平行不对中转子系统的电机电流特性

为通过监测电机电流信号以实现对转子系统故障的识别与诊断,考虑圆盘不平衡因素,建立平行不对中转子系统动力学模型,然后应用拉格朗日方程,推导出转子系统运动微分方程,并以电机的电磁扭矩为纽带,在MATLAB/Simulink环境下建立三相异步电动机—转子系统机电耦合模型,最后应用傅里叶变换对电流信号进行频谱分析,研究平行不对中故障激励下电机电流信号的耦合特性。仿真结果表明:不平行故障会使电流信号激发出的边频分量,随着不平衡量的增大,还会激发出的边频分量;考虑质量偏心,电流信号还会激发出的边频分量,但当时,的边频分量会被淹没,反之,该边频分量则比较明显。     

正弦扭矩激励下单跨转子的电机电流特性

为了通过监测电机电流以实现转子系统扭矩激励的辨识与有关故障的诊断,建立了三相异步电动机——机械转子系统机电耦合模型,在mATLAB/Simulink环境下进行仿真分析,并运用Fourier变换对电机电流信号进行处理,研究了转子系统的正弦扭矩激励与其拖动电机电流的耦合特性。研究结果表明:所建立的机电耦合模型可以研究转子系统在正弦扭矩激励下电机电流的特性,并实现某一频率的正弦扭矩激励的辨识,为研究转子系统动力学设计和故障诊断提供理论依据。     

转角不对中故障的转子系统非线性动力学特征

在刚性转子和小角度不对中量等假设条件下,考虑转子的转角不对中和质量不平衡等因素后,建立了转子系统的动力学模型.首先,根据Lagrange方程推导了系统的运动微分方程.理论分析表明,转角不对中转子系统是一个具有参激振动特征的强非线性振动系统;然后,基于谐波平衡法分析了系统的动力学特性,结果显示,当转子转角不对中时,系统不仅会产生与不平衡类似的工频振动,而且也会产生工频与转子不对中角方向振动频率倍数之和或之差组成的组合频率振动,其振幅与角不对中量和系统的物理参数有关;最后,采用数值方法分析了具有转角不对中故障转子系统的非线性动力学特性.     

变频器供电下异步电动机转子断条故障仿真研究

分析了变频器供电时所产生的谐波对电动机转子断条故障电流信号的影响,基于Matlab／Simulink建立了直接转矩控制变频器供电下异步电动机转子故障系统仿真模型,在变频器不同供电频率下针对电动机转子正常和故障情况进行仿真分析。理论上难了变频器谐波影响下电动机转子故障特征频率的正确性,利用连续细化傅立叶变换和自适应滤波方法实现了变频器不同频率供电下民步电动机转子故障的在线检测。     

双盘转子轴承系统不对中-碰摩耦合故障分析

针对由于轴承不对中而引起不对中-碰摩耦合故障的转子-轴承系统,建立了考虑电机联轴器影响的双盘不对中-碰摩耦合故障转子系统力学模型和有限元模型。基于非线性有限元方法,使用等效不对中力矩及接触理论研究了碰摩刚度和不对中角度两个重要参数对系统动力学特性的影响。通过对在不同碰摩刚度及不对中角度时系统动力学特性的研究分析,发现不对中-碰摩耦合故障常常以碰摩故障特征为主,并且二倍频出现较早及其峰值会急速增大,这一特性可以作为诊断不对中-碰摩耦合故障的一个依据。     

电流与振动信号融合的转子系统故障诊断研究

针对传统转子系统故障诊断信号的单一性,提出了基于电机电流和多传感器振动信号的融合信号的转子系统故障诊断方法。首先在单跨转子试验台上模拟转子系统的不平衡、不对中、碰磨故障,并采集不同故障类型下拖动电机的电流信号及不同位置的振动信号,其次利用小波包能量法对采集的信号进行特征值提取,最后利用贝叶斯网络对转子系统故障类型进行识别。试验结果表明:与只利用电机电流信号或振动信号相比,利用融合信息进行转子系统故障诊断准确率明显提高。     

联轴器不对中故障转子系统的动力学试验

建立了一个多跨转子-轴承系统试验台,并进行了具有联轴器不对中故障的转子-轴承系统动力学试验,重点分析了平行不对中和交角不对中转子的动力学特性和振动机理。试验结果表明,在不对中转子系统的稳态响应中,除了工频外还存在倍频振动分量,并且随着转速的提高倍频分量增大。在转速较低时,不对中转子的轴心运动具有同步振动特征;随着转速的增加,轴心轨迹呈现出"8"字形或多环椭圆形,且轴心轨迹在某些位置处曲率变化较大。对于具有平行不对中故障的转子-轴承系统,在转速较高时,还会出现和差型谐波振动分量。     

笼型感应电机转子断条故障诊断方法

依据多回路理论,本文建立了笼型感应电机正常及断条故障时的有限元模型.应用场路耦合有限元方法对电机转子断条故障前后的定子起动电流波形及气隙磁密基波、三次谐波进行仿真分析,并且仿真结果与利用探测线圈技术和示波器测得的数据进行了比较.另外,应用谐波分析程序得到电流及电压三次谐波随故障演化而变化的规律,从而提取故障特性量.理论研究与实验结果的比较证实了这些方法是切实可行的.     

行星齿轮故障下电机杂散磁场研究

行星齿轮箱在现代工业设备中被广泛使用,但是由于其使用条件恶劣,齿轮箱的部件往往容易发生故障。电机电流特征分析法(MCSA)已被广泛应用到故障监测中,但是由于电机结构的限制电流中并没有包含全部的特征信息。当行星齿轮发生故障时,传动轴转速的瞬态变化会造成电机气隙磁场波动,大部分信息存在于电机的气隙磁场中。同时由于制造误差、装配误差等原因电机转子往往存在着动态偏心故障,行星齿轮箱的故障与电机转子偏心同时存在时,故障的耦合情况还不得而知基于这些事实,本文推导了机电耦合下的三相异步电机气隙磁场特征,给出了转速波动和转角波动对电流的影响,并分析了耦合下的行星齿轮箱故障特征。     

基于非线性输出频率响应函数的转子不对中-碰摩耦合故障诊断方法研究

基于非线性输出频率响应函数(NOFRF)的独特优势,将非线性输出频率响应函数引入到转子不对中-碰摩耦合故障中,提出了基于非线性输出频率响应函数的转子不对中-碰摩耦合故障诊断方法。利用提出的方法辨识得到了不同对中度及其角度的转子系统的NOFRF值,对比分析了不对中度及其角度对转子系统各阶NOFRF值的影响。仿真结果表明随着不对中度和角度的增加,NOFRF中二次谐波二阶非线性输出频率响应函数和二次谐波四阶非线性输出频率响应函数有着较为明显的增幅;一次谐波三阶非线性输出频率响应函数随不对中角度的增加而减小。因此,可以依据二次谐波二阶非线性输出频率响应函数、二次谐波四阶非线性输出频率响应函数、一次谐波三阶非线性输出频率响应函数值的变化规律识别转子系统的不对中程度。最后通过试验结果验证了仿真结果的正确性,研究成果为具有不对中-碰摩耦合故障的转子系统的故障诊断提供了重要的依据。     

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.     

ANGULAR DISTORTION ALLOWABLE VALUE AND ASSESS METHOD OF WELD ON COKE TOWER

A graph as the new engineering method for estimate the safety of bulging deformation of coke tower is proposed. Through stresses analysis of circumferential weld of coke tower and comparing the stresses produced by pressure with heat stress of steady state, residual stress, bending stress produced by both itself weight and wind loads, it showed that the stresses produced by pressure on the angle distortion are the main factor of equivalent stress of the combined stress. After comparing four kinds of stress controlling conditions, the relation to stress with depth of angular distortion, grade of curvature of angular distortion and half of region of angular distortion has been inferred. Graph of deformation allowable value of coke tower for different condition by angular distortion and half of region of angular distortion has been plotted. The five steps for its engineering use have been explained. The lighter the grade of curvature is, the larger of bulge allowance, may be, and the bigger of depth of angular distortion may pose too. For the coke tower with a popular structure of Dg 5 400 mm×28 mm, the result by graph is nearly more than the result of two formulas formed by other research, the error is less than 7.0%. But, the graph can be easily applied to different size of angular distortion.