基于短时傅里叶变换的滚珠丝杠副丝杠滚道故障定位研究

针对滚珠丝杠副丝杠滚道故障定位困难问题,对存在单一点蚀故障的滚珠丝杠副进行了研究,提出了一种基于短时傅里叶变换(STFT)的滚珠丝杠副丝杠滚道故障定位方法,通过理论分析确定了针对滚珠丝杠副振动信号STFT理想的窗函数及其参数。利用STFT分析了滚珠丝杠副仿真与实验振动加速度信号,根据丝杠滚道出现故障时的频率响应特性以及信号瞬时频率随时间的变化,以瞬时频率为特征确定了故障位置。仿真与实验研究结果对比表明,STFT时频分析方法能够用于有效地识别出滚珠丝杠副的故障位置。     

中空滚珠丝杠副热动态特性分析

以传热学理论为基础,研究滚珠丝杠进给系统主要热源分布及热传导计算,分析中空滚珠丝杠副的热态特性及达到热稳定状态后进给系统的温度场。探讨了多热源作用下滚珠丝杠的一维温度响应,给出了滚珠丝杠系统的热传导方程。通过实验验证了理论结果的正确性,根据滚珠丝杠系统各主要部件的升温曲线对比,获得滚珠丝杠系统的温度场变化规律,并在此基础上分析了滚珠丝杠的热变形,确定滚珠丝杠的热伸长量,从而为滚珠丝杠的优化设计提供了参考。     

端块式滚珠丝杠副振动特性分析

为了分析高速下滚珠丝杠副的振动特性,以端块式滚珠丝杠副为研究对象,考虑螺母移动下的动态特性,建立了滚珠丝杠副的振动模型。首先基于可考虑螺母滚道与丝杠滚道接触界面润滑作用的刚度和阻尼矩阵,建立了柔性滚珠丝杠副的混合模型;其次在滚珠丝杠振动与噪声测试实验台上对振动数据进行了采集与分析;最后利用振动模型并结合实验,分析了不同转速和螺母位置的改变对其振动的影响。分析结果表明,螺母在整个振动系统中扮演着移动支撑的角色,螺母的移动对滚珠丝杠副的振动特性有显著影响。     

高速空心滚珠丝杠副动态性能试验平台的研发

为了研究空心滚珠丝杠副在高速运行状态下的性能状况,研发了一种用于测试高速空心滚珠丝杠副动态性能参数的试验平台。给出了高速滚珠丝杠副动态性能参数测试的实现过程,介绍了试验台机械系统和控制系统的设计方案。该实验平台由机械系统和测试系统两部分组成,选用空心滚珠丝杠副作为被测元件,利用LMS数据采集卡进行数据采集,可完成负载状态下滚珠丝杠副动态性能的在线实时检测。利用该试验平台可以对滚珠丝杠副的加速度、速度、温升、热位移、定位精度等动态性能参数进行测试,为空心滚珠丝杠产品性能的改进提供可靠的实验数据参考。     

滚珠丝杠副转速对摩擦力矩波动影响的分析与测试

根据赫兹接触理论分析了丝杠副滚珠接触的弹性变形量以及由弹性变形所造成的弹性势能。对滚珠进入丝杠滚道的受力过程进行了分析,认为滚珠进入滚道所引起的摩擦力矩变化的波动量与丝杠转速有关,当滚珠速度小于临界速度时,丝杠的摩擦力矩波动较大;当滚珠速度大于临界速度时,丝杠的摩擦力矩波动呈减小趋势。实验数据验证了丝杠在不同速度下摩擦力矩波动随转速变化的分析结果。     

滚珠丝杠副热伸长测量系统设计

针对滚珠丝杠副温位移测量的要求,设计了滚珠丝杆副热伸长测量系统。介绍了试验台的硬件组成及数据采集流程。根据已有的设备制定了2种实验方案,对比分析后采用更符合实际工况的试验方案2,对汉江生产的某型号P3级精度丝杠的热伸长量进行了检测。运用最小二乘法对实验数据进行了处理分析,得出丝杠温升与伸长的关系。     

滚珠丝杠副非协调性接触特性研究

滚珠丝杠副中滚珠与丝杠滚道和螺母滚道的接触是一种典型的非协调性接触,这种接触的特性对滚珠丝杠副的承载能力、传动效率和定位精度等都有着重要的影响。为此,采用Hertz接触理论建立了滚珠丝杠副轴向接触刚度的求解公式,然后从滚珠丝杠副轴向负载、设计参数和材料属性等方面分析了滚珠丝杠副的接触特性,最后运用有限元分析软件ANSYS对滚珠与丝杠滚道的接触进行仿真,仿真结果与理论结果非常相近,从而验证了理论分析的正确性。研究结果为高速、重载和精密滚珠丝杠副的设计与使用提供了理论指导。     

轴向载荷作用下滚珠丝杠副接触变形分析

依据弹塑性接触理论,考虑塑性变形对滚珠丝杠副接触变形的影响,对双螺母预紧的滚珠丝杠副进行了接触受力分析,利用赫兹接触理论、Mises屈服准则建立了滚珠丝杠副弹塑性接触变形的数学模型。以某一型号的滚珠丝杠副为例,分析了轴向工作载荷、螺旋升角及接触角对滚珠丝杠副接触特性的影响。分析结果表明,适当增大螺旋升角、接触角可以有效改善滚珠丝杠副传动性能,为新型滚珠丝杠副的高精度合理设计提供理论支撑。     

基于蠕滑理论的精密滚珠丝杠副摩擦力研究

考虑不同相位角处滚珠所受离心力及摩擦力的影响,建立了双螺母预紧式滚珠丝杠副多自由度动力学模型,该模型不再基于所有滚珠受力相等和运动相同的假设,使用蠕滑力模型来表征滚珠与滚道接触界面间的摩擦力;利用经验模态分解（EMD）包络分析方法进行了滚珠丝杠副振动信号撞击频率的提取,与理论计算结果进行对比,对动力学模型进行了验证;分析了丝杠转速、轴向载荷、滚道曲率比和导程对滚珠丝杠副摩擦力的影响规律。     

滚珠丝杠-螺母副结合部轴向动态特性参数测试与分析

为了获得滚珠丝杠-螺母副结合面轴向动态特性参数,建立了滚珠丝杠-螺母副滚动结合面轴向动力学参数识别模型并研发了测试平台,分析了不同丝杠结构尺寸参数对丝杠轴向动态刚度的影响规律。实验结果表明,丝杠直径、导程、螺旋升角、工作圈数的增大均可提高其轴向动态刚度,而丝杠装配过程中的预拉伸所产生的轴向应变量会减小丝杠结合面轴向动态刚度。最后建立了滚珠丝杠-螺母副结合面轴向动态刚度神经网络预测模型,预测结果表明计算刚度与实测值相差不超过8%。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.