Analysis for the Deployment of Single-Point Mooring Buoy System Based on Multi-Body Dynamics Method

Deployment of buoy systems is one of the most important procedures for the operation of buoy system. In the present study, a single-point mooring buoy system which contains surface buoy, cable segments with components, anchor and so on is modeled by applying multi-body dynamics method. The motion equations are developed in discrete node description and fully Cartesian coordinates. Then numerical method is used to solve the ordinary differential equations and dynamics simulations are achieved while anchor is casting from board. The trajectories and velocities of different nodes without current and with current in buoy system are obtained. The transient tension force of each part of the cable is analyzed in the process of deployment. Numerical results indicate that the transient payload increases to a peak value when the anchor is touching the seabed and the maximum tension force will vary with different floating configuration. This work is helpful for design and deployment planning of buoy system.

Multi-Body Dynamics Modeling and Simulation Analysis of a Vehicle Suspension Based on Graph Theory

Multi-body dynamics,relative coordinates and graph theory are combined to analyze the structure of a vehicle suspension.The dynamic equations of the left front suspension system are derived for modeling.First,The pure tire theory model is used as the input criteria of the suspension multibody system dynamic model in order to simulate the suspension K&C characteristics test.Then,it is important to verify the accuracy of this model by comparing and analyzing the experimental data and simulation results.The results show that the model has high precision and can predict the performance of the vehicle.It also provides a new solution for the vehicle dynamic modeling.

STUDY ON DYNAMICS, STABILITY AND CONTROL OF MULTI-BODY FLEXIBLE STRUCTURE SYSTEM IN FUNCTIONAL SPACE

The dynamics, stability and control problem of a kind of infinite dimensional system are studied in the functional space with the method of modern Mathematics. First, the dynamical control model of the distributed parameter system with multi-body flexible and multi-topological structure was established which has damping, gyroscopic parts and constrained damping. Secondly, the necessary and sufficient condition of controllability and observability, the stability theory and asymptotic property of the system were obtained. These results expand the theory of the field about the dynamics and control of the system with multi-body flexible structure, and have important engineering significance.

Articulated Lifting System Modeling Based on Dynamics of Flexible Multi-Body Systems

In lifting sub-system of deep-sea mining system, spherical joint is used to connect lifting pipes to replace fixed joint. Based on Dynamics of Flexible Multi-body systems, the mechanics model of articulated lifting system is established. Under the four-grade and six-grade oceanic condition, dynamic responses of lifting system are simulated and experiment verified. The simulation results are consistent with experimental ones. The maximum moment of flexion is 322 kN-m on the first pipe under six-grade sea condition. It is seen that the articulated connection can reduce the moment of flexion. The bending deformation of pipe center is researched, and the maximum is 0. 000479 m on the first pipe. Deformation has a little effect on the motion of system. It is feasible to analyze articulated lifting system by applying the theory of flexible multi-body dynamics. The articulated lifting system is obviously better than the fixed one.

Coupled Vibration Analysis of Vehicle-Bridge System Based on Multi-Boby Dynamics

For establishing the refined numerical simulation model for coupled vibration between vehicle and bridge, the refined three-dimensional vehicle model is setup by multi-body system dynamics method, and finite element method of dynamic model is adopted to model the bridge. Taking Yujiang River Bridge on Nanning-Guangzhou railway line in China as study background, the?refined numerical simulation model of whole vehicle and whole bridge system for coupled vibration analysis is set up. The dynamic analysis model of the cable-stayed bridge is established by finite element method, and the natural vibration properties of the bridge are analyzed. The German ICE Electric Multiple Unit (EMU) train refined three-dimensional space vehicle model is set up by multi-system dynamics software SIMPACK, and the multiple non-linear properties are considered. The space vibration responses are calculated by co-simulation based on multi-body system dynamics and finite element method when the ICE EMU train passes the long span cable-stayed bridge at different speeds. In order to test if the bridge has the sufficient lateral or vertical rigidity and the operation stability is fine. The calculation results show: The operation safety can be guaranteed, and comfort?index is “excellent”. The bridge has sufficient rigidity, and vibration is in good condition.

DYNAMIC CHARACTERISTICS ON PRECISION NC LATHE BASED ON MULTI-BODY SYSTEM THEORY

Based on multi-body system theory and the mainshafl system of precision NC lathe as object investigated, it is treated as a coupled rigid-flexible multi-body system which is made up of some rigid and elastic bodies in an especial linking mode. And a dynamic model is established, The problems of computing vibration characteristics are resolved by using multi-body system transfer matrix method, Resutts show that the mainshaft system of NC lathe is in the stable and reliable working area all the time. The method is simple and easy, the idea is clear. In addition, the method can be easily used and popularized in the other multi-body system.

基于UM的车辆-轨道耦合动力学建模及仿真分析

基于多体系统动力学理论,分析某动车各构造拓扑关系及其力学特性,利用多体动力学软件UM建立50个自由度的车辆-轨道动力学模型,仿真分析了车辆的非线性临界速度、脱轨系数、振动加速度及平稳性指数等动力学特性,获得了该型动车直线运行的非线性临界速度477km/h;以200km/h的时速通过曲线半径R=4 000m的曲线线路时车体横向、垂向Sperling平稳性指数分别为2.01和1.69;车体横向、垂向加速度分别为0.062g和0.046g;1位轮对的最大脱轨系数和轮重减载率分别为0.182和0.406 4.研究结果表明:该型动车具有较好的动力学性能.

UM-BUS总线及接入式体系结构

本文针对航天航空等领域综合电子系统在小型化、一体化设计及信息综合利用等方面的需求,提出一种可动态重构的高速串行通信总线(UM--BUS),采用N(≤32)通道并发传输,通信速率可达6.4Gbps,采用总线型拓扑结构,最大通信距离40m,支持最多30个节点直接互连,具有远程存储访问能力,采用命令应答式协议提供QoS与实时性保证;通过并发通道相互冗余与动态重构,在允许50%性能降低的情况下,能够对N/2通道故障动态容错.在UM-BUS总线基础上,本文提出一种新型的"接入式"体系结构模型,在不改变系统逻辑结构的前提下,能够突破机箱结构限制,将逻辑功能分散嵌入到控制测量对象内部,实现功能模块"接入即用",使得综合电子系统一体化设计成为可能.

基于UM的重载列车纵向冲动仿真分析

本文以两万吨的重载列车为研究对象,通过UM建立两万吨重载组合列车的三维模型及列车的运行线路模型;然后在UM simulation中对重载列车进行条件约束,仿真分析得到两种不同编组的两万吨列车的纵向车钩力,与大秦线的两万吨重载列车的试验值基本相近;最后基于UM软件对两万吨重载列车在不同编组、不同长大坡道、不同制动波速的状况下分析,分析结果表明:“1+2+1”编组方式更适合于两万吨重载列车,且列车在下坡度运行时,下坡度越小,纵向冲动就越小;列车在上坡度运行时,上坡度越大,拉钩力越大,纵向冲动随之增大,列车上坡的坡度最大值为8%;另外,列车的制动波速越大,列车的纵向冲动就越小.

Dynamic Analysis of the Seafloor Pilot Miner Based on Single-Body Vehicle Model and Discretized Track-Terrain Interaction Model

In order to achieve the complex dynamic analysis of the self-propelled seafloor pilot miner moving on the seafloor of extremely cohesive soft soil and further to make it possible to integrate the miner system with some subsystems to form the complete integrated deep ocean mining pilot system and perform dynamic analysis, a new method for the dynamic modeling and analysis of the miner is proposed and developed in this paper, resulting in a simplified 3D single-body vehicle model with three translational and three rotational degrees of freedom, while the track-terrain interaction model is built by partitioning the track-terrain interface into discrete elements with parameterized force dements built on the theory of terramechanics acting on each discrete dement. To evaluate and verify the correctness and effectiveness of this new modeling and analysis method, typical comparative studies with regard to computational efficiency and solution accuracy are carried out between the traditional modeling method of building the tracked vehicle as a multi-body model and the new modeling method. In full consideration of the particMar structure design of the pilot miner, the special characteristics of the seafioor soil and the hydrodynamic force of near-seafloor currnt, the dynamic simulation analysis of the miner is performed and discussed, which can provide useful guidance and reference for the practical miner system in design and operation. This new method can not only realize the rapid dynamic simulation analysis of the miner but also make possible the integration and rapid dynamic analysis of the complete integrated deep ocean mining pilot system in further researches.

An efficient formulation based on the Lagrangian method for contact–impact analysis of flexible multi-body system

In this paper,an efficien formulation based on the Lagrangian method is presented to investigate the contact–impact problems of f exible multi-body systems.Generally,the penalty method and the Hertz contact law are the most commonly used methods in engineering applications.However,these methods are highly dependent on various non-physical parameters,which have great effects on the simulation results.Moreover,a tremendous number of degrees of freedom in the contact–impact problems will influenc thenumericalefficien ysignificantl.Withtheconsideration of these two problems,a formulation combining the component mode synthesis method and the Lagrangian method is presented to investigate the contact–impact problems in fl xible multi-body system numerically.Meanwhile,the finit element meshing laws of the contact bodies will be studied preliminarily.A numerical example with experimental verificatio will certify the reliability of the presented formulationincontact–impactanalysis.Furthermore,aseries of numerical investigations explain how great the influenc of the finit element meshing has on the simulation results.Finally the limitations of the element size in different regions are summarized to satisfy both the accuracy and efficien y.

Numerical wear study of metal-on-ultrahigh molecular weight polyethylene-based cervical total disc arthroplasty by coupling finite element analysis and multi-body dynamics

In this study,the effects of in vivo(head flexion-extension,lateral bending,and axial rotation)and in vitro(ISO 18192-1)working conditions on the wear of ultrahigh mo-lecular weight polyethylene(UHWMPE)-based cervical disc prosthesis were studied via numerical simulation.A finite-element-based wear prediction framework was built by using a sliding distance and contact area dependent Archard wear law.Moreover,a pre-developed cervical spine multi-body dynamics model was incorporated to obtain the in vivo conditions.Contact mechanic analysis stated that in vitro conditions normally led to a higher contact stress and a longer sliding distance,with oval or crossing-path-typed sliding track.In contrast,in vivo conditions led to a curvilinear-typed sliding track.In general,the predicted in vivo wear rate was one order of magnitude smaller than that of in vitro.According to the yearly occurrence of head movement,the estimated total in vivo wear rate was 0.595 mg/annual.While,the wear rate given by the ISO standard test condition was 3.32 mg/annual.There is a significant impact of loading and kinematic condition on the wear of UHMWPE prosthesis.The work conducted in the present study provided a feasible way for quantitatively assessing the wear of joint prosthesis.

基于UM的CRH2型车曲线通过性能分析

轮轨间的动力学性能特别是车辆的曲线通过性能是影响行车安全的重要因素之一。基于多体动力学理论和轮轨简化接触理论,应用多体动力学软件UM建立CRH2型动车组拖车模型。在欠超高和过超高两种工况下,分析曲线半径、曲线通过速度、超高以及缓和曲线长度对各动力学指标的影响规律,进一步分析悬挂参数对曲线通过性能的影响。结果表明:分析曲线参数对曲线通过性能的影响趋势时,超高起主导作用;在轴箱弹簧垂向刚度取0.5~2.0 MN/m、横向和纵向刚度取0.9~1.5 MN/m、抗蛇行减振器阻尼取250~900(kN·s)/m时,车辆具有较好的动力学性能。

DYNAMIC BEHAVIOR OF THIN RECTANGULAR PLATE ATTACHED TO MOVING RIGID

A nonlinear dynamic model of a thin rectangular plate attached to a moving rigid was established by employing the general Hamilton＇s variational principle. Based on the new model, it is proved theoretically that both phenomena of dynamic stiffening and dynamic softening can occur in the plate when the rigid undergoes different large overall motions including overall translational and rotary motions. It was also proved that dynamic softening effect even can make the trivial equilibrium of the plate lose its stability through bifurcation. Assumed modes method was employed to validate the theoretical result and analyze the approximately critical bifurcation value and the postbuckling equilibria.

基于UM的重载铁路18号道岔动力特性分析

以18号固定辙叉式道岔为研究对象,利用多体动力学软件UM建立C80车辆模型和18号固定辙叉式道岔模型,然后在UM simulation中进行耦合,生成车辆-道岔耦合动力学模型.通过模拟得到车辆经过道岔时的动力响应,包括轮轨的相互作用、钢轨的振动加速度和位移.结果表明:在车辆进入道岔时,轮轨的相互作用在转辙区主要为横向作用,钢轨横移量最大,在辙叉区主要为垂向作用,钢轨垂向位移最大;在辙叉区还存在有害空间,轮轨垂向力瞬间降到0,轮子出现瞬间悬空状态;当车辆经过道岔时,轮轨冲击突然变大,使钢轨产生较大的横向加速度和垂向加速度.

Dynamic Response Analysis and Vibration Control for A Fixed-Bottom Offshore Wind Turbine Subjected to Multiple External Excitations

For the offshore wind turbines installed in earthquake areas,their operation is affected by seismic loads in addition to wind and wave loads.Therefore,it is necessary to study the dynamic responses and vibration control of the wind turbines.In previous studies,the structural responses of offshore wind turbines are usually investigated in the parked case,while the blade rotation effect is usually not considered.The evaluation on the structural responses may be inaccurate under this condition,further affecting the evaluation on the vibration control performance of a control system.In view of it,this paper established a complete multi-body model of a fixed-bottom offshore wind turbine considering pile-soil interaction,and then performed simulations when the wind turbine was subjected to multiple external excitations.Continued,a single tuned mass damper(STMD)system and a multiple tuned mass dampers(MTMDs)system were applied to control structural vibrations of the wind turbine.Then,based on the construction of a simplified main structure-TMD system,TMD parameters were optimized.Finally,twelve load cases including operating and parked conditions were selected to perform simulations.Results show that the influence of the seismic excitation on blade responses is greater under the parked condition than that under the operating condition.Moreover,STMD/MTMDS exhibit better performance under the parked condition than that under the operating condition.Compared with STMD,MTMDS can better suppress the vibrations at both the fundamental and high-order modes,and exhibits significant robustness under the condition of changing soil parameters.

Dynamic Analysis on the Main Transmission Device of Wooden Ice Cream Sticks Branding Machine

In order to reduce the labor intensity,improve the production efficiency and enhance the equipment stability and the branding accuracy of the pattern,we have completed a double-row high-efficiency wooden ice cream stick branding machine structural design.The rigid-flexible coupling dynamics model is established and the movement and stress of the first-stage chain drive are calculated and analyzed.The comparison of the theoretical calculation results shows that the dynamic modeling and the structural design of the equipment are reasonable and the result of dynamic calculation also provides the basis of load data for dynamic strength calculation of structural components.

Engine Noise Prediction by Using Multi-body Simulation

Abstract： This paper presents a coupled multi-body and FEM （finite element method）-BEM （boundary element method） methodology used to carry out a comprehensive NVH （noise, vibration and harshness） investigation of a four-cylinder internal combustion engine prototype. Firstly, a MBDS （multi-body dynamic simulation） of the internal combustion engine has been carried out, at a defined operating condition, in order to determine the excitation force of the powertrain exciting the cylinder block. In this way, the dynamics of the engine powertrain have been described taking into account both the effects of the gas forces of the combustion process and the inertia forces of the moving parts. Afterwards, the cylinder block excitation forces have been used to evaluate the engine block vibrations and to predict the external noise radiated with both the well-known ATV （acoustic transfer vectors） and MATV （modal acoustic transfer vectors） methodologies at a distance of 1 m from the engine, according to the standard ISO 3744. The dynamics of the engine powertrain and its vibro-acoustic behaviour have been described using LMS （learning management system） Engineering Innovation Virtual.Lab tools.

基于UM的列车纵向动力学仿真分析

基于多体动力学软件UM建立由2节机车、47节车辆和3节3D车辆组成的列车,分析多种工况下车辆模型的仿真数据,探索列车制动过程中的纵向动力学特性。研究表明车钩力受线路条件和车辆所在位置的影响。列车在启动的过程中最大拉钩力出现在列车前部的车辆上,而位于列车后部的车辆产生的拉钩力比较小。制动过程中最大压钩力和拉钩力呈正态分布,最大压钩力和拉钩力均发生在列车中部。上坡和过弯道过程能够缩短列车制动所需要的时间,下坡则增加列车制动所需要的时间。

Advantages of Multi-body Simulation within the Design Process of Heavy Drivetrains

For the further design of the particular gearbox components, the alternating cycles of the respective application mean an often insufficient knowledge of the actual loads occuring in use. Especially for the application within lifting units, such dynamic load cycles are very difficult to pre-estimate. The so-called slack rope test represents the most critical point in the load cycle and provides a special challenge for the gearbox design. Because of this missing expert knowledge, a test bench of such an application is installed and applied to practical movement cycles. Besides the test bench, a multi-body simulation model of the whole system is mapped within the MBS （multi-body simulation） environment SIMPACK. To verify this simulation model, the results are compared with the respective measurements of the test bench. These comparisons show very good agreements. Thus, one of the major advantages of using such simulation tools is the possibility to re-evaluate the internal and external loads during the whole design process. Finally, these simulations serve as a clarification of the load spectrum of the different drivetrain components. Gearbox series or different modifications of the design can now be analyzed prospectively without extensive testing.