轮胎机械特性虚拟试验场

轮胎对汽车性能具有十分重要的影响,因此对其进行机械特性试验是十分必要的.而传统的在室外进行的轮胎试验总有不少干扰,在室内进行试验又会受到实验室条件的限制.为了克服传统试验的不足,将虚拟试验场技术与有限元和动力学方法相结合,以P215/70R15轮胎有限元模型为对象,设计了轮胎径向刚度、外倾刚度和侧偏刚度虚拟试验场,分析了轮胎径向刚度、外倾刚度、侧偏刚度与胎压、径向载荷、车速等因素的关系,与实际比较符合,证明了轮胎机械特性虚拟试验场建立的可行性,为轮胎机械特性试验提供了一种新的有效的方法.     

波纹管有限元建模方法

为验证不同建模方法对波纹管结构力学特性有限元分析的适用性,根据EJMA方法求得波纹管轴向刚度、弯曲刚度和由轴向力引起的弯曲应力理论值,同时基于有限元法分别建立波纹管二维轴对称模型、三维壳模型和三维实体模型,求解波纹管的轴向刚度、弯曲刚度和最大应力值。通过对比3种有限元模型轴向刚度、弯曲刚度和最大应力有限元数值与理论值之间的关系,表明3种有限元模型均适用于波纹管结构力学特性有限元分析,同时给出3种有限元模型的适用范围,为波纹管设计分析提供参考。     

机械法向接触特性参数的实验方法

针对实验的方法获取机械结合面法向接触特性参数,首先将结合面间的接触状态等效成刚度和阻尼,建立了结合面法向接触的动力学数学模型,以该动力学模型为依据设计了实验试件结构和传感器安装结构。其次设计了实验数据采集与处理系统,获取机械结合面法向接触实验参数。     

基于Abaqus的有限元渐进损伤强度分析

以含损伤复合材料泡沫夹层板为例,介绍有限元渐进损伤强度分析方法在结构强度计算中的应用.对复合材料面板采用Hill Tsai强度理论和Tsai Wu张量理论作为强度判断依据,采用一定的材料性能退化方法,对有限元模型中破坏的单元进行刚度折减.使用Abaqus/CAE进行参数化建模,使用Python程序控制渐进损伤分析的整个过程.经过实验和算例验证,有限元渐进损伤强度分析的结果与实验结果极其吻合.因此,渐进损伤分析方法结合适当的强度理论、材料性能退化方法可以应用于复杂结构的强度分析.     

基于Marc的空气弹簧横向特性分析

为实现空气弹簧的横向特性和强度分析,基于有限元非线性接触技术,用Marc对空气弹簧的非线性横向刚度特性进行数值模拟,分析最大横向力作用下空气弹簧各部分的应力分布,横向刚度计算结果与试验结果基本一致,表明空气弹簧的建模与仿真方法的合理性,为空气弹簧优化设计和特性分析提供参考.     

民用飞机结构强度设计中的全机精细有限元 分析技术及其应用

借助大型计算机云计算资源,最大程度地保留结构细节特征进行全机精细有限元建模,并应用于大型民用飞机全机静力试验数值模拟仿真计算。全机精细有限元模型仿真数据与试验数据的对比结果表明：与传统的内力求解等效刚度有限元模型相比,精细模型在结构应力、稳定性和连接强度的计算精度方面具有独特优势。对全机精细有限元模型的建模特点、精度优势和技术难点进行剖析,探讨其在民用飞机结构强度设计中的应用前景。     

车辆橡胶防尘罩静力学特性分析

通过橡胶标准试件的轴向拉伸试验,得到有限元计算所需要的材料模型参数,分析了车辆防尘罩结构的刚度和强度,以及实际工况下防尘罩结构与轴杆是否存在干涉.根据橡胶产品的国家标准进行标准试样的拉伸试验,采用有限元模型中建立材料模型和建立相应的标准试样和橡胶防尘罩产品的有限元模型,并通过非线性有限元软件MSC-Marc进行了计算,得到标准试样和橡胶防尘罩产品的刚度,计算结果与原理分析吻合,从而验证了有限元计算中所建立材料模型是正确的,并对有限元软件分析的橡胶防尘罩应力分布问题.计算结果表明,能满足车辆防尘罩静力学分析的需要.     

卫星结构板优化设计

利用MSC Patran对某板式卫星结构进行有限元建模,采用MSC Nastran对卫星进行模态分析,获取整星结构的模态参数,并与试验结果进行比对,验证有限元模型的正确性和准确度。在满足结构强度和刚度的约束条件下,对安装有效载荷单机的关键底板进行刚度和强度优化设计。优化前后结构的有限元仿真分析表明：优化设计可有效抑制载荷单机处的振动位移响应。     

新型工业机器人结构设计及其全域刚度预估方法

设计了一种新型5自由度无间隙传动工业机器人结构,机器人机械臂采用平行四边形框架及电动缸对角驱动的桁架式结构,有利于提升机器人的综合刚度．腰部和腕部采用双电机驱动主从消隙控制消除传动间隙,臂部电动缸的滚珠丝杠副通过双丝母预紧消除反向间隙,实现机器人无间隙传动．根据机器人外部载荷和基于能量法计算的机器人末端变形建立机器人全域工作空间刚度预估模型,通过机器人的整机刚度有限元仿真结果及原理样机的实验结果验证了刚度预估模型的有效性．最后,分析了机器人的刚度分布特性并与Fanuc S900iB/400工业机器人进行了刚度比较,结果表明了本文机器人结构的刚性优势．     

虚拟实验环境中的实体及其建模

虚拟实验的元器件模型通过用数学模型来代替物理上存在的具体的物理器件,这种数学模型应该能够正确的反映器件的物理特性和电学特性,且便于在计算机上作数值计算。文章分析了虚拟实验环境中的虚拟实体的特性和行为特征,提出了一种虚拟实验的建模分类方法与虚拟元件的建模方法,将元器件的建模分为基于正向操作模型建立和基于逆向操作的模型建立,并通过分析电子实验的特点,探讨了电子实验的元件建模方法和元件的模型的类结构图,建立了电子实验的元件的模型类体系结构,并分析了这种建模方式的特点和优缺点。     

细长柔性空间结构几种动力学模型的比较

对于自由-自由边界的大型柔性梁式空间结构在轨搬运过程中,其大范围刚体运动和柔性振动会相互耦合,是一类典型的刚柔耦合动力学问题.建立相对准确的动力学模型是设计良好控制系统的前提,但现有文献在研究该问题时却采用了忽略刚柔耦合作用的动力学模型并依此设计控制器,因此有必要建立耦合模型,并探讨其与非耦合模型之间的区别和适用性.首先针对结构自身运动特点选择以瞬时质心为原点的浮动坐标系作为辅助坐标系,将结构两类不同的运动形式进行分解,并利用其产生的附加约束条件简化虚功表达式;其次选择Euler-Bernoulli梁变形形式描述结构变形并采用假设模态法对变形进行变量分离;基于虚功原理推导得到结构大范围运动的刚柔耦合动力学模型;通过仿真算例1对非耦合模型、零次近似模型和一次近似模型进行了对比,验证了非耦合模型的不合理性及零次近似简化模型的准确性和有效性;通过仿真算例2对零次近似简化模型和一次近似模型的对比,说明了二者的使用范围;仿真对比为后续的运动控制系统设计和振动抑制研究提供了依据.     

A novel transition model for lubricated revolute joints in planar multibody systems

The dynamic behavior and the life of machineries are greatly affected by lubricated clearance joints,which are inevitable in mechanical systems, whereas investigations on lubricated clearance joints are very limited due to the difficulty in coupling lubrication theory with dynamics. By analyzing the transition status and considering the hydrodynamic lubrication, elasto-hydrodynamic lubrication, and partial lubrication and contact a novel transition model for the lubricated clearance joint is proposed to tackle with the transition between the lubrication statuses and the contact status. With the novel transition model, we performed numerical dynamic simulations based on a slider crank mechanism with a lubricated clearance joint. Using the novel transition model and the existed transition model (Flores model) in numerical simulations, we obtained and compared dynamic results, which demonstrate that the novel transition model is more accurate, efficient, and feasible than the Flores model.     

Adaptive motion/force control of multiple manipulators with jointflexibility based on virtual decomposition

In this paper, a virtual decomposition-based adaptive motion/force control scheme is presented to deal with the control problem of coordinated multiple manipulators with flexible joints holding a common object in contact with the environment. The control scheme is essentially a generalized Newton-Euler approach in which the original system is virtually decomposed into several subsystems, including the held object, the rigid links, and the flexible joints, so that the control problem of the original system can be greatly simplified. An interesting result is that the dynamic coupling between every two physically connected subsystems is completely represented by the so-called virtual power flow (VPF) at the cutting point between them. The VPF takes a very simple form and is very easy to handle. Control design of the constraint/internal forces can be performed with respect to the held object. Asymptotic stability of the overall system is ensured in the sense of Lyapunov. Computer simulations of two manipulators transporting an object in the plane are given to show the validity of the proposed scheme     

含铰链间隙的刚-柔机械臂动力学模型

根据Hertz接触定律和Coulomb摩擦定律,建立了含间隙平面旋转铰的力学模型;采用几何变形约束法和模态缩聚技术描述柔性机械臂的非线性变形;同时考虑两个旋转铰的间隙特性和柔性臂的弹性变形,最终采用Kane方程建立了含铰链间隙的刚-柔机械臂系统的动力学模型．     

A Continuous Analysis Method for Planar Multibody Systems with Joint Clearance

Clearance from manufacturing tolerances or wear is likely to degrade the dynamic performance of connected machine parts. When joint clearance is introduced, the dynamic response of the mechanical system is substantially changed, seen as high acceleration and force peaks and dissipation of energy. Looking at contact models, the simpler ones, such as the linear Kelvin–Voigt or the nonlinear Hertz model, are characterized by a set of parameters. These include material parameters, coefficient of restitution and possibly a coefficient of friction. The analysis models can be divided into two groups – continuous and dis-continuous, related to whether integration is carried out through the period of contact, or stopped and restarted after the impact.Based on the equations of motion for a multibody system of rigid bodies, it is suggested that the continuous analysis approach is combined with a contact force model to describe joint clearance in rotational joints. Performing simulations with this methodology allows not only to quantify the overall mechanism behaviour, but also in-depth analysis of the impact mechanics in the clearance joint. Experimental data from a double pendulum impacting a rigid plate is used to verify the suggested continuous analysis method.     

一种新型高精度动平衡测量系统

根据瞬时运动中心的概念,提出了一种新型高精度动平衡测量系统.分析了该振动系统的机械结构特点,阐明了实际测量系统与虚拟测量系统的关系,推导了求取不平衡质量的平面分离方程.该系统由两个四杆机构通过柔性铰链串连组成,保证振动中心位于两个支承处,提高了平面分离度;将压电传感器安装在同一平面内,减小了外界环境因素对传感器的影响;最后采用FFT高精度提取整周期采样到的不平衡振动信号的参数.实验结果表明了该新型动平衡测量系统的优越性.     

超高速电梯系统动态仿真分析

电梯的振动是影响舒适性的最主要因素,针对4.0 m/s 超高速电梯系统,以轿厢- 轿架-导轨-钢丝绳耦合系统为研究对象,建立垂直系统振动动力学模型,结合机械系统动力学自 动分析虚拟样机技术,通过建立钢丝绳动力学模型、添加导轨与导靴之间的接触力、水平振动 激励及垂直振动激励,建立电梯整机虚拟样机模型,设定约束与驱动,进行动态特性仿真分析。 仿真结果表明,电梯垂直振动加速度、水平振动加速度等性能指标满足要求,为超高速电梯的 开发提供了设计依据。     

虚拟人骨骼结构的多刚体系统建模方法研究

提出了一种虚拟人骨骼结构的多刚体系统模型,可有效地克服DH表示法只能适用于单链结构的缺陷．首先通过合理的简化与假设,给出了一种16关节、39自由度的虚拟人简化模型;然后将该虚拟人模型抽象成为一个各肢体间通过机械转动铰相连的多刚体系统;最后引入树模型与低序体阵列来表达虚拟人的骨骼结构．分析结果表明,文中方法除能够自然地表达虚拟人的复杂分支结构外,还可以容易地实现虚拟人模型的任意分辨率扩展,并具备递归计算的优点,具有广泛的适用性。     

Dynamic Analysis for Planar Multibody Mechanical Systems with Lubricated Joints

The dynamic analysis of planar multibody systems with revolute clearance joints, including dry contact and lubrication effects is presented here. The clearances are always present in the kinematic joints. They are known to be the sources for impact forces, which ultimately result in wear and tear of the joints. A joint with clearance is included in the multibody system much like a revolute joint. If there is no lubricant in the joint, impacts occur in the system and the corresponding impulsive forces are transmitted throughout the multibody system. These impacts and the eventual continuous contact are described here by a force model that accounts for the geometric and material characteristics of the journal and bearing. In most of the machines and mechanisms, the joints are designed to operate with some lubricant fluid. The high pressures generated in the lubricant fluid act to keep the journal and the bearing surfaces apart. Moreover, the lubricant provides protection against wear and tear. The equations governing the dynamical behavior of the general mechanical systems incorporate the impact force due to the joint clearance without lubricant, as well as the hydrodynamic forces owing to the lubrication effect. A continuous contact model provides the intra-joint impact forces. The friction effects due to the contact in the joints are also represented. In addition, a general methodology for modeling lubricated revolute joints in multibody mechanical systems is also presented. Results for a slider-crank mechanism with a revolute clearance joint between the connecting rod and the slider are presented and used to discuss the assumptions and procedures adopted.