A review on spindle thermal error compensation in machine tools

Thermal error caused by the thermal deformation is one of the most significant factors influencing the accuracy of the machine tool. Among all the heat sources which lead to the thermal distortions, the spindle is the main one. This paper presents an overview of the research about the compensation of the spindle thermal error. Thermal error compensation is considered as a more convenient, effective and cost-efficient way to reduce the thermal error compared with other thermal error control and reduction methods. Based on the analytical calculation, numerical analysis and experimental tests of the spindle thermal error, the thermal error models are established and then applied for implementing the thermal error compensation. Different kinds of methods adopted in testing, modeling and compensating are listed and discussed. In addition, because the thermal key points are vital to the temperature testing, thermal error modeling, and even influence the effectiveness of compensation, various approaches of selecting thermal key points are introduced as well. This paper aims to give a basic introduction of the whole process of the spindle thermal error compensation and presents a summary of methods applied on different topics of it.     

Fault isolation schemes for a class of continuous-time stochastic dynamical systems

In this paper a new method for fault isolation in a class of continuous-time stochastic dynamical systems is proposed. The method is framed in the context of model-based analytical redundancy, consisting in the generation of a residual signal by means of a diagnostic observer, for its posterior analysis. Once a fault has been detected, and assuming some basic a priori knowledge about the set of possible failures in the plant, the isolation task is then formulated as a type of on-line statistical classification problem. The proposed isolation scheme employs in parallel different hypotheses tests on a statistic of the residual signal, one test for each possible fault. This isolation method is characterized by deriving for the unidimensional case, a sufficient isolability condition as well as an upperbound of the probability of missed isolation. Simulation examples illustrate the applicability of the proposed scheme.     

基于 KPCA-SVM 的表面肌电信号疲劳分类研究

为了提高手臂疲劳模型识别的准确率,本研究在常用时域、频域特征的基础上,引入了时频域、非线性和参数模型特征,提取3通道的表面肌电信号,构成特征集合.特征降维一般分为特征提取以及特征选择,分别采用特征提取中的主成分分析(PCA),核主成分分析(KPCA)方法以及特征选择中的互信息(MI)度量方法进行特征降维,采用支持向量机(SVM)和K近邻(KNN)作为分类器,通过3种降维方法分与SVM和KNN的不同组合构成疲劳分类模型.结果 表明,KPCA与SVM的组合模型对于疲劳的正确识别率最高达到99％,高于其他组合算法.     

基于NDIS中间层驱动程序的网络监测器

研究了W indows网络数据包过滤技术和ND IS,设计并实现了W indows 2000平台下基于ND IS中间层驱动程序的网络监测器,它由ND IS IMD包过滤程序和应用层包处理程序2个模块构成,分别负责网络数据包过滤、过滤条件设置与数据包分析处理。该网络监测器适用于W indows 2000平台下IP层及其上层网络协议数据包的过滤和处理。     

双波段、双通道对接系统测距误差补偿方法研究

为了完成空间航天对接任务,针对复杂光照条件下的对接孔位置测量问题,设计了一种双波段、双通道测距系统,并对其测距误差补偿方法进行了研究.在介绍了系统测距及误差补偿原理后,根据可见、近红外和双目的测距特点及误差分析结果,利用神经网络对双波段数据进行融合补偿处理,实现弱光照、强光照及无光照条件下的对接孔位置测量.通过实验测试...     

基于数据流截获技术的仪器状态监测方案

针对由计算机控制的仪器工作状态监测问题,提出一种基于计算机串口的数据流监测方案,采用纯软件的方式,规避硬件监测的风险,通过截获串口与仪器设备之间的数据流进行模式匹配,实现仪器状态监测。为提高数据流变化的检测效率,采用加权的核拟合密度估计算法代替传统的M-核估计方法,降低系统资源的占用率。     

核磁共振找水仪发射机主回路的设计与仿真

为保证核磁共振找水仪的发射机主回路发射大功率电流,加大探测地下淡水资源的深度,针对发射机主回路在运行中产生的瞬态电压和浪涌电流问题,对几种典型缓冲电路进行了分析与计算。通过仿真实验,确定了发射机主回路的缓冲电路和快速关断电路关键器件的最佳参数。使IGBT（Isolation Gate Bipolar Transistor）的C、E两端瞬态电压尖峰降低了150V,IGBT的电流不超过发射机所能发射的最大电流（最高电流为400A）。从而保证了IGBT的C、E两端电压平稳;保证大功率电流可靠、有效地发射。     

基于多道原子荧光光谱仪的通道合并设计

为进一步改善多道原子荧光光谱仪的检出限,提高检测能力,提出了通道合并的设计思想。阐明了应用这种方法的检测系统的工作原理、硬件构成,并通过与传统方法的实验对比,论证了此设计具有明显降低检出限的优点。     

Research on image encryption based on Erbium-doped fiber laser system with optical delay feedback

A novel image encryption algorithm that based on Erbium-doped fiber laser with an optical delay feedback (ODF-EDFL) system is proposed in this paper. First, by the dynamic analysis of this system, two different chaotic sequences are generated. Meanwhile, the statistic characteristic is verified on this chaotic sequence. On this basis, the image encryption algorithm is designed by using this chaotic sequence: the gray value of the original image is substituted with the chaotic sequence at beginning; then the space array of the image's pixel is mixed up by using both two chaotic sequences. The experimental results show that the proposed method can encrypt digital images quickly and effectively.     

V-doped In2O3 nanofibers for H2S detection at low temperature

Pristine and vanadium-doped In₂O₃ nanofibers were fabricated by electrospinning and their sensing properties to H₂S gas were studied. X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to investigate the inner structure and the surface morphology. The H₂S-sensing performances were characterized at different temperatures ranging from 50 to 170 °C. The sensor based on 6 mol% V-doped In₂O₃ nanofibers exhibit the highest response, i.e. 13.9–50 ppm H₂S at the relatively low temperature of 90 °C. In addition, the fast response (15 s) and recovery (18 s) time, and good selectivity were observed.