多刚体系统运动仿真中选择自然坐标的自适应调节方法

通过自动调节多刚体系统中每个构件上自然坐标系的形态,达到自动选择自然坐标的目的。提出了自然坐标系的自适应调节方法：首先,为标准自然坐标系找出周边所有基点空位和矢量空位并对其加权;然后,剔除冗余空位并调整权值;接着,找出最多4个权值总和最高的可行空位;最后,标准自然坐标系调节自身形态以占据所有可行空位。调节结果是实际的自然坐标系,它为该构件提供12个合理的自然坐标。在多体动力学仿真平台InteDyna上实现了该方法,提高了自然坐标法的建模效率和建模质量。     

汽车空气悬架的运动学仿真分析及优化设计

建立了某种型号汽车的空气悬架的多体运动学计算模型，进行了运动学分析研究。在此基础上建立了以转向轮接地点的侧向滑移量最小为目标函数的结构参数优化设计模型，进行了优化分析，得到了该型空气悬架的结构参数的较为合理的优化设计方案。     

麦弗逊独立悬架空间运动学分析

麦弗逊式独立悬架其运动学特性的优劣关系到汽车操纵稳定性、舒适性、行驶平顺性和轮胎的使用寿命等方面。悬架空间运动学分析的目的是通过建立和求解其运动学模型,确定悬架机构的空间几何参数及其变化规律,这是进行悬架设计以及分析悬架系统对汽车性能影响的基础。根据麦弗逊式独立悬架的结构特点及其定长约束和定向约束条件,应用空间解析几何的方法对其进行了运动学分析,并由此推导出了悬架运动特性参数的计算公式。通过实例计算表明,该方法直观明了,简便易行,有较好的实际应用价值。     

双横臂独立悬架运动学仿真分析

悬架的运动学性能直接影响操纵稳定性等汽车使用性能.利用Adams多体动力学软件建立双横臂独立悬架的多刚体模型,通过对模型中车轮施加运动约束从而对其进行运动学洼能的仿真分析,从而获得该车轮定位角的变化,将设计要求和分析结果对比可以得出此悬架结构设计的合理性及需性能改进的地方.     

可用于多连杆悬架的并联机构运动学分析

并联机构具有刚度大、响应快和精度高等优点,适用于悬架领域。提出了一种用于汽车多连杆悬架的新型并联机构。建立机构运动学模型,结合螺旋理论,通过位姿参数分析机构空间运动特点,得到表征运动的螺旋量近似为偶量;结合汽车悬架运动学概念,利用齐次变换矩阵给出车轮定位参数,运用螺旋理论提出了悬架瞬时运动学分析方法。     

发动机配气系统运动学仿真分析

配气机构是内燃机的重要组成部分,虚拟样机技术是研究配气机构的重要方法。本文基于多刚体系统运动学原理,并利用ADAMS中的专用模块ADAMS/Engine对某高速汽油机的配气机构进行了运动学建模及仿真研究,获得了气门在不同转速下的位移、速度和加速度曲线。通过分析仿真结果,得出了气门的运动规律,指出了气门冲击、振动随速度变化的趋势。这对发动机配气机构的结构设计、动力学分析、性能预测、故障诊断起到积极的作用。     

基于自然坐标建模方法的多体系统设计灵敏度分析方法

经典的自然坐标建模方法消除了欧拉角和欧拉参数,特别适用于多体系统灵敏度分析及优化问题的研究,但由于提供多种广义坐标选择标准,影响了其自动化建模的实施。提出一种基于改进的自然坐标建模方法的多体系统灵敏度分析方法。首先研究一种广义坐标选择方法,引入12个广义坐标来描述一个空间物体的位置和方向。在选定的广义坐标的基础上,推导出刚性约束条件、基本约束单元及多体系统控制方程组的初始条件。考虑到多体系统控制方程组的特点,使用广义-α积分方法求解方程组并给出算法流程。然后,在上述自然坐标建模体系下,研究多体系统一阶直接灵敏度分析方法及其求解策略。最后,为验证所提方法的有效性和精确性,进行平面转子滑块机构和空间曲柄滑块机构灵敏度分析。测试结果与有限差分法所得结果一致,其间偏差不超过3%。该方法不但便于多体系统的自动化建模,而且有助于降低灵敏度分析的复杂性。为多体系统优化问题提出一个实用且有效的灵敏度计算方法。     

基于ADAMS的车辆空气悬架-转向机构的运动学仿真

利用虚拟样机技术在ADAMS软件环境下建立了某种型号客车的包括转向机构在内的空气悬架转向系统的多体运动学计算模型,并进行了运动学仿真分析研究。得到了随着车轮跳动该型悬架的各项定位参数的变化规律,并且发现内、外侧车轮的偏转角度随时间的变化规律基本满足理想的转向轮偏转角之间的关系。     

CATIA DMU在麦弗逊悬架运动学特性分析上的应用

麦弗逊式独立悬架以其结构紧凑、易于布置横置发动机、构件受力小等优点在现代轿车及轻型客车上得到广泛应用。文中基于CATIA DMU模块对麦弗逊式独立悬架进行了运动学分析，得出某款轿车麦弗逊悬架的运动学特性，为整车K＆amp;C对标及系统设计提供了依据；同时通过与K＆amp;C试验结果对比，验证了该方法在麦弗逊式等受弹性件影响较小的独立悬架运动学分析上的应用具有普遍的适用性。     

Kinematic analysis of the multi-link five-point suspension system in point coordinates

In this paper, a numerical algorithm for the kinematic analysis of a multi-link five-point suspension system is presented. The kinematic analysis is carried out in terms of the rectangular Cartesian coordinates of some defined points in the links and at the joints. Geometric constraints are introduced to fix the relative positions between the points belonging to the same rigid body. Position, velocity and acceleration analyses are carried out. The presented formulation in terms of this system of coordinates is simple and involves only elementary mathematics. The results of the kinematic analysis are presented and discussed.     

机器人动力学分析的完全笛卡尔坐标方法

应用完全笛卡尔坐标的方法研究机器人动力学问题。这种方法是利用参考基点的笛卡尔坐标和参考基矢量的笛卡尔分量描述物体的位置与姿态。由于在提高计算效率方面的突出优点而受到重视,以空间五自由度机器人为例,通过仿真计算机表明该方法在求解机器人动力学问题上的有效的。     

Sensitivity analysis approach to multibody systems described by natural coordinates

The classical natural coordinate modeling method which removes the Euler angles and Euler parameters from the governing equations is particularly suitable for the sensitivity analysis and optimization of multibody systems. However, the formulation has so many principles in choosing the generalized coordinates that it hinders the implementation of modeling automation, A first order direct sensitivity analysis approach to multibody systems formulated with novel natural coordinates is presented. Firstly, a new selection method for natural coordinate is developed. The method introduces 12 coordinates to describe the position and orientation of a spatial object. On the basis of the proposed natural coordinates, rigid constraint conditions, the basic constraint elements as well as the initial conditions for the governing equations are derived. Considering the characteristics of the governing equations, the newly proposed generalized-ct integration method is used and the corresponding algorithm flowchart is discussed. The objective function, the detailed analysis process of first order direct sensitivity analysis and related solving strategy are provided based on the previous modeling system Finally, in order to verify the validity and accuracy of the method presented, the sensitivity analysis of a planar spinner-slider mechanism and a spatial crank-slider mechanism are conducted. The test results agree well with that of the finite difference method, and the maximum absolute deviation of the results is less than 3%. The proposed approach is not only convenient for automatic modeling, but also helpful for the reduction of the complexity of sensitivity analysis, which provides a practical and effective way to obtain sensitivity for the optimization problems of multibody systems.     

A straight methodology to include multibody dynamics in graduate and undergraduate subjects

Multibody dynamics discipline is so mature and has so many applications in the industry, that currently it is essential for mechanical engineering students to learn its basic theoretical foundations. However, universities cannot always integrate the matter as a standalone subject. This article presents an efficient methodology to teach kinematic and dynamic analysis of 3D multibody systems in courses with severe time constraints. A simple theoretical approach (the natural or fully Cartesian coordinates) and a high level programming language (MATLAB) are used. The theory level is shown with two examples: a closed-chain 3D robot and a McPherson car suspension system. Several real exam exercises at the end illustrate the skills acquired by the students in courses of 12 h of theory and 15 h of personal work. This methodology overcomes the limitation of time and the complexity of the issue, and turns out to be one of the simplest approaches to teach multibody systems theory in short graduate or undergraduate courses.     

Numerical kinematic analysis of the standard macpherson motor-vehicle suspension system

In this paper, an efficient numerical algorithm for the kinematic analysis of the standard MacPherson suspension system is presented. The kinematic analysis of the suspension mechanism is carried out in terms of the rectangular Cartesian coordinates of some defined points in the links and at the kinematic joints. Geometric constraints that fix the distances between the points belonging to the same rigid link are introduced. The nonlinear constraint equations are solved by iterative numerical methods. The corresponding linear equations of the velocity and acceleration are solved to yield the velocities and accelerations of the unknown points. The velocities and accelerations of other points of interest as well as the angular velocity and acceleration of any link in the mechanism can be calculated.     

A study on numerical solution method for efficient dynamic analysis of constrained multibody systems

A new and efficient computational method for constrained multibody systems is proposed. In the proposed method, local parametrization method is employed to apply the same solution method for position, velocity, and acceleration analyses since the coefficient matrices for each analysis have an identical matrix pattern. The skyline solution method is used to overcome numerical inefficiency when solving large scaled equations. Also, subsystem mpartitioning method is derived systematically to perform parallel processing for real time simulation. To show the numerical accuracy and efficiency of the proposed method, three numerical problems are solved.     

On the improvement of a fully recursive formulation for the dynamic analysis of multibody systems

Virtual work in multibody systems is frequently expressed as the inner product of the virtual displacement and the resultant force at the centroid. But provided that the resultant force is converted into the equipollent forces there is no restriction on where the analysis reference point is placed. There are basically three candidate points : the centroid, joint point and the instant global origin. The traditional fully recursive formulation uses the centroid, but the present work verifies that the instant global origin always shows better efficiency (e.g. 86% CPU time of the centroid for quarter car model) and joint point shows the efficiency between that of the centroid and the instant global origin. A discussion on how important it is to define the analysis reference point properly in a fully recursive formulation is also presented.     

悬架与整车系统的性能协调分析方法研究

基于车辆系统动力学分析与最优化技术,提出了一种用于悬架与整车系统性能协调分析的新方法,能够以给定的整车性能要求为依据,确定与之相匹配的悬架特性参数。然后,通过算例验证了所提方法的有效性。     

BKX-I型并联运动机床的实验模态分析及灵敏度分析

在对BKX-I型并联运动机床进行实验模态分析的基础上,获得了机床在典型位姿下的低阶固有频率、振型、阻尼比,同时通过对机床系统进行灵敏度分析确定其薄弱环节,并提出提高并联运动机床动态特性的具体措施,为并联运动机床结构的动态设计和优化设计提供了有效的方法。     

Modal analysis of constrained multibody systems undergoing constant accelerated motions

The modal characteristics of constrained multibody systems undergoing constant accelerated motions are investigated in this paper. Relative coordinates are employed to derive the equations of motion, which are generally nonlinear in terms of the coordinates. The dynamic equilibrium position of a constrained multibody system needs to be obtained from the nonlinear equations of motion, which are then linearized at the dynamic equilibrium position. The mass and the stiffness matrices for the modal analysis can be obtained from the linearized equations of motion. To verify the effectiveness and the accuracy of the proposed method, two numerical examples are solved and the results obtained by using the proposed method are compared with those obtained by analytical and other numerical methods. The proposed method is found to be accurate as well as effective in predicting the modal characteristics of constrained multibody systems undergoing constant accelerated motions.