Multi-layer quasi-zero-stiffness meta-structure for high-efficiency vibration isolation at low frequency

An easily stackable multi-layer quasi-zero-stiffness(ML-QZS)meta-structure is proposed to achieve highly efficient vibration isolation performance at low frequency.First,the distributed shape optimization method is used to design the unit cel,i.e.,the single-layer QZS(SL-QZS)meta-structure.Second,the stiffness feature of the unit cell is investigated and verified through static experiments.Third,the unit cells are stacked one by one along the direction of vibration isolation,and thus the ML-QZS meta-structure is constructed.Fourth,the dynamic modeling of the ML-QZS vibration isolation metastructure is conducted,and the dynamic responses are obtained from the equations of motion,and verified by finite element(FE)simulations.Finally,a prototype of the ML-QZS vibration isolation meta-structure is fabricated by additive manufacturing,and the vibration isolation performance is evaluated experimentally.The results show that the vibration isolation performance substantially enhances when the number of unit cells increases.More importantly,the ML-QZS meta-structure can be easily extended in the direction of vibration isolation when the unit cells are properly stacked.Hence,the ML-FQZS vibration isolation meta-structure should be a fascinating solution for highly efficient vibration isolation performance at low frequency.

A human-sensitive frequency band vibration isolator for heavy-duty truck seats

In this study,a human-sensitive frequency band vibration isolator(HFBVI)with quasi-zero stiffness(QZS)characteristics for heavy-duty truck seats is designed to improve the comfort of heavy-duty truck drivers on uneven roads.First,the analytical expressions for the force and displacement of the HFBVI are derived with the Lagrange equation and d'Alembert's principle,and are validated through the prototype restoring force testing.Second,the harmonic balance method(HBM)is used to obtain the dynamic responses under harmonic excitation,and further the influence of pre-stretching on the dynamic characteristics and transmissibility is discussed.Finally,the experimental prototype of the HFBVI is fabricated,and vibration experiments are conducted under harmonic excitation to verify the vibration isolation performance(VIP)of the proposed vibration isolator.The experimental results indicate that the HFBVI can effectively suppress the frequency band(4-8 Hz)to which the human body is sensitive to vertical vibration.In addition,under real random road spectrum excitation,the HFBVI can achieve low-frequency vibration isolation close to 2 Hz,providing new prospects for ensuring the health of heavy-duty truck drivers.

A vibration isolator with a controllable quasi-zero stiffness region based on nonlinear force design

To achieve stability optimization in low-frequency vibration control for precision instruments,this paper presents a quasi-zero stiffness(QZS)vibration isolator with adjustable nonlinear stiffness.Additionally,the stress-magnetism coupling model is established through meticulous theoretical derivation.The controllable QZS interval is constructed via parameter design and magnetic control,effectively segregating the high static stiffness bearing section from the QZS vibration isolation section.Furthermore,a displacement control scheme utilizing a magnetic force is proposed to regulate entry into the QZS working range for the vibration isolation platform.Experimental results demonstrate that the operation within this QZS region reduces the peak-to-peak acceleration signal by approximately 66.7%compared with the operation outside this region,thereby significantly improving the low frequency performance of the QZS vibration isolator.

Active Low-frequency Vertical Vibration Isolation System for Precision Measurements

Low-fi＇equency vertical vibration isolation systems play important roles in precision measurements to reduce seismic and environmental vibration noise. Several types of active vibration isolation systems have been developed. However, few researches focus on how to optimize the test mass install position in order to improve the vibration transmissibility. An active low-frequency vertical vibration isolation system based on an earlier instrument, the Super Spring, is designed and implemented. The system, which is simple and compact, consists of two stages： a parallelogram-shaped linkage to ensure vertical motion, and a simple spring-mass system. The theoretical analysis of the vibration isolation system is presented, including terms erroneously ignored before. By carefully choosing the mechanical parameters according to the above analysis and using feedback control, the resonance frequency of the system is reduced from 2.3 to 0.03 Hz, a reduction by a factor of more than 75. The vibration isolation system is installed as an inertial reference in an absolute gravimeter, where it improved the scatter of the absolute gravity values by a factor of 5. The experimental results verifies the improved performance of the isolation system, making it particularly suitable for precision experiments. The improved vertical vibration isolation system can be used as a prototype for designing high-performance active vertical isolation systems. An improved theoretical model of this active vibration isolation system with beam-pivot configuration is proposed, providing fundamental guidelines for vibration isolator design and assembling.

Cascaded quasi-zero stiffness nonlinear low-frequency vibration isolator inspired by human spine

Human motion induced vibration has very low frequency,ranging from 2 Hz to 5 Hz.Traditional vibration isolators are not effective in low-frequency regions due to the trade-off between the low natural frequency and the high load capacity.In this paper,inspired by the human spine,we propose a novel bionic human spine inspired quasi-zero stiffness(QZS)vibration isolator which consists of a cascaded multi-stage negative stiffness structure.The force and stiffness characteristics are investigated first,the dynamic model is established by Newton’s second law,and the isolation performance is analyzed by the harmonic balance method(HBM).Numerical results show that the bionic isolator can obtain better low-frequency isolation performance by increasing the number of negative structure stages,and reducing the damping values and external force values can obtain better low-frequency isolation performance.In comparison with the linear structure and existing traditional QZS isolator,the bionic spine isolator has better vibration isolation performance in low-frequency regions.It paves the way for the design of bionic ultra-low-frequency isolators and shows potential in many engineering applications.

Negative Poisson’s ratio locally resonant seismic metamaterials vibration isolation barrier

In recent decades,the application of seismic metamaterials to protect civil infrastructures being free of the damage of earthquakes has been attracting extensive attention.Specifically,the proposed locally resonant seismic metamaterials provide the probability of isolating the low-frequency seismic wave using a small-size isolation barrier.However,in previous studies,the energy absorption properties of locally resonant seismic metamaterials remain one of the least understood aspects of isolation.Benefit from the fascinating energy absorption characteristic of negative Poisson ratio(NPR)metamaterial,we creatively design a new seismic metamaterial structure by assembling the locally resonant seismic metamaterial and NPR metamaterial,to isolate seismic waves.The sound cone technique combining the transmission spectrum is employed to identify the surface wave from the hybrid waves.The generation mechanism of frequency bandgap and the isolation effectiveness of the proposed seismic metamaterial are discussed in detail.The results indicate that the generation of ultra-low and ultra-wide frequency bandgap with the range of 0.65 Hz–18.9 Hz is attributed to the locally resonant and energy absorption of the proposed seismic metamaterial structure and the excellent isolation effect is achieved by transforming the surface wave into the bulk wave.The frequency bandgap narrows as the distance increases between each resonator.In addition,the mechanical properties of the NPR bearing,such as the Poisson ratio,mass density,and elastic modulus,have remarkable impact on the frequency bandgap,especially on the upper bound frequency.In practical engineering,the NPR bearing with a low Poisson ratio,small mass density,and high elastic modulus is suggested for the design of the NPR locally resonant seismic metamaterial structures.Time domain analysis for the practical seismic wave verifies that the proposed seismic metamaterial has a promising application in isolating ultra-low and ultra-wide seismic waves,with the isolation effectiveness larger than 70%.This work contributes a new locally resonance seismic metamaterial design idea for isolating and adjusting the low-frequency seismic wave.

Design and Analysis of a Horizontal Quasi-Zero Stiffness Vibration Isolator by Combining Rolling-Ball and Disk Springs in Parallel

Combining disk springs having negative stiffness with a rolling-ball in parallel is proposed in this paper. It is used to reduce the system stiffness and the positioning error in a non-ideal environment.The characteristics of a disk spring are analyzed. The dynamic equation of its motion has been obtained based on Newton＇s second law. After definition of a error margin,the dynamic equation of the motion can be treated as a Duffing oscillator,and the influences of non-dimensional parameters on the stiffness and transmissibility are studied. The natural frequency and transmissibility are achieved in a linearization range,where the ratio of linear to nonlinear items is small enough.The influence of mass ratio and non-dimensional parameters on natural frequency are analyzed. Finally,a comparison of numerical example demonstrates that the QZS system can realize a lower stiffness within an increased range.

Dynamic design of a nonlinear energy sink with NiTiNOL-steel wire ropes based on nonlinear output frequency response functions

A novel vibration isolation device called the nonlinear energy sink(NES)with NiTiNOL-steel wire ropes(NiTi-ST)is applied to a whole-spacecraft system.The NiTi-ST is used to describe the damping of the NES,which is coupled with the modified Bouc-Wen model of hysteresis.The NES with NiTi-ST vibration reduction principle uses the irreversibility of targeted energy transfer(TET)to concentrate the energy locally on the nonlinear oscillator,and then dissipates it through damping in the NES with NiTi-ST.The generalized vibration transmissibility,obtained by the root mean square treatment of the harmonic response of the nonlinear output frequency response functions(NOFRFs),is first used as the evaluation index to analyze the whole-spacecraft system in the future.An optimization analysis of the impact of system responses is performed using different parameters of NES with NiTi-ST based on the transmissibility of NOFRFs.Finally,the effects of vibration suppression by varying the parameters of NiTi-ST are analyzed from the perspective of energy absorption.The results indicate that NES with NiTi-ST can reduce excessive vibration of the whole-spacecraft system,without changing its natural frequency.Moreover,the NES with NiTi-ST can be directly used in practical engineering applications.

An adjustable anti-resonance frequency controller for a dual-stage actuation semi-active vibration isolation system

In the semiconductor manufacturing industry,the dynamic model of a controlled object is usually obtained from a frequency sweeping method before motion control.However,the existing isolators cannot properly isolate the disturbance of the inertial force on the platform base during frequency sweeping(the frequency is between 0 Hz and the natural frequency).In this paper,an adjustable anti-resonance frequency controller for a dual-stage actuation semi-active vibration isolation system(DSASAVIS)is proposed.This system has a significant anti-resonance characteristic;that is,the vibration amplitude can drop to nearly zero at a particular frequency,which is called the anti-resonance frequency.The proposed controller is designed to add an adjustable anti-resonance frequency to fully use this unique anti-resonance characteristic.Experimental results show that the closed-loop transmissibility is less than−15 dB from 0 Hz to the initial anti-resonance frequency.Furthermore,it is less than−30 dB around an added anti-resonance frequency which can be adjusted from 0 Hz to the initial anti-resonance frequency by changing the parameters of the proposed controller.With the proposed controller,the disturbance amplitude of the payload decays from 4 to 0.5 mm/s with a reduction of 87.5%for the impulse disturbance applied to the platform base.Simultaneously,the system can adjust the anti-resonance frequency point in real time by tracking the frequency sweeping disturbances,and a good vibration isolation performance is achieved.This indicates that the DSA-SAVIS and the proposed controller can be applied in the guarantee of an ultra-low vibration environment,especially at frequency sweeping in the semiconductor manufacturing industry.

低频大幅隔振器设计及实验

为了突破传统隔振器刚度和承载能力之间的矛盾,需要隔振器具有高的静态刚度,低动态刚度的特性.如今的准零刚度隔振器技术可以实现低频微幅隔振,但是对于大幅振动,隔振效果并不明显甚至失效,因此突破宽幅隔振成为隔振领域亟待解决的问题.为此,我们利用多稳态折纸通过并联装配的方式,构造具有宽幅零刚度区间的折纸型隔振器,以解决传统隔振器振动抑制幅值较低的问题.本文建立了宽零刚度隔振器模型,提出宽幅零刚度的设计方法,并通过动力学分析分析了模型的隔振效果.最后搭建试验样机,验证了理论的正确性.这种设计打破了传统准零刚度隔振器单点准零的设计准则,能够在一个大幅范围内保证稳定性,同时实现零刚度,极大拓宽了隔振器的适用范围.这种设计理念能够被用在新隔振材料设计和航空、船舶等大幅低频动态环境中.

基于准零刚度支撑结构的低频主动隔振平台研究

针对量子科学试验、精密制造等先进应用对亚赫兹微振动的抑制需求,研究基于准零刚度支撑结构和分离式音圈作动器的低频主动隔振技术。首先,给出一种低频主动隔振平台设计方法,考虑准零刚度结构的等效动力学特性,采用牛顿-欧拉方法建立平台的动力学模型;然后,基于所建立动力学模型分析多自由度耦合下平台的扰动传递特性并设计主动隔振算法;最后,研制低频主动隔振平台进行试验验证。试验结果表明,所开发主动隔振平台能够在三个线自由度上实现优于98.3%的微振动抑制效果,在0.1~10.0 Hz内载荷z方向微振动小于1.3×10^(-8) g。

二级柔性减振系统设计及力学性能分析

为解决二级减振引起个别仪器振动的局部放大、使得力学环境不能满足运行要求的问题,首先,针对金属橡胶双层减振系统,充分考虑安装板的柔性刚度,建立了刚柔复合的二级减振系统模型;其次,基于目标频率对二级减振的频率响应函数进行系统的刚度解耦,实现了减振器刚度的求解,并应用有限元进行随机振动分析,验证了刚柔复合二级减振系统理论模型的可行性;最后,利用振动台进行了试验验证。结果表明,当二级减振系统满足工程刚度需求,其一阶固有频率低于40 Hz时,减振效率可达到70%以上,试验与仿真结果基本一致。

新型准零刚度空气悬架系统的设计与分析

为提高商用汽车在低频外部激励环境下的隔振性能以及行驶平顺性,基于准零刚度理论,采用正负刚度并联的方式,将负刚度碟形弹簧组与正刚度空气弹簧相结合,设计一种新型准零刚度悬架系统。通过静力学特性分析,建立力位移和刚度位移表达式,得到系统达到准零刚度的参数条件;通过动力学特性分析,建立系统的二自由度模型和简谐力作用下的非线性运动微分方程,得到力传递率特性曲线并对其进行分析。结果表明新结构的低频隔振性能显著提升。基于刚度位移表达式建立2自由度1/4悬架模型,分别对准零刚度系统与传统系统的垂向加速度、悬架动行程和轮胎动载荷等平顺性指标的差异性进行分析,仿真结果表明,该准零刚度系统的平顺性改善效果亦优于传统结构。

Dynamics Analysis of Active Variable Stiffness Vibration Isolator for Whole-Spacecraft Systems Based on Nonlinear Output Frequency Response Functions

In order to improve the harsh dynamic environment experienced by heavy rockets during different external excitations,this study presents a novel active variable stiffness vibration isolator(AVS-VI)used as the vibration isolation device to reduce excessive vibration of the whole-spacecraft isolation system.The AVS-VI is composed of horizontal stiffness spring,positive stiffness spring,parallelogram linkage mechanism,piezoelectric actuator,acceleration sensor,viscoelastic damping,and PID active controller.Based on the AVS-VI,the generalized vibration transmissibility determined by the nonlinear output frequency response functions and the energy absorption rate is applied to analyze the isolation performance of the whole-spacecraft system with AVS-VI.The AVS-VI can conduct adaptive vibration suppression with variable stiffness to the whole-spacecraft system,and the analysis results indicate that the AVS-VI is efTective in reducing the extravagant vibration of the whole-spacecraft system,where the vibration isolation is decreased up to above 65%under different acceleration excitations.Finally,different parameters of AVS-VI are considered to optimize the whole-spacecraft system based on the generalized vibration transmissibility and the energy absorption rate.

仿生隔振器设计方法研究进展

基于仿生学的思想,通过模仿生物系统的结构几何构成特性,创新优化隔振模型是当今隔振领域的热门问题.本文基于仿生灵感来源的不同,对现有的仿生隔振器进行了系统的分类,并对不同设计原理的仿生隔振器恢复力本构与隔振性能做了详细的阐述和对比,旨在通过隔振器隔振频带的横向对比厘清几何构型与可调参数的影响,以此厘清隔振器几何设计和隔振性能的关系.并且,本文展望了未来仿生隔振器的发展前景和研究方向.

基于橡胶本构模型管路隔振器性能仿真研究

采用管路隔振器是降低船舶管路系统振动噪声传递的有效手段,但舰船管路比较复杂需要根据管路规格设计系列化隔振器。如何有效地预报不同规格管路隔振器在实际使用过程中的性能是管路隔振器系列化设计亟待解决的问题。为此本文通过橡胶拉伸试验拟合橡胶超弹性本构参数,利用有限元方法对多款隔振器性能(静变形和固有频率)进行仿真计算,并由试验对计算结果进行验证。结果表明,设计的隔振器数值仿真与试验结果误差率均低于10%,证明该参数能有效预报多规格隔振器性能。本文结果可为舰船管路隔振器系列化设计提供指导。

基于凸轮-滚子结构的多自由度准零刚度系统设计

基于凸轮-滚子结构设计一种多自由度非线性准零刚度低频隔振装置。通过静力学特性计算,结合横向刚度计算理论,得到系统在多个自由度上实现准零刚度的参数条件。利用谐波平衡法分析了系统动力学特性,得出系统力传递率,并分析了预压、阻尼比及激励力对系统振动传递率的影响。为验证准零刚度系统隔振性能,搭建隔振测试系统,试验结果表明,相较于传统线性隔振系统,多自由度隔振系统在竖直方向上起始隔振频率从6.7 Hz降低至3.5 Hz,隔振效率最大提升约84.3%;水平方向上起始隔振频率从6.0 Hz降低至4.0 Hz,隔振效率最大提升约45.0%;在10.0 Hz以下,多自由度隔振系统的振动传递率远小于线性隔振系统。

真空装置车载环境隔振技术研究

针对车载环境设备隔振技术难以量化的技术难题,提出了一套车载设备隔振的设计、计算方法。该方法首先依据车载设备的特点提出隔振要求;其次结合二阶线性非其次方程求解相应频率,初步设计车载设备的隔振平台;再次确定车载设备必需满足的应力条件;最后利用有限元的方式计算车载设备的位移、加速度以及稳态应力水平。本文以车载真空装置为例,按照上述理论设计隔振平台,并通过有限元的方式验证可行性;最终表明设计的隔振平台满足振动特性方面的需求;该方法可适用于车载设备的隔振平台研制。

堆叠三浦折纸隔振器理论模型及低频隔振特性

低频振动衰减速度慢难以控制,严重影响高端装备的精度、稳定性和可靠性.线性隔振器因承载能力和隔振频带之间的固有矛盾无法有效隔离低频振动.因此,可通过引入非线性获得等效负刚度和非线性刚度构建准零刚度隔振器,以实现低频隔振.折纸结构具有双稳态、负泊松比和负刚度等独特的力学特性,近年来得到了广泛关注.受堆叠三浦折纸(stacked Miura-ori,SMO)启发,提出了一种新型SMO隔振器,由SMO结构和线性弹簧并联构成.基于能量法推导了SMO结构的势能方程,获得了竖直方向的力-位移关系,揭示了SMO结构大行程负刚度机理.研究了无应力条件下不同初始角和折痕刚度比对SMO隔振器的恢复力的影响规律,阐明了SMO隔振器非线性刚度调节机制.建立了SMO隔振器的理论模型,基于谐波平衡法推导了位移传递率.通过数值仿真研究了不同负载下的低频隔振性能.最后研制了SMO隔振器的原理样机,试验验证了SMO隔振器的恢复力和低频隔振性能.结果表明,折纸隔振器峰值频率可低至1.52 Hz,最小峰值传递率为1.29.本研究为低频折纸隔振结构的设计提供了一种新思路.

周期桁架结构设计及振动特性分析

为解决船舶动力系统低频振动噪声问题,本文基于声子晶体局域共振理论,设计了一种带周期振子桁架式浮筏结构。利用有限元法和Bloch理论,分析了周期振子桁架产生带隙的原因,讨论了振子质量、安装形式和桁架结构参数对带隙特性的影响规律,设计了周期振子桁架振动特性试验,探究了桁架结构振动传递特性。结果表明:振子质量越大,带隙宽度增加,胞元尺寸越大,带隙带宽减小;振子排列方式对带隙特性影响较小,增加振子数量,宽带特性显著;采用振子间隔安装方式,相较全安装方式,带隙特性变化较小,可有效减少振子数量。