基于ANSYS的车桥耦合振动分析

为准确分析车桥之间的相互作用,根据模态综合法推导车桥系统动力平衡方程,基于ANSYS前后处理器的桥梁建模和结果后处理功能,结合自主程序VBDIP(Vehicle Bridge Dynamic Interaction Program),形成1个通用工具用于分析车桥耦合振动问题.以单自由度质-弹系统通过简支梁桥模型为例,计算车桥的动力响应.所得结果与相关文献结果吻合良好,表明该方法正确有效,可用于分析各种车桥耦合振动问题.     

基于板单元形函数的公路桥梁车桥耦合振动分析方法研究

为研究公路多片式梁桥的车桥耦合振动问题,提出一种基于矩形薄板形函数的车桥耦合振动分析方法.该方法以车轮与桥面接触点为界,将车桥耦合系统分为汽车与桥梁2个子系统,分别采用虚功原理与有限元法建立各自的运动方程,并通过车轮与桥面接触处的位移协调条件及车桥相互作用力的平衡关系相耦合,采用矩形薄板形函数实现车桥接触点位移与桥梁节点位移的联系以及车桥相互作用力的分配,通过迭代求解汽车和桥梁的运动方程得到其动力响应.根据分析方法的计算流程,编制了汽车 桥梁耦合系统的动力分析程序,并通过算例分析验证其可行性.研究结果表明,使用基于矩形薄板形函数的公路桥梁车桥耦合振动分析方法得到的车桥动力响应具有较好的精度,该方法具有广泛的适用性,可为多片式梁桥的车桥耦合振动分析提供一种新思路.     

基于多体系统动力学和有限元法的联合仿真在车桥耦合振动研究中的应用*

为了实现车桥耦合振动精细化仿真研究,利用多体系统动力学软件SIMPACK建立完整的车辆空间模型,采用空间杆系和板壳混合单元有限元方法建立桥梁的动力分析模型;然后将车辆和桥梁两个子系统在轮轨接触面离散的信息点上进行数据交换,实现车桥耦合振动联合仿真分析。以高速铁路上的简支梁桥为研究对象,采用基于多体系统动力学和有限元法结合的联合仿真技术,计算了弹性轮轨接触时动车组列车以不同车速通过桥梁的空间耦合振动响应,证明了该研究方法的可行性。     

车桥耦合系统固有频率的研究

建立了用来计算车桥耦合系统各阶固有频率的特征值方法理论,研究了系统的各阶固有频率随车辆在桥梁上相对位置和车辆与桥梁相对刚度的变化规律,以及系统基频随车速和加速度的变化规律.数值算例结果表明,车桥耦合系统的各阶固有频率不仅与相对位置有关,而且与相对刚度有关,并且呈现一定的规律性,车速和加速度对耦合系统的基频也有一点程度的影响,若用桥梁的固有频率取代耦合系统的固有频率将会产生较大误差.     

移动车辆桥梁系统中的振动能量获取

本文对移动车辆作用下桥梁系统的振动能量俘获进行了研究.将车辆模型简化为车轮--弹簧--阻尼器--簧上车身质量体系,桥梁简化为对边简支对边自由板模型,压电俘能结构采用粘贴有压电晶体材料的悬臂梁并在其末端附加一质量块.对于这个耦合动力学模型,首先,通过板壳振动理论推导出了移动车辆作用下板的运动微分方程;其次,根据欧拉伯努利梁振动理论和基尔霍夫第一定律得到了以桥梁振动响应作为激励的悬臂梁动力学--压电耦合方程;最后,对耦合运动微分方程进行了求解并对其数值模拟结果进行了分析.结果表明:采用设计的压电俘能结构可以有效地收集桥梁系统的振动能量,而压电装置的位置、压电梁的厚度、集中质量、车辆速度对压电俘能效率都有一定影响.     

van der Pol系统极限环幅值的时滞控制

对含有时滞位移和时滞速度的van der Pol方程进行了研究,着重研究了时滞参数对van der Pol方程极限环幅值的影响．首先采用摄动法从理论上推导出极限环幅值与时滞参数之间的关系,分析时滞参数对幅值大小的影响,并着重讨论了不改变振动频率情况下对幅值的控制．最后用数值计算的方法验证了理论计算结果,结果表明数值计算结果与理论结果相当吻合．     

智能交通系统车道保持纵横向耦合控制

考虑车辆纵横向运动之间的相互影响,采用位置预瞄和固定车辆间距跟随策略,对基于一列车队的自动化公路系统车道保持纵横向耦合控制进行了研究.利用车载前后双位置传感器检测车辆位置偏差,基于车辆纵横向动力学耦合模型,推导了基于预瞄的车道保持控制系统数学模型;采用非奇异的终端滑模控制技术,设计了车道保持纵横向耦合控制规律.通过构造李雅普诺夫函数,结合相平面方法,分析了控制系统的有限时间收敛性.采用6车辆编队,通过计算机仿真,对文中设计的控制规律进行了验证.仿真结果显示,车队中每个被控车辆在纵向上跟随期望状态的同时能够实现对期望车道轨迹的理想跟踪,跟踪误差精度不超过0.05 m.     

MSC软件应用于铁路桥梁车桥耦合动力响应分析

介绍应用MSC Patran建立铁路客运专线桥梁的三维有限元计算模型,应用MSC Nastran结构分析程序进行桥梁自振频率计算,然后在MSC Adams/RAIL中建立整体车桥系统动力学仿真模型进行车桥耦合作用的仿真分析. 研究表明, 应用该软件可以建立准确的模型,对编组列车通过桥梁进行实时模拟,对于我国铁路客运专线桥梁建设和结构优化具有积极的意义.     

非线性末制导系统参数灵敏度分析

末制导系统参数随着飞行环境及飞行条件的改变而存在摄动,针对这一问题本文提出根据动态灵敏度来分析参数摄动对脱靶量的影响.基于伴随法推导出与系统动态方程相同规模的伴随方程,并通过一次伴随求解计算得到脱靶量对所有可调参数及摄动参数的动态灵敏度,有效的提高了计算效率.传统的直接分析法是将系统状态变量直接对参数变量进行微分,需要对每个参数变量求解一组代数或微分方程,对于状态变量及参数变量较多的情况效率较低.本文基于两种方法对末制导系统的参数灵敏度进行分析,分析结果揭示了参数摄动对脱靶量的影响程度,较小的参数灵敏度为提高系统的鲁棒性提供了依据.     

大气阻力摄动下平均轨道根数在轨实时确定方法

为了满足卫星长期自主运行的任务需求, 本文同时考虑了大气阻力摄动和非球形摄动带谐项两种摄动对卫星平均轨道根数的影响, 提出了采用滤波算法在轨实时估计平均轨道根数的方法. 基于指数大气密度模型推导了大气阻力摄动下平均轨道根数的变化率, 分析了非球形带谐项摄动势函数对平均轨道根数的影响并推导了该影响下平均轨道根数变化率的通用计算方法, 由此建立了滤波状态方程以及以瞬时轨道根数为观测量的量测方程并分析了测量噪声特性; 为减小计算量以便于在轨实现,提出采用基于球形单边Sigma采样的平方根UKF (Unscented Kalman filter)滤波来估计平均轨道根数. 数值仿真结果表明, 该算法有效、精度较高且鲁棒性好, 能够满足卫星长期自主在轨实时计算平均轨道根数的要求.     

求解非线性期权定价模型的自适应小波同伦摄动技术

Leland 模型是在考虑交易费用的情况下,对 Black - Scholes 模型进行修改得到的非线性期权定价模型. 本文针对 Leland 模型,提出了一种求解非线性动力学模型的自适应多尺度小波同伦摄动法. 该方法首先利用插值小波理论构造了用于逼近连续函数的多尺度小波插值算子,利用该算子可以将非线性期权定价模型方程自适应离散为非线性常微分方程组; 然后将用于求解非线性常微分方程组的同伦摄动技术和小波变换的动态过程相结合,构造了求解 Leland 模型的自适应数值求解方法. 数值模拟结果验证了该方法在数值精度和计算效率方面的优越性.     

Homotopy perturbation method for solving sixth-order boundary value problems

In this paper, we apply the homotopy perturbation method for solving the sixth-order boundary value problems by reformulating them as an equivalent system of integral equations. This equivalent formulation is obtained by using a suitable transformation. The analytical results of the integral equations have been obtained in terms of convergent series with easily computable components. Several examples are given to illustrate the efficiency and implementation of the homotopy perturbation method. Comparisons are made to confirm the reliability of the homotopy perturbation method. We have also considered an example where the homotopy perturbation method is not reliable.     

A new analytical method for solving systems of Volterra integral equations

In this paper, a new modified homotopy perturbation method (NHPM) is introduced for solving systems of Volterra integral equations of the second kind. Theorems of existence and uniqueness of the solutions to these equations are presented. Comparison of the results of applying the NHPM with those of the homotopy perturbation method and Adomian's decomposition method leads to significant consequences. Several examples, including the system of linear and nonlinear Volterra integral equations, are given to demonstrate the efficiency of the new method.     

陀螺系统微振动模态摄动分析与灵敏度计算

在状态空间下,将线性陀螺系统微振动问题导向哈密顿体系,可以得到一组加权共轭辛正交关系和模态展开定理．利用这种特点构造了陀螺系统模态摄动计算式与灵敏度计算式,从而解决了拉格朗日体系下陀螺系统模态摄动分析与灵敏度计算的困难,算例显示了文中计算方法的有效性．     

Modeling and stability analysis of cascade buck converters with N power stages

This paper presents a method for stability analysis of N-cell cascade step-down buck converters, which is a kind of complex nonlinear system. A nonlinear model in the form of time-variant state equations is derived, and then the loop gain describing the overall system is introduced. With the help of them, we obtain the equations for phase cross over frequency and gain margin by small-signal perturbation technique, harmonic balance method, and inverse iteration method. Based on the equations, the overall cascade system stability can be analyzed regardless of the number of converters cascaded. Finally, the cascade buck converter with three power stages is used to demonstrate the effectiveness of the proposed stability analysis method.     

Preservation of exponential stability for linear non-autonomous functional differential systems

We consider preservation of exponential stability for a system of linear equations with a distributed delay under the addition of new terms and a delay perturbation. As particular cases, the system includes models with concentrated delays and systems of integrodifferential equations. Our method is based on Bohl–Perron type theorems.     

Creep analysis of cylindrical shell by a finite difference method

The governing equations of the steady state creep of a two-dimensional thin shallow circular cylindrical shell are developed on the basis of Mises' criterion and the power law of creep.Stresses, membrane forces and bending moments expressed in terms of displacements are then linearized by expanding them in the neighbourhood of a certain approximate value of displacement. Substitution of these expressions into the equations of equilibrium reduces the problem into a set of simultaneous linear differential equations with respect to the small perturbation of the displacements. A method that may be interpreted as a modification of the Newton-Raphson method combined with the method of finite differences is used to solve the linear system of equations.Although calculations are made for a cylindrical panel with clamped edges subjected to normal pressure, the method is quite general and other types of shells, boundary conditions and geometries can be treated similarly.     

A Poincaré-Lindstedt approach to bifurcation problems for differential-delay equations

In this paper we shall develop a small parameter perturbation technique which can be used in the study of bifurcation phenomena for differential delay systems. Our analysis is styled along the lines of the method of Poincaré-Lindstedt for ordinary differential equations and can be viewed as a generalization of this method to differential delay equations.     

两自由度非线性系统1:3内共振的渐近摄动分析

提出了一种改进的渐近摄动法,并用该方法研究了同时含平方项和立方项的两自由度非线性系统在1:3内共振情况下的非线性动力学行为.分别在平均方程和原方程的基础上得到了幅频响应曲线和分叉图,对比表明两种结果基本吻合.改进后的渐近摄动法比原有渐近摄动法更容易应用于1:3内共振情况.     

Converting chaos into periodic motion by state feedback control

A simple control method is presented to convert chaos into periodic motion by using linear state feedback of an available system variable. The low-periodic orbits can be derived from the chaotic attractor with slight change of the dynamical structure in the original dynamics. Melnikov's perturbation method in generalized Hamiltonian systems is introduced to explain the control mechanism of directing chaotic motion towards low-periodic motion in the Lorenz equations. Moreover, the existence of periodic orbits is examined in the perturbed Lorenz system. Simulation results verify the effectiveness of Melnikov's analysis.