风力机行星齿轮传动系统动力学研究综述

风力机行星齿轮动力学研究对降低其振动和噪声、延长风力机使用寿命和提高运行可靠性具有重要意义。行星齿轮传动自由度多、结构复杂、非线性因素和内部激励丰富,而且风力机外部激励复杂,国内外学者已对其进行较为广泛、深入的研究。从系统建模、动力学方程求解、动力学特性分析、动力学优化设计等方面系统评述国内外学者对行星齿轮系统动力学的研究现状,从固有特性、参数稳定性、非线性动态响应等方面详细介绍动力学特性的研究进展,其中齿侧间隙、轴承间隙和齿面摩擦等是现有研究关注较多的非线性因素。根据风力机行星齿轮系统的工作环境和行星齿轮动力学研究的发展趋势,给出了风力机行星齿轮系统需要深入研究的方向。     

基于集中质量法的齿轮系统动力学发展动态综述

基于集中质量法详细阐述了国内外齿轮系统动力学的发展情况,围绕齿轮动力学的发展进程,以齿轮系统动力学方程为基础,首先从振动激励、研究目标、分析理论、数学模型、求解方法等方面评述了齿轮系统动力学研究进展。其次,根据已有的齿轮系统动力学的研究成果分析了动力学在齿轮工程上的应用,最后,根据齿轮系统动力学研究的发展趋势,提出了需要进一步研究的问题。     

基于温度效应的多自由度齿轮系统的非线性动力学分析

齿轮在工作时,由于功率损耗和环境温度等原因,引起齿轮轮体及箱体的温度发生变化,影响齿轮传动性能。以直齿圆柱齿轮传动系统为研究对象,考虑齿面摩擦、齿侧间隙和时变啮合刚度等非线性因素,引入温度变化的影响,建立六自由度的齿轮系统非线性动力学模型,并采用4~5阶龙格-库塔算法对模型进行求解,结合分岔图、相图和Poincare映射图,分析温度变化和激励频率对齿轮系统动力学的影响。结果表明,温度变化对系统的影响与激励频率取值有关;系统随着激励频率的变化会表现出不同的动态特性响应,包括单周期响应、多周期响应以及分岔和混沌响应。相关结论为进一步改善齿轮系统的设计和安装提供了参考。     

齿轮系统动力学误差激励合成方法研究

齿轮系统动力学计算中需要考虑多种因素,其中啮合刚度激励、误差激励等是齿轮系统的主要内部激励.误差激励是啮合轮齿之间的一种周期性位移激励,是产生齿轮振动的主要因素之一.对误差激励进行了分析和计算,在考虑重合度、齿轮误差及其随机变化的情况下,给出了行星齿轮传动系统中一对齿轮副短周期误差的合成原理以及详细求解过程.最后给出计算实例,其计算结果表明所提出方法是有效的.     

考虑制造误差的圆柱斜齿轮传动动力学计算与分析

制造误差是影响齿轮传动动态性能的不可忽略因素。在考虑时变啮合刚度、综合啮合误差和阻尼等非线性因素基础上,建立含有制造误差的六自由度斜齿轮动力学模型。采用蒙特卡洛法求解齿轮的制造误差,利用龙格卡库法求解建立的齿轮动力学模型,通过分析一对实际的啮合齿轮得到其传动动态特性。研究表明:制造误差是影响齿轮传动误差的最主要因素,齿轮的误差激励是影响高速重载齿轮动态特性的关键因素,对于高速重载齿轮需提高其制造精度以减小误差激励。     

机车转子系统的非线性动力学分析

随着机车速度的提高,对其运行安全和稳定性提出更高要求。为研究机车轮对转子系统的动力学特性,在考虑弹性支撑、齿轮时变刚度等复合非线性因素影响下,基于哈密尔顿最小势能原理建立非线性连续-质量转子系统的动力学模型。在此基础上,对系统进行无量纲化,求解系统振形函数及固有振动频率。利用多尺度法求取非线性转子系统的渐进解,分析系统支撑刚度、阻尼及其齿轮时变刚度参数作用下,转子的主共振稳态幅频响应。研究表明:复杂边界条件下,齿轮的位置将直接影响模态幅值。轮轨激励的变化,对系统低频幅值影响较大、高频较小。轮轨激励达到临界值时,系统出现饱和共振,其后轮轨激励的变化,将不再影响系统的幅值。齿轮冲击刚度增加,转子系统位移显著增大。研究结果为机车轮对转子系统的动态特性分析和故障诊断奠定了一定的基础。     

一种专用差速器齿轮传动系统的动力学分析

对实现交叉变轮距车辆底盘转向功能的一种新型可旋转差速器齿轮传动系统进行动力学分析。将该专用差速器齿轮传动系统视为具有库仑阻尼的弹簧-质量的非线性时变系统,建立了系统12自由度的弯-扭耦合振动模型;将车辆转弯过程中路面对车轮施加的负载转矩作为系统的外部激励条件,分析了内部激励因素对该专用差速器齿轮传动系统振动特性的影响并建立动力学数学模型;通过求解系统动力学数学模型以及固有频率,进行该齿轮传动系统的运动相轨迹分析,优化系统的特性参数;达到了减弱该系统的振荡性能并提高系统的响应速度,使系统具有满意的动态性能指标的目的。     

功率分流式齿轮系统均载特性影响因素分析

为了提出功率分流式齿轮系统有效的均载方法,对其进行了均载特性影响因素分析。采用动力学分析方法,建立了功率分流式齿轮系统动力学模型,通过对齿轮副特征矩阵进行装配快速的形成了系统动力学方程,并对动力学模型中激励参数的计算进行了分析。通过定义均载系数衡量均载性能,啮合误差、耦合刚度、支撑刚度和转速被认为是影响均载的主要因素,分析了其对均载系数的影响规律。研究得出:减小啮合误差和耦合刚度、增大支撑刚度,以及选取合适的工作转速有利于提高功率分流式齿轮系统的均载性能。提出的有效均载方法包括:提高加工精度,设计合理结构使系统具有软耦合、硬支撑,选取合适工作转速。     

载荷激励下齿轮-转子系统断齿故障的机理研究

以一级齿轮箱及其连接的双跨转子系统为研究对象,研究其载荷激励和断齿故障下的动力学机理。针对齿轮啮合刚度的时变性及其所连接的转子系统的不平衡,以转子系统动力学、齿轮系统动力学以及拉格朗日方程为基础,构建了齿轮-转子系统的弯扭耦合数学模型,并在Matlab/Simulink环境下建立其仿真模型。数值仿真了断齿故障信号,并通过信号发生器模拟不同的载荷激励,通过观察其时频图解析了不同载荷激励和断齿故障所引起的系统动力学响应。最后,通过不同载荷激励下的齿轮断齿故障试验,得到实测信号的时域图并进行频谱分析,验证了齿轮-转子系统模型的合理性,可为齿轮-转子系统的故障诊断提供重要的理论依据。     

齿轮系统动力学的理论体系

根据对国内外齿轮系统动力学研究成果的系统总结，阐述齿轮系统动力学理论的基本结构体系，说明齿轮动力学的发展过程；围绕动态激励，模型类型，建模和求２解方法以及齿轮系统的固有特性，动态响应和动力稳定性等介绍齿轮系统动力学所涉及的基本问题，讨论该理论的主要工程应用的基础上，提出了应进一步研究的方向与重点。     

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.