惯容器对隔振系统动态性能影响研究

本文设计了一种滚珠丝杠惯容器及ISD隔振系统,通过实验研究了惯性轮的转动惯量对惯容值的影响;同时,分析了滚珠丝杠惯容器的机械动力学特性,推导了ISD隔振系统的振动传递率计算公式,探讨了惯容器对ISD隔振系统动态特性的影响。在电机被动、主动和混合隔振工况下,开展了弹簧阻尼系统和ISD隔振系统的振动性能对比实验,验证了惯容器对振动系统固有频率和减振效果的影响规律。研究结果表明,惯容器可降低振动系统的固有频率,使共振频率向低频移动,共振振幅降低;在共振频率附近,惯容器可抑制共振振幅,惯容值越高,抑制效果越明显;ISD隔振系统在低频的减振效果优于传统的弹簧阻尼系统;随着频率比的增加,ISD隔振系统的传递率趋于稳定值,惯容器会引起高频隔振性能降低。     

分子弹簧的隔振机理与力学性能研究

分子弹簧是一种由水和布满微孔的疏水沸石颗粒组成的隔振缓冲介质. 当振动、冲击发生时,随着外力对分子弹簧加载卸载,水分子进出沸石颗粒的疏水微孔,实现能量的存储、释放和消耗. 通过疏水微孔内液柱受力平衡和界面层热力学平衡分别建立了水侵入单条疏水微孔的模型,分段模拟了水分子侵入大量疏水微孔的过程,推导了分子弹簧受压过程中力-变形的关系,采用准静态试验对理论分析结果进行了验证,并计算了分子弹簧的隔振性能,结果表明:理论与试验结果具较好的一致性,分子弹簧在加载与卸载过程中呈现高-低-高的三段分段刚度,使得分子弹簧隔振系统在工作段具有极低固有频率,特别适合于低频重载情况下的隔振缓冲应用.      

气动八作动器隔振平台的主动隔振研究

多自由度隔振平台可以有效地隔离运载器传递到卫星的振动载荷。本文采用气动八作动器隔振平台实现卫星的六自由度隔振。首先应用牛顿欧拉法建立了气动八作动器隔振平台的动力学模型,设计了平台的主动控制律,然后对平台的主、被动隔振特性进行了仿真分析。仿真分析和实验结果显示主动隔振使平台各方向的低频隔振性能均得到改善。     

带非线性弹簧的两自由度准零刚度隔振系统力传递率特性

基于多自由度系统中的反共振特性,分别在传统线性隔振系统的上、下两层引入非线性倾斜弹簧负刚度机构,构成两自由度准零刚度隔振器。通过静态特性分析,推导出系统满足零刚度条件时,各参数之间的关系,分析了力学参数及结构参数对系统刚度特性的影响。建立两自由度准零刚度隔振系统的非线性动力学方程,利用平均法求解,推导出力传递率表达式,结合数值分析方法,探讨系统在不同的上、下层隔振器阻尼比、竖直刚度比及质量比情况下的力传递率特性,并与单自由度准零刚度隔振系统及线性斜弹簧两自由度准零刚度隔振系统进行对比研究。结果表明：当结构参数 （即：倾斜弹簧处于静平衡位置的长度与倾斜弹簧原长的比值）较小且倾斜弹簧为软化弹簧时,可在平衡位置附近获得较小的系统刚度及较大的低刚度区间;通过选择适当的上、下层隔振器阻尼比、竖直刚度比与质量比,可减小系统的起始隔振频率,增宽隔振频带,加快系统力传递率在特定频段内的衰减速率,改善系统的低频隔振性能。     

非线性被动隔振的若干进展

工程中航空航天、船舶与海洋结构物及其上装备和精密仪器易受极端环境干扰和破坏,使得非线性隔振理论在近十年来迅猛发展;针对日益严峻的隔振和抗冲击等要求,工程师和科学家们已发展出各种不同的非线性隔振系统,包括主动、半主动、被动和复合隔振.利用非线性改善的被动隔振兼具传统被动隔振的鲁棒性和主动隔振的高效性成为振动控制领域的先进技术.本文主要综述了非线性隔振理论和应用的近十年进展,包括非线性隔振设计、建模、分析、仿真和实验.在隔振系统的构建中,既考虑了刚度非线性又考虑了阻尼非线性;动力学响应的研究中,既有确定性分析又有随机分析.首先提出了适用于非线性隔振系统改进的评价方式;其次综述了高静态低动态刚度隔振及其加强形式非线性阻尼加强和双层非线性隔振,混沌反控制技术、内共振影响、非线性能量阱应用等振动机制利用型隔振和非线性隔振功能材料.最后,对非线性隔振研究发展的热点和关键性问题进行了分析和展望.     

磁致伸缩主被动隔振装置中的磁机耦合效应研究

磁致伸缩材料和柔顺位移放大机构组成的主动驱动装置具有精度高、驱动力大等特点.将其与被动隔振装置并联,形成主被动隔振装置,可以弥补纯被动隔振在低频和微幅扰动工况下的不足.本文针对这类磁致伸缩主被动隔振装置进行磁机耦合效应研究.基于Jiles-Atherton模型,分析了磁致伸缩材料所受应力对有效磁场、磁化强度、磁致伸缩系数和材料杨氏模量的影响,表征了材料磁机耦合效应.在此基础上,建立了主被动隔振装置的动力学模型,分析了主动驱动装置与被动隔振装置间的耦合作用.在耦合作用影响下,若被动隔振装置刚度不同,即使输入磁场相同,驱动器产生的驱动位移和驱动力也不相同.磁致伸缩材料的变刚度效应使隔振装置整体等效刚度不再为定值,从而影响被动隔振效果.本文提出了通过柔顺机构参数设计减小前述两种耦合影响的方法.数值仿真结果表明,磁致伸缩主被动隔振装置在低于、接近和高于谐振频率三类扰动下,都能达到比被动隔振更好的振动抑制效果.此外,仿真结果验证了考虑磁机耦合效应的数值模型具有更高精度.      

新型准零刚度隔振器设计及动力学研究

针对传统被动隔振器低频隔振性能不足的问题,提出了一种连杆-倾斜弹簧负刚度机构,并将其与线性弹簧并联构成一种新型准零刚度(quasi-zero stiffness, QZS)隔振器。首先,对该隔振器进行静力学分析,建立无量纲力-位移和无量纲刚度-位移关系式,并讨论设计参数对隔振器刚度的影响,进一步得出隔振器在平衡位置处具有零刚度特性的参数条件;其次,通过动力学研究,建立隔振器在位移激励下的非线性动力学方程,并应用谐波平衡法推导出位移传递率;最后,采用四阶龙格库塔法对准零刚度隔振器在不同激励频率下进行数值仿真,并与不含负刚度机构的线性隔振器进行对比分析。结果表明,准零刚度隔振器在低频激励下的隔振效果明显优于线性隔振器,而在高频激励下具备与线性隔振器相当的隔振性能。     

对称扭杆弹簧系统隔振性能研究2000-04-03收稿.

对扭杆弹簧隔振系统的研究表明,扭臂的质量对系统的性能有比较大的影响。虽然系统可获得长的共振周期,但由于扭臂的质量不为零,地基振动的加速度被直接耦合进系统,从而严重地降低了系统的隔振性能。     

INVESTIGATION OF MOLECULAR SPRING ON VIBRATION ISOLATION MECHANISM AND MECHANICAL PROPERTIES

分子弹簧是一种由水和布满微孔的疏水沸石颗粒组成的隔振缓冲介质. 当振动、冲击发生时,随着外力对分子弹簧加载卸载,水分子进出沸石颗粒的疏水微孔,实现能量的存储、释放和消耗. 通过疏水微孔内液柱受力平衡和界面层热力学平衡分别建立了水侵入单条疏水微孔的模型,分段模拟了水分子侵入大量疏水微孔的过程,推导了分子弹簧受压过程中力-变形的关系,采用准静态试验对理论分析结果进行了验证,并计算了分子弹簧的隔振性能,结果表明：理论与试验结果具较好的一致性,分子弹簧在加载与卸载过程中呈现高-低-高的三段分段刚度,使得分子弹簧隔振系统在工作段具有极低固有频率,特别适合于低频重载情况下的隔振缓冲应用.     

空气弹簧在大型洗衣机隔振设计中的应用

本文论述了空气弹簧在大型洗衣机脱水工况的隔振设计中的应用.文中详细论述了空气弹簧的力学特性及有关隔振理论,并用机械阻抗法推导了隔振效率,振动幅值及最佳阻尼等公式.最后给出了空气弹簧在国产 XT260大型洗衣机上的应用效果.     

Performance of ultra-low frequency passive vertical vibration isolation system with reverse pendulum

A novel long period passive vertical vibration isolator constructed by mounting reverse pendulums on two pairs of torsion springs is presented. By theoretical analysis and numerical calculation, it is shown that the isolator can achieve much longer resonant period due to gravitational positive feedback and is smaller in size than the current torsion spring isolators with the same geometric parameters. Project supported by the Post-doctoral Foundation of Huazhong University of Science and Technology.     

A quasi-zero-stiffness isolator with a shear-thinning viscous damper

Quasi-zero-stiffness(QZS) vibration isolators have been widely studied,because they show excellent high static and low dynamic stiffnesses and can effectively solve low-frequency and ultralow-frequency vibration. However, traditional QZS(T-QZS)vibration isolators usually adopt linear damping, owing to which achieving good isolation performance at both low and high frequencies is difficult. T-QZS isolators exhibit hardening stiffness characteristics, and their vibration isolation performance is e...     

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.

     

Dynamic analysis and performance evaluation of nonlinear inerter-based vibration isolators

This paper investigates a nonlinear inertance mechanism (NIM) for vibration mitigation and evaluates the performance of nonlinear vibration isolators employing such mechanism. The NIM comprises a pair of oblique inerters with one common hinged terminal and the other terminals fixed. The addition of the NIM to a linear spring-damper isolator and to nonlinear quasi-zero-stiffness (QZS) isolators is considered. The harmonic balance method is used to derive the steady-state frequency response relationship and force transmissibility of the isolators subjected to harmonic force excitations. Different performance indices associated with the dynamic displacement response and force transmissibility are employed to evaluate the performance of the resulting isolators. It is found that the frequency response curve of the inerter-based nonlinear isolation system with the NIM and a linear stiffness bends towards the low-frequency range, similar to the characteristics of the Duffing oscillator with softening stiffness. It is shown that the addition of NIM to a QZS isolator enhances vibration isolation performance by providing a wider frequency band of low amplitude response and force transmissibility. These findings provide a better understanding of the functionality of the NIM and assist in better designs of nonlinear passive vibration mitigation systems with inerters.     

基于混杂双稳定层合板的准零刚度隔振装置

准零刚度隔振装置(quasi-zero stiffness,QZS)在其平衡位置处的刚度接近于零,能够有效地隔离加速度幅值较低的微振动.因此,准零刚度隔振装置在卫星等航天器结构的微振动抑制领域有较好的应用前景.准零刚度隔振装置通常由正刚度部件及负刚度部件并联而成.在众多准零刚度隔振装置概念中,负刚度部件通常需要多个弹性部件及特定约束边界形成负刚度特性,导致准零刚度隔振装置的整体质量及体积相对较大.然而,航天器结构对隔振装置的质量特性及安装空间提出较高要求,因此需开发新型准零刚度隔振装置,降低隔振装置的质量及体积以满足航天器结构的使用要求.本文提出了一种基于混杂双稳定复合材料层合板的准零刚度隔振装置.通过利用混杂双稳定复合材料层合板自身的负刚度特性,降低了准零刚度隔振装置的结构复杂程度.本文对提出的准零刚度隔振装置的力学原理进行说明,对其隔振效果进行了仿真分析,并进行了隔振效果验证试验.隔振试验表明,准零刚度隔振装置的振动传递率曲线不再具有峰值,其实际振动传递率低于具有相同正刚度的线性隔振系统.基于试验及仿真分析结果,本文对隔振装置隔振性能的影响因素进行了分析讨论.分析结果显示,隔震装置中线性弹簧刚度与双稳定层合板负刚度之间的差异以及微小装配误差将导致隔振装置的隔振效果出现降低.      

Modeling,analysis, and simulation of X-shape quasi-zero-stiffness-roller vibration isolators

Existing quasi-zero stiffness (QZS) isolators are reviewed. In terms of their advantages, a novel X-shape QZS isolator combined with the cam-roller-spring mechanism (CRSM) is proposed. Different from the existing X-shape isolators, oblique springs are used to enhance the negative stiffness of the system. Meanwhile, the CRSM is used to eliminate the gravity of the loading mass, while the X-shape structure leaves its static position. The existing QZS isolators are demonstrated and classified according to their nonlinearity mechanisms and classical shapes. It is shown that the oblique spring can realize negative stiffness based on the simplest mechanism. The X-shape has a strong capacity of loading mass, while the CRSM can achieve a designed restoring force at any position. The proposed isolator combines all these advantages together. Based on the harmonic balance method (HBM) and the simulation, the displacement transmissibilities of the proposed isolator, the X-shape isolators just with oblique springs, and the X-shape isolators in the traditional form are studied. The results show that the proposed isolator has the lowest beginning isolation frequency and the smallest maximum displacement transmissibility. However, it still has some disadvantages similar to the existing QZS isolators. This means that its parameters should be designed carefully so as to avoid becoming a bistable system, in which there are two potential wells in the potential energy curve and thus the isolation performance will be worsened.

     

Passive and active vibration isolation under isolator-structure interaction: application to vertical excitations

This work studies the influence of a vibration isolator on the response of a flexible base structure. Two strategies are compared: passive and active vibration isolation (PVI, AVI). Although the multiple advantages of AVI over PVI techniques are well known, their effect in the base structure has not to date been compared. This interaction has an important role in the performance of the general control system, especially when the vibration isolation system is not the only system on the base structure or when there are multiple isolators working simultaneously on it. In addition, the structural serviceability of the base structure can also be affected. The analysis of the vibration isolation problem is made from a wide perspective, including the effect that isolator has on the base structure. Hence assuming the base structure is a non-rigid system. The effect of the isolation system on the base response is studied for an extensive range of base structures, thus showing different possible scenarios. The influence is quantified by comparing the peak magnitude response of the base when both passive and active vibration isolation techniques are used. The theoretical results have been corroborated by undertaking experimental tests on a full-scale laboratory structure.

     

A high-static–low-dynamic-stiffness vibration isolator with the auxiliary system

High-static–low-dynamic-stiffness (HSLDS) vibration isolators seek to widen the frequency range of isolation by decreasing the dynamic stiffness so as to reduce the natural frequency, while maintaining the same static displacement as equivalent linear isolators. However, in many cases especially under light damping or large excitations, the peak transmissibility is very large and the hardening nonlinearity causes the transmissibility curve to bend to the right seriously or in other words causes the jump phenomenon, resulting in a greatly reduced isolation region. In this paper, an auxiliary system is added to the HSLDS isolator to overcome these disadvantages, with the static displacement of the isolation object remaining unchanged. Coefficient-varying harmonic balance method is proposed in this paper to find the dynamic response and most importantly analyze the stability of the steady-state response. The isolation performance of the HSLDS-AS isolator, which is evaluated by displacement transmissibility, is compared with that of the equivalent HSLDS isolator. The effects of system parameters on the isolation performance are investigated. It is shown that the auxiliary system can lower the peak transmissibility and eliminate the jump phenomenon, resulting in a wide isolation region, and the HSLDS-AS isolator has strong designability with many parameters tunable.