Multibody dynamics study on galloping of power transmission line

When the power transmission line (PTL) passes through a region of high mountains and heavy snowfall, maintaining the stability of the PTL and avoiding sleet jump and galloping are necessary. In this study, PTL is modeled as the mass-spring-damper system by using the multi-body dynamics analysis program, RecurDyn. The lumped mass model is compared with the finite element model based on deflection. To analyze the dynamic behavior of the PTL under icing and wind conditions, we obtained a damping coefficient for a multibody model from the free vibration test and Rayleigh damping theory. The icing cross-section of the transmission line is assumed to have ellipse and triangle shapes. The aerodynamic coefficients for each cross-section are derived by using the commercial CFD program, ANSYS Fluent. The occurrence of galloping is simulated for each shape according to the attack angle. Results indicate that the dynamic behavior of the PTL and the galloping conditions such as the icing shape, thickness, and attack angle, can be analyzed. Furthermore, the effects of each factor are evaluated. In the elliptical icing section, the effect of icing thickness is high; whereas in the triangular icing section, the wind velocity highly affects galloping.     

Multibody contact dynamics on mechanisms with deep groove ball bearing joints

The dynamics of ball bearings are important to fatigue breakage, dynamic performance and motion precision of mechanisms connected by ball bearings joints with multi-clearances. In this study, a new method is proposed for multibody dynamics analysis on mechanisms under the effects of radial internal clearances and impact of balls/cage pockets interactions of ball bearings. Including balls/rings interactions and balls/cage pockets interactions, the three dimensional dynamics models of the crank slider mechanism are established and calculated by generalized-α algorithms on the basis of Hertzian contact theory and penalty function method. The rules of eccentric trajectories of inner and outer ring center for one ball bearing joint are verified with the results calculated by XU’s references. The results of dynamic errors, motion trajectories, dynamic forces are achieved under different speeds, radial clearances and number of ball bearings. The speeds and radial clearances are critical to the dynamic performances and motion precision of mechanisms, especially the number of ball bearings. The number of ball bearings is important to impact force and motion stability of the mechanism.     

Multibody dynamics of closed,open, and switching loop mechanical systems

The vast mechanical systems could be classified as closed loop system, open loop system and open & closed (switching) system In the closed loop system, the kinematics and dynamics of 3-D mechanisms will be reviewed and closed form solutions using the direction cosine matrix method and reflection transformation method will be introduced In the open loop system, kinematic & dynamic analysis methods regarding the redundant system which has more degrees of freedom in joint space than those of task space are leviewed and discussed Finally, switching system which changes its phase between closed and open loop motion is investigated with the pinciple of dynamical balance Among switching systems, the human gait in biomechanics and humanoid in robotics are presented     

Multibody approach to dynamic analysis of driver-interactive seatbelt system with motorized retractor

The purpose of this research was to analyze the dynamic behavior of a seatbelt system, focusing on the kinematics of its motorized retractor mechanism as well as its overall performance. The motorized retractor was modeled based on the multibody principle, taking into consideration of the detailed kinematic configuration of the one-way clutch mechanism, which is the critical component of the system. The conditions for fail-safe operation along with the effects of the design parameters of the clutch were studied. It was found that groove length is the most significant design parameter in the engagement and disengagement process. The seatbelt model was setup integrating motorized retractor, flexible webbing and dummy models into a single dynamics system. The validity of the model was confirmed by the good correlation of the simulated and measured webbing forces values obtained from a pre-tensioner detonation test. Using this model, the dynamic performance of the motorized-retractor-driven seatbelt system was evaluated according to a predetermined scenario, and the effectiveness of the retractor’s control of driver posture regardless of the initial torso position was investigated. It was concluded that the seatbelt-driver interaction model can be used as an effective and practical design tool for motorized retractors as well as entire seatbelt systems.     

多体动力学的休斯敦方法及其发展

介绍多体动力学休斯敦方法的核心内容（含低序体阵列、变换矩阵、广义坐标及其导数、运动参数计算和动力学方程等）及其发展,即柔性体的有限段方法及综合模态分析方法。将变形表示为二阶小量形式,基于小变形原理,适时进行线性化,以获取动力刚化项和一致线性化动力学方程。     

多体动力学在机械工程领域的应用

介绍多体系统动力学的休斯敦方法及其发展。重点介绍在机械工程领域的应用和取得的成果。首先是工业机器人的时间域和频率域分析。其次是数控机床全误差模型的,误差参数辨识和软件补偿的实现。最后是柔性机械臂的振最后是可用于航天器的具有大范围运动的柔性体支学分析。通过实践,进一步推动了多刚体和多柔体系统力学的发展。     

系统动态学在区域物流系统研究中的应用

目前,研究区域物流系统的有效方法与手段还比较少,而系统动态学与区域物流系统相结合的研究方法更是一种新的尝试。通过建立区域物流系统动态学模型、对模型的仿真以及对仿真结果的分析,证明用系统动态学方法研究区域物流问题是可行和有效的。     

柔性多体系统动力学的递推建模与算法

基于将２种变量的耦合运算降低到最少的数学模型的建立,是解决柔性多体系统动力学数值病态的关键。提出一种柔性多体系动力学的单向递推建模方法。在此基础上提出了一种新的违约校正方法,在数值计算上给予保证,最后,通过对一个闭环柔性多体系统的动力学与控制仿真计算的实现,表明上述方法的可行性。     

一种改进的齿轮多体系统动力学模型

运用多体动力学理论建立了齿轮多体系统模型,该模型由可沿圆周转动的轮齿、弹性单元和齿轮本体组成,轮齿和齿轮本体虽然仍是刚体,但它们以转动弹簧-阻尼器相连接。采用了迟滞接触力模型分析轮齿间的啮合,为了验证该模型,分别以该模型、有限元模型和其他文献的模型研究单对渐开线直齿圆柱齿轮的啮合过程,对比分析表明:该模型的计算结果更接近于有限元方法,非常适用于齿轮系统的多体动力学分析。     

一种多体动力学优化方法的研究与实现

介绍了一种多体动力学优化设计方法,基于iSIGHT软件集成Pro/E和ADAMS,建立了优化设计平台.以夹紧装置优化设计为例,验证了该平台的有效性和合理性.     

Multibody dynamic analysis of a duplicate bimodal tram

This study aimed to dynamically analyze a simulated bimodal tram by determining the motion equations for computer-aided analysis with Newton-Euler equations of motion, which algebraically represent motion. We utilized the multi-body dynamics analysis program, MSC.Adams, to evaluate the equations of motion, running stability, curving performance, and ride comfort of the simulated bimodal tram in comparison with single fleet and double fleet trams. For the double fleet tram, the characteristic equation was deduced to control the all-wheel steering mechanism by independently moving all the wheels characterizing an articulated vehicle. Our study aimed to design a double fleet bimodal tram. We confirmed that domestic and international standards were satisfied via the design and analysis of the simulation. Steering control equations are the significant preliminary data for coupling device research and development for double fleet bimodal trams.     

蛙式打夯机的单边约束多体系统动力学建模与数值模拟

蛙式打夯机的建模与数值模拟问题是典型的受到多个含摩擦单边约束作用的多体系统动力学问题.通过对蛙式打夯机及其工作环境的合理假设,建立蛙式打夯机的简化多体模型.利用第一类拉格朗日方程,得到其动力学方程,它受到两个含摩擦单边约束的作用.采用冲量-速度层面上的时间步长算法以及与判断stick-slip状态转换条件等价的线性互补公式,对蛙式打夯机的整个工作过程进行数值模拟.计算结果完整地模拟了蛙式打夯机的行进过程中的stick-slip现象和周期性离地-夯击地面的过程.利用数值结果对衡量打夯机性能的两个重要参数,即蛙式打夯机行进速度和每次夯击过程中地面吸收的机械能进行计算.     

多体动力学的键合图表达及其在Modelica中的实现

给出了多体动力学第一类拉格朗日方程的键合图表达,并采用键合图的Modelica库在Dymola中对示例进行了建模和仿真,结果表明,多体动力学拉格朗日方程的键合图表示是非常简单的,清晰地表明了拉格朗日乘子的物理含义,可将其容易地扩展到柔性多体动力学领域,是一种非常合适的多体动力学表达方法.     

含间隙多体系统销轴磨损动力学仿真研究

为了准确预测旋转铰磨损趋势,并能够准确的将其结果应用于磨损动力学仿真与计算,基于含间隙曲柄滑块机构的动力学模型,考虑接触过程中销轴和孔的接触面曲率半径变化趋势,建立了一种依据接触宽度变化计算的曲率半径外推法磨损仿真模型,并利用计算结果,对机构的磨损动力学变化趋势进行了仿真研究,得到销轴在系统不同载荷下的受力分布规律、磨损规律以及动力学特征,找到了系统功能退化的规律。     

多体系统发射动力学进展与应用

现代战争对诸如多管火箭、火炮、坦克、装甲车辆等常规武器的射击密集度的要求不断提高。射击密集度差、试验用弹量大、发射不安全成为制约现代常规武器发展的难题。武器射击密集度和发射安全性取决于武器系统动力学规律,发射动力学作为研究武器系统发射过程中受力和运动规律的一门新兴学科分支,在国际上已成为提高武器射击密集度和发射安全性的新技术突破口。针对上述情况,介绍了多体系统发射动力学理论与技术进展及其在武器射击密集度和安全性设计与试验中的应用,为武器射击密集度和安全性设计与试验提供新理论与技术。     

Assessing capacity scalability policies in RMS using system dynamics

This paper presents a model for assessing different capacity scalability policies in Reconfigurable Manufacturing System (RMS) for different changing demand scenarios. The novelty of this approach is two fold: (1) it is the first attempt to explore different capacity scalability policies in RMS based on multiple performance measures, mainly scaling rate, Work In Process level, inventory level and backlog level; and (2) the dynamic scalability process in RMS is modeled for the first time using System Dynamics. Different policies for capacity scalability for various demand scenarios were assessed. Numerical simulation results obtained using the developed capacity scalability model showed that the best capacity scalability policy to be adopted for RMS is dependent on the anticipated demand pattern as well as the various manufacturing objectives. The presented assessment results will help the capacity scalability planners better decide the different tradeoffs between the competing strategic and operational objectives of the manufacturing enterprise, before setting the suitable capacity scalability plan parameters.

多体动力学的键合图表达及其在Modelica中的实现

给出了多体动力学第一类拉格朗日方程的键合图表达,并采用键合图的Modelica库在Dymola中对示例进行了建模和仿真,结果表明,多体动力学拉格朗日方程的键合图表示是非常简单的,清晰地表明了拉格朗日乘子的物理含义,可将其容易地扩展到柔性多体动力学领域,是一种非常合适的多体动力学表达方法。     

多体动力学仿真数据驱动的列车运行可视化

针对传统多体动力学软件无法直观体现出列车真实运行环境,而目前主流的列车虚拟运行仿真系统又无法实现对列车运行平稳性评估的现状,提出了一种多体动力学仿真数据驱动的列车运行可视化方法。采用三维GIS技术,实现了不同线路环境下列车运行三维场景高精度模型的构建。使用多体动力学软件SIMPACK对列车在不同速度和不同轨道谱下的运行进行动力学仿真,并基于仿真后处理数据建立了最小二乘线性回归模型,预测出列车在不同运行状态下的垂向平稳性指标值。借助三维可视化引擎UNIGINE,实现了以列车运行的多体动力学仿真数据来驱动列车模型运动的三维可视化。     

输送带柔性多体动力学建模方法研究

考虑到输送带的黏弹性,结合有限元离散方法和多体动力学理论,提出用刚体单元描述输送带的刚性特征,以弹簧阻尼单元描述输送带的柔性特征,对输送带进行离散建模。运用拉格朗日方法推导刚体元的动力学微分方程,用递推组集方法建立带式输送机系统的柔性多体动力学方程。用该方法对一带式输送机的起动阶段运行速度进行了仿真分析,通过仿真分析结果与实测数据的对比,验证了方法的正确性和实用性,为带式输送机动态设计方法的进一步研究提供了可借鉴的参考数据和理论依据。