作大范围运动的平面柔性梁的有限元动力学建模

文中在精确描述柔性梁非线性变形的基础上,利用有限元方法对梁结构进行离散,然后针对具有大范围运动的平面柔性梁结构利用Lagrange方程建立系统的精确动力学方程.该方程在原有一次耦合模型的基础上,增加了新的表征纵向、横向、侧向弯曲变形,以及扭转变形的耦合项.所得方程可用于研究非惯性系下的结构动力学问题,也可用于大范围运动为未知的刚柔耦合问题.     

空间柔性梁的刚-柔耦合动力学特性分析与仿真

针对大范围运动规律为未知的刚-柔耦合系统,利用有限元方法对柔性梁进行离散,采用Lagrange方程建立空间柔性梁的刚-柔耦合动力学方程,研究在大范围运动为自由情况下,空间柔性梁的大范围运动和变形运动的相互耦合机理,比较零次模型、一次耦合模型、精确模型的差异,探讨各种模型的适用性。     

机械臂协调操作柔性负载鲁棒神经网络控制

针对多变量刚柔耦合的双机械臂协调操作柔性负载系统,基于奇异摄动理论研究该系统有限元模型的分解以及轨迹跟踪控制问题.考虑动力学模型的复杂性,通过双时标变换将协调系统分解成表征系统大范围刚性运动的慢变子系统和表征系统弹性振动的快变子系统.基于反演思想在慢变子系统中设计鲁棒神经网络控制策略,实现系统轨迹跟踪性能;针对快变子系统,设计鲁棒最优控制策略抑制系统的弹性振动.仿真研究结果表明,该控制策略增强了系统的跟踪性能和鲁棒性.     

一般柔性体连续系统的动力学建模方法

基于Ｈａｍｉｌｔｏｎ原理,建立了考虑刚弹耦合作用的一般柔性体连续系统的动力学模型,并针对在水平面内作大范围回转运动的柔性梁,在Ｅｕｌｅｒ－Ｂｅｒｎｏｕｌｉ梁模型的假设前提下,根据轴向不可伸长的柔性梁的几何约束条件,采用假设模态法,推导出柔性梁有限维离散化动力学方程。研究表明,作大范围回转运动的柔性梁,由于运动和变形的耦合将产生动力刚化现象。文中最后给出了仿真算例,验证了该方法的有效性。     

非惯性坐标系下柔性梁的动力学分析与压缩建模

文章针对大范围运动已知的空间柔性梁结构建立其动力学方程.通过研究与分析,提出了文中精确模型,各项矩阵较原有一次耦合模型新增了2类耦合项:即变形耦合项和基点速度和角速度耦合项.通过仿真计算,比较其动力学特性与零次、一次耦合模型的差异,确定各种耦合项的作用,并进行了定性分析.最后研究了复杂系统的压缩建模问题,为工程实际和今后的研究奠定了理论基础.     

作大范围运动弹性结构振动频率及模态的摄动解

根据参数摄动理论，建立了作大范围运动弹性结构特征频率与模态的摄动理论，推导了作大范围运动弹性结构的特征频率与模态的1阶、2阶摄动方程．以作大范围运动弹性梁为例，求解了作大范围转动弹性梁振动频率与模态的1阶、2阶摄动近似解，并与结构动力学意义下的频率与模态进行了比较．该方法解决了在柔性多体系统中大范围运动对柔性体变形运动的振动频率与模态的影响这类刚-柔耦合问题，同时为任意柔性多体系统刚-柔耦合动力学程式化建模提供了高效、精确的离散方法．     

大型刚-柔耦合动力学系统建模中柔性梁的非线性变形研究

在一次耦合模型变形模式的基础上,根据大型刚-柔耦合动力学系统中柔性梁的结构特点,从连续介质力学原理出发,在柔性梁的纵向变形中计及了变形的二次耦合项;在空间柔性梁的3个方向变形中均考虑了变形的相互耦合作用及轴向扭转效应,得出了描述柔性体变形的较为精确的几何非线性变形模式。从变形位移-应变关系出发,对一次耦合模型和文中模型的剪应变进行了分析,在相同的简化下,对平面柔性梁,采用文中模型得出的剪应变为零;对空间柔性梁,采用文中模型得出的剪应变值小于一次耦合模型,从而说明采用文中模型更有理由忽略剪切效应,符合细长梁的建模理论。     

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.     

空间两连杆柔性构件弯扭耦合振动主动控制

为了研究空间柔性结构的耦合振动，提出一种由柔性杆和柔性梁组成的两连杆柔性构件系统，对此柔性构件系统的弯扭耦合振动进行了研究，运用拉格朗日方程和假设模态法推导了此柔性系统的动力学方程．在柔性杆根部粘贴一只压电扭转驱动器抑制柔性杆的扭转振动，在柔性梁根部粘贴一只压电剪切驱动器抑制柔性梁的弯曲振动．采用一种基于Lyapunov稳定性的速度反馈控制策略进行了实验仿真研究．结果表明, 施控后的系统是稳定的，弯扭的各阶模态均能得到有效抑制，柔性梁末端的位移振动能得到显著衰减．     

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     

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     

Rigid-Flexible Coupling Dynamic Analysis of Sub-Launched Vehicle During the Vertical Tube-Exit Stage

During the launching stage,hydrodynamic pressure and adapters’ reaction loads can influence the vehicle’s rigid motion as well as cause its structural vibration,which is a typical rigid-flexible coupling dynamic problem. This paper presents a 2-D rigid-flexible coupling model to calculate the vehicle’s dynamic responses in that period.The vehicle was equivalent to a flexure beam with axial deformation. Hybrid coordinate and modal superposition methods were used to describe its large rigid displacement and small deformation. By the second Lagrange equation,the vehicle centroid’s displacements,rotational angle and modal coordinates were chosen as generalized coordinates and then the vehicle ’s rigid-flexible coupling dynamic equations were obtained. By numerical simulation,the results of vehicle’s motion parameters and transverse internal loads were acquired.The calculation results showed that differences of the vehicle’s motion parameters between the rigid-flexible coupling model and the rigid body assumption are noticeable and the peak magnitude of the vehicle’s transverse internal loads in the rigid-flexible coupling model is higher remarkably than that in the rigid body assumption.     

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。     

考虑弯扭耦合旋转叶片的动力学分析

应用拉格朗日方程建立了旋转柔性叶片非线性动力学控制方程.文中考虑了由于质量偏心所造成的弯曲与扭转振动的耦合,并假设了弯曲与扭转的一价振型对方程进行了离散,通过数值仿真给出了旋转运动所产生的叶片端部弯曲位移及转角位移,揭示了在叶片扭转刚度较大时,转角位移非常小.本文所建立的动力学方程可用于考虑弯扭耦合时实际旋转叶片的动力学分析.     

Rigid-flexible coupling dynamic modeling and vibration control for flexible spacecraft based on its global analytical modes

In this study, we used global analytical modeswfny(GAMs) to develop a rigid-flexible dynamic modeling approach for spacecraft with large flexible appendages(SwLFA). This approach enables the convenient and precise calculation of the natural characteristics for designing an attitude control law for the spacecraft while simultaneously suppressing the active vibration of its flexible appendages. We simplify the flexible spacecraft as a rigid-flexible coupling hub-beam system with tip mass and derive the system's governing equations of motion based on Hamilton's principle. By solving the linearized form of those equations with their associated boundary conditions, we obtain the frequencies as well as the corresponding GAMs of flexible spacecraft,which we use to discretize the equations of motion. Using this approach, we performed numerical simulations to investigate the system's global modes and assess the performance of the controller based on the GAM model. The results reveal that the GAM model can be used to directly calculate the exact global modes of SwLFAs and that the controller based on the discrete GAM model can achieve a control-index for a SwLFA in a shorter time with less input energy than other methods.     

基于耦合滑模面的机械臂操作柔性负载系统分布参数控制

针对多变量刚柔耦合的机械臂操作柔性负载系统,提出了一种自适应滑模控制方法,研究了系统存在参数不确定性和外部干扰影响下的位置控制和振动抑制问题。系统动态特性由偏微分方程表示的分布参数模型来描述,避免了集中参数模型导致的溢出问题。基于对柔性负载的能量动态分析,设计了一种自适应滑模控制器,其中滑模面定义为关节角误差、关节角速度误差和柔性负载的根部应变和剪切力的耦合。利用LaSalle不变性原理,证明了闭环系统的渐近稳定性。最后仿真验证了所设计控制方法的有效性。     

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。     

基于刚柔耦合模型的月球车振动特性仿真

为了分析月球车在月表环境下的振动特性,将其作为一个刚柔耦合多体系统,基于三维实体造型和多体动力学分析软件建立了刚柔耦合动力学模型。根据美国国家航空航天局的研究,建立了月球表面位移功率谱数学模型,结合谐波叠加法获得了月表不平度。以六轮月球车样机JLUIV-6为研究对象,通过典型越障工况试验验证了所建模型的可靠性。以月面不平度作为振动激励对所建立的动力学模型进行了仿真,分析了月球车车体的振动响应及振动加速度幅频特性。结果表明,月球车在0.8～1.8Hz处存在明显的共振区域,为月球车系统设计及优化提供了依据。     

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.     

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.