Novel method for research on exposure to nonlinear vibration transferred by suspension of vehicle

The paper presents novel method for research on exposure to nonlinear vibration of passenger car suspension as nonlinear dynamical system. Also paper provides a discussion on the results of studies addressing the impact exerted by damping properties of shock absorber on the vibrations being generated. The research was conducted on the car forced to vibration by the exciter machine with changeable frequency. The paper addresses results of analysis of application of one of the time-frequency representation techniques to the identification of structure of vibration. The obtained representation of the vibration allows determining time function of separate frequency bands, which represents the isolated vibration dynamics phenomena. Considering the variability of the time and frequency distribution of the vibration even in selected analysed bands, the time function was developed as exposure to vibration estimator. The recommended method makes use of function of exposure to vibration. The advantage of these method is possibilities of precise analysis of chosen frequency bands. The investigations conducted confirm considerable susceptibility to changes in the technical condition of shock absorber with regard to the assessment of human exposure to vibrations.     

连续小波变换离散化的爆炸振动特征分析

应用连续小波变换的离散化关系,针对一个改进的L-P（littlewood-paley）小波基函数,给出了一种实现频率完全分割的时频特征分析方法,并对爆炸振动时频特征进行了研究。80 kg TNT地面爆炸时地面垂向振动速度的时间能量密度分布情况表明,在质点振动峰值速度到达时刻爆炸振动的频率范围比较宽,而其他时刻的振动频率相对较为集中,时频能量分布的峰值正好对应于爆炸振动速度的峰值到达时间。基于小波变换的爆炸振动频谱特征与Fourier变换的结果具有良好的一致性。此外,还给出了利用小波变换结果建立爆炸振动随机演变理论模型的基本方法。     

Ride dynamics mathematical model for a single station representation of tracked vehicle

Tracked vehicles are exposed to severe ride environment due to dynamic terrain-vehicle interactions. Hence it is essential to understand the vibration levels transmitted to the vehicle, as it negotiates different types of terrains at different speeds. The present study is focused on the development of single station representation of tracked vehicles with trailing arm hydro-gas suspension systems, simulating the ride dynamics. The kinematics of hydro-gas suspension system have been derived in order to determine the non-linear stiffness characteristics at various charging pressures. Then, incorporating the actual suspension kinematics, non-linear governing equations of motion have been derived for the sprung and unsprung masses and solved by coding in Matlab. Effect of suspension non-linear dynamics on the single station ride vibrations have been analyzed and validated with a multi-body dynamics model developed using MSC.ADAMS. The above mathematical models would help in estimating the ride vibration levels of the tracked vehicle, negotiating different types of terrains at various speeds and also enable the designers to fine-tune the suspension characteristics such that the ride vibrations are within acceptable limits. The mathematical ride model would also assist in development of non-linear ride vibration model of full tracked vehicle and estimate the sprung mass dynamics.     

基于改进匹配追踪算法的化爆地震波信号时频特征提取

通过化爆地震波信号的时频分析可以获取丰富的地下岩层信息,为进一步的化爆地震波特性研究提供支撑。本文中利用爆炸地震波信号的非平稳随机特性,提出一种改进的匹配追踪算法(matching pursuits),该方法能更有效地获取化爆地震波信号的时频信息。该算法首先对地震波信号进行Hibert变换,将其转换成复数信号,获得爆炸地震波信号瞬时频率相位参数,再进行子波分解,从而显著提高了匹配追踪算法的运算速率;用分解后的信号计算其魏格纳威利分布(Wigner Ville distribution),有效地消除了交叉干扰项的影响。将该方法用于实测地震波信号的时频分析,获得了分辨率较高的时频分布图,且运算速率大大提高。     

基于小波变换的爆破振动信号能量分布特征分析

为了深入研究爆破地震波特性,应用小波变换方法对具有短时非平稳特点的爆破振动信号进行了能量分布特征分析。根据小波变换的时-频特性和分层分解展开关系,将爆破振动时间历史信号用分层重构信号进行扫描,应用这些信号得到了不同频率带上爆破振动的相对能量分布和振动强度的时间变化规律。爆破振动信号实测结果分析表明,基于小波变换的能量分布特征分析可以更准确地给出爆破振动信号的细节信息。研究结果为分析爆破振动结构安全性提供了新的途径。     

柔性轮对的离散时间传递矩阵法建模及垂向振动

针对铁道车辆轮对系统的弹性振动及台架高频激振试验仿真问题, 以离散时间传递矩阵法建立了柔性轮对振动模型. 基于Newmark-β隐式法积分格式推导了分布质量弹性轮轴、集总质量车轮及弹簧-阻尼单元的离散时间传递矩阵, 采用Riccati法、Newmark-β法实现轮对系统垂向振动加速度以及速度、位移的求解, 将轮对模型与采用新型显式积分法求解的构架、轨道轮组动力学模型集成, 完成机车车辆单轴滚振试验台的动力学建模, 提出了混合积分模式下动态仿真求解流程. 基于滚振试验台, 开展了轨道轮初始表面粗糙度、打磨多边形及局部凹陷状态下300 ~ 400 km/h高速运行试验, 同步开展了相应的动力学仿真, 通过在时域-频域对测试和计算结果的比较, 检验了理论模型. 结果表明, 在振动加速度的时域-频域特性和幅值分布上, 单轮对柔体模型总体能够较好反映500 Hz频率下系统的中高频振动规律, 有效捕捉车轮不圆、多边形磨耗、局部凹陷等动态激扰, 三种轨面状态下计算的轴箱加速度幅值误差总体低于9%, 模型具有较好的适应性和准确性. 但相关建模方法如何在复杂空间结构中应用需要进一步探索.      

移动随机荷载作用下梁桥非平稳随机振动的PEM-FFT方法

针对移动随机载荷作用下桥梁结构非平稳随机振动问题,建立了一种基于频域分析的虚拟激励-傅里叶变换方法(PEM-FFT)。与通常的非平稳随机振动的时频分析方法不同,提出的方法完全在频域上执行。其主要特色是能够给出随机输入与随机输出的频域关系,表明移动载荷作用下结构非平稳随机振动分析仅需对载荷的确定性移动函数项进行计算。数值算例考虑了等截面/变截面简支梁受移动随机载荷作用的问题,首先与通常的时频分析方法进行对比,验证了PEM-FFT方法的正确性和有效性,进一步讨论了不同结构形式以及不同载荷移动速度对响应演变统计量的影响。     

基于小波分析的实船水下爆炸船体响应特征

为了研究水下爆炸条件下船体冲击振动响应时频特征,针对某实船非接触水下爆炸实验冲击响应测试实验数据,基于小波分析及能量统计方法对响应信号进行时频特性分析,得到了实船非接触水下爆炸冲击振动响应的时频分布和能量分布。分析结果表明,采用基于小波变换的时频分析方法,可以成功获得船体冲击响应信号不同频率段下的强度、能量和作用时间等时频细节信息,包括响应信号各频段冲击峰值、衰减过程、振动能量及其在全频率段上所占的分数。通过对小波频段能量统计以及冲击强度分析发现,冲击响应能量频段分布较广,主甲板及以下甲板全频段振动能量的80%以上在312.5 Hz以上,上层建筑甲板平台各频段冲击振动能量分数向低频段转移。     

爆破震动信号的小波分析与HHT变换

以实测的爆破震动信号为例,分别应用小波分析和HHT(Hilbert-Huang Transform)变换从不同方面进行对比分析,讨论了爆破震动信号的特征提取和时频分布。结果表明:小波分析和HHT变换都是处理非平稳信号的两种好方法,都能很好地提取信号的主要特征信息和进行滤波、消噪。然而,小波分析存在选择小波基的困难,而HHT变换不需要预先选择基函数,其EMD（empirical mode decomposition）得到的IMF(intrinsic mode function)能反映原始信号的固有特性,通常具有实际物理意义;小波谱的能量在频率范围内分布较宽,而Hilbert能量谱能清晰地表明能量随时频的具体分布,大部分能量都集中在有限的能量谱线上;小波分析中时间、频率分辨率受Heisenberg测不准原理的限制,而HHT变换中时间分辨率不变且精度很高,其频率分辨率则可随信号内在的特性进行自适应调节。分析表明:HHT变换在分析非平稳信号时较小波分析更具适应性,在岩石中波的传播、衰减规律、结构动态响应特征和爆破震动破坏等研究中有着广阔的应用前景。     

基于虚拟激励法的车-轨-桥耦合系统的随机振动响应分析

轨道随机不平顺作为引起车辆-轨道-桥梁耦合系统振动的最重要的激励源,对列车过桥平稳性有着至关重要的影响．建立车辆-轨道-桥梁耦合垂向振动模型,采用虚拟激励法,计算随机不平顺激励下车辆运行的平稳性以及轨道和桥梁结构的振动特性,避免了繁复的时频转换和复杂的数值积分．数值分析了不同速度下列车过桥的平稳性和列车对不平顺波长的敏感范围．经过分析得到,列车运行速度越大,过桥平稳性指标越大,即舒适性越差;而且影响列车平稳性的不平顺波长越长,其影响范围越大．     

Analysis of vibration and frequency transmission of high speed EMU with flexible model

When the operation speed of the high-speed train increases and the weight of the carbody becomes lighter,not only does the sensitivity of the wheel/rail contact get higher,but also the vibration frequency range of the vehicle system gets enlarged and more frequencies are transmitted from the wheelset to the carbody.It is important to investigate the vibration characteristics and the dynamic frequency transmission from the wheel/rail interface to the carbody of the high-speed electric multi-uint（EMU）.An elastic highspeed vehicle dynamics model is established in which the carbody,bogieframes,and wheelsets are all dealt with as flexible body.A rigid high-speed vehicle dynamics model is set up to compare with the simulation results of the elastic model.In the rigid vehicle model,the carbody,bogieframes and wheelsets are treated as rigid component while the suspension and structure parameters are the same as used in the elastic model.The dynamic characteristic of the elastic high speed vehicle is investigated in time and frequency domains and the di ff erence of the acceleration,frequency distribution and transmission of the two types of models are presented.The results show that the spectrum power density of the vehicle decreases from the wheelset to the carbody and the acceleration transmission ratio is approximately from 1%to 10%for each suspension system.The frequency of the wheelset rotation is evident in the vibration of the flexible model and is transmitted from the wheelset to the bogieframe and to thecarbody.The results of the flexible model are more reasonable than that of the rigid model.A field test data of the high speed train are presented to verify the simulation results.It shows that the simulation results are coincident with the field test data.     

洗衣机悬挂系统动态特性的实验研究

悬挂系统是全自动洗衣机最重要的部件之一,其动态特性直接影响整机的工作平稳性或鲁棒性。本文通过压电式加速度计拾取脱水工况下滚筒式洗衣机外筒上各测点的响应信号,运用DASP（Data Acquisition ＆ Signal Processing）信号采集分析处理系统,分别采用频域自互谱法和时域随机子空间法对其进行模态参数识别。结果表明,工作状态振动实验足以识别出该型号洗衣机所感兴趣的模态参数;其结果可以作为有限元模型修正的参考依据。     

Tractor ride vibration—A review

All human occupants vibrate to some degree in any moving vehicle, whether it is a car, truck, train, aeroplane or boat. The reviews on the effect of vibration on human health have shown serious evidence of operator ill health that may be attributed to tractor drivers. The frequency range of 2–6 Hz has been observed to be the most harmful for the human operator because resonance occurs within this frequency range. Considerable effort has been made to establish the optimum design parameters for tractor seats. Further reductions in the level of ride vibrations experienced by tractor operators appear to be necessary and some possible methods of achieving significant improvements have been outlined. These methods have led to the evolution of several seat suspension systems and emphasise the use of the principles of ergonomics in the operator's seat design. In this paper, a review of the work done in this area, particularly with respect to tractor operators, is presented and discussed.     

Nonlinear dynamic analysis for coupled vehicle-bridge system with harmonic excitation

In this paper, a multi-degree-of-freedom lumped parameter coupled vehicle-bridge dynamic model is proposed considering the nonlinearities of suspension and tire stiffness/damping and the nonlinear foundation of bridge. In terms of modelling, the continuous expressions of the kinetic energy, potential energy and the dissipation function are constructed. The dynamic equations of the coupled vehicle-bridge system (CVBS) are derived and discretized using Galerkin’s scheme, which yield a set of second-order nonlinear ordinary differential equations with coupled terms. The numerical simulations are conducted by using the Newmark-β integration method to perform a parametric study of the effects on excitation amplitude, suspension stiffness and position relation. The bifurcation diagram, 3-D frequency spectrum and largest Lyapunov exponent are demonstrated in order to better understand the vibration properties and interaction between the vehicle and bridge with the key system parameters. It can be found that the nonlinear dynamic characteristics such as parametric resonance, jump phenomena, periodic, quasi-periodic and chaotic motions are strongly attributed to the interaction between vehicle and bridge. Significantly, under the combined internal and external excitations, the vibration amplitudes of the CVBS have a certain degree of dependence on the external excitation. Suspension stiffness could lead to complex dynamics such as the higher-order bifurcations increase and the chaotic regions broaden. The increasing of distance could effectively control the nonlinear vibration of CVBS. The application of the proposed nonlinear coupled vehicle-bridge model would bring higher computational accuracy and make it possible to design the vehicle and bridge simultaneously.     

New analytical method to evaluate the powerplant and chassis coupling in the improvement vehicle NVH

The design of an automotive powerplant mounting system is an essential part in vehicle safety and improving the vehicle noise, vibration and harshness (NVH) characteristics. One of the main problems encountered in the automotive design is isolating low frequency vibrations of the powerplant from the rest of the vehicle. The significant powerplant mass makes the choice of frequency and mode arrangements a critical design decision. Several powerplant mounting schemes have been developed to improve NVH properties concentrating on the positioning and design of resilient supports. However these methods are based on decoupling rigid body modes from a grounded powerplant model which ignores chassis and suspension system interactions. But it cannot be stated that decoupling the grounded rigid body modes of the powerplant will systematically reduce chassis vibrations. In this paper, a new analytical method is proposed to examine the mechanisms of coupling between the powerplant and the vehicle chassis and subsystems. The analytical procedure expands the equation of motion of the vehicle components to such that a domain of boundary conditions used in the 6 degrees-of-freedom powerplant mounting model can be defined. An example of this new procedure is given for improving NVH chassis response at idle speed using the torque roll axis decoupling strategy.     

基于小波包能量谱爆炸参量对爆破振动信号能量分布的影响

基于现场实测爆破振动数据,根据爆破振动信号具有短时非平稳的特点,采用小波包分析技术对不同爆炸参量(爆心距、最大段药量和微差雷管段数)下产生的爆破振动信号进行小波包能量谱分析,获得了爆破振动信号不同频带的能量分布,研究了不同爆炸参量下的爆破振动信号能量分布特征,从爆破振动信号能量角度探讨了不同爆炸参量下爆破地震波的衰减规律,为研究爆破地震效应提供了一种新的分析技术。     

高速飞行器中空翼结构高温热振动特性试验研究

远程高速飞行器飞行速度快, 滞空时间长, 飞行过程中翼、舵等结构会出现长时间的剧烈振动, 由气动加热产生的高温还会使飞行器材料和结构的弹性性能发生变化, 从而引起翼、舵等结构振动特性的改变.因此获得高温与振动复合环境下的远程高速飞行器翼、舵等结构的振动特性参数对于高速飞行器的安全设计具有非常重要的意义.将高温热环境试验系统与振动试验系统相结合, 在对中空翼面结构进行振动激励的同时使用红外辐射加热方式对翼面结构生成可控的热环境, 并通过自行设计的耐高温引伸装置将中空翼结构的振动信号传递到非高温区进行数据采集与分析的方式, 实现了高达800℃~900℃的力热复合环境下的翼结构固有频率、模态等振动特性参数的试验测试, 其试验结果为远程高速飞行器中空翼结构在高温振动环境下的动特性分析和安全可靠性设计提供了重要依据.     

基于数据驱动的全线控底盘纵臂式悬架系统研究

汽车在越野类极限路况下行驶, 对车身高度有一定范围的调节需求, 传统悬架方案与全线控底盘进行技术融合时, 存在机构运动干涉、底盘升降过程中车轮外倾程度过大、车轮发生侧向位移等现象, 易导致轮胎过度磨损, 致使行驶失稳. 将车身高度变化对轮胎侧向参数的影响转化为车轮纵向滚动, 进而实现稳定的大行程车身高度调节, 是解决上述问题的关键. 本研究建立整车七自由度动力学模型, 对悬架系统导向机构展开力学分析, 集两者作为系统研究的输入信息; 通过正弦波激振台对弹性元件、减振器进行相关特性参数获取, 基于数据驱动开展一体化电动轮的运动学仿真测试, 包括对悬架系统关键铰接位置进行力学性能分析、对电动轮整体结构进行运动学特性研究, 以此定义系统关键性能指标, 结合理论研究与仿真测试, 确定双纵臂式主动悬架系统方案. 仿真结果与实车验证综合表明, 搭载本研究系统方案的全线控平台, 进行大行程高度调节过程中, 车轮外倾问题得到有效解决, 一体化电动轮具备良好的独立运行能力, 本研究对提高车辆在极限路况下的通过性具有重要意义.      

Evolutionary algorithm-based PID controller tuning for nonlinear quarter-car electrohydraulic vehicle suspensions

The basic challenge associated with the design of vehicle suspension system is the attainment of an optimal trade-off between the various design objectives. This study presents the design of proportional-integral-derivative (PID) controller for a quarter-car active vehicle suspension system (AVSS) using evolutionary algorithms (EA) such as the particle swarm optimization (PSO), genetic algorithm (GA) and differential evolution (DE). Each of the EA-based PID controllers showed overall improvement in suspension travel, ride comfort, settling time and road holding from the manually tuned controller and the passive vehicle suspension system. These improvements were, however, achieved at the cost of increased actuator force, power consumption and spool-valve displacement. DE-optimized PID control resulted in the best minimized suspension performance, followed by the GA and PSO, respectively. Frequency-domain analysis showed that all the signals were attenuated within the whole body vibration frequency range and the EA-optimized controllers had RMS frequency weighted body acceleration of the vehicle within allowable limits for vibration exposure. Robustness analysis of the DE-optimized PID-controlled AVSS to model uncertainties is carried out in the form of variation in vehicle sprung mass loading, tyre stiffness and speed.     

Vibration suppression for high-speed railway bridges using tuned mass dampers

This paper deals with the applicability of passive tuned mass dampers (PTMDs) to suppress train-induced vibration on bridges. A railway bridge is modeled as an Euler–Bernouli beam and a train is simulated as series of moving forces, moving masses or moving suspension masses to investigate the influence of various vehicle models on the bridge features with or without PTMD. According to the train load frequency analysis, the resonant effects will occur as the modal frequencies of the bridges are close to the multiple of the impact frequency of the train load to the bridge. A single PTMD system is then designed to alter the bridge dynamic characteristics to avoid excessive vibrations. Numerical results from simply supported bridges of Taiwan High-Speed Railway (THSR) under German I.C.E., Japanese S.K.S. and French T.G.V. trains show that the proposed PTMD is a useful vibration control device in reducing bridge vertical displacements, absolute accelerations, end rotations and train accelerations during resonant speeds, as the train axle arrangement is regular. It is also found that the inner space of bridge box girder of THSR is wide and deep enough for the installation and movement of PTMD.