有频率与振型节线位置要求的结构动力学设计

本文提出了一种同时满足固有频率、振型节线（点）位置要求的结构动力学设计方法。该方法先建立了振型节线（点）位置及变化与独立设计参数的关系，然后在某些约束下利用优化方法求解设计结果；文中同时还给出在模态空间中的固有频率、固有振型的灵敏度分析数值计算方法．算例表明它能有效地解决一些工程结构设计时涉及到固有频率、振型节线（点）位置要求的结构动力学设计问题。     

用附加质量和刚度修改结构固有频率与局部振型

对在结构局部自由度上附加质量与刚度，从而使结构某阶固有频率与局部振型分量满足给定设计要求的动力修改问题提出了一种求解方法。本文方法仅需利用结构局部自由度上的动柔度参数，计算过程简便。给出了一悬臂梁的固有频率与局部振型修改算例来说明方法的有效性。     

大型风力机塔筒的模态分析

结合工程算法和有限元方法对风力机组的塔筒进行模态分析;结合风力发电机组案例,分析了模态主要聚集能量的振型——阶振型与二阶振型;结合有限元方法,对四种工况的固有频率进行分析与比较,得出经简化计算的模型与未简化模型的差异,并且归纳出对固有频率的影响因素。     

开孔对薄板振动频率影响的有限元分析

从理论上讨论了开孔板的固有频率的计算方法；通过有限元分析计算了开有不同尺寸和形状孔的薄板的三阶固有频率值，得到了其振型图；并分析了开孔对薄板固有频率影响的原因，得到了其固有频率值随孔的尺寸和形状的变化规律。     

纤维增强复合薄壳固有特性计算及验证

对悬臂纤维增强复合薄壳的固有特性进行了计算及实验验证。针对纤维增强复合薄壳的结构特点,对其进行了理论建模;通过Rayleigh-Ritz法获得了复合薄壳的固有频率和振型结果;以T300碳纤维/树脂基复合薄壳为例,通过实验测试获得了前8阶固有频率和模态振型。验证结果表明求解的纤维增强复合薄壳固有频率计算结果与实验结果的误差在2.2%~9.3%之间,且两种方法获得的振型结果也吻合,验证了所提出的计算方法的正确性。     

焦炭塔结构的固有频率和振型研究

在传统的直立塔设备固有频率和振型的计算中,将塔设备简化为悬臂梁计算模型,但实际塔的薄壁圆筒结构与梁模型不符,为此对焦炭塔建立有限元分析模型进行模态分析,得到焦炭塔的固有频率和振型,计算分析表明,由于焦碳塔特殊的结构特点使得焦炭塔的振动特性与传统大型直立设备简化为悬臂梁计算模型所得振动特性相比有所不同,因此焦炭塔结构的计算中涉及到高阶振型与固有频率时,不宜简化为悬臂梁计算模型。     

基于MATLAB语言的多自由度振动系统的固有频率及主振型计算分析

多自由度振动系统固有频率及主振型计算分析是研究其振动特性的基础,矩阵迭代法是计算固有频率及主振型的基本方法之一.根据矩阵迭代的方法,利用MATLAB编程并验证程序的正确性.通过程序的运行,能快速获得多自由度振动系统的固有频率以及主振型,为设计人员提供了防止系统共振的理论依据,也为初步分析各构件的振动情况以及解耦分析系统响应奠定了基础.     

含间隙并联腿步行机器人的固有频率分析

针对步行机器人运行中出现振动与关节异响这一现象,采用动力学方法模拟运动副间隙模型的接触状态,分析了含间隙步行机器人的固有频率,避免了计算模态分析方法在仿真分析时会忽略非线性因素的问题.通过瞬态动力学仿真,计算出含间隙步行机器人的位移响应,再经过傅里叶变换,得到频率响应曲线,曲线峰值对应频率即为含间隙步行机器人的固有频率.仿真结果表明,关节间隙的存在会降低步行机器人的各阶固有频率,但间隙不会影响模态振型,1阶振型均为平台与支腿沿X轴的摇摆振动,2阶振型与1阶振型正交,3阶振型均为平台与支腿沿Z轴的扭转振动.     

裂纹对齿轮轮齿结构振动的影响

建立具有裂纹的齿轮轮齿的动力学模型，分析齿轮轮齿发生裂纹后轮齿结构的动力响应及动力特性，并对裂纹出现位置和裂纹尺寸对齿轮结构动力特性的影响进行深入探讨；通过分析计算和有限元数值模拟验证表明，裂纹发生位置对齿轮轮齿振型影响较大，在裂纹发生处振型发生突变；而裂纹大小对其振型和固有频率影响都较大，当裂纹出现后齿轮固有频率发生下降，振型也发生变化，随着裂纹深度的增加，固有频率更加下降，低阶下降显著，而高阶下降缓慢，振型也与无裂纹的情形完全不同。这显示出裂纹对齿轮轮齿结构振动的影响随裂纹尺寸的增加而强烈。     

核电站反应堆冷却剂泵的模态分析

以某核电站反应堆冷却剂泵（以下简称核泵）为研究对象，对核泵结构进行适当简化后，建立有限元模型，并在有连杆和无连杆两种工况下，计算核泵的固有频率，得出了其前12阶固有频率和振型，并结合核泵具体结构对其固有频率和振型进行了简要说明，计算了阻尼器、拉杆和立柱刚度对核泵固有频率的影响。分析结果可以为下一步进行核泵的地震响应分析提供理论依据。     

各向异性材料应力应变分析方法的研究

由于各向异性材料的弹性常数随方向而变化 ,这就使通常用于各向同性材料的光弹性贴片法的基本方程失效。本文从光弹性贴片法的基本原理出发 ,给出正交各向异性板内任一点的应力计算公式 ,同时也提出了正交各向异性板厚度效应的修正系数。文中对带圆孔正交各向异性板孔边应力分布做了光贴片实验并与文献 [2 ]中的有关数值解进行了比较 ,验证了本文工作的正确性     

Analysis of periodic vibrations of a high-power internal combustion engine in the presence of clearances in connections of gears

An efficient method for calculating periodic vibrations of multimass elastic systems with complicated structure by transforming them to chain systems is proposed. The method extends to the case of nonlinear elastic characteristics. The method developed can be used for studying the dynamics of high-power internal combustion engines.     

一种基于虚拟样机的弹性机构固有频率分析的新方法

对弹性机构固有频率的计算提出了一种基于虚拟样机的新方法。使用该方法可以方便迅速的计算任意空间弹性机构在整个周期中的各阶固有频率。     

线阵传感器在弹性元件冲击位移测量中的应用

讨论了线阵传感器在舰船动力装置弹性元件冲击位移测量中的应用情况.首先阐述了应用线振传感器进行弹性元件冲击位移测量的原理及测量方法的技术特点.并结合某型舰用弹性联轴器冲击位移测量的实例,验证了该测量方法的可行性,指出了测量方法工程应用前景.研究成果可应用于橡胶隔振器、弹性联轴器、挠性接管等舰用弹性元件冲击位移测量.     

Large Deformation Analysis and Synthesis of Elastic Closed-loop Mechanism Made of a Certain Spring Wire Described by Free Curves

Recently novel mechanisms with compact size and without many mechanical elements such as bearing are strongly required for medical devices such as surgical operation devices. This paper describes analy...     

Dynamic modeling, input-shaped maneuvering and vibration suppression of flexible body using quasi-coordinates and euler parameters

In dealing with the dynamics of a flexible body, the rigid-body motions and elastic vibrations are analyzed separately. However, rigidbody motions cause vibrations, and elastic vibrations affect rigid-body motions, indicating the inherent coupling between rigid-body motions and elastic vibrations. The coupled equations of motion for a flexible body can be derived by means of Lagrange’s equations in terms of quasi-coordinates. The resulting equations of motion are hybrid and nonlinear. This paper proposes a unified approach for the equations of motion for a flexible body based on the perturbation method and the Lagrange’s equations of motion in terms of quasicoordinates and Euler parameters to analyze a more general case maneuvering. The resulting equations consist of zero-order nonlinear equations of motion which depict rigid-body motions and first-order time-varying linear equations of motion which depict perturbed rigid-body motions and elastic vibration. Hence, the input-shaped maneuvering can be applied to the zero-order equation considering the induced vibrations. Since the input-shaped maneuvering alone cannot achieve vibration suppression, the vibration suppression controller combined with the input-shaped maneuvering is proposed in this study. As a numerical example, a hub with elastic appendages is considered. Numerical results show that the unified modeling approach proposed in this paper is effective in numerical simulation and control design.     

基于测量臂构型的单点残差修正方法

测量臂杆件和关节的弹性变形与臂的摆放构型相关,会影响臂的测量精度.提出了一种基于测量臂构型的单点测量残差修正方法.通过分析测量臂在某一构型下的关节角度与测量臂末端点坐标偏差值之间的映射关系,再根据有序摆放构型下单点测量坐标相对平均坐标的变化曲线,利用不同构型下的关节角度和相应的坐标变化值建立了残差修正数据库,进而应用该数据库对测量臂任意构型下的末端坐标值进行修正.实验证实了其有效性和正确性.     

Nondestructive Electromagnetic Method of Flaw Detection of Products from Dielectric Materials

A nondestructive method of electromagnetic flaw detection of products is proposed. The method is based on the relation between the characteristics of the electromagnetic response to impact excitation in the elastic deformation zone when structure flaws are present in the product. The coordinates of flaw location inside the tested product can be determined using the method proposed in the study.     

Elasto-geometrical error modeling and compensation of a five-axis parallel machining robot

Parallel manipulators have the potentials of high efficiency and high precision in the field of machining and manufacturing. However, accuracy improvement of the parallel manipulator is still an essential and challenging issue, encountering two important problems. Firstly, the ignorance of elastic deformation caused by gravity or deviations of static stiffness model restricts further improvement of accuracy. To solve this problem, an elasto-geometrical error modeling method is proposed. The comprehensive effects of structural errors, elastic deformation under gravity and compliance parameter errors on pose deviations are disclosed. On this basis, the identification equation of actual structural errors and compliance parameter errors can be established. Secondly, the ill-conditioned identification matrix and the identification equation with anisotropic residual error can lead to inaccurate identification results. To solve this problem, a weighted regularization method is proposed. The identification equation with isotropic residual error is built, and accurate identification can be realized with the regularization method. Based on the proposed methods, the error compensation experiment is conducted on the prototype of a five-axis parallel machining robot using a laser tracker. Experiment results show that the accuracy of the machining robot is significantly improved after compensation. An M1_160 test piece and an S-shaped test piece are machined and measured to further validate the effectiveness of the proposed methods. The elasto-geometrical error modeling method and the weighted regularization method can be applied to other parallel manipulators’ accuracy improvement.     

Set-point control of elastic joint robots using only position measurements

Motivated by the dynamic output feedback passification results, point-to-point control laws for an elastic joint robot are presented when only the position measurements are available. The proposed method makes a parallel connection of the robot system and an input-dimensional linear system which obtains the effect of the desired differentiators. It is shown that the closed-loop nonlinear robot system can be rendered output strictly passive and the regulation of the system is achieved in the end. Robustness analysis is also given with regard to uncertainties on the robot parameters. Performance of the proposed control law is illustrated in the simulation studies of a manipulator with three revolute elastic joints.