机械多体系统动力学可视化仿真方法研究

应用低序体阵列描述多体系统拓扑构型，采用AutoDesk公司的MechanicalDeskTop(MDT)建立三维几何模型，使用AVI数字视频压缩对多体系统的运动过程进行可视化处理，实现多体系统动力学可视化仿真，采用面向对象的程序设计方法，开发了集成化的软件系统MDAS。该系统可者多体系统动力学计算机、数据处理和多体系统可视化仿真，最后，以带有太阳帆板的复杂卫星系统为例，对MDAS软件的合理性，有效性和正确性进行了分析验证。     

基于CORBA的多体系统动力学分布式仿真

基于多体系统动力学与运动学的机械系统计算机辅助分析(CAA)已成为该领域计算机辅助工程(CAE)的核心内容。该文分析了多体系统动力学方程建立及求解方法，结合CORBA技术、数值分析方法、OpeaGL图形技术，开发了基于CORBA的多体系统动力学分布式仿真系统，实现了分布式环境下的多体系统动力学的数值分析与仿真。     

汽车整车多体系统动力学建模和仿真

该文利用多体理论对SGZ4032型牵引车建立整车系统动力学模型,模型中将钢板弹簧离散为多个无质量Timoshenko梁连接的柔性体,以此模拟钢板弹簧的非线性特性。将整车模型在方向盘正弦输入下进行仿真,仿真结果表明：车辆的性能参数与方向盘输入有较好的跟随性,但由于非线性特性的影响而存在滞后现象,同时由于载荷的转移,车辆转弯时内侧的侧向力比外侧的侧向力小,且变化相对平缓。该模型较好地反映车辆实际运行的动力学特性,其建模方法可以应用于类似车辆的动力学性能研究中。     

海上航行横向干货补给滑车加减速控制仿真

在海上航行横向干货补给滑车在传输过程中受两船相对运动和滑车加减速过程的影响,会出现很大晃动,极端条件下会同接收舰相撞,为保证滑车平稳传输,需对滑车进行全程自动控制,并对其加减速进行控制.在分析滑车在高架索上的运动状态及滑车全程自动传输控制性能的基础上,建立了海上航行横向干货补给滑车传输系统的数学模型,采用Matlab/simulink软件建立了仿真模型,分别对采用梯形、S型和三角函数加减速控制方法的海上航行横向干货补给系统进行了仿真,通过对滑车在两船相对运动和高架索波动情况下的传输速度和加速度分析,表明滑车加减速控制采用三角函数方法和S型方法是可行的,保证滑车能在高架索上平稳传输.     

虚拟环境中基于多体动力学的实时仿真

该文通过分析主流虚拟现实开发工具的特点和不足,提出在虚拟现实开发过程中运用多体动力学的理论和方法,使得虚拟环境中的对象行为更加符合真实世界,并介绍了使用虚拟现实开发工具worldlbolKit结合多体动力学仿真开发引擎Vortex在此领域做出的有益尝试。同时,该文对Vortex采用的仿真机制和算法进行了充分的分析和挖掘,并详细介绍了在开发过程中的一些理解和体会,以期能对我国从事虚拟现实技术开发和应用的工作者提供一些有用的思路。     

多体系统动力学软件技术

本文根据凯恩－休斯顿多体系统动力学理论,开发了一套计算机分析软件,重点描述了该软件的实现技术,最后给出了例题计算。     

无人机飞行仿真系统多智能体建模分析与应用研究

无人机飞行仿真系统包含多个功能模块,采用多智能体(multi-Agent)技术研究无人机飞行仿真系统,分析并建立基于多智能体的飞行仿真系统的层次结构和运行机制,进而利用智能体对无人机仿真模型的各子模块模型运行过程进行建模,最后在JADE环境下建立了多智能体无人机飞行仿真系统的实例模型.这种方法可以通过仿真模型各子系统智能体之间的交互来完成无人机飞行仿真系统中飞行仿真的主要功能,从而满足无人机模拟训练系统的设计需求,在无人机模拟训练系统研究中具有广阔的应用前景.     

基于多体动力学的火箭飞行仿真

火箭飞行过程伴随着质量、质心、惯性矩的变化和控制力的调整,其模拟仿真是个非常复杂的学术和技术问题.基于多体动力学软件Adams,建立火箭箭体的三维模型,编制火箭飞行过程仿真的流程控制子程序、重力变化子程序、控制力子程序和气动力函数,搭建火箭的飞行仿真平台,实现火箭飞行过程中的质量、质心变化的仿真,并且给出关键功能的验证和应用算例.     

虚拟原型多体动力学中设计模式仿真模型研究

通过分析机械系统多体动力学解算模型特点。从机械产品的协作开发与仿真角度。研究了基于组件方法建立机械系统虚拟原型,提出利用MVC设计模式构建多体动力学解算仿真模型。这种解算模式,实现了多体动力学解算仿真中。模型与解算逻辑的分离,维护了系统仿真中构件、铰约束、力元等组件的状态一致性。利于在不同的解算逻辑下组件和仿真方案的配置,方便了基于组件的协同开发与仿真。结果表明,基于组件的机械虚拟原型模型与多体动力学MVC仿真模型是可行的。     

航天器帆板展开过程动力学建模与仿真

阐述了应用柔性多体动力学和Kane方程进行航天器帆板展开过程建模的方法，将帆板视为柔性体并进行模态分析，采用有限元法与模态缩聚技术建立了帆板的离散化模型．以国产某型号航天器为例，同时考虑4块帆板的柔性，应用ADAMS软件对帆板的展开过程进行了建模与仿真，得到了帆板的变形、大范围运动等动力学参量，为航天器帆板的设计提供了一定的依据．     

Multibody Dynamics Modeling of Variable Length Cable Systems

This paper presents a procedure for studying the dynamics ofvariable length cable systems. Such systems commonly occur in deploymentand retrieval (pay-out and reel-in) in cable towing systems such as inship and marine applications.The cable is modeled as a chainand treated as a multibody system. The chain links in turn are modeledas lumped masses. The pay-out/reel-in process is modeled with variablelength links near the towing point.Application in marine systems are presented and discussed.     

Multibody system dynamics simulator for process simulation of ships and offshore plants in shipyards

Since various existing simulation tools based on multibody system dynamics focus on conventional mechanical systems, such as machinery, cars, and spacecraft, there are some problems with the application of such simulation tools to shipbuilding domains due to the absence of specific items in the field of naval architecture and ocean engineering, such as hydrostatics, hydrodynamics, and mooring forces. Thus, in this study, we developed a multibody system dynamics simulator for the process simulation of ships and offshore structures. We based the simulator on six kernels: the multibody system dynamics kernel, the force calculation kernel, the numerical analysis kernel, the hybrid simulation kernel, the scenario management kernel, and the collision detection kernel. Based on these kernels, we implemented a simulator that had the following Graphic User Interfaces (GUIs): the modeling, visualization, and report GUIs. In addition, the geometric properties of blocks and facilities in shipyards are needed to configure the simulation for the production of ships and offshore plants, so these are managed in a database and connected to a specific commercial CAD system in shipyards. We used the simulator we developed in various cases of the process simulation of ships and offshore plants. The results show that the simulator is useful for various simulations of operations in shipyards and offshore industries.     

横向液货补给索道-软管的强迫振动数值分析

考虑索道倾斜角度、鞍座位置、索道跨距等因素影响,对舰船横向液货补给索道-软管动力学问题进行研究.基于静力学原理得到各鞍座位置索道及软管受力情况,进而将横向液货补给系统索道-软管动力学问题简化为具有多个集中质量索道系统的动力学问题.基于Galerkin原理,对偏微分动力学模型进行高阶模态截断,并对典型工况下系统动力学特性进行分析.研究表明,系统存在周期、混沌等典型复杂动力学特性.重点分析了索道跨距、阻尼等对系统动力学特性的影响.     

Sensitivity Analysis of Rigid-Flexible Multibody Systems

An important step in the application of automated design techniques to rigid-flexible multibody systems is the calculation of the sensitivities with respect to design variables. Thispaper presents a general formulation for thecalculation of the first order analytical designsensitivities based on the direct differentiationmethod. The analytical sensitivities are comparedwith the numerical results obtained by the finitedifferences method and the accuracy and validity ofboth methods is discussed. Cartesian co-ordinates areused for the dynamic analysis of rigid-flexiblemultibody systems. To reduce the number ofco-ordinates associated with the flexible bodies, thecomponent mode synthesis method is used. Theequations of the sensitivities are obtainedsymbolically and integrated in time simultaneouslywith the dynamic equations. Examples of 2Dsensitivity analysis of the transient response of aslider-crank and of a vehicle with a flexible chassisare presented, and the accuracy and characteristics ofthe sensitivities are analyzed and discussed.     

Spatial Formulation of Elastic Multibody Systems with Impulsive Constraints

The problem of modeling the transient dynamics ofthree-dimensional multibody mechanical systems which encounter impulsiveexcitations during their functional usage is addressed. The dynamicbehavior is represented by a nonlinear dynamic model comprising a mixedset of reference and local elastic coordinates. The finite-elementmethod is employed to represent the local deformations ofthree-dimensional beam-like elastic components by either a finite set ofnodal coordinates or a truncated set of modal coordinates. Thefinite-element formulation will permit beam elements with variablegeometry. The governing equations of motion of the three-dimensionalmultibody configurations will be derived using the Lagrangianconstrained formulation. The generalized impulse-momentum-balance methodis extended to accommodate the persistent type of the impulsiveconstraints. The developed formulation is implemented into a multibodysimulation program that assembles the equations of motion and proceedswith its solution. Numerical examples are presented to demonstrate theapplicability of the developed method and to display its potential ingaining more insight into the dynamic behavior of such systems.     

Analysis of Large Flexible Body Deformation in Multibody Systems Using Absolute Coordinates

To consider large deformation problems in multibody system simulations afinite element approach, called absolute nodal coordinate.formulation,has been proposed. In this formulation absolute nodal coordinates andtheir material derivatives are applied to represent both deformation andrigid body motion. The choice of nodal variables allows a fullynonlinear representation of rigid body motion and can provide the exactrigid body inertia in the case of large rotations. The methodology isespecially suited for but not limited to modeling of beams, cables andshells in multibody dynamics.This paper summarizes the absolute nodal coordinate formulation for a 3D Euler–Bernoulli beam model, in particular the definition of nodal variables, corresponding generalized elastic and inertia forces and equations of motion. The element stiffness matrix is a nonlinear function of the nodal variables even in the case of linearized strain/displacement relations. Nonlinear strain/displacement relations can be calculated from the global displacements using quadrature formulae.Computational examples are given which demonstrate the capabilities of the applied methodology. Consequences of the choice of shape.functions on the representation of internal forces are discussed. Linearized strain/displacement modeling is compared to the nonlinear approach and significant advantages of the latter, when using the absolute nodal coordinate formulation, are outlined.     

Dynamic Response Calculation of Spatial Elastic Multibody Systems with High-Frequency Excitation

The objective of this paper is to establish a computationalscheme for dynamic response calculations of a three-dimensionalmultibody mechanical system with impulsive forces, which give rise tohigh-frequency excitations. The finite-element method is employed torepresent the local deformations of three-dimensional beam-like elasticcomponents by either a finite set of nodal coordinates or a truncatedset of modal coordinates. A reduced-order model is obtained by invokinga modal transformation. Both planar and complex modal reduction schemesare established. The developed formulation is implemented into amultibody simulation program that assembles the equations of motion andproceeds with its solution. The computational scheme permits a change inthe basis of the modal space in order to regulate the admittance ofhigher frequencies and to accommodate any change in the kinematicconfiguration. Numerical examples are presented to demonstrate theapplicability of the developed computational scheme.     

Multibody Dynamics of Very Flexible Damped Systems

An efficient multibody dynamics formulation is presented for simulating the forward dynamics of open and closed loop mechanical systems comprised of rigid and flexible bodies interconnected by revolute, prismatic, free, and fixed joints. Geometrically nonlinear deformation of flexible bodies is included and the formulation does not impose restrictions on the representation of material damping within flexible bodies.The approach is based on Kane's equation without multipliers and the resulting formulation generates 2ndof+m first order ordinary differential equations directly where ndof is the smallest number of system degrees of freedom that can completely describe the system configuration and m is the number of loop closure velocity constraint equations. The equations are integrated numerically in the time domain to propagate the solution.Flexible bodies are discretized using a finite element approach. The mass and stiffness matrices for a six-degree-of-freedom planar beam element are developed including mass coupling terms, rotary inertia, centripetal and Coriolis forces, and geometric stiffening terms.The formulation is implemented in the general purpose multibody dynamics computer program flxdyn. Extensive validation of the formulation and corresponding computer program is accomplished by comparing results with analytically derived equations, alternative approximate solutions, and benchmark problems selected from the literature. The formulation is found to perform well in terms of accuracy and solution efficiency.This article develops the formulation and presents a set of validation problems including a sliding pendulum, seven link mechanism, flexible beam spin-up problem, and flexible slider crank mechanism.     

Multibody modeling and vibration dynamics analysis of washing machines

In this paper a computational model of a horizontal axis washing machine is presented. The model has been built using a theoretical-experimental methodology consisting of integration of multibody system (MBS) formalism, detailed modeling of machine functional components and experimental data-based validation. The complete model of a washing machine is implemented in the commercial MBS environment Adams/View from MSC.Software. An undesirable impact of washing machine operation on the surroundings is vibration and noise. The impact comes from system dynamics and poorly distributed load inside the drum, creating an imbalance. To get insight into vibration dynamics extensive simulations have been performed for washing machines in service as well as for machines in the developing stage by using the created computational model. This paper presents several results of numerical studies of the vibration dynamics of washing machines including the study of sensitivity of system dynamics with respect to suspension structural parameters, and the results of investigation of the potential of the automatic counterbalancing technology for vibration output reduction. In particular, simulations of the considered two-plane balancing device has shown an existing significant potential in eliminating unbalanced load at supercritical spinning speed, resulting in a substantial vibration reduction in washing machines.     

Multibody modeling of human body for the inverse dynamics analysis of sagittal plane movements

A multibody methodology for systematic construction of a two-dimensional biomechanical model of a human body is presented, aimed at effective determination of the muscle forces and joint reaction forces in the lower extremities during sagittal plane movements such as vertical jump, standing long jump or jumping down from a height. While the hip, knee and ankle joints are modeled as enforced directly by the muscle forces applied to the foot, shank, thigh and pelvis at the muscle attachment points, the actuation of the other joints is simplified to the torques representing the respective muscle action. The developed formulation is applicable to both the flying and support phases, enhanced by an effective scheme for the determination of reaction forces exclusively in the lower extremity joints. The determination of reactions from the ground is also provided. The problem of muscle force redundancy in the lower extremities is solved by applying the pseudoinverse method, with post-processing procedures used to assure the muscle being tensile. Results of the inverse dynamics analysis of vertical jump are reported.