不平衡磁拉力作用下裂纹转子系统的分岔

针对大型旋转机械转子系统机电耦合具有强非线性特征的问题,根据磁拉力与转子偏心的关系,推导出不平衡磁拉力(Unbalanced magnetic pull,UMP)的解析式,建立UMP作用下裂纹转子—轴承系统的动力学模型,并采用数值积分方法研究此类裂纹转子的分岔与混沌特性.通过分岔图、Poincaré图和频谱幅值图分析UMP和裂纹深度对转子运动的影响,结果表明:UMP使转子系统随速度变化的典型动力学响应有所提前,振幅增大,幅值谱图中出现了连续幅值较大的谐波分量;随着裂纹深度的不断增加,转子系统在亚临界转速区出现了短暂的混沌运动,在临界转速附近的混沌区域不断减小,其混沌特征有所变化,且进入混沌区域的倍周期分岔运动基本消失,而在超临界转速区则出现了较长的周期7运动.研究结果为深入解析机电耦合转子系统故障机理提供有益的理论参考.     

磁齿轮啮合型双转子电机建模及控制器设计

磁齿轮啮合双转子永磁电机将永磁电机结构与磁力齿轮结构融合,可以实现低转速大转矩输出,对于提高电机的运行效率和转矩密度开辟了崭新的思路。但是,这类元件的机电动力学建模以及高性能控制却是个亟待解决的问题。文章旨在建立磁啮合电机的机电耦合动力学解析模型,掌握控制器参数对驱动系统性能的影响规律。从电机运行原理出发,将磁啮合电机的电枢-高速转子部分等效为永磁同步电机子模型,而磁力齿轮部分等效为具有弹性相互作用的双转子动力学子模型,两部分通过高速转子转速相结合。在MATLAB/Simulink中建立了磁啮合电机数值模型,同时使用PID控制对整个系统进行调控。利用PID参数整定方法,对控制器系统的性能进行仿真和优化。仿真结果表明,虽然系统存在非线性和耦合问题,但是整定后的PID控制可以使系统对输入信号进行良好跟踪,系统能够达到较好的综合性能指标。     

强非线性条件下的磁轴承高速电动机

为解决磁轴承高速电动机转子中,永磁电动机磁偏拉力与转子残余不平衡导致的磁轴承电磁力非线性问题,实现转子高速稳定运行,采用全局线性化方法对电磁力进行线性化;同时,改进控制器的设计,使用增益调度方法实现转子平稳通过刚性临界转速,并通过有效降低控制器在转子工作频率附近的增益,使转子在高速下能近似围绕质量中心转动,避免电磁力的饱和。最终实现了强非线性条件下磁轴承电动机的高速稳定运行。     

考虑接触效应的拉杆转子非线性动力学特性分析

本文建立了两盘拉杆式转子轴承系统动力学模型,模型受不平衡力和非线性油膜力激励,拉杆转子轮盘之间接触刚度由接触理论计算得到,采用4阶龙格库塔法进行求解,并使用分岔图和Poincare映射对比分析了不同的转速下,拉杆转子与单盘整体转子的非线性动特性的差异。通过研究得到以下结论:随着转速变化,相比于单盘整体式转子,考虑盘间接触效应的影响会使系统非线性动力学行为更加复杂,在中高转速范围内拉杆转子系统响应状态在周期运动与准周期运动或混沌运动状态之间出现多次反复,拉杆转子系统初次发生分岔的转速值变大,响应的幅值减小,在低转速范围内,盘间接触状态对系统状态影响较小,系统不受转速变化影响。     

滚动转子式压缩机转子动力学分析

文中研究了压缩机转子临界转速和不平衡响应的分析计算。电机在旋转过程中产生的径向不平衡磁拉力,作用在转子上,会对其临界转速产生影响。利用有限元法提取了电机气隙径向磁密,合成不平衡磁拉力,并计算在不平衡磁拉力影响下的压缩机转子临界转速;计算转子对于某些位置上的不平衡量的敏感程度;求解轴承-转子系统频率方程并求得复频率,画出了复特征值对应的对数衰减率曲线,分析了轴系的稳定性。     

不平衡磁拉力作用下电机柔性转子非线性振动研究

建立了电机柔性转子非线性动力学模型,并使用多尺度法计算了系统的一次近似主共振响应。通过定常解分析发现转子主共振响应中存在幅频曲线左偏这一软非线性现象,并且不平衡磁拉力的线性部分使系统固有频率下降,非线性部分使主共振峰左偏量增大。使用MATLAB软件中的“ode23”函数绘制出系统的时间历程图及相图,数值积分的结果验证了解析解的正确性。从理论上揭示了转子长度、转子外径以及平均气隙长度等电机参数对非线性振动的影响,为电机的优化设计和控制提供了理论依据。     

双铁芯结构电机转子的极限转速优化分析

共轴双铁芯电机在同一根电机转轴上安装了两套铁芯,电机可在不改变控制系统和线路容量的情况下实现双路输入,双铁芯电机可显著提升电机整体的输出功率。对于于共轴双铁芯结构的永磁同步电机,由于转子结构的特殊性在进行转子极限转速计算时与传统单铁芯电机有所不同。为探索经济可靠的双铁芯电机转子结构方案,对比了三种相同尺寸不同结构的铁芯布置方案,分别用ANSYS分析计算了不同结构的转子的极限转速,发现使用转毂结构对提升转子极限转速有着显著的作用。将有限元仿真结果与解析法计算结果进行对比,两种计算方法结果偏差在3%左右,证明了计算结果的准确性。单边磁拉力是转子不平衡响应的主要外力贡献者,对于短跨距转子来说单边磁拉力按集中载荷校核误差不大,对于长跨距的转子来说用集中载荷计算会使得计算结果于真实值相差较大,以共轴双铁芯电机转子为例,对比了转子不平衡响应时单边磁拉力做集中载荷和均布载荷的仿真计算结果,发现更符合实际的均布载荷比集中载荷计算出的极限转速高20%。     

考虑感应电动机模型的质量偏心单盘转子系统Sommerfeld效应及不平衡响应分析

Sommerfeld效应是由于非理想原动机在转子系统临界转速附近无法提供足够的动力而产生的一种非线性跳跃现象。研究了由感应电动机驱动的一个质量偏心单盘转子系统的Sommerfeld效应及不平衡响应。将感应电动机的动力学模型引入到转子系统中,建立了电动机-转子系统动力学模型。在充分考虑电动机与转子系统相互作用的基础上,得到了供电频率与转子转速之间的关系表达式,并进行了稳定性分析。对具有不同质量偏心的电动机-转子系统的不平衡响应进行了分析,并基于Matlab/Simulink进行了仿真验证。结果表明:当转子偏心质量与转子总质量的质量比η<0.026时,电动机能够提供足够动力使转子系统平稳通过临界转速,电动机-转子系统不会出现Sommerfeld效应;当质量比满足0.026<η<0.083时,在转子系统临界转速附近,电动机所提供的最大电磁转矩小于转子系统平稳通过临界转速所需输出转矩,电动机-转子系统出现Sommerfeld效应;当η>0.083时,随着感应电动机供电频率的增加,电动机将无法提供足够的动力使转子系统通过临界转速,转子系统转速将始终低于临界转速。通过研究,...     

连续式风洞电机-联轴器-压缩机转子轴系横向振动分析

以某型连续式风洞的动力系统轴系为研究对象,建立了电机转子-联轴器-压缩机转子轴系的动力学模型,同时考虑到轴承动刚度、动阻尼、支撑刚度以及电机磁拉力等因素,使用DYNAMICS软件得到轴系的临界转速和振型等计算结果,并和实验数据进行对比,二者偏差范围小于±5%,轴系的理论不平衡响应也和实验数据有较好的吻合。研究表明,本文采用的建模方法正确,计算精度较高,满足工程实际需要。本文的研究阐明了电机柔性转子的临界转速分叉现象,揭示了电机转子和压缩机转子之间的振动耦合特性,对于机组的运行维护具有指导意义。     

基于多尺度法的电机转子在不平衡磁拉力作用下的自由振动特性分析

即使动平衡精度很高的电机转子,其质量偏心可忽略,但由于车用永磁同步电机工况复杂,换段过程、路面不平度、发动机激励等都可对转子系统形成径向扰动,转子将产生自由涡动,引起动态偏心,进而不平衡磁拉力对电机转子系统的自由涡动产生影响。根据转子系统的刚度特性讨论了动力学方程中非线性项系数以确定多尺度法的应用条件,利用该方法得到了不平衡磁拉力作用下转子系统自由振动的解析解并研究其振动特性。由于不平衡磁拉力的非线性使得转子正反自由涡动的复振幅是时变的,其大小保持常数不变而其相位随时间线性变化,其变化率取决于正反涡动的振幅,这将导致正反涡动的频率降低。若正反涡动振幅大小相等且非零则正反涡动频率相等,转子中心运动轨迹为直线;若正反涡动振幅有一个为零,则转子中心轨迹为圆;更一般的情况是正反涡动振幅大小不等且均不为零,两种涡动产生耦合其频率也不再相等,转子自由涡动的轨迹是一个旋转的近似椭圆其位移分量产生调幅现象。当转子涡动振幅不大时,利用多尺度法获得的解析解与数值计算结果吻合较好具有较高的精度。     

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.     

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....     

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。     

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.