity. Contemporarily, the design of the experiments and the interpretation of acquired data benefit of the realism of available numerical models and of the enhanced effectiveness of several computing tools. Advances achievable by the synergetic coupling of experimental and computational mechanics are illustrated in this contribution with the aid of some selected applications.     

A study of geometric and true levelling in electroplating using stylus methods

Under suitable conditions the process of electroplating improves the surface characteristics of the workpiece. This effect is called levelling and arises from two fundamental mechanisms: (i) geometric levelling and (ii) true levelling. Assessment of percentage levelling using surface profilometry (R_a) is well established. However, the present work suggests that the use of more complex surface parameters obtained by digital surface metrology gives a better understanding of the mechanisms involved. Since the techniques are both quick and reliable they should form a major tool in the development of plating solutions and the establishment of the optimum plating conditions. The relations between the original surface finish R_a, the average surface slope and the levelling achieved for varying plating thicknesses with geometric levelling and combinations of geometric and true levelling are discussed. Finally some preliminary results are reported for computer simulations of geometric and true levelling of actual surfaces.