ADAMS刚柔耦合多体系统动力学建模

刚柔耦合是多体系统最常见的力学模型,探讨其建模规律是多体系统动力学研究的重要内容.用ANSYS和ADAMS软件为一四杆机构分别建立了一个多柔体模型和刚柔耦合模型,以前者动特性为参考,研究刚柔耦合模型对系统动态特性的影响,探索多体系统刚柔耦合建模规律.结果表明,从低阶模态来看,各构件经恰当处理后刚柔耦合模型能够较好地反映系统的动态特性.     

整车刚柔耦合建模及随机激励下的平顺性分析

基于多体动力学理论、有限元及模态综合法,建立了某轿车的整车刚柔耦合动力学模型,其中包括前悬架、转向系等刚体子系统及后悬架柔体子系统.建立B级随机路面模型,采用该数字化试验道路对整车的平顺性进行仿真计算,得到不同车速下的车身质心处垂向加速度以及驾驶员座椅坐垫上方、座椅靠背以及脚支撑面处的加权加速度均方根值.结果表明,所建的刚柔耦合整车模型正确,该轿车的平顺性良好.     

刚柔耦合系统的输入成形控制

为实现对大范围运动刚柔耦合系统的振动抑制,提出基于一次近似动力学模型的输入成形控制方法.针对中心刚体-柔性旋臂梁系统,在变形位移的描述中计及纵向变形的二次耦合项,建立一次近似动力学模型用于振动控制.考虑到大范围运动刚柔耦合系统中柔性梁有别于结构动力学中定边界梁的模态特性,设计抑制柔性振动的鲁棒多模态输入成形器.仿真结果...     

Complete geometric nonlinear formulation for rigid-flexible coupling dynamics

A complete geometric nonlinear formulation for rigid-flexible coupling dynamics of a flexible beam undergoing large overall motion was proposed based on virtual work principle, in which all the high-order terms related to coupling deformation were included in dynamic equations. Simulation examples of the flexible beam with prescribed rotation and free rotation were investigated. Numerical results show that the use of the first-order approximation coupling (FOAC) model may lead to a significant error when the flexible beam experiences large deformation or large deformation velocity. However, the correct solutions can always be obtained by using the present complete model. The difference in essence between this model and the FOAC model is revealed. These coupling high-order terms, which are ignored in FOAC model, have a remarkable effect on the dynamic behavior of the flexible body. Therefore, these terms should be included for the rigid-flexible dynamic modeling and analysis of flexible body undergoing motions with high speed. Foundation item: Project(10772113) supported by the National Natural Science Foundation of China     

Dynamic modeling and simulation for the flexible spacecraft with dynamic stiffening

A rigid flexible coupling physical model which can represent a flexible spacecraft is investigated in this paper. By applying the mechanics theory in a non-inertial coordinate system, the rigid flexible coupling dynamic model with dynamic stiffening is established via the subsystem modeling framework. It is clearly elucidated for the first time that, dynamic stiffening is produced by the coupling effect of the centrifugal inertial load distributed on the beam and the transverse vibration deformation of the beam. The modeling approach in this paper successfully avoids problems which are caused by other popular modeling methods nowadays: the derivation process is too complex by using only one dynamic principle; a clearly theoretical explanation for dynamic stiffening can't be provided. First, the continuous dynamic models of the flexible beam and the central rigid body are established via structural dynamics and angular momentum theory respectively. Then, based on the conclusions of orthogonalization about the normal constrained modes, the finite dimensional dynamic model suitable for controller design is obtained. The numerical simulation validations show that: dynamic stiffening is successfully incorporated into the dynamic characteristics of the first-order model established in this paper, which can indicate the dynamic responses of the rigid flexible coupling system with large overall motion accurately, and has a clear modeling mechanism, concise expressions and a good convergence.     

Impacts of flexible obstructive working environment on dynamic performances of inspection robot for power transmission line

The rigid-flexible coupling dynamic modeling and simulation of an inspection robot were conducted to study the influences of the flexible obstructive working environment i.e. overhead transmission line on the robot＇s dynamic performance. First, considering the structure of the obstacles and symmetrical mechanism of the robot prototype, four basic subactions were abstracted to fulfill full-path kinematic tasks. Then, a multi-rigid-body dynamic model of the robot was built with Lagrange equation, whil~e a multi-flexible-body dynamic model of a span of lin~ was obtained by combining finite element method （FEM）, modal synthesis method and Lagrange equation. The two subsystem models were coupled under rolling along no-obstacle segment and overcoming obstacle poses, and these simulations of three subactions along different spans of line were performed in ADMAS. The simulation results, including the coupling vibration parameters and driving moment of joint motors, show the dynamic performances of the robot along ftexibile obstructive working path： in flexible obstructive working environment, the robot can fulfill the preset motion goals; it responses slower in more flexible path; the fluctuation of robot as well as driving moment of the corresponding joint in startup and brake region is greater than that in rigid environment; the fluctuation amplitude increases with increasing working environment flexibility.     

基于刚-柔混合建模的时变结构动力学分析

为适应液压挖掘机高速、轻量化的要求，以具有时变固频特性的液压挖掘机工作装置为研究对象，提出了以角加速度判断时变结构的关键工况，利用刚性多体动力学和有限元方法对液压挖掘机在整个作业循环中的动力学特性进行建模和分析.分析了液压挖掘机工作装置在受力最大处的动态应力分布，并与传统刚性体模型的分析结果进行了比较.结果表明，刚 柔混合建模方法与刚性体建模方法相比，获得的位移和应力较小，反映出以往的设计偏于保守，为轻量化设计提供了依据.     

基于小变形的柔性多体系统运动学分析

多体系统中柔性体运动一般分为体参考系的范围运动和变形运动。在多数场合,柔性体的变形运动是较小的,可以用对变形广义坐标线性化的动力学方程描述系统动力学行为。但是,目前通用的一些动力学建模方法用于柔性体动力学建模时,存在过早线性化缺陷,导致最终的动力学方程遗失了一些重要的刚柔耦合项。本文采用非线性变形场描述,计及含有变形广义坐标及其导数的二阶小量项,将这种非线性保留到求出偏速度后,再线性化,建立了柔性     

抛物面天线柔性对焦点动特性的影响分析

为研究星体进行调姿运动时柔性抛物面天线的弹性变形对其视在相位中心的影响,建立了计算抛物面天线动态几何焦点的数学模型,并通过航天器动力学模型对姿态调整过程中天线焦点的动态响应进行数值求解.建立由抛物面天线、太阳帆板和中心星体组成的整星有限元模型,并求出天线无约束边界条件下的固有频率和振型.通过有限元模型和ADAMS联合仿真建立航天器零次刚柔耦合动力学模型并求得姿态调整过程中天线几何焦点的动态响应特性.结果表明,航天器进行姿态调整时,柔性天线面在做大范围整体运动的同时发生弹性振动,使其几何焦点在平衡位置震荡,严重影响星载天线的指向精度.     

具有库仑摩擦力的结构动力分析

应用振型叠加法对具有库仑摩擦力的结构进行动力分析，用假想力矢量表示因摩擦力引起的非线性，用有限元求解运动方程，在地震期间，地面上的结构可能滑移，相应的位移包括弹性位移和刚体运动2部分，考虑刚体运动需要进行高模态的瞬态分析，算例分析了地震期间地面上平板的动力响应。     

含动力刚化项的一般多柔体系统动力学研究

为获取柔性体的动力刚化项,将任意形状柔性体的非线性变形场表达为直至广义坐标的二阶小量形式．在小变形条件下,用Green应变张量得到了柔性体的耦合形函数．把约束引入多柔体系统,依据Kane方程建立了包含动力刚化项的一般柔性多体系统动力学方程．通过数值仿真算例,界定了传统多柔体系统动力学建模方法的适用范围．     

条烟配送系统动力学建模及影响因素研究

烟草二次配送运输系统中,装有条烟的金属笼车、缓冲包装物、运载汽车、路面组成了一个复杂的动力学系统。以该系统的动力学仿真和笼车的可靠性为研究内容,利用刚柔耦合理论来建立系统模型。同时以随机输入和脉冲激励来模拟实际路面,进行运输平顺性仿真分析。通过分析主副笼加速度变化曲线,得出同一路况不同车速下运输的平顺性差别;同时通过分析主副笼加速度功率谱密度曲线,得出货物受到振动的能量主要集中频率区间,可为车身的设计和最高车速的限制提供数据支持。     

Motion function reliability analysis of a rotating flexible beam with random parameters

The assumed mode method and stochastic response surface method are combined to analyze the motion function reliability of a rotating flexible beam with random parameters. Firstly, based on Lagrange's equations and the assumed mode method, the rigid-flexible coupling dynamic model which takes the coupling term of the deformation in the expression of longitudinal deformation is studied. Then considering the physical and geometrical parameters under randomness, the probability analysis is made by the stochastic response surface method. The rationality and efficiency of the modeling and the method presented are verified by an example. The results demonstrate that the third order stochastic response surface method leads to good precision with acceptable time consumption compared with the Monte Carlo (MC) method, and that the randomness of density has a greater effect on the reliability of the system.     

共轭凸轮打纬机构的刚柔耦合动力学仿真研究

针对织机中的共轭凸轮打纬机构进行刚柔耦合动力学研究.利用ANSYS分析软件生成模态中性文件,利用ADAMS/Flex模块导入ADAMS中,从而完成数据的双向传输.分析了柔性打纬摇轴的模态、振型等振动特性,并进行打纬机构刚柔耦合分析,对柔性打纬摇轴的共轭凸轮打纬机构的动态特性进行了研究.仿真结果表明:考虑构件柔性的情况下,机构的运动性能与刚体构件差别微小,但动力学性能相差较大.本文成果可为后续进行机构的运动精度分析及可靠性设计提供数据支持,为高速织机的设计制造提供参考.     

三轴移动载荷对半刚性路面性能影响分析

为研究多轴车辆移动载荷对半刚性路面性能影响规律,针对半刚性路面的特点,依据弹性层状体系理论,将半刚性路面的沥青层、半刚性基层、半刚性底基层及土基层按线弹性考虑,建立了半刚性路面的三维有限元分析模型,分析了车辆三轴移动载荷对半刚性路面性能影响。结果表明,3轴载荷作用下路面应力变化与车辆轴数有关,当车桥依次驶过路面时,路面应力出现3次突变,沥青层三向压应力、半刚性基层和底基层的垂直压应力、横向拉应力和水平拉应力均增大,最大拉应力出现在半刚性基层和底基层结合处;前轴驶过时轮迹带中心区域各层的横向剪应力最大,后轴驶过时轮迹带边缘区域各层的横向剪应力最大,最大值出现在沥青层底部;中轴驶过时路面各层的水平剪应力最大,最大值也出现在沥青层底部。因此,设计路面结构时,半刚性基层和半刚性底基层应选取抗弯和抗拉强度较高的材料,并应加强沥青面层的抗剪强度。     

Application of DVA theory in vibration reduction of carbody with suspended equipment for high-speed EMU

The theory of dynamic vibration absorber (DVA) was applied to restrain the vibration of carbody for high-speed electric multiple unit (EMU). The carbody was modeled as an Euler-Bernoulli beam with the equipment mounted on the chassis regarded as a DVA. Suspension parameters of the equipment were optimized based on the modal analysis of the beam and parameter optimization of the DVA. Vertical motion equations of the carbody and equipment were derived to study the effect of the suspension parameters on the vibration of carbody, which included the suspension frequency, damping ratio, mounting position and mass. Then a 3D rigid-flexible coupled vehicle system dynamics model was built to simulate the response of carbody and equipment to track excitation. The results show that the equipment mounted on the carbody chassis can be regarded as a DVA to reduce the flexible vibration of carbody, and the optimum suspension frequency can be calculated theoretically with the first-order vertical bending mode of carbody considered. Heavy equipment should be mounted to the carbody center as close as possible to obtain a significant vibration reduction, while light equipment has quite limited contribution to that. Also, a laboratory test was conducted on the full-scale test rig which shows a good agreement with the theoretical analysis and dynamic simulations. The faster the vehicle runs, the more significant are the advantages of the elastic suspension.     

汽车刚柔耦合建模及平顺性分析

汽车行驶过程中因路面不平引起的振动冲击,会使一些受力较大的部件产生弹性变形。本文依据某型汽车参数,结合有限元软件ANSYS和ADAMS,分别创建了该车刚体模型和刚柔耦合模型。通过B级随机路面平顺性仿真实验,对两模型的质心加速度、悬架动行程和轮胎动载荷进行了比较分析,浅析了部件弹性变形对汽车平顺性的影响,并对该车的平顺性进行了初步分析。     

重型商用车驾驶室空气悬置系统的匹配优化

采用虚拟样机技术建立了重型商用车驾驶室空气悬置多刚体动力学仿真模型,通过道路试验对仿真模型进行了验证,分析了其模态特性及乘坐舒适性。以驾驶室悬置元件刚度、阻尼为因子,运用正交试验技术对驾驶室悬置系统参数进行了匹配优化,结果表明,采用优化后的驾驶室空气悬置参数可使驾驶室的乘坐舒适性有一定程度的提高。     

油膜润滑的发动机曲轴疲劳寿命分析

在Virtual lab中建立某型V8发动机曲轴系统的多体动力学模型,考虑曲轴系统的油膜润滑条件,创建主轴颈处润滑的油膜文件,通过多体动力学仿真计算,得到曲轴在弹性支撑下的载荷历程,并将其作为疲劳寿命分析的输入参数;利用Virtual.Lab的Durability模块对曲轴进行疲劳寿命计算,获得精确的曲轴损伤分布和疲劳寿命。仿真结果表明:通过系统多体动力学仿真能够得到部件准确的载荷情况,考虑油膜润滑真实的反映了曲轴受载情况;曲轴寿命最短处为第一曲拐与第二主轴颈过渡处内侧。     

基于油气悬挂系统的1/4车数学模型与仿真研究

建立了汽车油气悬挂系统非线性数学模型和1／4车数学模型，应用Matlab软件编制了计算机仿真程序，利用仿真程序得到了悬挂系统受力，悬挂质量、非悬挂质量和座椅的振动加速度，车轮动载、悬挂动行程等参数，为对汽车机平顺性、行驶安全性进行评价奠定了基础。