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.

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.

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

Smart material and structure (SMS) is a challenging novel technique for the 21 century especially in fields of aviation and aerospace. Vibration and noise suppression smart structure is an important branch of SMS. There are several typical structures such as the cabin of an airplane, space station, the solar board of satellite and the rotor blade of a helicopter, of which the vibrations and radiation noises have bad influences on precise equipments and aiming systems. In order to suppress vibrations and noises of these structures, several algorithms are applied to the models which simulate the structures. Experiments are performed to suppress vibrations and noises by bonding sensors and actuators to the structures at the optimized locations and using computer based measurement and control systems. For the blade vibration control of a helicopter, a non contact method of signal transmission by magneto electric coupling is discussed. The experimental results demonstrate that the methods used for active control are effective.

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.

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.

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.

阻尼层敷贴法对钻井振动筛降噪效果的影响

针对钻井振动筛工作噪声问题,提出了在钻井振动筛筛箱侧板敷贴阻尼层以减弱其噪声辐射的方法。通过筛箱振声模型,采用有限元法和模态应变能法对侧板敷贴阻尼前后的振动模态和侧板声辐射进行分析,利用COMSOL进行仿真求解,比较分析了不同材料、不同厚度的阻尼层对筛箱表面噪声辐射的影响。研究表明,表面阻尼结构能减弱噪声辐射;敷贴较硬的材料能对侧板起到一定的振动约束作用;需要根据材料属性选取最佳厚度,达到最佳减振降噪效果。

超高层办公建筑暖通空调系统噪声控制分析

营造良好的室内声环境对人员身心健康至关重要。本文以某超高层办公楼为研究对象,分析了超高层办公建筑声学方面的特点、典型暖通空调系统的噪声传递途径;针对办公楼层剖析了声源降噪、隔绝机房噪声、办公区内空调末端及管道的噪声控制措施,并针对机电层的不同设备区域提出了相应的隔振、隔声、降噪做法。

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%。

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。

用于汽车压缩机振动噪声控制的声子晶体设计与试验

针对汽车压缩机低频振动噪声控制难的问题,基于局域共振机理在压缩机外壳设计一种声子晶体结构。借助有限元法,计算声子晶体带隙范围,阐明声子晶体结构参数与在压缩机外壳布置方式选取原因,分析其具备的优势。而后,定制各部分材料组装声子晶体实体并布置于压缩机外壳后端面,搭建压缩机振动噪声台架试验台,选取4个声学场点采集辐射噪声,并记录压缩机本体振动变化情况。进一步,选取某型号汽车搭建压缩机整车振动噪声试验台,在驾驶员座椅右侧靠近人耳处设置声学传声器采集驾驶室内辐射噪声,并记录压缩机本体振动变化情况。试验结果表明,压缩机外壳安装声子晶体后,在声子晶体带隙频率范围对应转速内,台架与整车试验测得总辐射噪声与压缩机本体各向振动加速度均方根值基本存在改善,且部分转速范围效果显著。该文为汽车压缩机低频振动噪声控制研究提供了新的参考。

次级源和误差传感器布放对带弹性障板的充液直管声振复合有源控制的影响

针对充液管路系统噪声有源控制问题,研究了次级源和误差传感器布放对带弹性障板的充液直管管路系统有源消声与有源消振复合控制效果的影响。基于声固耦合方法建立了带弹性障板的充液直管管路系统的有限元模型,在声激励下对比了次级声源布放对系统有源消声性能的影响,并在组合激励下分析了次级力源、次级声源和误差传感器布放对系统复合有源控制的影响。结果表明,非对称分布的次级声源容易激起管壁振动,进而带动障板振动,导致有源消声效果不佳;采用对称分布的次级声源可使低频段的降噪量提高10 dB以上。复合有源控制可进一步提升全频段的控制效果。通过增加振动误差传感器数量,可使绝大多数频点的降噪量提高1∼20 dB不等。此外,在管壁上布放的两圈次级力源的间距小于管壁振动波长的1/4,且都不位于管壁振动节点附近时控制效果更好。

红外探测器振动噪声自动采集系统设计

红外探测器应用时受环境影响或外力作用会产生机械振动,从而引起振动噪声。噪声电压干扰会极大地降低探测器的跟踪能力和探测距离。因此振动噪声引起广泛关注,它是评价探测器的重要参数,也是剔除不合格探测器的重要手段。随着国内与国际市场对红外探测器的需求日益增加,传统人工监测并记录的测试方法已不能满足目前的产能需求。研究了一款支持不同规格红外探测器的振动噪声自动采集系统,主要介绍了系统设计原理、系统组成、各模块功能等。该系统的成功应用有效解决了红外探测器振动噪声测试效率低、准确率低的问题。以一款多元探测器为例,测试效率提高3倍,准确率为100%。该系统实现了振动噪声测试自动采集、无人值守,节约了人力成本。

某船舶餐厅振动噪声分析及治理

某船舶大餐厅与机舱公用部分钢围壁导致餐厅噪声水平超标,严重影响船员就餐舒适性。基于统计能量分析法和经验分析法,对餐厅所在舱段进行声学仿真,通过对比数值计算结果与实测数据,分析餐厅噪声来源及组成,确定在外部控制振源,在内部敷设浮筑地板、吸隔声材料的综合治理方案,最终有效控制餐厅噪声。从工程实践角度为毗邻主要声源的船舶舱室噪声治理提供一种参考方法,并提出一些建议。