光盘轴向机械动态特性的计算机自动测试系统

光盘系统的开发者和光盘介质的提供者需要一种能自动、方便测量光盘轴向机械动态特性的测试系统 .本文系统介绍了一种新型、基于激光三角法的、适用于自动化生产线的光盘机械动态特性计算机自动测试系统 .系统构成框图、主要测试步骤以及测量结果和对测量结果的分析均在文中给出     

核心机轴向力测量与应用研究

轴向力测量是确定核心机推力轴承载荷的有效手段。介绍了核心机轴向力两类测量方法,即由参数测试值间接估算和用轴向力测量装置直接测量;给出了间接估算法所需的测试参数和估算方法,以及进行弹性环测试所必需的改装;并分析了两种测量方法应用于某型核心机试验中的试验结果。研究结果表明,两种测量方法的测量结果趋势相同,均可以用来测量核心机轴向力。     

行星减速机的反向间隙的测量方法研究

介绍了行星减速机反向间隙的定义,分析了行星减速机的内部传动结构及反向间隙产生的缘由,以及行星减速机反向间隙对其的整体精度的影响.对塞规测量和咬铅条法这两种常见的测量反向间隙的方法进行比较.最终根据现场实际状况以及摆杆偏摆的理论模型,给出了一种比较简易快速的行星减速机反向间隙的测量方法,给出了判断反向间隙是否超标的依据.     

启动光盘的制作原理及过程

启动光盘是指可以启动计算的一种特殊光盘，它分为单引导和多重引导启动光盘两种，其制作技术较新。本文重点介绍了启动光盘原理及其制作方法。     

评价磁记录盘机械特性的方法

本文提出了三种评价磁记录盘机械特性的方法。 第一种方法关系到盘的润滑,因此能用新开发的装置精密地测量出头盘之间的摩擦系数及粘着力。 第二种方法关系到头盘之间的接触,因此能用浮动的带有声发射信号传感器的头浮动快检测出凸起物的高度分布。 第三种方法关系到轴向偏摆加速度与飞行高度的波动,因此能计算出盘轴向运动的允许范围。     

一种基于Linux的附网光盘镜像服务器的研究与实现

本文研究了附网存储的体系结构和关键技术，分析了它在实现光盘镜像服务器时的运用，并阐述了一种基于Linux的光盘镜像网存储服务器的设计方案及部分实现。     

一种吊钩摆角远程无线监测系统的设计

起重机吊装作业中吊钩若出现偏摆则可能会造成事故,因此加强吊钩摆角监测十分重要.在充分分析了起重机吊装作业的实际环境,以及对吊钩偏摆监测的应用模式基础上,提出了一种基于微机电系统(MEMS)的吊钩摆角无线测量方案,通过测量吊钩的姿态角与起重机的方位角,建立数学模型,进行融合计算得出吊钩的偏摆角.所设计的系统采用JY901模块作为传感单元,以ZigBee作为无线传感网络,采用3G通信技术将数据传输到云端解析,最后基于B/S模式进行远程监测.该系统易于安装,便于监测,完全适用于起重机现场的作业环境.     

用IT技术进行频率精确与快速测量方法的研究

工频频率的检测历史悠久。以往工频频率的测量方法存在计算量偏大，在测量精度和测量速度上不能获得较好统一的缺点，影响了实际应用。本文提出了一种新的频率测量方法——“周期查表法”，利用测周期记数结果，可直接从数据表（已建立的）中查得与之一一对应的工频频率!快速而精确，并进而，探索出了一种由单片机控制的频率测量控制系统。     

一个图书光盘资料在线下载插件的设计与实现

在研究现有网络图书光盘资料访问方式的基础上,本文提出了一种新的图书光盘资料下载方式,描述了一个图书资料在线下载插件的设计与实现.首先对设计思想进行了探讨,简要介绍了插件的设计方案,分析了插件的一些关键性技术并给出了一个应用举例.最后,进行了总结和展望.     

高性能光盘镜像服务器的研究与实现

随着网络上光盘资源的增长，光盘镜像服务器成为光盘网络接享的重要技术。针对传统光盘镜像服务器的缺点，文章实现了一个新的基于iSCSI协议思想的高性能光盘镜像服务器，详细介绍了这种光盘镜像服务器的设计方案，并进行了相应的试验测试和性能分析。     

A corotational procedure that handles large rotations of spatial beam structures

A practical motion process of the three dimensional beam element is presented to remove the restriction of small rotations between two successive increments for large displacement and large rotation analysis of space frames using incremental-iterative methods. In order to improve convergence properties of the equilibrium iteration, an n-cycle iteration scheme is introduced.

The nonlinear formulation is based on the corotational formulation. The transformation of the element coordinate system is assumed to be accomplished by a translation and two successive rigid body rotations: a transverse rotation followed by an axial rotation. The element formulation is derived based on the small deflection beam theory with the inclusion of the effect of axial force in the element coordinate system. The membrane strain along the deformed beam axis obtained from the elongation of the arc length of the beam element is assumed to be constant. The element internal nodal forces are calculated using the total deformational nodal rotations. Two methods, referred to as direct method and incremental method, are proposed in this paper to calculate the total deformational rotations.

An incremental-iterative method based on the Newton-Raphson method combined with arc length control is adopted. Numerical studies are presented to demonstrate the accuracy and efficiency of the present method.     

Vertebral axial rotation measurement method

This study presents a new method for measuring axial rotation of vertebra. Anatomical landmarks of the vertebral body were first recognized in X-ray film. By employing appropriate geometrical relationships, vertebral body shape parameters and a computer iteration method, the rotation angle of vertebra on the transverse plane can rapidly be obtained. A cadaver lumbar spine axial rotation-fixation device was designed to confirm the accuracy of the proposed methodology. Rotation angles on CT images were adopted as the golden standard and compared with analytical results based on X-ray films. Analytical results demonstrated that the proposed method obtained more accurate and reliable results than previous methods.     

An effective method of determining the residual stress gradients in a micro-cantilever

A method of determining the micro-cantilever residual stress gradients by studying its deflection and curvature is presented. The stress gradients contribute to both axial load and bending moment, which, in prebuckling regime, cause the structural stiffness change and curving up/down, respectively. As the axial load corresponds to the even polynomial terms of stress gradients and bending moment corresponds to the the odd polynomial terms, the deflection itself is not enough to determine the axial load and bending moment. Curvature together with the deflection can uniquely determine these two parameters. Both linear analysis and nonlinear analysis of micro-cantilever deflection under axial load and bending moment are presented. Because of the stiffening effect due to the nonlinearity of (large) deformation, the difference between linear and nonlinear analyses enlarges as the micro-cantilever deflection increases. The model developed in this paper determines the resultant axial load and bending moment due to the stress gradients. Under proper assumptions, the stress gradients profile is obtained through the resultant axial load and bending moment.     

Robust design optimization of electro-thermal microactuator using probabilistic methods

Micromachining of microelectromechanical systems which is similar to other fabrication processes has inherent variation that leads to uncertain dimensional and material properties. Methods for optimization under uncertainty analysis can be used to reduce microdevice sensitivity to these uncertainties in order to create a more robust design, thereby increasing reliability and yield. In this paper, approaches for uncertainty and sensitivity analysis, and robust optimization of an electro-thermal microactuator are applied to take into account the influence of dimensional and material property uncertainties on microactuator tip deflection. These uncertainties include variation of thickness, length and width of cold and hot arms, gap, Young modulus and thermal expansion coefficient. A simple and efficient uncertainty analysis method is performed by creating second-order metamodel through Box-Behnken design and Monte Carlo simulation. Also, the influence of uncertainties has been examined using direct Monte Carlo Simulation method. The results show that the standard deviations of tip deflection generated by these uncertainty analysis methods are very close to each other. Simulation results of tip deflection have been validated by a comparison with experimental results in literature. The analysis is performed at multiple input voltages to estimate uncertainty bands around the deflection curve. Experimental data fall within 95 % confidence boundary obtained by simulation results. Also, the sensitivity analysis results demonstrate that microactuator performance has been affected more by thermal expansion coefficient and microactuator gap uncertainties. Finally, approaches for robust optimization to achieve the optimal designs for microactuator are used. The proposed robust microactuators are less sensitive to uncertainties. For this goal, two methods including Genetic Algorithm and Non-dominated Sorting Genetic Algorithm are employed to find the robust designs for microactuator.     

Longitudinal vibration of carbon nanotubes with elastically restrained ends using doublet mechanics

Free axial vibration analysis of axially restrained carbon nanotubes (CNTs) is studied within the framework of doublet mechanics theory. Fourier sine series are utilized for describing the axial deflection of the carbon nanotube. An eigenvalue approximation is constructed for vibrational modes with the aid of Stokes’ transformation to deformable axial springs. This unclassified approximation bridges the gap between the deformable and rigid boundary conditions. The comparison studies are carried out to verify the efficiency and accuracy of the proposed analytical model by assigning proper values to elastic spring coefficients. The results indicate that the axial springs and small scale parameter of carbon nanotube have considerable effects on the axial vibration behavior of NTs. Similarly, the dependencies of the vibration frequencies on material scale parameter and axial restraints are significant. Similar higher order effects are predicted for other nano or micro structures, all of that confirmed the smaller is stiffer phenomenon.

     

基于神经网络的不可靠数据恢复研究

智能系统中单点或少数传感器采集的数据在某一段时间出现不可靠问题,在装备有许多传感器的智能系统中普遍存在,即使在由先进的传感器构成的桥梁结构健康监测系统中,80%以上的虚假报警也是由于测量数据的不可靠性造成的.传统上对于不可靠数据的处理主要应用线性回归法、平均法等方法进行恢复,然而,大多数测量数据在时域上表现为非线性特征,传统方法恢复的数据在精度上是很难达到要求.以桥梁挠度数据作为研究对象,利用原始数据对挠度测量点进行了关联分析,并依据RBF神经网络强大的函数逼近能力,提出了一种基于神经网络模型来恢复不可靠测量数据的方法,并在仿真实验中,通过对比实验(该方法的均方误差为2E-9,线性回归法均方误差为0.6974)证实了该方法在理论和实践上的精确性和可行性.     

边缘识别的二维正交多项式拟合及结构变形检测

数字图像中边缘附近的灰度是沿边缘方向和跨边缘方向二维变化的,以前边缘识别的多项式拟合大多采用跨边缘方向的一维拟合。介绍一种采用二维正交多项式进行边缘识别的新方法,由于二维拟合更符合边缘附近小区域内像素灰度二维变化的实际,因此拟合结果优于一维拟合。在进行拟合时,利用正交多项式的正交性将优化方程对角化,避免求逆或解方程,没有多项式拟合优化方程的病态问题,采用高阶多项式拟合可以提高拟合精度。对生成图像的边缘识别结果表明,二维正交多项式拟合识别边缘的精度和稳定性较好。简支梁模型试验表明,采用正交多项式边缘拟合方法检测梁的静变形,图像变形检测精度在0.1像素之内,适当选择图像采集设备和采集范围,点检测精度与传统检测方法的精度相当,边缘检测属线状高密度检测,检测范围远大于传统方法。     

An improved method for on-line calculation and compensation of the static deflection at a robot end-effector

Traditionally, robotic deflection analysis for a low-weight robot has been performed based on an assumption that each link is treated as a cantilever beam, which leads to no angular deflection at a joint. In practice, a robotic intermediate joint is linearly and angularly deflected when a load is applied at the end-effector. It is found in this study that the additional link deflection resulting from the angular deflection of a robotic revolute joint substantially contributes to the end-effector's total deflection. This article presents an improved method via a combination of classical beam theory, energy methods and the concepts of differential relationships to more accurately calculate the static deflection at the end-effector. A systematic approach to deflection calculation through three different Jacobians are presented. The study also shows that the end-effector's deflection heavily depends on robotic arm configurations. The deflection is then compensated based on the selected optimum configuration. The theoretical deflection analysis is verified by experimental results. A planar two-link robot and a six-degree-of-freedom Elbow Manipulator are used for numerical illustration and calculation procedure.     

无线MEMS电容式加速度传感器在港口吊机动挠度测试中的应用

港口吊机抓斗运行时,横梁将产生动挠度.动挠度仪或涡流传感器可以直接测量物理位移,但需要固定的安装点,其使用环境受限.动挠度信号主要以低频为主,普通的直接安装在吊机梁上的传感器因不能测得低频信号而无法测量动挠度.为此,开发了种基于电容式低频振动传感器的无线动挠度测试系统,相对目前其他动挠度测试仪器及测试方法,系统使用方便...     

Series method for analyzing 3D nonlinear torsional divergence of suspension bridges

A simplified method for analyzing 3D nonlinear torsional divergence of suspension bridges is proposed in this paper. The geometric nonlinearity in the deflection theory and the three components of displacement-dependent wind loads are taken into account in the method. This method is a two-step process: the calculation of deflection response under the displacement-dependent wind loads, and the calculation of the critical wind velocity. The response under the displacement-dependent wind loads is calculated from Fourier series. The critical wind velocity is calculated by means of an iterative method. It is found that a small number of iteration cycles and Fourier coefficients are sufficient enough for convergence. The advantages of the proposed method are showed by a comparing the numerical results of this method with those obtained from the linear method and nonlinear finite element methods.