MEMS magnetometer based on magnetorheological elastomer

To develop a simple and low-cost MEMS magnetometer, a novel sensor based on the magnetostrictive effect of magnetorheological elastomer is proposed. The micromechanical sensor consists of a silicon sensitivity diaphragm embedded with a piezoresistive Wheatstone bridge, and a magnetorheological elastomer layer attached on the sensitivity diaphragm. The interaction between the magnetic field and the elastomer generates a deflection of the sensitivity diaphragm, which changes the piezoresistance and unbalances a Wheatstone bridge. The experimental results show that the sensor has good linearity in the magnetic field range of 0-120 kA/m and the saturation magnetic field is ∼150 kA/m. This simple, low-cost, low-power sensor is easily integrated with electronic circuits using the MEMS processes.     

Highly-sensitive analog magnetometer based on a null-picovoltmeter

The principle of measurement of small magnetic moments using superconducting null-picovoltmeter (SNPV) is described. It is shown that in the mode with optimal voltage sensitivity (≥10^–12 V), the sensitivity of SNPV to a magnetic moment can reach 10^–8 emu, the level only implemented in SQUIDs. An example is given of using SNPV to measure the magnetic susceptibility of superconducting diamagnetic and paramagnetic samples, approximately 1 mm³ in volume, with different signs of the magnetization in the magnetizing alternating magnetic fields with induction of about 1 G, at low temperatures.     

基于FLANN的三轴磁强计误差校正研究

提出一种基于函数链接型神经网络(FLANN)的三轴磁强计误差修正方法.由于三轴非正交、灵敏度不一致及零点漂移所引起的误差降低了三轴磁强计的测量精度,因此有必要进行校正.本文先对与三轴磁强计系统参数有关的测量进行详细分析和理论计算;然后,设计矩阵形式的数学模型对该误差进行修正.通过构造相应的FLANN网络结构,实现对模型参数矩阵的辨识.用实际地磁场测量数据进行测试,结果表明,三轴磁强计的转向误差由800 nT修正到12 nT以下.因此,该研究为提高三轴磁强计性能提供了一种可行方法.     

A novel vibration isolator for vibrating screen based on magnetorheological damper

Journal of Mechanical Science and Technology - A vibrating screen is widely used in raw coal screening, but intensive resonance in the startup and shutdown stages shortens the service life of the...     

基于球形反馈线圈的三轴磁通门磁强计

在高精度三轴磁通门磁强计的设计中,均匀的反馈磁场有助于提高仪器输出的温度稳定性和线性度,同时也可在一定程度上减小由于磁强计各个分量互扰产生的零点偏移。通过简单的物理模型计算,提出了球形反馈线圈的设计方案,并给出了ansys电磁场仿真结果及反馈线圈内部磁场均匀性测试实验结果。经过测试,在此基础上制作的实验样机的线性度达到0.0038%FS,灵敏度温度系数达到0.0000755%FS/℃,且噪声性能也达到9.0807pT/(Hz)～(1/2)。     

基于HYPERWORKS的某客车车架有限元分析

车架是汽车重要的基础部件之一,须具有足够的强度和刚度.应用HYPERWORKS建立了车架的有限元模型,根据对该模型进行的受力分析,施加了合理的约束条件和载荷,对车架最为典型的四种工况进行了静力学研究,并根据车架的应力应变云图,预测出车架的薄弱部位,提出了前瞻性的建议,为车架的优化设计和车架结构的改进提供了非常重要的理论依据.     

基于无迹卡尔曼滤波和设备的三轴磁强计校正

采用无迹卡尔曼滤波(unscented Kalman filter,UKF)磁强计模型参数估计方法,提出对三轴磁强计的总量及分量误差进行校正。采用高精度质子磁力仪提供磁场基准值,借助无磁转台实现磁强计全方位转动,对一款DM-050三轴磁强计进行了参数估计,并将参数估计值运用到总量和分量校正。仿真结果表明,参数估计值与磁强计实际参数值一致。校正后,磁强计总量误差从427.9 nT减少到2.06 nT;X、Y、Z轴分量误差分别减少到1.84 nT、1.96 nT、1.72 nT。而且证明了UKF对磁强计模型参数估计的重复性良好,并研究了噪声幅度大小对UKF的性能影响程度。实验结果表明,磁强计误差从114.94 nT减少到14.47 nT,表明该方法能有效提高磁强计测量精度。     

一种基于磁强计和倾角传感器的钻井测斜仪

描述了利用两轴倾斜角传感器与三轴磁强计测量钻井过程中的地下钻具顶角、磁方位角和工具面角的方法。针对目前已公开的磁方位角的解算数学模型存在缺陷的问题,结合空间坐标变换、空间直线方程和狗腿角的定义推导出磁方位角的数学模型,并给出了详细的软件和硬件实现方案及测斜仪工作流程。测试结果表明,该方案能获得精准的钻具姿态数据,顶角和工具面角数据非常稳定,磁方位角数据在±1°范围内波动,且成本低廉、体积小巧,是钻井测斜的理想选择。     

基于高斯牛顿迭代算法的三轴磁强计校正

三轴磁强计存在各轴刻度因子、零偏和轴间非正交性误差,需要研究其校正方法。基于标量校正法思想,对磁强计校正模型进行了推导,提出基于高斯牛顿迭代法的磁强计校正方法。采用高精度质子磁力仪提供磁场基准值。借助无磁转台转动磁强计,转动过程中磁强计连续采样,测量数据更具代表性和实用性。仿真结果表明,磁强计误差从162.135 nT降低到1.467 nT。实验结果表明,校正后,磁强计绕3个轴转动的测量值误差分别从1133.887 nT、1317.554 nT、1303.994 nT降低到36.964 nT、20.922 nT、15.664 nT。表明该方法能有效降低磁强计测量误差,磁强计精度明显得到提高。     

基于ANSYS的单梁筛分析和改进

以新型结构筛—单梁激振筛为研究对象,用动力学基本原理作为基础,以有限元分析软件ANSYS为主要工具,结合单梁激振筛的结构特点,建立了单梁激振筛的系统动力学模型,对振动筛进行了系统动力学研究。同时,在设计分析的基础上利用ANSYS软件对结构进行优化,以提高振动筛结构的可靠性和各零部件设计的合理性。     

A high accurate static contact angle algorithm based on Hough transformation

The static contact angle for blurry drop images is more intricate to obtain. To improve the accuracy of the Hough transformation for the static contact angle calculation, the water drop images with different volumes are generated by the Laplace equation, and the influence of the volume on the accuracy of the Hough transformation is analyzed. The results reveal that the circle Hough transformation is particularly well suited to the cases with small drop volume. At the same time, the critical water drop volume value corresponding to a contact angle error of 3° is given, a modified Hough transformation algorithm in conjunction with the critical water drop volume is proposed, and at the same time, the accuracy of the static contact angle calculation for blurry water drop images is significantly improved. The proposed algorithm is a powerful approach to estimate the static contact angle for blurry water drop images.     

基于ANSYS的振动筛偏心轴模态分析

为了确定振动筛偏心轴的振动特性,通过工程分析软件ANSYS对其进行了建模与模态分析。详细阐述了模态分析的全过程,从建模环境的选择,偏心轴实体模型和有限元模型的建立,到最后的模态分析。其中,有限元建模中用弹性支承单元COMBIN14代替将轴承简单处理为刚性约束的方式,更加真实的分析得出轴的前10阶固有频率和振型。对比传递矩阵法,方法简便,计算快捷,得到直观振型形象。模态分析有效预估了结构的振动特性,为选择电机参数提供依据,并为谐响应分析及瞬态分析奠定基础。     

基于SVDD的分类新方法

为了实现对大规模数据集的分类,提出了一种基于支持向量数据描述（SVDD）的新算法。把两类的支持向量机（SVM）问题转化为软间隔的SVDD问题,然后用核集迭代的方法得到了近似最优解。实验结果表明,提出的算法与传统的SVM方法预测精度相当,但是训练时间和测试时间更短,产生的支持向量数也更少,适用于大规模数据的分类。     

A novel magnetostrictive static force sensor based on the giant magnetostrictive material

In order to realize static force measuring and improve the sensitivity of magnetostrictive force sensor, a novel magnetostrictive static force sensor with giant magnetostrictive material rod is presented. A Hall sensor integrated in the sensor is used to measure magnetic flux density variation under force. A special structure surrounding Hall sensor is proposed to improve the sensitivity. The design method of the giant magnetostrictive force sensor is expounded firstly. The magnetic characteristics are analyzed by FEM. A model is developed based on the coupled linear magnetomechanical constitutive equations and the experimental result shows that the model is good at reflecting the force. The optimal bias magnetic field and sensitivity are studied through experiments. The sensor sensitivity is 6.14 times higher than that of the sensor which dose not have a stainless steel ring. The paper lays a foundation for the development of magnetostrictive force sensor with giant magnetostrictive material.     

基于UBET的振动挤压螺纹扭矩的有限元动态仿真

刀具所受扭矩是设计机床、夹具等的必要依据。根据金属塑性成形理论,利用上限元法(UBET)建立了振动挤压攻丝的数学模型。并利用DEFORM-3D对内螺纹的振动挤压进行了模拟。研究了内螺纹的振动挤压成形,分析了工件预制底孔直径、冷却润滑液种类等影响振动挤压攻丝扭矩的主要因素,根据模拟结果揭示出各主要因素对攻丝扭矩的影响及其变化的基本规律。这些规律对减小扭矩、提高内螺纹质量、改善攻丝效果都有一定理论和实践指导意义。     

基于智能控件化虚拟仪的振动筛动态特性检测

介绍了振动筛动态特性测试的必要性，基于秦氏模型的概念和原理，将智能控件化虚拟仪器这一全新的概念引入振动筛的动态特性检测过程中。并以振动筛阻尼系数、固有频率和振型为例，介绍了基于智能控件化虚拟仪器技术的钻井振动筛动态特性检测方法。     

A theoretical experimental method based on modal analysis for estimating the damping capacity of vibrating structures

The purpose of the present paper is to suggest a methodology to study quantitatively the damping features of vibrating structures. These features are given as function of the time necessary for the structure to dissipate a pre-fixed percentage of the energy provided by an ideal external impact excitation. The dissipation can derive either from internal friction of the material or from eventual dampers really existing in the system. In this paper the proposed computation, based on the parameters obtained by experimental modal analysis is used only for proportional damping but it can be extended to other types of damping.     

一种小波变换与矢量量化结合的图象压缩编码算法

本文提出了一种新的小波变换与矢量量化相结合的图象压缩编码算法.首先根据小波图象中各子带系数的带间相关性对其进行四叉树分类,然后利用同一子带内高频系数的兄弟相关性采用变换的方法进行系数重排,以产生新的树结构.最后,根据系数的重要性,利用剪枝算法从每棵树中提取一个矢量,进行矢量量化编码.试验证明,在较高压缩比的情况下,使用此方法得到的重构图象质量（视觉效果和峰值信噪比）比通常的小波压缩算法有了较大的提高.     

基于系统聚类和自适应量子遗传算法的钢卷拼卷方法

为解决冷轧薄板厂冷轧机组的钢卷拼卷问题,建立了该问题的多目标多背包模型.该模型考虑拼卷方式和最大卷重约束,并将最大化拼卷数和最小化卷重偏差作为模型的评价目标.首先,利用系统聚类法确定钢卷分类和背包中心,简化模型的求解;随后设计一种自适应量子遗传算法,求解每类钢卷的拼卷模型,构造的量子门旋转角度和量子非门变异率根据种群的聚散程度和进化状态自适应调节,在保证算法寻优能力的同时,加快了算法的收敛速度.最后对经典背包问题和实际生产数据进行了仿真,结果表明,所提的模型和算法可行且有效.     

静力压桩机自动调平系统的逆动力学模型研究

静力压桩机调平系统的逆向动力学模型是求解自动调平控制系统的关键,压桩机实时控制过程中出现"虚腿"的原因之一即是缺少动力学分析.为此,从压桩机的结构入手,考虑平台运动和液压控制系统的耦合,建立调平机构动力学模型,并对其进行动态过程研究,结果满足调平系统快速高精度的要求,自动调平运动过程中未出现"虚腿"现象.