时变速度和阻尼激励下地铁齿轮传动系统的动力学响应分析

为探究地铁不同车速阻尼对传动系统非线性动力学响应的影响,建立地铁斜齿轮弯-扭-轴动力学模型,模型考虑了齿轮副啮合过程中产生的时变啮合刚度、啮合误差以及间隙非线性等系统参数,以及地铁运行工况下的外部参数。通过对六自由度系统微分方程的无量刚处理以及方程归一化,运用变步长四阶Runge-Kutta数值积分法对齿轮动力学模型进行数值分析,获得齿轮系统动态响应状态图。借助时间历程图、相平面图、庞加莱截面图和分岔图等系统状态判定标准,定性分析系统激励频率、啮合阻尼比变化下系统周期运动、拟周期运动、分岔和混沌运动等的演化历程。结果表明,当地铁高速运转、啮合阻尼比大时斜齿轮传动系统运动稳定。最后通过实验验证了其正确性。     

特种汽车轮边减速系统齿轮传动力学特性分析

针对特种汽车轮边减速系统太阳轮一行星轮进行减速的传动方式,采用扭转振动模型,建立了考虑齿侧间隙、啮合刚度、传动误差在内的齿轮非线性动力学方程,利用Runge-Kutta法对齿轮的运动微分方程进行求解.通过建模、求解得到分岔图并进行分析,研究单自由度齿轮在齿侧间隙和阻尼比影响下的动力学特性.研究结果表明:随着齿侧间隙的增加,齿轮运动受到的冲击越大,系统状态越混沌;固定齿侧间隙,随着阻尼比的增加,齿轮运动趋于稳定.     

端曲面齿轮传动系统的非线性动态特性

为了研究端曲面齿轮传动系统的非线性动态特性以及参数对系统动态特性的影响，建立了端曲面齿轮系统的非线性动力学模型；选取无量纲啮合频率为控制参数，通过分岔图、相图、时间历程图、Poincaré映射图，研究了系统的动力学特性。研究表明，系统经跳跃分岔由无冲击状态转迁为单边冲击状态，随后经连续的倍化分岔通向混沌运动；当增大综合传动误差或减小转矩时，系统无冲击状态区域逐渐收缩，跳跃分岔值和倍化分岔值发生超前，使系统提前发生跳跃现象；无冲击—单边冲击的转迁方式发生改变，亚谐运动区域逐渐扩展并发生前移，系统运动类型增多，运动周期数增大，混沌运动区域逐渐扩大，系统稳定性下降。     

星型齿轮系统定常吸引子共存现象的研究

建立了星型齿轮系统的非线性动力学计算模型，并肜数值方法进行了求解，研究了4自由度有间隙的非线性星型齿轮系统稳态响应的定常吸引子共问题，分别对在3种参数情况下各自在不同的初值条件下得到的共存的简谐，非谐单周期，次谐波和准周期稳态响应做了比较，通过分析系统各齿轮副的动态啮合力，区分了在齿轮系统中因间隙而导致的齿轮副啮合过程中出现的无冲击状态，单边冲击状态，双边冲击状态，并分析了由于星轮载荷不均匀分布状态和均匀分布状态分别对应的系统稳态响应的共存现象。     

齿侧间隙对星型齿轮传动扭振特性的影响研究

建立了受传递误差和时变啮合刚度激励的星型齿轮传动的间隙型多自由度非线性扭转振动模型,并用自适应变步长Gill数值积分方法进行了求解。结合Poincar啨映射和相平面研究了在不同齿侧间隙下系统出现的简谐、非谐单周期、次谐、拟周期以及混沌响应,并得到了改变间隙时系统的动力学分岔特性。通过分析各齿轮副的动载荷系数变化规律,讨论了各齿轮副啮合状态在非冲击、单边冲击以及双边冲击状态之间的转化过程和齿侧间隙的关系。从理论上分析了齿侧间隙对系统的稳态响应、动载荷等动态特性的影响。     

考虑啮合刚度随机扰动的斜齿轮系统分岔特性研究

为了研究时变啮合刚度的随机扰动对斜齿轮传动系统动力学的影响,基于牛顿定律,建立单对6自由度斜齿轮传动系统的随机动力学模型并进行无量纲化处理。结合系统的分岔图、庞加莱映射图、李雅普诺夫指数图、相图和时间历程曲线图,对考虑啮合刚度随机扰动的斜齿轮传动系统的分岔特性进行分析。数值仿真分析结果表明,斜齿轮的时变啮合刚度在不断增大时,斜齿轮传动系统逐渐从周期运动通过倍化分岔变为混沌运动;随机扰动的增大使系统分岔特性发生变化,提前分岔进入混沌,对系统产生本质影响,故在设计时需选择合理参数,保证系统稳定性。     

不同Poincaré截面上齿轮扭振系统动力学特性分析

以典型的单自由度齿轮扭转振动系统为研究对象,对系统的非光滑动力学特性进行细致研究。定义瞬时接触面和零相位面为Poincaré截面,计算截面上系统的分岔图、最大Lyapunov指数谱和吸引域,得到多吸引子共存现象产生和消失过程中系统全局和局部响应的变化规律;计算截面上系统的分岔图,得到齿轮啮合-脱啮运动的周期性;计算系统的频谱瀑布图,得到系统啮合-脱啮运动频响特性。通过对比,发现齿轮系统在不同Poincaré截面上体现出更加丰富的动力学行为。     

齿面摩擦对齿轮传动系统分岔与混沌特性的影响分析

为研究齿面摩擦对直齿圆柱齿轮传动系统振动特性的影响,建立了包含齿面摩擦在内的六自由度齿轮啮合耦合型动力学模型。模型采用能量法计算齿轮啮合的时变啮合刚度,同时考虑了啮合误差、间隙非线性以及负载扭矩等因素。通过四阶变步长Runge-Kutta积分法对模型进行数值分析,得到齿轮系统随齿面摩擦系数变化下的时间历程图、相位图、Poincare截面图、分岔图等,定性分析了齿轮系统对齿面摩擦变化下的动力学周期、拟周期、分叉和混沌的运动演化历程,并通过实验进行了验证。结果表明,随着齿面摩擦系数的增大,齿轮系统动态特性响应逐渐复杂。     

行星齿轮传动非线性动力学模型与方程

建立了２Ｋ－Ｈ型行星齿轮传动的弯扭耦合非线性动力学模型，模型中考虑了太阳轮的横向振动、齿轮啮合综合误差、齿轮副啮合间隙以及时变啮合刚度，获得了系统的运动微分方程。针对系统微分方程的半正定、变参数和非线性特点，采用以齿轮副相对啮合位移作为系统的广义坐标，将线性与非线性恢复力共存的方程组转换为统一形式的矩阵形式，并对方程进行量纲一化处理，方便地达到了将单自由度的非线性方程的解法推广到多自由度非线性微分方程组中。     

考虑齿面摩擦的斜齿轮系统建模及动力学特性分析

为研究斜齿轮传动系统的动力学特性,根据单级斜齿轮副传动情况,建立考虑齿面时变摩擦的5自由度弯—扭—轴耦合传动系统动力学模型。依据重合度对啮合时间进行划分,由Buckingham半经验公式得到齿面摩擦因数随啮合点位置的变化规律。采用变步长Runge-kutta法对系统运动微分方程组进行数值求解,得到系统分岔图、最大Lyapunov指数、最大幅值云图和幅频特性叠加图,分析系统随激励变化的动力学特性。研究发现,系统在特定参数下发生强共振响应及幅值跳跃现象。     

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...     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

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.     

Fifth International Summer School on Screw-Theory Based Methods in Robotics

正3-11 September,2014University of Bologna,Bologna,Italy www.summerscrews.org summerscrews2014.ing.unibo.it SUMMER 20SCREWS 14In 2014,our screw-theory school comes to the world's oldest university.In early September,Summer Screws'14 will gather six experts in the application of screw theory in robotics and up to 40 participants at the University of Bologna,Bologna,Italy.The school will teach attendees how to apply existing methods and empower them to develop new ones in their own research.The basic theoretical notions will be introduced in a rigorous manner,emphasizing examples,applications,and exercises.Scholarships are available.     

电站锅炉模糊风险评价方法研究与应用

针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。     

INDUSTRIAL ENGINEERING AND VISUALISATION-A PRODUCT DEVELOPMENT PERSPECTIVE

Taking the actual project of teaching and researching process for example, the relationship between the industrial engineering and product development is discussed. And use the novel visualization technology to support the industrial engineering and product development. How to use the new computer modeling and simulating technologies to support the product development and industrial engineering, is introduced especially. The support includes both domestic products and industrial systems. The visualization and computer technologies take a very important role in some system or multi-direction modeling, those technologies mentioned above can help the industrial engineers study the effect of design on the whole life circle, including the producing steps. So the engineers can avoid making the wrong decision which may cause bad effects on the whole industrial engineering.     

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.