Vibration Reduction by a Partitioned Dynamic Vibration Absorber with Acoustic Black Hole Features

Vibration quality is a vital indicator for assessing the progress of modern equipment.The dynamic vibration absorber(DVA)based on the acoustic black hole(ABH)feature is a new passive control method that manipulates waves.It offers efficient energy focalization and broad-spectrum vibration suppression,making it highly promising for applications in large equipment such as aircraft,trains,and ships.Despite previous advancements in ABH-DVA development,certain challenges remain,particularly in ensuring effective coupling with host structures during control.To address these issues,this study proposes a partitioned ABH-featured dynamic vibration absorber(PABH-DVA)with partitions in the radial direction of the disc.By employing a plate as the host structure,simulations and experiments were conducted,demonstrating that the PABH-DVA outperforms the original symmetric ABH-DVA in terms of damping performance.The study also calculated and compared the coupling coefficients of the two ABH-DVAs to uncover the mechanism behind the enhanced damping.Simulation results revealed that the PABH-DVA exhibits more coupled modes,occasionally with lower coupling coefficients than the symmetric ABH-DVA.The influence of frequency ratio and modal mass was further analyzed to explain the reasons behind the PABH-DVA's superior damping performance.Additionally,the study discussed the impact of the number of slits and their orientation.This research further explains the coupling mechanism between the ABH-DVA and the controlled structure,and provides new ideas for the further application of ABH in engineering.

Study on vibration reduction of two-scale system coupled with dynamic vibration absorber

The dynamic vibration absorber with inerter and grounded stiffness(IGDVA)is used to control a two-scale system subject to a weak periodic perturbation.The vibration suppression effect is remarkable.The amplitude of the main system coupled with absorber is significantly reduced,and the high frequency vibration completely disappears.First,through the slow-fast analysis and stability theory,it is found that the stability of the autonomous system exerts a notable regulating effect on the vibration response of the non-autonomous system.After adding the dynamic vibrator absorber,the center in the autonomous system changes to an asymptotically stable focus,consequently suppressing the vibration in the non-autonomous system.Further research reveals that the parameters of the absorber affect the real parts of the eigenvalues of the autonomous system,thereby regulating the stability of the system.Transitioning from a qualitative standpoint to a quantitative approach,a comparison of the solutions before and after the introduction of the dynamic absorber reveals that,when the grounded stiffness ratio and the mass ratio of the dynamic absorber are not equal,the high-frequency part in the analytical solution disappears.As a result,this leads to a reduction in the amplitude of the trajectory,achieving a vibration reduction effect.

Transmission and Dissipation of Vibration in a Dynamic Vibration Absorber-Roller System Based on Particle Damping Technology

The research of rolling mill vibration theory has always been a scientific problem in the field of rolling forming,which is very important to the quality of sheet metal and the stable operation of equipment.The essence of rolling mill vibration is the transfer of energy,which is generated from inside and outside.Based on particle damping technology,a dynamic vibration absorber(DVA)is proposed to control the vertical vibration of roll in the rolling process from the point of energy transfer and dissipation.A nonlinear vibration equation for the DVA-roller system is solved by the incremental harmonic balance method.Based on the obtained solutions,the effects of the basic parameters of the DVA on the properties of vibration transmission are investigated by using the power flow method,which provides theoretical guidance for the selection of the basic parameters of the DVA.Furthermore,the influence of the parameters of the particles on the overall dissipation of energy of the particle group is analyzed in a more systematic way,which provides a reference for the selection of the material and diameter and other parameters of the particles in the practical application of the DVA.The effect of particle parameters on roll amplitude inhibition is studied by experiments.The experimental results agree with the theoretical analysis,which proves the correctness of the theoretical analysis and the feasibility of the particle damping absorber.This research proposes a particle damping absorber to absorb and dissipate the energy transfer in rolling process,which provides a new idea for nonlinear dynamic analysis and stability control of rolling mills,and has important guiding significance for practical production.

An electromagnetic semi-active dynamic vibration absorber for thin-walled workpiece vibration suppression in mirror milling

As critical components of aircraft skins and rocket fuel storage tank shells,large thin-walled workpieces are susceptible to vibration and deformation during machining due to their weak local stiffness.To address these challenges,we propose a novel tunable electromagnetic semi-active dynamic vibration absorber(ESADVA),which integrates with a magnetic suction follower to form a followed ESADVA(follow-ESADVA)for mirror milling.This system combines a tunable magnet oscillator with a follower,enabling real-time vibration absorption and condition feedback throughout the milling process.Additionally,the device supports self-sensing and frequency adjustment by providing feedback to a linear actuator,which alters the distance between magnets.This resolves the traditional issue of being unable to directly monitor vibration at the machining point due to space constraints and tool interference.The frequency shift characteristics and vibration absorption performance are comprehensively investigated.Theoretical and experimental results demonstrate that the prototyped follow-ESADVA achieves frequency synchronization with the milling tool,resulting in a vibration suppression rate of approximately 47.57%.Moreover,the roughness of the machined surface decreases by18.95%,significantly enhancing the surface quality.The results of this work pave the way for higher-quality machined surfaces and a more stable mirror milling process.

Research on the Damping Mechanism of Time-Delay Coupled Negative Stiffness Dynamic Absorber in Nonlinear Vibration Damping System

A study was conducted on the effect of time delay and structural parameters on the vibration reduction of a time delayed coupled negative stiffness dynamic absorber in nonlinear vibration reduction systems. Taking dynamic absorbers with different structural and control parameters as examples, the effects of third-order nonlinear coefficients, time-delay control parameters, and negative stiffness coefficients on reducing the replication of the main system were discussed. The nonlinear dynamic absorber has a very good vibration reduction effect at the resonance point of the main system and a nearby area, and when 1 increases to a certain level, the stable region of the system continues to increase. The amplitude curve of the main system of a nonlinear dynamic absorber will generate Hop bifurcation and saddle node bifurcation in the region far from the resonance point, resulting in almost periodic motion and jumping phenomena in the system. For nonlinear dynamic absorbers with determined structural parameters, time-delay feedback control can be adopted to control the amplitude of the main system. For different negative stiffness coefficients, there exists a minimum damping point for the amplitude of the main system under the determined system structural parameters and time-delay feedback control parameters.

Dynamical Stability of Cantilevered Pipe Conveying Fluid with Inerter-Based Dynamic Vibration Absorber

Cantilevered pipe conveying fluid may become unstable and flutter instability would occur when the velocity of the fluid flow in the pipe exceeds a critical value.In the present study,the theoretical model of a cantilevered fluid-conveying pipe attached by an inerter-based dynamic vibration absorber(IDVA)is proposed and the stability of this dynamical system is explored.Based on linear governing equations of the pipe and the IDVA,the effects of damping coefficient,weight,inerter,location and spring stiffness of the IDVAon the critical flow velocities of the pipe system is examined.It is shown that the stability of the pipe may be significantly affected by the IDVA.In many cases,the stability of the cantilevered pipe can be enhanced by designing the parameter values of the IDVA.By solving nonlinear governing equations of the dynamical system,the nonlinear oscillations of the pipe with IDVA for sufficiently high flow velocity beyond the critical value are determined,showing that the oscillation amplitudes of the pipe can also be suppressed to some extent with a suitable design of the IDVA.

Analysis of radial stiffness of rubber bush used in dynamic vibration absorber

In order to study the influence of the structural parameters of the rubber bush on its radial stiffness, the constitutive relation of rubber materiel is used to obtain the calculation formula of the dimensionless radial stiffness coefficient. The obtained theoretical result is consistent with previous research results in both long rubber bushes and short rubber bushes. The simulation case was conducted by the finite element method to verify the correctness of the theory. The axial compression experiment was conducted to obtain the parameters needed in the simulation. The result shows that the percentage difference between the theoretical result and the simulation one is only 2.75%. A series of simulations were conducted to compare with previous work, and the largest magnitude of the percentage difference is only about 5%. Finally, the radial stiffness experiment was conducted by using a dynamic vibration absorber, and the influence of the structural parameters of the rubber bush on its radial stiffness is obtained. The result shows that the radial stiffness of the rubber bush increases with the increase in the length and the inner radius, but decreases with the increase in the outer radius.

The Effect of Mass Ratio and Air Damper Characteristics on the Resonant Response of an Air Damped Dynamic Vibration Absorber

In this paper, it is shown that, a road vehicle 2DOF air damped quartercar suspension system can conveniently be transformed into a 2DOF air damped vibrating system representing an air damped dynamic vibration absorber (DVA) with an appropriate change in the ratio μ of the main mass and the absorber mass i.e. when mass ratio μ >> 1. Also the effect of variation of the mass ratio, air damping ratio and air spring rate ratio, on the motion transmissibility at the resonant frequency of the main mass of the DVA has been dis- cussed. It is shown that, as the air damping ratio in the absorber system increases, there is a substantial decrease in the motion transmissibility of the main mass system where the air damper has been modeled as a Maxwell type. Optimal value of the air damping ratio for the minimum motion transmissibility of the main mass of the system has been determined. An experimental setup has been designed and developed with a control system to vary air pressure in the damper in the absorber system. The motion transmissibility characteristics of the main mass system have been obtained, and the optimal value of the air damping ratio has been determined for minimum motion transmissibility of the main mass of the

Design and experiment of an adaptive dynamic vibration absorber with smart leaf springs

An adaptive dynamic vibration absorber(ADVA)is designed for lowfrequency vibration suppression.The leaf springs are applied as the tuning stiffness elements.The principle of variable stiffness is analyzed to obtain the effective range of the first natural frequency variation.A classic simply supported manipulator is selected as the controlled system.The coupled dynamic model of the manipulator-ADVA system is built to obtain the maximum damping efficiency and the vibration absorption capacity of the designed ADVA.An experimental platform is set up to verify the theoretical results.It is revealed that the ADVA can adjust the first natural frequency on a large scale by changing the curvature of the leaf springs.The amplitude of the manipulator is reduced obviously with the installation of the designed ADVA.Finally,based on the short-time Fourier transformation(STFT),a stepwise optimization algorithm is proposed to achieve a quick tuning of the natural frequency of the ADVA so that it can always coincide with the frequency of the prime structure.Through the above steps,the intelligent frequency tuning of the ADVA is realized with high vibration absorption performance in a wide frequency range.

Vibration Suppression of Unbalanced Machines UsingLumped Mass Dynamic Vibration Absorber

The vibration of machines due to rotating parts unbalance disturbs the machine functioning and shortens the lifetime of its parts. A dynamic vibration absorber is a favorite solution to suppress the machine vibration since its implementation does not require any modification neither on the machine nor on its installation. The paper considers an unbalanced machine to which a lumped mass dynamic vibration absorber is attached. Firstly, the machine equipped with the absorber is modeled, and the vibration expressions are extracted. Secondly, an original approach to optimize the absorber parameters is presented, and simulation results are advanced, when the absorber is undamped and damped. Thirdly, the absorber optimal parameters allowing the best vibration reduction of the machine are identified, showing bow the absorber should be designed, when the disturbance frequency is stable or unstable. The results are a significant contribution in the vibration control of unbalanced machines.

Design of distributed dynamic absorbers for vibration suppression of panel structures

Distributed dynamic absorbers have many advantages such as wide frequency bandwidth for vibration suppression,strong detuning adaptability,and high system stability,making them very suitable for the vibration and noise control of continuous structures.Therefore,they have broad application prospects in various fields such as transportation,aviation,and aerospace.However,there are still many challenges in the engineering applications of distributed dynamic absorbers for vibration suppression,including the engineering realization of the optimal damping of traditional optimal coherence dynamic absorbers,and the engineering applicability of the finite periodic array dynamic absorbers.Based on the damping material properties obtained by the dynamic mechanical analyzer tests,this paper establishes the finite element model of the cantilever-beam-type dynamic absorber with constrained damping layers,aiming to realize the accurate determination of the optimal damping.Experiments are conducted by attaching the traditional dynamic absorbers with the optimal damping to a thin-walled panel with four clamped edges.Results show that the vibration of the panel is well suppressed,with the reduction of the frequency response peak larger than 14 dB and the reduction ratio of RMS larger than 58%within 500 Hz.Afterwards,the periodically arrayed dynamic absorbers are designed according to the bandgap regulation method.The tuning behavior of the arrayed dynamic absorbers by changing designing parameters is investigated.The vibration reduction effect of arrayed dynamic absorbers is compared with that of the traditional dynamic absorbers under the same mass ratio through experiments.Results indicate that the arrayed dynamic absorbers are easier to design,and have a similar reduction effect on the modal vibration of the thin panel as the traditional dynamic absorbers within a narrow frequency range near the natural frequency,while they perform unsatisfactory in a broad band.Significantly,if the appropriate frequency and damping of the arrayed absorbers are chosen,a relatively wide bandgap can also be generated,which shows high engineering applicability.The research work in this paper provides beneficial reference for the design of distributed dynamic absorbers suitable for vibration suppression of thinwalled panel structures.

A review on the gun barrel vibrations and control for a main battle tank

Achieving high hitting accuracy for a main battle tank is challenging while the tank is on the move. This can be reached by proper design of a weapon control and gun system. In order to design an effective gun system while the tank is moving, better understanding of the dynamic behavior of the gun system is required. In this study, the dynamic behaviour of a gun system is discussed in this respect. Both experimental and numerical applications for the determination of the dynamic behaviour of a tank gun system are investigated. Methods such as the use of muzzle reference system(MRS) and vibration absorbers, and active vibration control technology for the control and the reduction of the muzzle tip deflections are also reviewed. For the existing gun systems without making substantial modifications,MRS could be useful in controlling the deflections of gun barrels with estimation/prediction algorithms.The vibration levels could be cut into half by the use of optimised vibration absorbers for an existing gun.A new gun system with a longer barrel can be as accurate as the one with a short barrel with the appropriate structural modifications.

Novel approach for active vibration control of a flexible missile

This paper investigates the feasibility of using an active dynamic vibration absorber(ADVA) for active vibration control of a flexible missile system through simulation.Based on the principles of a dynamic vibration absorber(DVA),a ring-type ADVA is first designed to attenuate the elastic vibration of the flexible missile,and the design of the active controller adopts the proportional-integral-derivative(PID)control algorithm.The motion equations of a flexible missile with an ADVA,which is subjected to follower thrust at its aft end,are derived using the Lagrangian approach.Taking the minimum of the root mean square(RMS) of the lateral displacement response of the center of mass as the objective function,a genetic algorithm(GA) is used to optimize the parameter of the DVA and PID controller.The numerical calculations show that the ADVA and DVA are effective in suppressing the vibration and provide approximately 41.2% and 17.6% improvement,respectively,compa red with the case of no DVA,The ADVA has better performance than the DVA,When the missile is subjected to follower thrust,the effect of vibration reduction is more effective than the case without follower thrust.It is feasible to reduce vibration and improve the stability of flexible missiles by means of the ADVA.

基于多模态控制理论的箱梁MDVA参数优化及对低频振动影响分析

由于多重动力吸振器(MDVA)具有减振效果好、吸振器质量分散的特点,因而,将通过MDVA的参数合理优化进而降低车辆载荷作用下箱梁各板件多个频段内的振动作为研究的主要内容。基于单自由度系统定点理论与多自由度多模态控制理论,推导了多目标模态的MDVA的参数优化方法;建立车-轨-桥有限元模型,根据仿真得到的箱梁振动频谱特征与模态特征,合理设置MDVA参数与安装位置,并对比了有无MDVA工况下箱梁的振动差异(1~250 Hz),结果表明,MDVA对箱梁多个频段均有较好的吸振效果。此外,钢轨与车轮的动力响应结果表明,MDVA对二者的低频振动同样有一定的抑制效果。

基于动力吸振器的微耕机扶手架减振设计

微耕机的扶手架结构较为简单,在田间作业时会造成扶手架的强烈振动,长时间的强烈振动会给操作者身心带来不适甚至严重伤害,针对此问题,对微耕机扶手架进行了减振设计。对于结构相对简单的构件,振动问题大多是由于主振动系统自身结构阻尼的不足导致的。为此,结合微耕机实际情况,将动力吸振器的设计方法应用于微耕机扶手架上,对动力吸振器进行结构设计并试制样件。最后,对动力吸振器样件的减振效果进行试验测试,结果表明:在安装动力吸振器样件后,其手把处的振动强度在空挡和耕作状态下分别降低了13.9%和11.2%。

考虑SSI效应的升降作业平台惯容减振优化设计

升降作业平台在野外工地、河滩等环境中高空作业时,其支腿底盘的明置基础与软土地基会发生动力相互作用,从而改变作业平台系统的动力特性。提出了考虑土与结构相互作用效应下的含3种不同惯容减振系统(SIS,SPIS-1,SPIS-2)的升降作业平台动力学模型,推导了作业平台在简谐激励下的振幅放大因子以及在随机激励下的响应均方值的解析表达式。利用遗传算法分别求解了位于中硬土、中软土以及软弱土3种地基表面的作业平台在H_(∞)和H_(2)优化准则下,惯容减振系统的最优设计刚度比和阻尼比。对最优状态下的各减振系统进行减振效果分析,结果表明:SPIS-2减振系统效果最佳,不仅最大程度地抑制了升降作业平台的共振效应,而且更有效地拓宽频带范围;SSI效应可以降低简谐激励下作业平台的位移振幅放大因子和随机激励下作业平台绝对位移的均方值;SSI效应对简谐激励和随机激励下惯容减振系统的最优设计参数影响很小,因此针对3种惯容减振系统位于不同地基表面下的最优设计参数拟合出经验公式,为升降作业平台的研发和减振设计奠定了理论基础。

浅议振动类课程教学中的动力减振器

动力减振器是振动类课程中重要的内容,理论严谨,工程应用广泛,但该部分内容在教与学两方面都相对比较困难。文章回顾并总结了邓哈托、铁摩辛柯直到最近的振动类经典教材关于动力减振器的描述。依据附加系统阻尼比本身的定义,使用变量代换,简化并给出了最佳阻尼比参数的获取过程,同时对减振器理论分析的全过程给出了教学上的几点建议,期望能促进动力减振器内容的教与学。

动力吸振器在直升机减振上的应用及效果验证

基于无阻尼动力吸振器设计原理和直升机实际指标需求设计了一种可变刚度和可调质量的动力吸振器,并利用有限元模型对吸振器进行了动特性分析和减振效率分析,最终通过飞行试验验证动力吸振器的实际装机效果。测试数据结果表明动力吸振器有较好的减振效果,为后续其它型号的动力吸振器研制积累了工程经验,提供了参考。

基于振幅放大机制的浮置板轨道低频轻质减振

为探讨在浮置板轨道低频振动控制中实现轻质减振和有效减振兼容的可行性,基于振幅放大机制,设计一种杠杆式动力吸振器(LT-DVA)。采用能量泛函变分法建立了配置有LT-DVA的钢弹簧浮置板轨道动力分析模型,以轨道结构的力传递率、位移导纳为评价指标,通过与普通动力吸振器(DVA)进行对比验证LT-DVA的有效性。在此基础上,利用多频控制的思路,在浮置板上引入多个杠杆式动力吸振器(LT-MDVA),以实现宽频控制、高衰减的效果。进一步考虑列车荷载的作用,分析验证动态轮轨力作用下LT-MDVA的低频隔振性能以及对轨道结构动力响应的影响。结果表明:由于振幅放大机制(振幅放大系数为α)的有益效果,LT-DVA的有效惯性质量、刚度、阻尼是同参数DVA的α^(2)倍,即工作能力是DVA的α^(2)倍;在LT-DVA的基础上,LT-MDVA能够有效拓宽振动衰减频段且提升振动衰减能力;相较于普通钢弹簧浮置板轨道,在动态轮轨力作用下,质量比仅为0.02的LT-MDVA不仅能够有效减小传递至下部基础的力(最大衰减约7.5dB),还能有效减小轨道结构的响应(钢轨和浮置板振动最大衰减约7.2dB和7.1dB),抑制浮置板轨道的振动放大现象,而同参数的MDVA几乎没有效果,证明了LT-MDVA能够在浮置板轨道低频振动控制中实现轻质减振和有效减振兼容。

可变重心线路巡检机器人摆振分析及抑制

针对野外输电线巡检机器人(power transmission line inspection robot,PTLIR)受自然风影响出现的机身摆动问题,提出一种在机器人的可变重心箱体中加装摆式动力吸振器(dynamic vibration absorber,DVA)的摆振抑制策略。描述了输电线系统与巡检机器人加装摆式动力吸振器的结构特点。基于Davenport风速谱与输电线系统的特点建立了风扰动模型。分析了机器人行走对输电线的影响,建立了简化后风扰动影响下机器人摆动的动力学模型,仿真了抑振前机器人在风扰动影响下的风振响应;基于拉格朗日方程建立了加装动力吸振器优化后的巡检机器人动力学模型,并完成了吸振器的参数设计。通过仿真不同风速下机器人的风振响应,验证所提出的振动抑制策略的有效性。基于改进结构下的巡检机器人样机,开展了室内风扰动试验。结果表明,所提出的吸振器抑振策略可在一定程度上抑制机器人的机身摆动,提高工作稳定性。该研究过程对其他摆式结构设备的振动抑制具有一定的参考价值。