数控铣床光电跟踪伺服系统仿真及优化研究

数控铣床控制系统的稳定性、动态性能和稳态性能是影响加工精度的关键因素.本文对数控铣床的原光电跟踪控制系统进行了SIMULINK仿真分析计算,针对其性能上的不足,提出了基于PID校正的三种改进方案.利用MATLAB建模进行全数字的系统仿真.通过仿真结果的比较分析,提出合理的系统优化方案,最终确定较好优化参数KP、TI、TD,使控制系统性能得到提高.     

白车身扭转刚度分析与优化

对某白车身建立有限元模,利用MSC Nastran软件进行扭转刚度和模态分析,在此基础上以车身重量为优化目标,在满足扭转刚度要求的条件下对零件厚度进行敏感度分析和优化分析,得到了符合设计要求的改进方案.     

叉指微加速度计的设计与闭环检测研究

设计了一种“叉指式”微机械加速度计和相应的闭环检测电路,介绍了此微加速度计的加工工艺,并使用Ansys软件进行了模态分析和机械分析,仿真结果跟理论计算相吻合。最后对该闭环微加速度计进行了测试,得到的测量线性度为2.5%,刻度因子为3V/g。     

A note on a linear time algorithm for constructing adjacency graphs of 3D FEA data

In this paper, we present an algorithm for constructing adjacency graphs of 3D finite element analysis (FEA) data. Adjacency graphs are created to represent the connectivities of FEA data cells. They are used in most visualization methods for FEA data. We stress that in many engineering applications FEA data sets do not contain the adjacency information. This is opposite to computer-aided geometric design where, e.g., the winged edge geometrical representation is usually generated and utilized. By establishing intermediate data structures and using bin-sorting, we developed an efficient algorithm for constructing such graphs. The total time complexity of the algorithm is linear in the number of data cells.     

Multilevel optimization of composite panels under complex load and boundary conditions

Due to their complexity and large numbers of design variables, aerospace structures, such as aircraft wings, are best optimized using a multi-level process. In addition to simplifying the optimization procedure, such an approach allows a combination of different methods to be used, increasing the efficiency of the analysis. This paper presents a technique based on the usage of exact finite strip software, VICONOPT, with the finite element analysis package, ABAQUS. The computer programme VICONOPT is computationally efficient but provides solutions for a restricted range of geometries and loading conditions. Finite element analysis allows accurate models of structures with complex geometries to be created but is computationally expensive. By combining the two, these limitations are minimised, whilst the strengths of each are exploited. The fundamental principles of this multi-level procedure are demonstrated by optimizing a series of curved composite panels under combined shear and in-plane bending subject to buckling constraints. Presented at the 7th World Congress on Computational Mechanics, LA, USA, July 2006.     

基于有限元法液压支架底座的结构优化

为提高液压支架底座的可靠性和稳定性,对ZZC8800/20/38型六柱支撑式固体充填液压支架底座进行有限元分析;建立底座模型并进行分析,确定其危险工况和其加载的方式;建立有限元模型并对其分析,确定了应力集中和位移变形最大位置以及每种危险工况的加载方式。根据有限元的分析结果,对底座结构进行拓扑优化,并以质量、最大应力和最大变形位移为优化目标,进行尺寸优化。优化后底座最大应力最大减小了79.7%,最大变形位移最大减小了53%,质量减少了3.7%,底座的整体强度得到了提高,同时实现了底座的轻量化,疲劳损伤和变形位移较小,达到了预期的优化目的,安全系数均得到了提高。     

磁浮列车底盘梁的有限元优化减重设计

为在已有型号基础上获得更轻型有效的底盘梁结构而保持相对稳定的动力特性,首先利用ANSYS软件建立磁浮列车车体结构的有限元模型,利用Block Lanczos Method进行模态求解并得到结构一阶弹性固有频率.然后以结构一阶弹性固有频率值为约束函数,以车厢底盘梁8个截面上17个主要厚度参数为设计变量,以底盘梁总体积为目标函数,建立磁浮列车底盘梁减重优化的数学模型并进行计算.结果表明,磁浮列车一阶弹性固有模态为前后扭转的振型,在满足模态频率值不小于8.OHz的设计要求下,底盘梁减重20%的设计目标可以达到.说明以一阶弹性固有模态频率值为约束函数的优化方案可行且效果良好.     

非满管电磁流量计权重函数有限元数值分析

采用有限元数值分析法,对长弧形电极非满管电磁流量传感器的权重函数进行了研究,并给出了不同液位下的权重函数分布图谱。计算结果表明,非满管电磁流量传感器的权重函数与管内液体充满度有关,两者呈复杂函数关系。该研究结果为优化非满管电磁流量传感器结构提供了理论依据。     

基于有限元分析的ICF靶半自动装配系统的微夹钳设计

根据惯性约束聚变(ICF)靶零件的特点,确定用于ICF靶半自动装配系统微夹钳的技术指标,并完成其结构设计.该微夹钳采用柔性铰链机构和压电陶瓷驱动,可根据需要更换不同形状和开口距离的夹口,以适应夹持不同靶零件.以压电陶瓷的2种极限参数为载荷,分析了微夹钳的张合量、应力分布、应变量,并采用非线性接触分析对夹持力和夹持效果进...     

Optimization of the shape (and topology) of the initial conditions for diffusion parameter identification

The design of an experiment, e.g., the setting of initial conditions, strongly influences the accuracy of the whole process of determining model parameters from data. We impose a sensitivity-based approach for choosing optimal experimental design variables and study the optimization of the shape (and topology) of the initial conditions for an inverse problem of a diffusion parameter identification. Our approach, although case independent, is illustrated at the FRAP (Fluorescence Recovery After Photobleaching) experimental technique. The core idea resides in the maximization of a sensitivity measure, which depends on a specific experimental setting of initial conditions. By a numerical optimization, considering radially symmetric shapes only, we find an interesting pattern of increasingly complicated (with respect to connectivity) optimal initial shapes. The proposed modification of the FRAP experimental protocol is rather surprising but entirely realistic and the resulting enhancement of the parameter estimate accuracy is significant.     

On the Wiberg Algorithm for Matrix Factorization in the Presence of Missing Components

This paper considers the problem of factorizing a matrix with missing components into a product of two smaller matrices, also known as principal component analysis with missing data (PCAMD). The Wiberg algorithm is a numerical algorithm developed for the problem in the community of applied mathematics. We argue that the algorithm has not been correctly understood in the computer vision community. Although there are many studies in our community, almost every one of which refers to the Wiberg study, as far as we know, there is no literature in which the performance of the Wiberg algorithm is investigated or the detail of the algorithm is presented. In this paper, we present derivation of the algorithm along with a problem in its implementation that needs to be carefully considered, and then examine its performance. The experimental results demonstrate that the Wiberg algorithm shows a considerably good performance, which should contradict the conventional view in our community, namely that minimization-based algorithms tend to fail to converge to a global minimum relatively frequently. The performance of the Wiberg algorithm is such that even starting with random initial values, it converges in most cases to a correct solution, even when the matrix has many missing components and the data are contaminated with very strong noise. Our conclusion is that the Wiberg algorithm can also be used as a standard algorithm for the problems of computer vision.