转角振型的全模态试验识别

本文针对传统的试验模态分析中转角自由度截断所造成的误差,给出了一种转角自由度的识别方法.该方法利用平动—转动传感器,通过全模态试验和全模态参数辨识,以估计结构振动中的转角自由度和平动自由度,识别其包括转角振型在内的全模态振型.通过Timoshenko梁的实例验证,讨论了本方法的特点及可行性.     

换热管缺陷扭转模态导波检测的仿真研究

换热管作为换热器的关键部件之一,对其进行检测至关重要。扭转模态T（0,1）超声导波具有无频散特性,在换热管检测中有广阔的应用前景。采用ANSYS 有限元方法对T（0,1）模态导波检测进行仿真研究,为克服在ANSYS中Solid 164单元无旋转自由度而无法加载转角或扭矩的问题,提出了通过施加刚体转动间接激励T（0,1）模态导波的方法。研究了转角加载和扭矩加载两种不同激励方式,仿真结果表明两种激励方式都可以成功激励出T（0,1）模态导波,缺陷定位准确,且扭转模态导波在弯管中衰减更大。     

利用模态参数—有限元扩充振型的结构动力修改法

本文提出了利用模态参数一有限元扩充振型结构的动力修改法。该方法用结构有限元动力模型对测试位移振型进行扩充,得到转角振型和满振型。用此满振型{φ}作为实际结构振型,进而对结构进行动力修改预测。由于考了转角自由度和转动惯量的变化,预测精度比现有的利用测试模态参数进行结构动力修改法好。数值计算的仿真实例及多盘转子系统结构动力修改实例表明,该方法是桁确的、有效的。     

钢质圆盘单自由度导纳圆法模态分析

针对钢质圆盘自由振动问题,应用单自由度导纳圆法模态方法,得到其固有频率,振型及阻尼比,并将实验数据与有限元仿真比较。结果表明:频率的计算值与实验值吻合良好,前5阶次最大误差为9.39%,可以满足工程需要。可以辨识出对称的模态振型,而且实验结果可靠,证明了本方法的有效性。     

二自由度球关节电机转角与球关节角映射研究

球关节广泛用于微创手术机器人。针对一种运动灵活、加工方便、控制简单的二自由度球关节,研究其电机转角与真实球关节的转角之间的映射关系。利用建立数学模型、编程计算等方法,求解出每一时刻真实球关节的转角所对应的二自由度球关节电机转角。并建立三维模型,将两个球关节的转角值和三维模型导入Adams中进行仿真,得出两球关节末端点的运动轨迹数据,然后采用Matlab对运动轨迹数据进行偏差分析,从而论证了映射关系的正确性,为实际运动控制提供数据支持。     

六自由度并联平台的模态分析方法研究

通过实验模态分析和灵敏度分析的方法可以获得六自由度并联平台在典型位姿下的低阶固有频率、振型、阻尼比,并确定其薄弱环节.以BKX-Ⅰ型并联机床为例对六自由度并联平台的实验模态分析和灵敏度分析方法进行了研究,并提出了提高六自由度并联平台动态特性的具体措施,为其结构的动态设计和优化设计提供了有效方法.     

基于应变模态的模态应变能损伤识别方法

传统模态应变能计算需要完备模态振型信息,而模态振型信息中存在转角自由度难以准确获取的问题,为解决该问题,开展基于应变模态的模态应变能损伤识别研究,实现了结构损伤的定量识别。首先,通过基于应变与位移之间的联系,推导出应变模态与位移模态之间的转换矩阵;其次,利用应变模态代替位移模态计算单元模态应变能,建立基于灵敏度分析的损伤识别方程组;最后,根据奇异值截断法求解该方程组识别结构损伤。以一两端固支梁结构为对象,开展数值仿真和实验研究。结果表明,该方法可以有效识别出结构的损伤位置和损伤程度,相对于基于振型扩充的模态应变能损伤识别方法,具有更好精度和抗噪性能。     

Matlab与VB结合在机械振动模态分析中的应用

阐述了应用MATLAB与VB编程工具相结合的手段开发机械振动特性研究软件的方法 ,以二自由度可解耦系统的振动模态分析为例编制了相应程序 ,可快速有效地进行不同物理常数时模态数据计算和波形表达。     

工程车辆驾驶室振动特性分析及悬置优化

针对现有车型所存在的振动问题,应用振动测试设备对实车进行摸底实验,采集实验数据,分析所存在的问题为近一步的理论分析和有限元仿真等研究提供依据。建立挖掘机驾驶室有限元模型,运用模态分析方法对驾驶室有限元模型进行求解,得出驾驶室模态参数。综合发动机激振频率、驾驶室模态共振频率及实验数据等因素合理选择驾驶室悬置参数,改进驾驶室悬置,并对比改进前后驾驶室振动响应数据,验证优化方案的可行性,为同类研究提供参考。     

一种加权频域子空间模态参数辨识方法的改进

为解决频域子空间模态参数辨识方法受噪声影响的问题,提出一种加权频域子空间方法。运用该方法对多次实验得到的频域数据的方差进行估计,把输入、输出频域点估计的方差倒数作为加权系数,构成加权系数矩阵。考虑了输入及输出噪声,根据噪声的频域方差分配权重。为验证改进方法的有效性,在一个二自由度系统上进行了仿真验证。以某变截面轴的模态分析为例,进行了实验验证。仿真及实验结果表明,提出的改进加权算法能够在较强噪声时准确分辨模态参数。     

Vibration characteristics investigation of mistuned blisks with receptance substructure component modal synthesis method

To improve the simulation efficiency of mistuned blisk, a method called receptance substructure component modal synthesis method (RSCMSM) is proposed to reduce its degrees of freedom (DOFs). The advantage of this method is that only the interface DOFs need to be solved, which observably enhances the computational efficiency. The modal frequencies, maximum modal shape and frequency response function are calculated via RSCMSM. It is seen that the smooth frequency band is governed by blade vibration and the steep frequency band is governed by disk or bladed-disk coupling vibration. In addition, a peak is observed for the tuned blisk but many peaks appear for the mistuned blisk and many small wave crests are observed near the peak. To verify validity of this method, the computational time of RSCMSM is compared with high fidelity finite element method (HFFEM) and classical substructure component modal synthesis method (CSCMSM), which manifests that the computational efficiency increases by 32.19 %–80.82 % than that of HFFEM when the mistuned level is 0 %~5 %. Moreover, computational efficiency of RSCMSM is increased by 0.85 %–7.56 % than that of CSCMSM. The validity of RSCMSM is verified for calculating the complex mechanical structure.

     

Type synthesis of 4-DOF parallel kinematic mechanisms based on Grassmann line geometry and atlas method

Many methods are proposed to deal with the type synthesis of parallel kinematic mechanisms（PKMs）, but most of them are less intuitive to some extent. Thus, to propose a concise and intuitive type synthesis method for engineering application is a very challenging issue, which should be further studied in the field. Grassmann line geometry, which can investigate the dimensions of spatial line-clusters in a concise way, is taken as the mathematic foundation. Atlas method is introduced to visually describe the degrees of freedom（DOFs） and constraints of a mechanism, and the dual rule is brought in to realize the mutual conversion of the freedom-space and constraint-space. Consequently, a systematic method based on Grassmann line geometry and Atlas method is generated and the entire type synthesis process is presented. Three type 4-DOF PKMs, i.e., 1T3R, 2T2R and 3T1R（T： translational DOF; R： rotational DOF）, are classified according to the different combinations of the translational DOFs and rotational DOFs. The type synthesis of 4-DOF PKMs is carried out and the possible configurations are thoroughly investigated. Some new PKMs with useful functions are generated during this procedure. The type synthesis method based on Grassmann line geometry and Atlas method is intuitive and concise, and can reduce the complexity of the PKMs＇ type synthesis. Moreover, this method can provide theoretical guidance for other PKMs＇ type synthesis and engineering application. A novel type synthesis method is proposed, which solves the existing methods＇ problems in terms of complicated, not intuitive and unsuitable for practical application.     

求解运动激励结构动态响应的固定边界-模态叠加法

针对运动激励下结构动态响应的模态叠加法求解问题,在分析传统的大质量法、大刚度法的局限性的基础上,提出一种新的运动激励转化方法——固定边界-模态叠加法:基于响应等效和约束反力动力平衡原理,将运动激励转化为其作用单元的等效节点载荷,并在运动激励自由度上施加固定约束,进而可以采用一般的力激励模态叠加算法进行结构动态响应计算。固定边界转化方法没有改变原有结构的固有振动特性,在理论上是精确的,克服了大质量法、大刚度法需要补充新的单元修改有限元模型和人为选择参数的缺点,并且可以通过局部有限元网格细化,提高转换载荷矢量近似计算的精度。通过一个平面应力结构的频率响应分析和一辆轻型货车三维板壳模型的瞬态响应分析验证了固定边界-模态叠加法的有效性。     

On a component mode synthesis on multi-level and its application to dynamics analysis of vehicle system supported with spring-stiffness damper system

The component mode synthesis (CMS) method on multi-level, called as recursive component mode synthesis (RCMS) method, is implemented for the free vibration analysis of a vehicle system supported on damper-controlled spring-stiffness suspension. The nonproportional damping is considered to describe the suspension system. The focus of the RCMS method is the out-of-core concept that uses disk space rather than memory when computing large scale vehicle FE models. After the eigensolutions are obtained, the mode superposition method is used to compute the dynamic response in the frequency domain. The proposed method can deal with a damped structural system with a general damping system. The performance and accuracy of the proposed method compared to the Lanczos method are demonstrated through an example FE model.     

Nonlinear vibration analysis of spacecraft with local nonlinearity

Most spacecraft are usually assembled from some simple substructures by different kinds of connectors, which include various kinds of joints and hinges. Most of the connectors have properties of nonlinearity, and can strongly affect the dynamic characteristics of spacecraft. Mathematical models of such spacecraft usually have a large number of degrees of freedom (DOFs), but their nonlinear connectors are generally spatially localized. In general, it is impractical and time-consuming to directly calculate the frequency response of the spacecraft using current methods. To enhance the calculation efficiency of the frequency response, an improved approach is proposed in the present paper. With describing functions (DFs) and linear receptance data, the kinetic equations are firstly converted into a set of complex algebraic equations whose dimension is only associated with nonlinear DOFs and interested DOFs. Subsequently the number of iterative equations is reduced and only related to nonlinear DOFs. Hence the improved approach can be applicable to large-scale and complicated finite element (FE) models. An FE model of a satellite with some nonlinear joints is used to show and demonstrate the usefulness of the proposed method. Besides, the effects induced by nonlinear joints on payloads’ vibration of the satellite are discussed.     

Data fusion of acceleration and angular velocity for improved model updating

In the traditional finite element (FE) model updating, translational responses, such as acceleration, have generally been employed to identify the structural properties. However, the boundary conditions of a structure are associated with both translational and rotational DOFs. Thus, the combinational measurement of translational and rotational responses (e.g., angular velocity) would increase accuracy of FE model updating of structures, especially in identifying their boundary conditions. This paper proposes data fusion of translational and rotational responses for improved system identification using FE model updating technique. In the proposed method, the accelerometers and gyroscopes are installed in between and near the supports of a structure, respectively, and FE model updating is carried out using the natural frequencies, the translational mode shapes obtained from accelerations, and the rotational mode shapes obtained from angular velocities. Numerical and experimental verifications are carried out on simply-supported beam structures. The verifications show that the proposed FE model updating strategy based on the data fusion results in more accurate assessment of both structural properties and boundary conditions than the traditional FE model updating using translational responses only.     

平板式可变电容器宏建模及其在MEMS设计中的应用实例

平板式可变电容器是MEMS重要的机电耦合部件,建立其宏模型是MEMS系统级快速仿真的迫切需求。本文采用解析法在三维空间内建立了可描述活动极板六自由度运动的宏模型,并以MAST为模型编码语言实现了其多端口参数化组件模型。在SABER仿真平台上构建了电容检测式微加速度计系统级模型,时域仿真结果表明使用该系统级模型能够快速进行有限元分析软件难以实现的复杂机电耦合系统时域行为分析。     

避免设计位形下发生平台奇异的三自由度转动并联机器人设计方法

设计一种基于反螺旋理论的系统方法,给出了具有三个转动自由度的并联机器人的设计要求。分析了产生平台奇异时三条支链所提供的反螺旋的线性关系,利用三条支链对平台所提供的特殊约束,避免设计位形下发生平台奇异现象。给出了设计该类结构的运动副组成类型和空间放置原则。     

随机参数压电智能梁结构的动态特性分析

针对压电智能梁结构，采用6个位移自由度、2个电自由度的有限元模型，利用Hamilton原理推导了结构的动力学方程。基于随机因子法分析了随机参数压电智能梁结构的动态特性；从结构振动的Rayleigh商出发，利用代数综合法推导出结构固有频率随机变量数字特征的计算表达式。以智能悬臂梁为例，分别利用文中的方法和Monte arlo数值模拟法对其动态特性进行了计算和比较。结果表明，随机因子法是处理智能结构随机性的一种比较方便、实用而精确的方法。