空气弹簧隔振台特性试验及信号处理算法研究

超精密测量对环境振动要求非常严格,其仪器设备中多安装隔振装置。为评估某重点实验室圆度仪中使用的仪用小型空气弹簧隔振台的隔振性能,利用压电式加速度传感器设计振动测试试验。根据振动测试中信号的实际情况,设计信号处理算法,对采集到的加速度信号进行预处理、积分运算、频谱分析,消除信号中低频趋势项和干扰噪声,还原实际振动状况,准确获取隔振系统振动位移曲线及其固有频率。试验表明,该空气弹簧隔振系统各项指标满足隔振要求。信号处理算法对振动测试中的加速度信号处理具有一定指导意义,也可作为故障诊断中加速度信号处理的参考。     

基于ANSYS的速度时程求解方法

针对动力方程数值求解中采用由位移时程求导得到速度时程的方法会造成数值误差的问题,提出在动力方程的求解过程中引入速度变量,并对速度和位移这2个状态变量共同求解的方法,从理论层面证明该方法的可行性.基于ANSYS提出虚拟自由度法（Dummy Freedom Degree Method,DFDM）,并用APDL进行二次开发,达到在数值模拟中直接获取速度时程的目的.工程算例分析结果表明：2个实例表明该方法求解速度时程有效、实用;在直接获得结构速度时程的同时,可将加速度时程的求导阶数降为1阶.     

基于虚拟仪器的远程振动测试及分析系统

针对传统振动测试方法的不足,运用图形化编程语言LabVIEW设计了远程振动参数测试及动态特性分析系统.实现了对振动物体加速度、速度、位移信号的实时处理、显示以及频谱分析.通过样条插值得到了振动系统幅频特性曲线.在此基础上完成了固有频率、阻尼比等动态特性参数的估计.同时利用Data Socket技术实现了基于网络的远程自动测试.     

基于Push over分析的钢 混凝土组合框架抗震性能研究

通过建立push-over分析方法中的等效单自由度体系,分析得到钢一混凝土组合框架结构的等延性需求谱．利用有限元软件对组合框架进行非线性静力推覆分析,基于位移模式把多自由度体系转换为等效单自由度体系,建立其等效加速度与等效位移曲线．按现行抗震规范建立组合框架结构谱加速度与谱位移曲线,从而对该类结构进行抗震评估．用非线性动力时程分析方法对本文提出方法进行了比较,验证了该方法的可靠性．     

含零漂的遥测加速度振动信号时域积分方法研究

提出通过遥测加速度振动信号时域数值积分和最小二乘相结合的方法消除零漂对积分结果精度的影响,即采用最小二乘原则对加速度振动信号时域数值积分结果根据其包含的趋势项形式进行多项式拟合,获得修正参数,进一步对积分结果进行修正,获取遥测速度和位移振动信号的修正值。方法在仿真信号上进行了应用,修正结果和真实结果的误差较小,结果精度较高,说明方法的有效性,在此基础上将方法在遥测加速度振动信号的处理上进行了应用,鉴于方法模型的在仿真信号上的有效性,可以推断获取的遥测速度和位移振动信号的修正结果具有较高的置信度。     

基于单片机的发动机振动速度、位移和加速度测量方法

本文介绍了一种基于单片机的发动机振动速度、位移和加速度测量方法。该方法首先对发动机的振动传感器信号进行高、低通滤波,然后通过模拟开关将其转化为电压信号,再经过RMS幅值测量元件和压频转换器转变成频率信号,由单片机对频率信号进行计数、计算和显示测量结果。对振动速度进行积分和微分,可得到振动位移和加速度,实测结果表明,该方法可以有效地减少环境因素对电子元件的影响,提高测量精度。     

地震作用下高层钢 混组合结构的抗震性能分析

根据结构抗震设计规范,分别采用精细时程积分法和结构分析软件Midas/gen建模,对高层钢框架-混凝土核心筒的混合结构的动力特性和地震时程反应进行分析,得到自振周期及地震作用下的位移和加速度响应.通过对比可知精细时程分析方法和Midas/gen两种不同建模方法得到的计算结果吻合较好,说明精细积分分析方法和Midas/gen的分析方法都是适用可靠的,均能为此类结构的抗震性能研究提供有效的途径.     

一种直升机旋翼振动测试方法

为能够有效测量直升机旋翼的振动特性，提出了一种基于三轴MEMS加速度传感器及无线传输技术的直升机旋翼振动测试方法并研制了相应的测试装置。测试系统主要包括三轴MEMS加速度传感器、A/D转换模块、无线传输模块以及PC上位机。无线传输模块将采集的加速度信号发送到振动测试接收电路，再通过串口通信发送到计算机上，计算机软件对加速度信号积分得到位移信号，并通过傅里叶变换得到旋翼振动的幅频特性曲线。在直升机模型上完成了振动测试实验，实验结果表明该方法能有效地对旋翼振动信号进行测试。     

基于等效模态阻尼的复合隔振系统振动计算方法

基于线性黏弹性假设,将应变能阻尼理论推广到复合隔振系统的等效模态阻尼计算中,运用Python和Abaqus编制相应的计算程序,该程序可考虑材料阻尼的频变特性。以多种材料组成的船舶双层复合隔振系统为算例,计算其等效模态阻尼和隔振器等效阻尼系数。分别采用直接积分法和模态叠加法计算系统振动响应,对比设备、筏架、船底壳的振动加速度响应,验证基于等效模态阻尼的模态叠加法的准确性。结果表明,该方法可以准确计算复杂组合模型的模态阻尼,算例的振动响应计算结果一致性较好,用模态叠加法可以大幅提高复合隔振系统稳态振动响应的计算效率。     

平面六杆机构运动学仿真系统研究

研究平面连杆机构动态特性,为提高动态技术性能,采用封闭矢量法分析推导了牛头刨床平面六杆机构运动学求解数学模型.在此基础上,采用软件开发了一套适用于平面六杆机构的运动学仿真系统.在MATLAB平台上进行了牛头刨床主体机构的运动学仿真与动画显示,绘制出了连杆的角度、角速度和角加速度曲线以及滑块和滑枕的位移、速度和加速度曲线.结果证明,该系统不仅分析机构直观方便,通过改变参数后能实现机构优化运动特性,并为设计提供依据.     

Seismic analysis of base isolated buildings

Summary  This paper presents a survey of the numerical simulation of base isolation systems for the vibration control of buildings and their equipment, primarilly against earthquakes. Base isolation has received much attention in the recent twenty years and many buildings have been protected using this technology. The article focusses mainly on the different numerical methods used in the analysis of base isolated buildings. The conventional form of solving the equations of motion governing the seismic response of building structures with nonlinear base isolation consists of using monolithic step by step integration methods. As an efficient alternative static condensation and block iterative schemes can be applied. The particularities of the equations of motion of buildings equiped with various base isolation systems are described. The linear theory of base isolated buildings is then presented. After this, numerical solution techniques for the analysis of the seismic response of buildings with isolation systems are developed in detail in the paper. Finally, numerical results for elastic and inelastic structures are described. A complete set of references coverning a wide range of studies is included.     

周期性冲击载荷作用下井字梁楼盖竖向振动的控制

针对周期性冲击载荷作用下井字梁楼盖异常振动问题,对某工业厂房井字梁楼盖进行现场动力特性测试,采用Abaqus软件建立局部楼盖有限元模型,研究周期性冲击载荷作用下井字梁楼盖的动力特性,并提出设置调谐质量阻尼器(tuned mass damper,TMD)、增设隔振支座等2种减振方案.结果 表明:4种不同TMD布置方式的减振效果不同,在设备4个支座处布置TMD的减振效果最佳;增设隔振支座后,采用有限元法得到各测点减振率为83.91％ ～88.80％.2种方案均能有效降低楼盖的竖向振动,可为结构振动控制提供参考.     

双单体组合隔震结构振动随机最优控制

用作动器将相距很近的两结构连为一体,并对其中一个结构施加隔震,形成一种新的结构体系—组合隔震结构体系.推导了其振动及控制方程,假定地震动输入为白噪声,运用随机最优控制原理,分析研究了组合结构振动控制性能及隔震度、阻尼及场地等参数的影响.研究结果表明:经过优化控制参数,组合隔震结构振动控制体系能对结构地震响应进行有效控制,并且控制成本降低.     

Characterization of structural effects from above-ground explosion using coupled numerical simulation

The response of a building structure to a nearby explosion is complicated by the drastic spatial and time variation of the blast load. Existing studies on the structural responses to explosion effects often employ simplified structural model with assumed loading patterns, such as element-based (beam-column, slab) models, single degree of freedom or lumped mass systems. The validity of a simplified approach depends on whether the governing response and failure mechanisms are well represented in the simplified scheme. For such validation more sophisticated models are required. This paper presents a numerical simulation study aiming to characterize the various structural effects of above-ground explosions. A coupled numerical approach with combined Lagrangian and Eulerian methods is adopted to allow for the incorporation of the essential processes, namely the explosion, shock wave propagation, shock wave-structure interaction and structural response, in the same model. The computational domain extends to the soil around the base of the structure, allowing also for an evaluation of the significance of the ground vibration effect. Results show that for a typical above-ground explosion scenario, the critical structural damage is dominated by air shock loading, while the ground shock induces only some additional vibration whose structural effect is minor. The distribution of structural damage tends to be governed by member level effects on the front face of the structure, whereas the global dynamic response of the system appears to be insignificant. Similar modeling approach may be applied to explore other blast-induced complex response phenomena.     

Integrated design,fabrication, and experimental study of a parallel micro-nano positioning-vibration isolation stage

Positioning and vibration isolation are two important steps for sensitive payloads to realize precision observation in space environment. However, current base stages applied to sensitive payloads often focus on one function, thus limiting their engineering applications. This paper presents a novel parallel micro-nano positioning-vibration isolation stage (PVI stage), which could realize the two functions simultaneously. The advantages of the presented stage lie in the compactness and convenience, which determine its feasibility in limited volume. Through combination of giant magnetostrictive actuator (GMA) and compliant amplification mechanism, the requirements of large-stroke positioning and passive vibration isolation could be achieved. And three auxiliary unloading devices are designed to bear the sensitive payload for resisting the static deformations of compliant mechanism. The detailed scheme and corresponding dynamic model are constructed for showing the stage. Furthermore, finite element simulation is carried out to verify the desired performance. Finally, a prototype is fabricated and experimental tests are conducted to validate the capabilities of the stage. The test results prove that the proposed positioning-vibration isolation stage owns a compact structure and realizes micro-nano positioning and vibration isolation simultaneously, and thus shows a promising prospect in aerospace field.     

A method for system identification using the optimality criteria optimization approach

An algorithm similar to the optimality criteria approach used in structural optimization is presented for identifying stiffnesses of structural members by using vibration test data. A set of equivalent static inertia forces are obtained from the vibration analysis using d'Alembert's principle and are used to solve the multiple displacement constraint problem. The displacement constraint values are specified based on the measured experimental modal displacement data at critical locations. The algorithm is used to find the changes needed in the stiffnesses of the elements and the distribution of nonstructural mass of the nominal analytical model to correlate the analytical and experimental data. The algorithm alternates between the vibration analysis and static analysis to find the equivalent load vector and modify the stiffnesses. The identified stiffness properties of the structural elements can be used to control and study the dynamic response of the structure.     

柔性支撑Stewart平台自适应交互PID隔振控制

为了实现500 m口径球面射电望远镜(five hundred meter aperture spherical radio telescope, FAST)二级精调稳定平台对馈源舱隔振控制的定位和指向精度, 首先提出了基于并联机构学原理的3维机动目标跟踪预测算法, 对柔性支撑Stewart平台的基座运动进行跟踪预测. 进而,在Stewart平台关节空间设计了自适应交互PID控制器, 引入自适应交互算法解决PID参数的实时调整, 以适应柔性支撑Stewart平台的参数变化对不同控制参数的需求. 采用现代机电系统仿真策略, 对柔性支撑Stewart平台隔振系统的动力学与控制问题进行了仿真, 结果表明: 与传统的PID控制器相比, 自适应交互PID控制器大大改善了隔振效果, 完全满足隔振目标的要求.     

Dynamic response analysis of linear structural systems subject to component changes

A method of analysis is developed for determining transient responses of large multiply-connected structural systems subjected to changes of structural components. A dynamic system is divided into two subsystems: the support which remains unaltered and the branch which is liable to change. The response characteristics of an original system are used as a basis for evaluating the new response of the altered system. The responses of the support interface coordinates due to external excitations on it are called base motion. The equations of motion of the system are formulated using subsystem modal properties such that the base motions are the generalized forcing functions. This enables incorporation of the alternative properties in the new analysis without having recourse to the entire system modal properties. The method is applied to a 16-storey building rigid frame model. The methods gives response results comparable with the conventional integrated system analysis. Approximations due to modal truncation are the same as component mode substitution method.     

Active vibration isolation in a “smart spring” mount using a repetitive control approach

In a variety of different engineering systems there is a requirement to isolate sensitive equipment from foundation vibration or alternatively, isolate the foundation from machinery vibration. Passive solutions to this problem provide some isolation but performance is significantly degraded in the presence of structural compliance. A recently proposed hybrid active/passive solution known as the “Smart Spring” mounting system specifically addresses this problem of compliance. The work reported here investigates the application of a repetitive control approach to deal with periodic vibration sources in such a mounting system. The industrial potential of the approach has been shown using an experimental facility where isolation results in the region of 50 dB have been achieved.     

GA-fuzzy control of smart base isolated benchmark building using supervisory control technique

The effectiveness of a supervisory fuzzy control technique for reduction of seismic response of a smart base isolation system is investigated in this study. To this end, a first generation, base isolated, benchmark building is employed for numerical simulation. The benchmark structure under consideration has eight stories and an irregular plan. Furthermore it is equipped with low damping elastomeric bearings and magnetorheological (MR) dampers for seismic protection. The proposed control technique employs a hierarchical structure of fuzzy logic controllers (FLC) consisting of two lower-level controllers (sub-FLC) and a higher-level supervisory controller. One sub-FLC has been optimized for near-fault earthquakes and the other sub-FLC is well-suited for far-fault earthquakes. These sub-FLCs are optimized by use of a multi-objective genetic algorithm. Four objectives, i.e. reduction of peak superstructure acceleration, peak isolation system deformation, RMS superstructure acceleration and RMS isolation system deformation are used in a multi-objective optimization process. When an earthquake is applied to the benchmark building, each of the sub-FLCs provides different command voltages for the semi-active controllers and the supervisory fuzzy controller appropriately combines the two command voltages based on a fuzzy inference system in real time. Results from numerical simulations demonstrate that isolation system deformation as well as superstructure responses can be effectively reduced using the proposed supervisory fuzzy control technique in comparison with a sample clipped optimal controller.