液压振动台小量级振动超差分析及改进

动态特性是考察液压振动台系统的最关键因素，对振动试验结果的准确性影响巨大。针对实际液压振动台系统在试验过程中的小量级振动超差现象，分别从振动台结构特性和液压系统特性两方面进行研究分析和理论计算。在结构特性方面对液压振动台系统整体进行模态试验和分析，在液压系统特性方面提出增大液压系统阻尼的改进方法并进行试验验证。最终确认增大液压系统阻尼的方法可以消除液压振动台小量级振动超差问题，使液压振动台试验系统动态特性进一步得到改善。     

气动式振动台理想激励信号的特性

气动式振动台是一类重要的可靠性振动强化试验设备,目前国内尚未对其关键技术及自主研发展开全面研究。根据薄板振动理论建立气动式振动台的力学模型,采用能量法(Rayleigh-Ritz法)分析和计算振动台面的固有频率和正则振型,将用于机械系统动力学分析的传递函数引入到振动台系统,推导气锤安装位置与振动台面任意响应位置之间的力―加速度传递函数,在此基础上,构建气动式振动台的动力学模型,揭示振动台面受到的激励力信号与其加速度响应信号之间的关系,针对振动台的“理想”加速度响应信号,进一步计算与之对应的“理想”激励力信号,并分析该激励信号的特性,为该类设备的性能改善乃至自主研发提供理论指导。     

具有强非线性振动台动力学特性研究

建立了考虑几何非线性和支撑非线性等因素的振动台系统的动力学模型,推导了振动台的动力学微分方程,并采用Galerkin方法对其进行离散化处理。在此基础上,应用增量谐波平衡法对振动台系统进行求解进而获得其近似解析解。研究了外激励幅值、支撑位置等参数的变化对振动台动态特性的影响。随着激励幅值的增大和支撑位置向两边间移动,振动系统的最大稳态幅值明显增大,硬式非线性增强,主共振附近的滞后区域变宽,多解区域变宽。除此之外,随着参数的变化,振动系统的超谐波共振减弱。     

磁流体动力学微角振动传感器自动标定系统设计

基于磁流体动力学(magnetohydrodynamics, MHD)微角振动传感器研制过程中,需要对其频响特性及输出线性度等指标进行测试,这便需要宽频带(3 Hz～1 kHz)内的恒定角速率激励装置及高精度角振动检测装置。基于105-AVT角振动台和XL-80激光干涉仪搭建了适用于MHD微角振动传感器的自动标定系统,鉴于105-AVT角振动台无法提供恒定角速率激励,建立了角振动台输入电压与输出角速度间的对应关系,并将其移植到LabVIEW软件中,实现了105-AVT角振动台的恒定角速率激励。利用激光干涉仪XL-80输出信号作为测量角速度基准,对MHD微角振动传感器特性进行了实验测试。结果表明,可实现带宽高于1 kHz, 0.004～0.12 rad/s的恒定角速率激励,实现自动标定。     

D-350型振动台工作原理及维修方法

介绍了一种振动台,它能产生正弦力为3430N的简谐振动源,能够模拟元件或产品在实际使用过程中遭受的振动环境。该振动台是一种用途广泛而重要的大型试验设备,是集机、电、磁、气等多学科知识于一体的产品。振动台的恒流幅频特性、恒压幅频特性,描述的是幅频特性和低频端及高频端的共振特性凸峰。解读了电器控制部分的原理,并对电子管电路常见和复杂故障的基本修理方法作了分析说明。     

振动台在顺臂安装条件下的离心力克服方法研究

在振动离心复合环境仿真系统中,当振动台动圈受离心力影响偏离原来的平衡工作位置时,将会影响振动台的正常工作。为了消除这种影响,本文提出了一种使用具有位置控制阀系统的空气弹簧来克服离心力的方法。并对地面振动台和离心机上振动台的振动分别进行了仿真计算,仿真结果表明:这种方法可以满足克服离心力的要求。     

基于ADAMS的离心机-振动台系统动力学仿真分析

为了研究离心机振动台系统的动力学特性,基于ADAMS仿真软件平台,结合Pro/E建立起离心机-振动台系统的虚拟样机,并采用ANSYS有限元软件生成了离心机臂与动圈的模态中性文件,将整个系统视为刚柔耦合动力学系统,对整机进行了运动学与动力学仿真分析,并研究了离心机转速及振动台频率对系统输出性能的影响,为建立离心机-振动台复合环境试验系统提供了参考依据.     

基于系统辨识的宽频大尺寸振动台正弦扫频控制

宽频大尺寸振动台在其频率范围内具有复杂的动态特性,一般的控制方法很难实现高精度的扫频控制.提出了基于系统辨识的正弦扫频控制方法,首先对振动台进行了系统辨识分析,求出了振动台在指定频率范围内的幅频响应函数,据此得出了系统在每个频率点的输入,然后进行了正弦扫频,按照一定的规律改变频率,保持振幅不变;扫频过程中结合分段PID算法,对控制中出现的误差进行了实时修正,从而保证了正弦扫频的精度.最后给出了运用该方法对宽频大尺寸振动台进行控制的实验结果.结果表明,这种控制方法可以实现宽频大尺寸振动台高精度的扫频控制.     

转台速率波动自适应抑制方案的设计

提出了一种能够有效地抑制转台速率波动的自适应补偿方法,阐述了该方法的原理、结构配置,开发了自适应控制律,进行了系统稳定性分析,并进行了仿真和试验研究。结果表明:该方法能够有效地抑制位置反馈元件周期性误差导致的速率波动,提高转台的速率平稳性。采用该方案,对转台输入200°/s的速率指令,在经过大约6 s的自适应调节时间后其速率波动由原来的5°/s降低到0.4°/s,波动量减少到自适应前的1/12;试验结果与仿真结果是一致的,验证了该方法的有效性和可行性。     

飞行器虚拟振动试验平台构建

针对用振动台进行飞行器振动环境试验时存在试验周期长、耗费高及易发生过试验或欠试验等问题,采用虚拟现实技术建立了飞行器虚拟振动试验平台.采用系统仿真软件LMS AMESim建立了电振动台正弦振动控制仪模型;通过多学科系统仿真软件LMS Virtual.Lab建立了振动台的多体系统动力学模型,进行了振动台多体动力学模型与电磁作动系统模型的机电联合仿真;实现了振动控制系统、电磁作动系统、振动台与试件机械系统的闭环仿真,构建了飞行器虚拟振动试验平台.利用该虚拟振动试验平台系统进行了盒式试件的正弦振动试验.结果表明,采用机电耦合建模方法构建的虚拟振动试验平台综合考虑了试件、振动台机械系统、控制系统及电气系统的耦合效应,可为飞行器的试前分析和虚拟振动试验提供试验环境.     

Motion Error Compensation Method for Hydrostatic Tables Using Actively Controlled Capillaries

To compensate for the motion errors in hydrostatic tables, a method to actively control the clearance of a bearing corresponding to the amount of error using actively controlled capillaries is introduced in this paper. The design method for an actively controlled capillary that considers the output rate of a piezo actuator and the amount of error that must be corrected is described. The basic characteristics of such a system were tested, such as the maximum controllable range of the error, micro-step response, and available dynamic bandwidth when the capillary was installed in a hydrostatic table. The tests demonstrated that the maximum controllable range was 2.4 /im, the resolution was 27 nm, and the frequency bandwidth was 5.5 Hz. Simultaneous compensation of the linear and angular motion errors using two actively controlled capillaries was also performed for a hydrostatic table driven by a ballscrew and a DC servomotor. An iterative compensation method was applied to improve the compensation characteristics. Experimental results showed that the linear and angular motion errors were improved to 0.12 μm and 0.20 arcsec, which were about 1/15^th and l/6^th of the initial motion errors, respectively. These results confirmed that the proposed compensation method improves the motion accuracy of hydrostatic tables very effectively.     

基于微定位工作台的精密磨削过程动力学建模与误差补偿技术

为了消除传统平面磨床砂轮振动对加工精度的影响,提出了采用自行设计的纳米级微定位工作台进行在线动态补偿的方法。为了对平面磨床的动平台上安装有微定位工作台的新型机床磨削过程的特性进行研究,分析了磨头-砂轮-微定位工作台组成系统的动力学行为。运用模态综合理论和拉格朗日方程建立了磨削过程模态坐标下的动力学模型,并利用状态空间方法得到了磨床在模态坐标下振动响应的数值计算公式。由振型叠加原理,得到具有微定位工作台补偿装置的新型平面磨床在物理坐标下的响应。在此基础上分析了磨床系统的动态特性和补偿前后的加工精度。仿真结果表明,采用微定位工作台进行在线振动补偿,可有效地提高加工工件的表面质量。     

Characteristic of torsional vibration of mill main drive excited by electromechanical coupling

In the study of electromechanical coupling vibration of mill main drive system, the influence of electrical system on the mechanical transmission is considered generally, however the research for the mechanism of electromechanical interaction is lacked. In order to research the electromechanical coupling resonance of main drive system on the F3 mill in a plant, the cycloconverter and synchronous motor are modeled and simulated by the MTLAB/SIMULINK firstly, simulation result show that the current harmonic of the cycloconverter can lead to the pulsating torque of motor output. Then the natural characteristics of the mechanical drive system are calculated by ANSYS, the result show that the modal frequency contains the component which is close to the coupling vibration frequency of 42Hz. According to the simulation result of the mechanical and electrical system, the closed loop feedback model including the two systems are built, and the mechanism analysis of electromechanical coupling presents that there is the interaction between the current harmonic of electrical system and the speed of the mechanical drive system. At last, by building and computing the equivalent nonlinear dynamics model of the mechanical drive system, the dynamic characteristics of system changing with the stiffness, damping coefficient and the electromagnetic torque are obtained. Such electromechanical interaction process is suggested to consider in research of mill vibration, which can induce strong coupling vibration behavior in the rolling mill drive system.     

飞轮组件微振动对高分辨率光学卫星光轴的影响

为了研究高分辨率光学卫星星上飞轮的微振动对卫星成像质量的影响,分别建立了飞轮扰动模型和整星结构动力学模型。首先,对飞轮组件系统进行了地面扰动测试,对实测扰动数据的分析表明,飞轮组件在与转速相关的一阶频率50Hz处产生一次谐波,在190Hz与280Hz左右存在与转速无关的一系列峰值。然后,对整星进行了单位正弦激励,获得了光轴角位移响应,并对其与飞轮实测扰动数据进行了集成分析。分析结果表明:整星在50~80 Hz和230~280Hz的角位移响应有较多的谐振响应频率成分,沿光轴方向和垂直光轴方向整星光轴的角位移最大谐振响应幅值分别为2.718″、2.739″,在245Hz左右存在较多幅值为0.5″量级的谐波。分析显示飞轮组件微振动对高分辨率光学卫星成像质量影响较大,得到的结果可为整星系统的优化设计和隔振补偿措施提供参考依据。     

机载光电平台隔振系统振动耦合分析

为避免载机线振动耦合为光电平台角振动,减小角振动对成像质量和指向精度的影响,对机载光电平台隔振系统进行了分析与研究。针对以往单自由度振动模型仅能分析线振动衰减,无法分析线振动与角振动耦合的缺点,建立了隔振系统的双自由度振动模型,推导出载机线振动与光电平台角振动间的传递函数,分析了减振器刚度、阻尼参数偏差以及减振器布局不合理对振动耦合的影响,为隔振系统的设计和安装提供理论基础。结合工程实际,提出了减小光电平台隔振系统振动耦合的具体措施。     

Damping identification in rotors from run-up beat responses using Hilbert transforms

In a rotor bearing system operating with constant angular acceleration, after passing through the critical speed, typical beat characteristics are observed because the transverse vibration response contains both excited and natural motion, and shortly after passing resonance, vibrations with close frequencies appear. The present study explains a method for estimating damping of rotor bearing systems from transient beat vibration signals observed during run up stage. A mathematical derivation to prove that a part of run-up vibration of the rotor system consists of beat phenomenon when the system crosses critical speed. It is also observed from the mathematical model that the beat vibrations depend on the damping in the system. This beat response is considered for Hilbert analysis and the damping is estimated. Increase in angular acceleration of the rotor will increase the damping. This paper investigates how the damping varies with respect to different angular acceleration values of the rotor bearing system. Experimental validation of the beat phenomenon and damping estimation are done for the rotor system. The proposed method is validated by using half-power band width method applied to run-up response.     

超低频振动台数字化改造

通过改善振动台标定系统的线性来减小其信号失真度是振动台标定系统的一个关键问题,对振动台标定系统实现数字化标定是技术上的重要发展趋势。本文提出采用主频信号提取技术去除由振动台标定系统的非线性引起而产生的噪声信号和减小振动台标定系统的信号失真度。本文同时提出了一种局部细化傅立叶变换方法和采用了数据库来管理振动台对振动仪器的标定结果,编写了数字化标定软件,设计了采集仪,从而实现了XS型超低频振动台标定系统的数字化改造,提高了标定结果的精度。     

Three-dimensional modeling for predicting the vibration modes of twin ball screw driving table

As a redundant drive mechanism, twin ball screw feed system has the advantage of high stiffness and little yaw vibration in the feeding process, while leads to increased difficulty with vibration characteristics analysis and structure optimization. Only low-dimensional structure and dynamics parameters are considered in the existing research, the complete and effective model for predicting the table＇s vibrations is lacked. A three-dimensional（3D） mechanical model of twin ball screw driving table is proposed. In order to predict the vibration modes of the table quantitatively, an analytical formulation following a comprehensive approach is developed, where the drive system is modeled as a lumped mass-spring system, and the Lagrangian method is used to obtain the table＇s independent and coupled axial, yaw, and pitch vibration modes. The frequency variation of each mode is studied for different heights of the center of gravity, nut positions and table masses by numerical simulations. Modal experiment is carried out on the Z-axis feed table of the horizontal machining center MCH63. The results show that for each mode, the error between the estimated and the measured frequencies is less than 13%. The independent and coupled vibration modes are in accordance with the experimental results, respectively The proposed work can serve a better understanding of the table＇s dynamics and be beneficial for optimizing the structure parameters of twin ball screw drive system in the design stage.     

曲轴组件动平衡检测系统中振动台设计

振动台是检测曲轴组件动平衡系统中很重要的部件，在此提出了一种振动台设计方法，建立了振动台分析模型，并根据振动理论，推导出了计算振动台固有频率的公式和方法，对研究动平衡及其相关设计具有重要意义。     

晶振和频综器的二次隔振系统

介绍了对晶体振荡器进行一次隔振的晶振隔振器,以及晶振和频综器采用的二次隔振系统.试验表明,对中、高频段振动特别敏感的晶体振荡器,进行二次隔振可以有效地提高其相位噪声电特性.