变压器振动在典型建筑结构中的衰减特性*

为掌握10 kV居民区配电变压器振动在建筑中的衰减规律,将实测的变压器振动加速度转化为激励力,作用于剪力墙和框架建筑上,采用有限元法仿真研究变压器振动在建筑中的衰减特性。结果表明,在具有相同层高、层数的剪力墙、框架高层建筑中,位于负一层的变压器传播至各楼层的铅垂向振动加速度级(0～500 Hz),随楼层离地高度h对数值(lg h)的增加线性下降,其斜率分别为33.26和24.84,前者的衰减速率(lg h每增加1振动加速度级的衰减量)约为后者的1.3倍;在剪力墙、框架多层建筑中斜率分别为31.87和20.07,前者的衰减速率约为后者的1.6倍。可见,当建筑层高、层数相同时,变压器振动在剪力墙建筑中比框架建筑中衰减更快;当建筑结构相同时,振动在高层建筑中的衰减速率略大于多层建筑。对0～80 Hz环境振动,变压器振动在剪力墙高层建筑中的铅垂向Z振级衰减速率约为框架高层建筑的2.4倍;剪力墙多层建筑振动衰减速率约为框架多层建筑的3.7倍。在此基础上,建立了变压器传播至剪力墙、框架建筑不同楼层的振动单值和分频段预测模型,可为变压器引起的建筑室内振动预测和控制提供依据。     

基于小波神经网络的振动速度传感器幅频特性补偿研究

为了实现超低频振动速度测量, 提出补偿其幅频特性的小波神经网络方法.该方法以振动速度传感器动态实验数据为基础, 通过小波神经网络训练来确定传感器幅频特性补偿网络.介绍振动速度传感器幅频特性补偿原理, 分析网络的拓扑结构, 给出网络参数训练和初始化方法.采用引入动量项的最速下降法训练网络权值、尺度因子和平移因子, 将小波网络参数的初始化与小波类型、小波时频参数和学习样本等联系起来.结果表明, 采用小波神经网络进行振动速度传感器幅频特性补偿具有良好的鲁棒性,并能实现在线补偿,网络训练的速度和精度优于同等规模的BP网络,在测试领域有重要的实用价值. 关键词： 振动速度传感器 小波神经网络 幅频特性 补偿     

Adaptive fuzzy neural network control on the acoustic field in a duct

Base on the principle of the superposition of waves, active noise control is achieved by adaptively tuning a secondary source which produces an anti-noise of equal amplitude and opposite phase with primary source. This paper presents the study on the acoustic attenuation in a duct by using the combination of fuzzy neural network with error back propagation algorithm to control secondary source. The most important advantage of fuzzy inference system is that the structured knowledge is represented in the form of fuzzy IF-THEN rules. But it lacks the ability to accommodate the change of external environments. Combining neural network with fuzzy system can help in this tuning process by adapting fuzzy sets and creating fuzzy rules. The performance of attenuation and control error can be measured by the microphone placed in the downstream of duct. The results of this study, show that the acoustic attenuation by 40 dB for pure-tone noise and nearly 30 dB for dual-tones noise are obtained.     

基于CMAC神经网络的能动磨盘智能控制实验研究

 针对能动磨盘面形控制系统的非线性和多变量特点，提出了基于CMAC神经网络的能动磨盘面形智能控制方法，以CMAC神经网络来映射磨盘面型和控制脉冲之间复杂的关系。为验证上述智能控制方法，搭建了由有效变形口径为420 mm能动磨盘和60路微位移阵列传感器组成的3单元能动磨盘面形检测实验平台，在该实验平台上进行了多组实验，利用微位移阵列传感器分别检测出能动磨盘在1单元、2单元和3单元驱动器作用下实验面形相对于理论面形的偏差，其中峰谷值分别为0.99，2.34和2.68 mm，均方根值分别为0.19，0.59和0.57 mm，实验结果验证了能动磨盘CMAC神经网络智能控制的可行性。     

氮分子固体中配位环境对其分子振动的影响

研究了孤立氮分子与处于氮分子固体中氮分子之间的振动频率差异.基于α-N_2晶体结构建立了5种不同氮分子数的氮分子固体团簇模型,采用密度泛函理论计算了孤立自由氮分子及各固体模型中氮分子的振动频率,并对它们的频率进行了比较和讨论.比较发现:受集体效应的影响,处于分子固体模型中的所有氮分子的键长较孤立自由氮分子的键长更短,振动频率更高;就固体模型本身而言,分子数越多,平均振动频率越大,而且,内部氮分子的振动频率总是大于表面氮分子的振动频率,整体来说,频率大小关系为v_(内部)v_(表面)v_(孤立).讨论分析认为这种频率差异主要是由于孤立自由氮分子、固体表面和内部分子的配位关系不同引起的;表面分子存在大量配位缺陷,与其相互作用的分子相对较少,氮分子键力较弱,从而频率更低.     

Boundary control of an axially moving string via fuzzy sliding-mode control and fuzzy neural network methods

The objective of this study is to develop intelligent control schemes for the transverse vibration reduction of an axially moving string. The proposed approaches are backboned by the methods of fuzzy sliding-mode control (FSMC) and fuzzy neural network control (FNNC). In practice, the control effort for the system is realized through a typical mass-damper-spring (MDS) system attached at the right-hand side boundary of the moving string. The dynamic coupling between the string and the MDS system provides an actuation force to suppress transverse vibration. In the first phase of this study, the framework of FSMC is designed, in which the techniques of region-wise linear fuzzy logic control design and generic algorithm technique are employed to facilitate FSMC to reduce a large number of fuzzy rule bases and to select optimal control gains, respectively. In the second phase, the FNNC is developed, which is, compared to the FSMC, easier to design the control rule, more robust against environment and capable of on-line learning. Numerical simulations are conducted and the comparison between various controllers is made based on simulations. The simulated results show that the transverse vibration can be well suppressed by both approaches. FSMC offers the capability to regulate the transient response, while FNNC holds advantage of on-line learning capability.     

基于滑模鲁棒算法的超低频主动隔振系统

振动噪声的有效隔离是冷原子重力仪的关键技术之一.为了减小冷原子重力仪中拉曼反射镜的振动噪声,研制了一套紧凑型低频主动隔振系统.其原理是利用滑模鲁棒控制系统处理和反馈由地震仪采集到的振动信号,利用音圈电机控制和消除被动隔振平台的运动.在0.1—10 Hz频域范围内,滑模鲁棒控制系统的残余振动噪声功率谱密度比被动隔振平台最大降低了99.9%,比超前滞后补偿控制方法最大降低了83.3%.滑模鲁棒控制算法还具有整定参数少、抗干扰能力强等特点.     

Parametric control of an axially moving string via fuzzy sliding-mode and fuzzy neural network methods

This study is dedicated to design effective control schemes to suppress transverse vibration of an axially moving string system by adjusting the axial tension of the string. To this end, a continuous model in the form of partial differential equations is first established to describe the system dynamics. Using an energy-like system functional as a Lyapunov function, a sliding-mode controller (SMC) is designed to be applied when the level of vibration is not small. Due to non-analyticity of the SMC control effort generated as vibration level becoming small, two intelligent control schemes are proposed to complete the task — fuzzy sliding-mode control (FSMC) and fuzzy neural network control (FNNC). Both control approaches are based on a common structure of fuzzy control, taking switching function and its derivative as inputs and tension variation as output to reduce the transverse vibration of the string. In the framework of FSMC, genetic algorithm (GA) is utilized to search for the optimal scalings for the inputs; in addition, the technique of regionwise linear fuzzy logic control (RLFLC) is employed to simplify the computation procedure of the fuzzy reasoning. On the other hand, FNNC is proposed for conducting on-line tuning of control parameters to overcome model uncertainty. Numerical simulations are conducted to verify the effectiveness of controllers. Satisfactory stability and vibration suppression are attained for all controllers with the findings that the FSMC assisted by GA holds the advantage of fast convergence with a precise model while the FNNC is robust to model uncertainty and environmental disturbance although a relatively slower convergence could be present.     

Coupled FEM/BEM for control of noise radiation and sound transmission using piezoelectric shunt damping

In this paper, we present a coupled finite element/boundary element method (FEM/BEM) for control of noise radiation and sound transmission of vibrating structure by passive piezoelectric techniques. The system consists of an elastic structure (with surface mounted piezoelectric patches) coupled to external/internal acoustic domains. The passive shunt damping strategy is employed for vibration attenuation in the low frequency range. The originality of the present paper lies in evaluating the classically used FEM/BEM methods for structural–acoustics problems when taking account smart systems at the fluid–structure interfaces.     

振动噪声等高图的电驱动桥噪声预测及优化*

在项目开发前期通过优化电驱动桥扭矩特性的设计,可以规避噪声大问题。根据电驱动桥台架在对应扭矩下的振动噪声特性,提出了一套稳定高效的测试流程和分析方法。首先设计了一套完整的试验流程,制定了精准的数据分析方法。然后绘制出能够全面反映电驱动桥振动噪声特性的等高图。最后利用电驱动桥台架的振动噪声等高图,准确评估电驱动桥加速工况下振动噪声风险,为主机厂和电驱动桥零部件企业提供电驱动桥扭矩特性设计前期指导。利用该方法成功识别到某电驱动桥匀速及加速工况下电机及齿轮的啸叫问题。通过优化电驱动桥扭矩特性设计,电机48阶噪声峰值降低了8.5dB(A),确认该方法准确可靠,具备推广应用价值。     

Influence of the torsional vibration of the periodically attached perpendicular beam resonator on the flexural band of a Euler-Bernoulli beam

The bending and torsional vibration of the periodic perpendicular cantilever beam-mass resonators (PCBMR) is idealized as translational and rotational oscillators attached to the main beam. In this paper, the effect of that torsional vibration of the PCBMR on the dynamics of an infinitely long Euler-Bernoulli beam is evaluated. The band-structure is explored by implementing the transfer matrix method in conjunction with Bloch-Floquet's theorem. The combination of the translational and rotational oscillator modifies the relative position of the coupling coefficient in the transfer matrix, which plays a pivotal role in the band-gap formation. The flexural band-structure is highly sensitive to the torsional vibration while the radius of gyration of the tip mass is considerably higher than the length of the PCBMR. Ill-tuning leads to split and reduction of attenuation band to 50%; whereas, around 38% elongation of the attenuation band in the low frequency regime can be achieved by proper tuning.     

Vibration isolation via a scissor-like structured platform

More and more attentions are attracted to the analysis and design of nonlinear vibration control/isolation systems for better isolation performance. In this study, an isolation platform with n-layer scissor-like truss structure is investigated to explore novel design of passive/semi-active/active vibration control/isolation systems and to exploit potential nonlinear benefits in vibration suppression. Due to the special scissor-like structure, the dynamic response of the platform has inherent nonlinearities both in equivalent damping and stiffness characteristics (although only linear components are applied), and demonstrates good loading capacity and excellent equilibrium stability. With the mathematical modeling and analysis of the equivalent stiffness and damping of the system, it is shown that: (a) the structural nonlinearity in the system is very helpful in vibration isolation, (b) both equivalent stiffness and damping characteristics are nonlinear and could be designed/adjusted to a desired nonlinearity by tuning structural parameters, and (c) superior vibration isolation performances (e.g., quasi-zero stiffness characteristics etc.) can be achieved with different structural parameters. This scissor-like truss structure can potentially be employed in different engineering practices for much better vibration isolation or control.     

Design and analysis of an intelligent vibration isolation platform for reaction/momentum wheel assemblies

This study focuses on design and analysis of an intelligent vibration isolation platform for reaction wheel assemblies (RWAs) and momentum wheel assemblies (MWAs). A passive platform consisting of four folded beams is designed and analysed for MWAs. A simple and effective mathematical model is developed for the system consisting of the platform and MWAs, and this model is used to investigate the passive vibration isolation performance. Further development is performed to produce an intelligent platform for RWAs, with piezoelectric sensors and actuators bonded to the vertical beams. The flywheel imbalance and impulse load are assumed to be input disturbances for the investigation of the active vibration isolation performance by the finite element method (FEM). The simulation results show that the passive vibration isolation platform is particularly effective for the suppression of a high frequency range vibration for MWAs, and the intelligent platform using velocity feedback control effectively attenuates the dynamic amplification of amplitude at resonance for RWAs. Thus, it is concluded that the passive platform can be used as a vibration isolation platform for MWAs and that the intelligent one can be used for RWAs.     

High-order harmonic generation of CO_2 with different vibrational modes in an intense laser field

We apply the strong-field Lewenstein model to demonstrate the high-order harmonic generation of CO_2 with three vibrational modes(balance vibration,bending vibration,and stretching vibration) driven by an intense laser field.The results show that the intensity of harmonic spectra is sensitive to molecular vibrational modes,and the high harmonic efficiency with stretching vibrational mode is the strongest.The underlying physical mechanism of the harmonic emission can be well explained by the corresponding ionization yield and the time-frequency analysis.Finally,we demonstrate the attosecond pulse generation with different vibrational modes and an isolated attosecond pulse with a duration of about 112 as is generated.     

振动噪声对高Q光学微腔耦合系统的影响及抑制方法

在研究微球腔和锥形光纤耦合的基础上,介绍了耦合系统中外界空气流动等带来的振动噪声对耦合距离的影响,并系统地分析了耦合距离与系统耦合状态的关系.为进一步验证外界各种振动噪声对系统稳定性的影响并解决这些因素对谐振谱线造成的干扰,采取了两种方法来进行抑制;一种是设计了隔离罩将耦合系统与外界环境隔离,另一种是用紫外胶将锥形光纤...     

光学系统受迫振动的激光测量方法

将激光信号与高帧频CCD结合,解决了光学系统中振动信号和激光信号之间的转换问题,不仅能够测量振动对系统光束指向稳定性的影响,而且能够得到振动信号本身的频率特性。利用该方法对振源为150 Hz和200 Hz两种条件下的光学系统受迫振动进行测量,得到了与输入信号相吻合的振动信号属性。通过实验与分析得知:时域振幅测量精度为6.25 m,频域分辨力为2 Hz,方法简便高效,测量结果准确,已应用于角多路准分子激光主振荡功率放大器系统打靶试验平台光束指向稳定性的研究中。     

A stable adaptive neural-network-based scheme for dynamical system control

A stable adaptive neural-network-based control scheme for dynamical systems is presented and a continuous recurrent neural network model of dynamical systems is constructed in this paper. A novel algorithm for updating weights in the neural network, which is not derived from the conventional back propagation algorithm, is also constructed. The proposed control law is obtained adaptively by a continuous recurrent neural network identifier, but not by a conventional neural network controller. In such a way, the stability in the sense of the Lyapunov stability can be guaranteed theoretically. The control error converges to a range near the zero point and remains within the domain throughout the course of the execution. Numerical experiments for a longitudinal vibration ultrasonic motor show that the proposed control scheme has good control performance.     

基于近红外光谱技术的石油组分定量分析新方法

针对石油化工产品生产控制和质量检查的需要,为提高测定产品组成的效率,将近红外光谱法作为基础测定方法,以直馏柴油、加氢精制柴油和催化裂化柴油为校正模型的训练样本,测定其中饱和烃、胶质、单环芳烃、双环芳烃、三环芳烃和环烷烃的组成,论述了采用模糊神经网络建立校正模型测定石油化工产品组成的可行性。基于dSPACE硬件平台,用验证样本对模糊神经网络校正模型进行了检验,实验结果表明,该方法响应快、误差小、鲁棒性强,在近红外长波区内,校正样品和验证样品的均方误差小于10-6。该方法可用于石油化工产品的生产工艺研究中。     

Electrical Properties of Isotactic Polypropylene/Multiwalled Carbon Nanotubes Composites Prepared by Vibration Injection Molding

To study the effect of vibration field on the electrical conductivity properties of nanocomposites, isotactic polypropylene (iPP)/multiwalled carbon nanotubes (MWCNT) composites were prepared by conventional injection molding and vibration injection molding. Results showed that the electrical conductivity of iPP/MWCNT composites was significantly promoted by vibration injection molding. Vibration injection molded samples had a percolation threshold of about 2.7 wt% compared with the threshold of about 4.5 wt% for conventional injection molded samples. The effects of test locations and vibration frequency on the electrical conductivity of composites were investigated. The samples exhibited an inhomogeneity along the injection direction. The electrical conductivity of the samples was different at different test locations and increased with increasing vibration frequency. Polarized light microscopy (PLM) results indicated that vibration injection molding can induce MWCNT aggregates to be stretched and oriented along the flow direction, which could form conductive networks and greatly enhance the electrical conductivity of iPP/MWCNT composites.     

利用深度神经网络实现分布式相干瑞利光纤振动事件分类

该文利用分布式相干瑞利光纤传感系统,在西气东输一线无锡至苏州段开展现场测试,采集了光纤沿线车辆行走、机械挖掘、人工锄地、定向钻孔等8种振动作业产生的光纤信号,并提出了一种具有5层结构的全连接深度神经网络用于振动事件分类识别以实现不同振动作业的分级管理。振动作业产生的光纤信号能量集中在低频,该文利用梅尔对数频率的非均匀特性提取了25维单帧信号特征量,并将连续40帧信号特征量组合成高维向量作为网络输入特征向量,实现对不同振动作业时变特性的建模。分类识别结果表明,基于深度神经网络结构的振动信号分类识别器能够有效识别不同振动作业类型,实际线路实验验证了该文算法的有效性。