考虑受电弓非线性的弓网动态特性仿真研究

在以往的弓网研究中,常采用受电弓质量块模型,一般都未考虑受电弓的非线性特性。为此首先重新推导了受电弓非线性框架模型,然后研究了受电弓工作高度对归算参数的影响。最后考虑受电弓动态归算参数的影响修正了弓网耦合动力学方程,并采用龙格库塔法对其进行求解,研究受电弓非线性对弓网动态受流特性的影响。结果表明:归算质量随工作高度的变化不大,归算刚度随受电弓工作高度的变化有较大的振荡;考虑受电弓非线性因素使接触压力变化更加剧烈,列车运行速度越高,受电弓非线性特性对接触压力的影响越大,在研究高速弓网关系时,考虑受电弓非线性因素是很有必要的,可为精确研究高速弓网关系提供借鉴。     

受电弓空气动力对列车弓网特性的影响仿真

为研究列车在高速运行时,受电弓空气动力特性对弓网动力学性能的影响,建立受电弓的简化三维模型。采用流体分析软件FLUENT,基于三维定常不可压缩N-S方程和k-ε两方程湍流模型,对高速受电弓的气动力进行数值模拟,得到受电弓的空气动力特性。利用有限元分析软件ANSYS,建立受电弓-接触网系统仿真模型,仿真分析了受电弓空气抬升力对弓网动态接触压力的影响,仿真结果表明,受电弓的空气动抬升力与速度的平方成正比,高速情况下空气抬升力使弓网接触压力大幅增加,弓网受流质量变差。     

基于NARMA-L2模型的弓网系统振动主动控制

建立简单链型悬挂接触网模型和受电弓系统三元质量模型,并给出了动力学方程;介绍NARMA-L2神经网络模型,将NARMA-L2模型应用到弓网振动控制系统中并给出了主动控制方案;针对列车速度为200km·h-1、250km·h-1、300km·h-1、350km·h-1,分别对控制器控制效果进行仿真研究,得到弓网接触力和受电弓抬升量仿真曲线,对仿真得到的数据从最大值、最小值、平均值、标准差四个方面进行分析,并与没有引入NARMA-L2模型控制所得的仿真结果做了对比研究;对比结果表明:与无NARMA-L2控制相比,在车速为200km·h-1时,弓网接触力标准差降低59.46%,受电弓抬升量标准差降低37.72%;车速为250km·h-1时分别降低60.04%、37.99%;车速为300km·h-1时分别降低59.91%、36.74%;车速为350km·h-1时分别降低59.53%、35.84%;因此,基于NARMA-L2神经网络的弓网振动控制系统可以大大降低弓网振动幅度,增强弓网耦合性,从而使弓网接触更稳定,实现更好的受流。     

电气化铁路弓网系统建模与仿真分析

研究电气化铁路受电弓一接触网结构系统优化建模问题,分析了接触线预弛度对弓网受流的影响.传统的弓网模型多采用模态振型叠加法进行求解,过程比较繁琐,且容易引起截断误差.针对上述问题,将接触网看作一个刚度不断变化的系统,与受电弓系统联立,给出了弓网运动方程,并提出采用Newmark方法进行直接积分求解.根据上述方法,使用ANSYS软件建立了弓网仿真模型,分析了预弛度对弓网受流质量的影响.仿真结果能够满足实际要求,可为接触网的设计提供参考.     

振动破碎系统的建模与动力学分析

对振动破碎机的多刚体-散体(物料层)耦合动力学问题进行了深入研究．首先通过实验识别出物料层的非线性滞回力的数学模型和参数,然后根据拉格朗日方程建立了振动破碎机的动力学方程,并用数值方法分析了该系统中刚散耦合的动力学特性,初步揭示了物料层对四动颚的相对运动轨迹的影响规律,并通过动力学试验验证了数值分析结果的正确性．为实际振动破碎机的动力学设计和产品开发奠定了基础．     

滑动式磁力耦合车路能量收集装置设计、建模与实验

风致振动能量俘获技术是振动能量俘获技术领域的一个研究重点方向,具有解决无线传感器自供电的潜力.本文研究了非线性三稳态风致振动能量俘获系统的输出特性,并建立了动力学模型,对比分析了具有对称和非对称势能阱的三稳态风致振动能量俘获系统输出特性.分析结果表明,具有非对称势能阱的三稳态风致振动能量俘获系统初始工作风速较低,实现大振幅振荡的工作风速区间较宽.此外,分析了系统在不同外接电阻、等效质量和等效刚度线性项条件下的输出特性,通过分析发现,在定风速条件下,系统的输出电压随着外接电阻的增加而增加,当外接电阻大于10 MΩ时,输出电压的变化趋于平缓.最后,通过分析发现系统的等效质量和等效刚度线性项会对系统初始工作风速和有效工作风速区间产生影响.     

弓网接触力反馈线性化控制

通过扩展状态变量得到受电弓的非线性模型,利用非线性系统的微分几何理论,构造微分同胚变换和状态反馈表达式,得到了受电弓线性化模型,设计反馈控制律解决弓网接触力的跟踪问题,并证明了内状态的一致最终有界性,考虑弓头易受干扰问题,采用非线性干扰观测器补偿反馈控制律.研究对比表明,所提出的基于干扰观测器的反馈线性化控制策略能有效解决弓网接触力的跟踪问题,同时克服了反馈线性化控制依赖于精确模型的缺点,为一定工况下弓网最优接触力的跟踪控制提供可行方案.     

弓网监测系统的设计与实现

在追综国外先进的弓网监测技术的同时,自主开发了一套基于嵌入式系统的弓网监测系统,该系统通过检测受电弓与接触网的接触压力和拉出值进而分析弓网运行状况;文章主要介绍了该套系统整体设计方案,对其核心部分--车顶电气测控系统的功能需求与软硬件设计思路作了比较详细的说明;经试验证明,该系统在实验室的高频强磁场干扰、高频振动和高温环境下仍运行稳定可靠且满足实际应用的需求.     

基于弓网电弧检测系统的电弧电流分析

基于弓网放电机理,提取电弧发生时刻放电特征量—(250±10)nm波段的紫外光,作为在线检测目标,研制出了一种非接触式紫外弓网电弧检测系统。利用该检测系统对广州地铁二号线弓网电弧现象,进行现场检测,利用经验模态分解(EMD)方法筛除电弧电流的趋势信号,对处理后的电流信号进行分析,结果表明:电弧的发生导致牵引电流中0~50 Hz谐波幅值明显增加。     

车削加工中的振动原因分析及消振措施探讨

受机床床身、主轴结构、刀具安装、工件装夹等组成的工艺系统的影响,在机械加工过程中无可避免的会产生受迫振动和自激振动。本文从现有机械加工过程中产生了哪几种振动,这些振动为什么会产生,以及振动产生的影响这三方面人手,提出通过改善机械工艺来解决振动问题。     

Experimental evaluation of uncertainty in hand-arm vibration measurements

Hand-arm vibration measurements are necessary for vibration exposure risk assessment and for the determination of vibration emission values in hand-guided machines. It has been reported that there is a high degree of uncertainty associated with this kind of measurement. The main goal of the present work is to investigate which factors cause uncertainty in hand-arm vibration evaluation and how much they contribute to the total uncertainty of the measurements. Some experiments were carried out in order to evaluate separately the factors relating to instrumentation and the methods of fixing accelerometers. The experiments were performed with handles belonging to real machines while being handheld by an operator. The results of this investigation show that the fixing method and the accelerometer behaviour are the two main sources of uncertainty. The total uncertainty of the measurements in this work, considering both instrumentation and fixing method, reaches up to 8% of the values measured. It is concluded that the adaptors for fixing the accelerometer with metallic stripe hose clips cause less uncertainty than handheld adaptors and should therefore be used as the first option.

Relevance to industry

A good accuracy in hand-arm measurements is the key for a correct assessment of the risk of developing HAVS (Hand-Arm Vibration Syndrome). Knowledge of the uncertainty factors will help the technicians who carry out the measurements to improve their quality.     

基于虚拟仪器的旋转设备振动监测与分析系统设计

针对旋转设备振动监测的改造升级项目的用户需求,采用虚拟仪器技术,设计开发了一种分布式的振动监测与分析系统,可对多个设备进行监测并提供多种振动分析图形。系统保留了原有监视仪表的使用,从其BUFFER口或串口采集振动信号,降低了改造费用,实现了平稳升级。LabWindows/CVI软件开发平台的使用,使显示界面和仪表相类似,便于操作人员使用,还大大缩短了开发周期。本文论述了该系统的总体结构和软件功能开发,系统已在工业现场进行了初步测试,效果良好,具有实用价值。     

Command-induced vibration analysis using input shaping principles

Input shaping is a well-established technique used for reducing the vibratory response of dynamic systems. Analytical tools are available for systems utilizing input shaping. These tools aid in performance analysis by providing intuitive and computationally simple methods for determining key system attributes, such as the residual vibration in response to a command. This paper describes methods whereby arbitrary reference commands may be interpreted as input-shaped commands. This capability allows input shaping analysis tools to be used on systems without input shapers. Experimental results obtained from an industrial 10-ton bridge crane validate the theoretical developments.     

Finite element-based analysis of shunted piezoelectric structures for vibration damping

Piezoelectric patches shunted with passive electrical networks can be attached to a host structure for reduction of structural vibrations. This approach is frequently called “shunted piezo damping” and has the advantage of guaranteed stability and low complexity in implementation. For numerical treatment of such structures, a finite element modelling methodology is presented that incorporates both the piezoelectric coupling effects of the patches and the electrical dynamics of the connected passive electrical circuits. It allows direct computation of the achieved modal damping ratios as a major design criterion of interest. The damping ratios are determined from the eigenvalue problem corresponding to the coupled model containing piezoelectric structure and passive electrical circuit. The model includes local stiffening and mass effects as a result of the attached patches and, therefore, enables accurate prediction of the natural frequencies and corresponding modal damping ratios. This becomes crucial for choosing the patch thickness to achieve optimal modal damping for a given host structure. Additionally, structures with complex geometry or spatially varying material properties can easily be handled. Furthermore, the use of a finite element formulation for the coupled model of piezoelectric patches and a host structure facilitates design modifications and systematic investigations of parameter dependencies. In this paper, the impact of parameters of the passive electrical network on modal damping ratios as well as the variation of the patch thickness are studied. An application of this modelling method is realized by commercial software packages by importing fully coupled ANSYS^© – models in MATLAB^©. Afterwards, modal truncation is applied, the dynamic equations of the passive electrical network are integrated into the piezoelectric model and eigenvalue problems are solved to extract the increase in modal damping ratios. The numerical results are verified by experiments.     

Electromagnetic vibration energy harvesting device optimization by synchronous energy extraction

This paper investigates a new application of nonlinear techniques for vibration energy harvesting. The Synchronous Electric Charge Extraction (SECE) energy harvesting technique for piezoelectric generators is extended and adapted to electromagnetic generators. This new circuit, which is the dual of the SECE circuit, is named SMFE for Synchronous Magnetic Flux Extraction. A theoretical model is developed, and the harvested power is simulated. Comparisons with a classical energy extraction approach show that between 2.5 more power and 10% less power can be harvested, depending on the generator characteristics. It also allows the maximum power to be harvested whatever the value of the load. Finally, the SMFE circuit was embedded and tested on a simple centimeter-scale electromagnetic harvester. Measurements confirm the theoretical operating principle of the circuit.     

Software modeling and analysis using a hierarchical object-oriented Petri net

Petri net is used widely to analyze and model various systems formally. Recently, many Petri nets mania devote their efforts to enhancing and extending the expressive power of Petri nets. One such effort is to extend Petri nets with object-oriented concepts. An object-oriented paradigm provides excellent concepts to model real-world problems. Object-oriented concepts allow us to build software systems easily, intuitively, and naturally. Although several high-level Petri nets with the concept of objects are suggested, these nets do not fully support the object-oriented concepts. In this paper, we propose a hierarchical object-oriented Petri net (HOONet). The formal syntax and semantics of HOONet are explained in detail. HOONet supports a wide range of object-oriented features including abstract, encapsulated and modularized objects, object interaction by message passing, inheritance, and ploymorphism. HOONet also supports a variety of modeling and analysis mechanisms such as incremental modeling of evolving systems, unfolding the HOONet to lower level Petri net, and incremental reachability analysis for HOONet models. We demonstrate the usefulness of HOONet by applying it to modeling and analysis with an example.     

带有星型齿轮传动结构的转子系统不平衡耦合振动分析

齿轮传动风扇发动机(GTF)的低压转子系统由于带有星型齿轮传动结构,使得其具有有别于传统发动机的动力学特性,因此由于这种齿轮柔性转子耦合系统而产生的振动问题更为复杂.本文基于该低压转子的结构特点,建立了具有星型齿轮传动结构的三支点转子系统有限元模型,通过对高速转子轮盘施加偏心质量,研究不平衡矢量激励下转子系统的耦合振动特性,并进行了相关试验分析.结果表明：在双盘不平衡激励下,由于不平衡之间耦合效应,转子系统各轴段均存在振动减弱的情况.并且与中心齿轮相比,环形齿圈与游星齿轮之间的啮合力更大,且受不平衡初始相位的影响更显著.此外,当相位差为180°时,不平衡对转子系统的危害较大.     

Atomic-scale friction control by vibration using friction force microscope

Manipulation of friction at the nanoscale has been traditionally approached by chemical means (lubrication). Recent friction force microscopy (FFM) experiments demonstrated that it can be done mechanically by applying vibration to accessible elements of the system. This paper provides analytic understanding on why vibration can reduce friction based on a 1D model imitating the FFM tip moving on a substrate. Open-loop stability is first studied, and a feedback vibration control is then designed using the accessible variable. Comparing to the open-loop system, friction force is significantly reduced in the closed-loop system. Numerical simulations show satisfactory performances.     

平带系统非线性振动实验研究

为研究传动带在运转过程中的非线性振动问题，建立了一套平带传动实验系统．通过多功能控制卡输出的电压模拟量控制伺服电机控制器驱动电机转动，进而产生带的传动．利刖激光位移传感器及L．K—Navigator软件采集并保存带传动过程中的横向振动位移．选取平带系统在匀速转动和有激励扰动的情况下进行多组实验，实验数据的分析证明带在传动过程中存在周期、倍周期、混沌等非线性现象．