Effect of integral squeeze film damper on vibration and noise of spur gear with center-distance error

When the actual installation center distance between a pair of spur gears is greater than the theoretical center distance,backlash increases,leading to increased vibration and noise.The structural parameters of an integral squeeze film damper(ISFD)were designed with the stiffness of rigid support as reference to investigate the effect of an ISFD on the dynamic characteristics of a spur gear transmission system with center-distance installation error.A spur gear test bench with center distance-error was built to investigate the vibration and noise reduction characteristics of ISFD.The experimental results indicate that,compared with a rigid support,the ISFD can reduce vibration by approximately 40%and noise by approximately 5 d B.ISFD can effectively absorb the impact energy caused by an increase of in backlash,which is conducive to the stable operation of the spur gear transmission system.

SMART STRUCTURES USING PIEZOELEMENTS FOR ACTIVE VIBRATION AND NOISE SUPPRESSION IN AVIATION AND AEROSPACE

具有减振降噪功能的压电智能结构是智能材料与结构的一个重要分支。在航空航天领域存在一些典型结构，如飞机机舱、空间站、卫星太阳能帆板和通讯天线以及直升机旋翼等，其振动与辐射噪声造成很多不利影响。为了研究这些结构的振动与噪声控制方法，制作了几个实验模型如大型薄壁复合材料圆桶、柔性梁、钢架及旋翼系统模型，通过压电传感器、驱动器布置数量和位置的优化，采用不同的控制算法，在基于个人计算机的测控平台上进行了振动控制实验，取得了明显的减振降噪效果。

Reduction of current chopping noise with DSP controller in switched reluctance motor drive system

A novel current chopping mode was used in a switched reluctance motor drive system to make full use of the characteristics of digital signal processor (DSP) TMS320F240. The necessity of this 180° phase-shift current control (PSCC) mode is introduced first and then the principle of PSCC covering both hardware requirement and software programming is described in detail. The analysis made indicated that with this mode, the chopping frequency in winding can reach 20 kHz with 10 kHz power switches and the control frequency can reach 40 kHz at the same time. Subsequently, based on the linear and nonlinear mathematical models of the switched reluctance motor (SRM), some simulation work has been done. The simulation results show that when this mode is applied to SRM drive (SRD) system, the current waveform becomes better. So the ripple of the torque is reduced simultaneously and the vibration and acoustic noise are reduced involuntarily. Stationary tests show that the acoustic noise is greatly diminished. Finally, some experiments were made using a 50 kW SRD system for electric vehicle (EV). Experimental results indicate that this mode can be implemented feasibly and it has a good action on the SRD system.

AN ADAPTIVE OPTIMAL KALMAN FILTER FOR STOCHASTIC VIBRATION CONTROL SYSTEM WITH UNKNOWN NOISE VARIANCES

In this paper, an optimal criterion is presented for adaptive Kalman filter in a control system with unknown variances of stochastic vibration by constructing a function of noise variances and minimizing the function. We solve the model and measure variances by using DFP optimal method to guarantee the results of Kalman filter to be optimized. Finally, the control of vibration can be implemented by LQG method.

Application and optimization design of non-obstructive particle damping-phononic crystal vibration isolator in viaduct structure-borne noise reduction

The problems associated with vibrations of viaducts and low-frequency structural noise radiation caused by train excitation continue to increase in importance.A new floating-slab track vibration isolator-non-obstructive particle damping-phononic crystal vibration isolator is proposed herein,which uses the particle damping vibration absorption technology and bandgap vibration control theory.The vibration reduction performance of the NOPD-PCVI was analyzed from the perspective of vibration control.The paper explores the structure-borne noise reduction performance of the NOPD-PCVIs installed on different bridge structures under varying service conditions encountered in practical engineering applications.The load transferred to the bridge is obtained from a coupled train-FST-bridge analytical model considering the different structural parameters of bridges.The vibration responses are obtained using the finite element method,while the structural noise radiation is simulated using the frequency-domain boundary element method.Using the particle swarm optimization algorithm,the parameters of the NOPD-PCVI are optimized so that its frequency bandgap matches the dominant bridge structural noise frequency range.The noise reduction performance of the NOPD-PCVIs is compared to the steel-spring isolation under different service conditions.

Review of recent progress in studies on noise emanating from rail transit bridges

In recent years, there has been rapid growth of Chinese rail transit networks. Many of these networks require elevated bridges. This results in a bridge-borne noise source, which occurs in addition to the main noise source （i.e., wheel-rail interactions）. Bridge-borne noise is attracting increasing attention because of its low-frequency noise characteristics. This review paper first analyzes the space distribution, spectral characteristics, and sound pressure levels of noise radiated by all-concrete, steel- concrete composite, and all-steel bridges, mainly according to experimental studies. Second, this paper reviews exist- ing theoretical prediction models of noise emanating from bridges： the semianalytical method, the Rayleigh integral method, the boundary element method, and statistical energy analysis. Several case studies are reviewed, and their results are discussed. Finally, according to the results of the current review, the main factors affecting bridgeborne noise are analyzed, several noise reduction measures are proposed for different types of bridges, and their effectiveness is demonstrated.

Vibro-acoustic performance of steel–concrete composite and prestressed concrete box girders subjected to train excitations

Owning to good mechanical properties,steel–concrete composite(SCC)and prestressed concrete(PC)box girders are the types of elevated structures used most in urban rail transit.However,their vibro-acoustic differences are yet to be explored in depth,while structure-radiated noise is becoming a main concern in noise-sensitive environments.In this work,numerical simulation is used to investigate the vibration and noise characteristics of both types of box girders induced by running trains,and the numerical procedure is verified with data measured from a PC box girder.The mechanism of vibration transmission and vibro-acoustic comparisons between SCC and PC box girders are investigated in detail,revealing that more vibration and noise arise from SCC box girders.The vibration differences between them are around 7.7 dB(A)at the bottom plate,19.3 dB(A)at the web,and 6.7 dB(A)at the flange,while for structure-radiated noise,the difference is around 5.9 dB(A).Then,potential vibroacoustic control strategies for SCC box girders are discussed.As the vibro-acoustic responses of two types of girders are dominated by the force transmitted to the bridge deck,track isolation is better than structural enhancement.It is shown that using a floating track slab can make the vibration and noise of an SCC box girder lower than those of a PC box girder.However,structural enhancement for the SCC box girder is extremely limited in effects.The six proposed structural enhancement measures reduce vibration by only 1.1–3.6 dB(A) and noise by up to1.5 dB(A).

A Method for Reducing Noise Radiated from Structures with Vibration Absorbers by Using an Accelerated Neural Network

A method for reducing noise radiated from structures by vibration absorbers is presented. Since usual design method for the absorbers is invalid for noise reduction, the peaks of noise power in the frequency domain as cost functions are applied. Hence, the equations for obtaining optimal parameters of the absorbers become nonlinear expressions. To have the parameters, an accelerated neural network procedure has been presented. Numerical calculations have been carried out for a plate type cantilever beam with a large width, and experimental tests have been also performed for the same beam. It is clarified that the present method is valid for reducing noise radiated from structures. As for the usual design method for the absorbers, model analysis has been given, so the number of absorbers should be the same as that of the considered modes. While the nonlinear problem can be dealt with by the present method, there is no restriction on the number of absorbers or the model number.

大型耙吸挖泥船结构设计要点

为实现大型耙吸挖泥船结构设计安全、合理、可靠,以某大型耙吸挖泥船为例,分析大型耙吸挖泥船结构设计特点,从结构设计、强度评估、疲劳评估和振动评估等角度论证其设计要点,通过对泥舱结构设计分析,给出泥舱设计的关键节点,对关键节点进行强度分析和疲劳分析,结果表明,该船局部关键区域应力水平较高,低周疲劳在关键区域的疲劳中占据主要地位,建立三维有限元模型计算挖泥船固有频率,对比该大型耙吸挖泥船激励频率与固有频率,结果表明,船体总振动固有频率通常可以避开激励频率,生活楼固有频率与激励频率较为接近。

Experimental research of active vibration and noise control of electrically controlled rotor

Electrically Controlled Rotor(ECR),also called as swashplateless rotor,applies blade pitch inputs via trailing-edge flaps system instead of traditional swashplate mechanism.In addition to primary control,rotor vibration reduction and noise alleviation are also achievable via applying higher harmonic control inputs with the trailing-edge flaps.In this paper,the feasibility of ECR to reduce vibration and noise actively is verified experimentally.Firstly,the test scheme of ECR active vibration and noise control is proposed,and the ECR test platform is modified according to the test scheme.Then,an adaptive control algorithm based on Kalman filter is developed.Lastly,hover and wind tunnel tests is performed to verify the feasibility of ECR active vibration and noise control.The results demonstrate that the ECR are effective for reducing rotor vibration and noise simultaneously.In the hover condition,the ECR can reduce the in-plane hub vibration by 42%and the inplane noise by 4dB.In wind tunnel condition,ECR can reduce the hub vibration by 75%and the BVI noise by 3dB.

基于声学黑洞波动控制技术的槽型轨动力吸振器减振降噪特性研究

轨道交通引起的环境振动噪声问题持续增加,即使目前具有多种控制效果良好的减振降噪措施,但仍有望做进一步的提升。在该研究中提出了一种新型的槽型轨道动力吸振器,将声学黑洞波动控制技术与动力吸振原理相结合。该吸振器设计的目标是保证主结构强度与刚度的前提下,采用附加的声学黑洞阻尼振子作为吸能单元,对主结构的振动能量进行传递、吸收与耗散。为了研究声学黑洞型动力吸振器对槽型轨道振动特性和声辐射特性的影响,利用仿真分析对不同类型的动力吸振器下槽型轨道的位移导纳和振动衰减率进行了评估;采用滚动噪声预测模型计算分析了声学黑洞型动力吸振器的降噪效果并探究了其参数对轮轨振动噪声的影响规律。结果表明:槽型轨在800~1000 Hz频段内的一阶pinned-pinned在未采取措施的情况下振动响应显著,振动衰减率仅为0.68 dB/m,在安装了声学黑洞型动力吸振器之后轨道结构的振动衰减率上升到1.80 dB/m,提高率可达265%。

船舶主机基座系统振动分析及控制技术

船舶主机基座系统是由基座结构和控制系统等2个部分组成。在主机持续工作的情况下,产生的交变载荷会通过基座系统传递,引起船体结构振动,可能对船体结构的安全构成威胁。通过合理设计基座结构和控制系统,可有效控制船舶主机传递到船底结构的振动,以满足更高的减振要求。首先介绍船舶主机引起振动的机理和振动分析方法,详细综述船舶主机基座结构、被动控制系统和主动控制系统的减振机理和优化研究成果,并对未来的研究进行一定的展望,为船舶主机基座系统的减振设计提供有益的参考。

基于MDO理论的船舶总体设计方法

为提高船舶总体设计质效,本文基于船舶设计、多学科设计优化(Multi-disciplinary Design and Optimization,MDO)理论及其应用的相关资料,在梳理现阶段船舶设计理论及基本流程的基础上,分析MDO理论在指导船舶设计中应用的可行性。结果表明,在船舶设计过程中应重点关注船舶型线设计、推进系统设计及振动噪声性能控制等关键技术。通过分析上述技术方面的研究进展,并基于MDO理论提出若干关于提高船舶总体设计质效的建议,对改进船舶总体设计方法具有一定工程指导价值。

Sigmoid变换的滤波-x四元数最小均方算法

滤波-x最小均方(Filtered-x Least Mean Square,FxLMS)算法是主动噪声控制系统中常用的算法,对中低频噪声有较好的控制作用,但在某些环境噪声中传统的算法可能达不到期望的抑制效果。提出一种基于sigmoid变换的滤波-x四元数最小均方算法,该算法利用四元数的空间特性使噪声信号在超复数域内部相互耦合和关联,并通过sigmoid函数对误差信号进行非线性变换来约束噪声信号以减低对权值更新的影响力度,避免权值在更新过程中发散,从而实现优异的收敛性能以及增强的鲁棒性。同时通过研究步长分析该算法的稳态特性,并在汽车、工厂噪声环境下验证提出算法性能的优越性,仿真结果支持了该结论。

船用合流型三通调节阀声流固耦合声学特性研究

针对合流型三通调节阀噪声声压频谱、声指向性等声学特性规律不明确的问题,基于声流固耦合理论,以PN50 DN250三通调节阀为研究对象开展声学特性研究。基于k-ε模型分析阀门定常流动,在定常流动收敛的基础上开展LES非定常流动分析,并导出流固耦合面及流体域内的时域脉动信息作为噪声激励源,开展三通调节阀不同工况下的声学特性研究。搭建三通调节阀流噪声试验台,试验工况下数值模拟噪声与实测噪声声压仅相差1.85 dB(A),验证声流固耦合数值模拟方法的准确性。分别数值模拟阀门实际工况下80%及60%开度下的噪声声学特性,总结出阀门噪声声压级分别为51.18和54.13 dB(A),验证三通调节阀噪声满足使用要求,提出的声流固耦合数值模拟方法可为合流型三通调节阀声学特性分析提供一定参考。

基于SYSNOISE的环境敏感点声屏障设计仿真研究

声屏障是降低交通噪声等流动性声源的一种有效而经济的方法。通过分析声屏障的降噪原理,研究和探讨不同声源状况的声屏障插入损失计算模型以及城市主干道声屏障的声学设计方法,选择噪音超标的校园作为研究对象,根据得到的插入损失计算模型对所选校园设计出相应的声屏障,并对声屏障进行验证,结果表明所设计的声屏障具有良好的隔声降噪效果。

改进小波阈值降噪方法在振动-高动态离心复合试验控制系统中的应用

目的 针对振动-高动态离心复合试验控制系统中控制信号受噪声干扰导致控制效果不佳的情况,进行降噪处理,以提升试验控制能力。方法 利用改进的小波阈值降噪方法,对振动-高动态离心复合试验控制系统中控制信号进行降噪处理,通过分析信号特性,结合小波阈值降噪方法原理,提出阈值准则随分解尺度自适应动态变化的改进方法。结果 通过本文改进方法和其他小波阈值降噪方法的对比分析表明,本文所提方法对于振动-高动态离心系统所存在的中高频噪声干扰起到了明显抑制作用,可有效保留控制信号特征,获得了更佳的综合降噪效果,信噪比提升近10 dB,满足试验控制所需的降噪要求。结论 采用自适应动态变化的阈值准则的小波阈值降噪方法对振动-高动态离心复合试验系统的控制信号进行降噪处理有效且可靠,可对后续相关试验技术研究方向提供一种可行思路。

地铁沿线某星级酒店建筑振动及二次辐射噪声的分析与控制

为了解决既有浅埋地铁运营时引起邻近拟建某酒店建筑物内振动及二次辐射噪声扰民问题,以及在控制建造成本的前提下如何实现更优的减振降噪效果等问题。采用了基于结构和声学有限元方法,建立基于实测结果“试错-修正”的耦合数值仿真计算模型,通过了K预测和B预测对比,验证了数值仿真的有效性。结果表明:酒店内一部分客房的二次辐射噪声超标,超标量为09~62dB(A),超过限值需要处理。考虑建造成本,综合利用带XPS地下连续隔振沟、浮筑地板以及室内吸声等办法,可以综合提供7dB(A)的改善量,再考虑现场修正,减振降噪控制后满足《城市轨道交通引起建筑物振动与二次辐射噪声限值及其测量方法标准》(JGJ/T 170—2009)对2类声功能区建筑物的室内二次辐射噪声限值要求,室内装修工程完工后,竣工验收合格。

多耐压壳体结构振动传递控制技术研究

相对单耐压壳体,由于多耐压壳体通过舷间连接结构相互耦合,受激励耐压壳体向临近的舷间结构/舷间声介质、临近耐压壳体、轻外壳等主构件传递振动,总体上呈现多路径相互叠加的树形结构,传递路径复杂。采用数值方法,通过建立多耐压壳体有限元模型,基于多耐压壳体耦合特征,分析振动传递路径上基座、激励位置、舷间结构等相关参数对多耐压壳体声学特性影响,从传递路径上开展针对性的结构声学噪声控制技术研究。分析结果可为多体结构的工程设计和振动噪声控制提供有效参考。

变反激励力作用下齿轮箱减振降噪方法研究

从主动振动控制原理出发,通过改变反激励力的方式研究齿轮箱减振降噪效果。建立齿轮箱系统动力学模型,分析获取轴承支反力,采用有限元方法对齿轮箱进行振动特性分析,并建立箱体振动实验平台,结合有限元分析与实验测试结果确定次级力源布放位置;基于主动振动控制方法,在次级力源上施加不同激励力抑制其振动,分析在不同激励力作用下的减振效果;将获取的箱体表面振动数据作为边界条件导入LMS Virtual.Lab声学软件中计算齿轮箱向外声场辐射的噪声。研究结果表明:施加相位相反、振幅相同的反激励力减振效果最佳,相比于无控制状态平均位移减小0.18mm,施加抑制主导模态的反激励力时降噪效果最佳,在1191Hz处最高降噪量达到50.13dB。