碟形弹簧负刚度在低频精密隔振中的应用研究

负刚度机构可用于系统的低频隔振,本文设计了一种新型的利用碟形弹簧负刚度的低频被动垂直隔振系统。碟形弹簧具有非线性变形特性,并且在一定条件下,碟形弹簧具有负刚度的特性。将碟形弹簧在负刚度区间与正刚度弹簧并联,通过合理选择参数,使得隔振系统的刚度在平衡点附近趋向于零,隔振系统的固有频率可以达到极低,从而使其隔振频带加宽,可实现低频隔振的目的。通过计算机仿真计算,证明并联机构具有良好的低频隔振效果。     

新型非线性超低频水平隔振系统的研制

通过对正负刚度并联隔振机理的分析，研制了新型正倒摆并联非线性超低频水平隔振系统。其正摆具有正刚度特性，倒摆具有负刚度特性。通过分析，得出了系统在平衡位置处的零刚度条件，系统水平刚度随两个摆长之比和下端弹簧刚度而变化的关系。试验研究表明：该隔振系统的固有频率由单一正摆时的1．75Hz降为0．5Hz，从而使其隔振频带加宽，隔振能力显著提高，而系统的结构保持较小尺寸。     

欧拉压杆在超低频垂直隔振系统中的应用研究

研制一种新型超低频垂直隔振系统。该隔振系统采用欧拉压杆作为负载弹簧，使隔振系统的被隔振质量与负载弹簧质量之比达到最大，显著地提高隔振系统产生内共振的频率；导出欧拉压杆力学特性及以欧拉压杆为弹性元件的隔振系统固有频率表达式；在平衡位置处采用负刚度弹簧与欧拉压杆弹簧并联，使隔振系统的刚度在平衡点趋向于零，可显著降低系统固有频率，隔振性能明显提高。     

正负刚度并联机构动力学分析及隔振仿真

正负刚度并联,可使系统的总刚度在平衡点附近趋近于零,从而有效降低系统的固有频率,实现超低频隔振。文中对一种正负刚度并联机构进行了分析,建立了其非线性动力学模型,采用谐波平衡法进行近似求解,并与数值方法求解进行比较,证明谐波平衡法对于该非线性系统的求解足够精确。文中还对该系统隔振效果进行了仿真,证明采用正负刚度并联的机构可以实现超低频的微幅精密隔振。     

基于负刚度原理隔振机构的建模与仿真

振动控制是关系到设备安全的重要问题,随着科技的发展,隔振显得越来越重要.有效的减小振动带来的危害,是振动控制研究的重要课题.通过正负刚度并联的原理,可使得系统的总刚度在平衡点附近趋近于零,从而可以有效降低系统的固有频率,实现低频隔振.本文建立了正负刚度并联结构的模型,并对其行了仿真,证明采用设计的模型可以有效实现低频的微幅隔振.     

负刚度结构的座椅悬架优化及隔振分析

为进一步提升车辆座椅悬架的隔振性能,利用连杆弹簧负刚度结构与正刚度弹性元件并联的方式,设计了 一种具有准零刚度的座椅悬架系统.基于多 目标参数协调优化原理,进行了结构参数优化,获得了使座椅悬架刚度动刚度趋于准零刚度的最佳值.通过对座椅悬架隔振系统的动力学响应分析,以及仿真实验,验证了座椅悬架隔振系统优化的有效性.研究结果表明,采用连杆弹簧负刚度结构的座椅悬架系统能有效提升座椅的隔振效果,并可降低系统本身的固有频率,实现低频和超低频隔振.     

气动准零非线性隔振器的刚度特性与参数调控

针对大载荷、低动态频率的机械装备的隔振需求，提出了气动准零刚度非线性隔振技术方案，利用气体负压为静载、波纹管结构提供动刚度，实现了隔振装置的高静态低动态刚度特性。阐述了光滑型气动准零隔振器的结构及工作原理，根据气体状态方程推导了隔振装置的非线性刚度理论模型。为了得到符合设计要求的刚度特性，分别研究了气体占比与初始压强等参数对隔振装置刚度特性的调控规律，发现了合理的气/液比例，既可以实现较低的动态刚度，同时起到大幅振动下位移限位的效果。探讨了过载加速度对隔振系统固有特性的影响，研究发现，过载的存在使得隔振静平衡位置偏离设计的平衡点，因此其线化系统固有频率会发生较明显的变化，这是工程设计根据实际情况需要考量的一点。     

用于原子干涉重力仪的隔振平台模型辨识及验证

负刚度隔振平台广泛应用于原子干涉重力仪等量子精密测量设备,其低频性能和环境自适应能力对设备性能影响较 大,为此本文对典型商用负刚度隔振平台进行了半主动改造,以进一步增强隔振平台综合性能。 首先从理论上对力-位移关系 做了简要分析,着重探讨了负刚度特性和承载能力的决定因素;然后建立并分析了系统运动模型,分别在时域和频域对模型参 数做了精准辨识,根据测试结果对半主动隔振做了仿真分析,并采用贝叶斯优化算法快速找到最优控制参数;最后在真实系统 上进一步验证了该方案,结果表明半主动隔振可将系统的低频共振峰衰减 357 倍,系统在低于 0. 3 Hz 和高于 8 Hz 的频段能起 到良好的隔振效果,超低频隔振性能有显著提升,文中所提方案可广泛应用于量子精密测量相关隔振设备。     

多自由度系统模型在光电吊舱隔振系统设计的应用

为减小振动对光电吊舱成像质量的影响,依据多自由度系统模型理论、隔振理论和实际振动环境设计了小型光电吊舱被动隔振系统,该隔振系统能够合理的配置光电吊舱隔振系统的各阶频率。基于多自由度系统模型理论对隔振系统的各阶固有频率进行配置,指导隔振器的空间布局及相对位置、隔振器的三向刚度及阻尼值和隔震系统支架结构的设计。通过Adams/Vibration模块进行仿真分析,利用振动台对光电吊舱隔振系统进行验证试验,结果显示理论计算、仿真分析和振动试验获得的隔振系统各阶固有频率接近,最大误差不超过10%,且在激振力频率92.5 Hz附近隔振效果明显。外场试飞试验也验证了小型光电吊舱隔振系统的隔振性能。     

康复机器人准零刚度隔振特性分析与实验

为了解决康复机器人低频振动对人体的影响问题,提出并设计一种具有准零刚度特性的新型被动隔振机构,它由两个对称的具有负刚度特性的拉伸弹簧并联一个线性正刚度弹簧实现。首先,通过静力学特性,建立此隔振机构的力-位移和刚度-位移关系式,得出机构在静态平衡位置处具有准零刚度特性的参数条件;其次,通过动力学特性,建立其分别在简谐力和简谐位移激励下的非线性微分动力学方程,采用谐波平衡法分析机构参数与激励对系统力传递率、位移传递率的影响;最后,通过实验验证在有、无负刚度情况下,输入与输出的曲线。结果表明,在有负刚度机构的情况下,隔振系统具有一定范围的准零刚度特性,且低频隔振性能较好,达到了高静态、低动态刚度的效果。本研究对机器人低频隔振具有创新性和指导意义。     

A negative stiffness vibration isolator using magnetic spring combined with rubber membrane

The most important characteristic of a passive vibration isolator is its natural frequency and load capacity. The vibration isolation performance of a passive vibration isolator in low input frequencies is considerably improved by reducing its natural frequency. This paper presents a negative stiffness magnetic suspension vibration isolator (NSMSVI) using a magnetic spring combined with rubber membranes to obtain lower natural frequency. To study the vibration isolation performance of the NSMSVI, the stretching force of the rubber membrane is measured through experiments. The stiffness of the rubber membrane comes from the derivative of the stretching force. A parametric study of load capacity, axial magnetic stiffness, and natural frequency of the magnetic spring is also performed. Consequently, as a case study, the size dimensions of the magnetic spring are determined. An NSMSVI table is set up for experimental validation, after which the transmissibility curves of the NSMSVI are calculated and tested. Experimental results show that the lowest natural frequency of the NSMSVI reaches 1.5 Hz with a maximum attenuation of -40 dB between 0 Hz and 100 Hz, whereas the NSMSVI has the maximum load capacity at the lowest stiffness. This paper essentially provides an efficient method to construct a negative stiffness vibration isolator for practical applications.     

Parameter identification of analytical and experimental rubber isolators represented by Maxwell models

A parameter identification method based on constraint optimization is developed for a single mass elastomeric isolation system where the isolator is represented by a Maxwell model with two or more Maxwell elements. The method utilizes measured static stiffness and frequency response of the isolator in a single mass configuration with constraints on the natural frequency and damping ratio. It is revealed through analytical examples that Maxwell models consisting of only one or two Maxwell elements can accurately replicate the dynamic behavior of Maxwell systems having two or more Maxwell elements. To experimentally evaluate the method, three different rubber isolators are considered. For all three rubber isolators, it is shown that Voigt models are incapable of accurately representing the measured static stiffness and frequency response. Although identified Maxwell models having only one Maxwell element can match the measured natural frequency, damping ratio and static stiffness, they cannot match the measured frequency response curves well. However, identified Maxwell models with two Maxwell elements can accurately represent the measured static and dynamic characteristics of the real elastomeric isolation systems.     

准零刚度扭转隔振器振动传递特性研究

针对一种应用连杆弹簧负刚度结构所设计的正负刚度并联扭转隔振器,通过分析其设计参数,得到了其在静平衡位置达到准零刚度的条件。针对所述系统,建立二自由度非线性动力学微分方程,应用谐波平衡法求解了准零刚度隔振器的振动响应。考虑激励幅值、系统阻尼和转动惯量等因素,从扭转振动力矩传递和扭转振动功率流传递两个角度分析了准零刚度隔振系统的非线性振动传递特性。结果表明,此隔振系统具有良好的低频隔振效果,且表现为振动传递的硬特性;从功率流角度的分析还表明,系统的瞬时传递功率流峰值与输入功率流和耗散功率流的变化趋势保持一致。在低于共振区域的低频区间内,隔振系统前后两端的转动惯量对系统振动具有较大影响。最后,对扭转隔振器的振动隔离特性进行了试验验证,试验结果表明,隔振器具有良好的低频振动隔离特性。     

磁流变弹性体变刚度隔振系统的设计与仿真分析

磁流变弹性体兼有磁流变液和弹性体的优点,其剪切模量可由外加磁场控制,在振动控制等方面具有广阔的应用前景。现有的隔振系统中隔振器刚度一般都是固定值,这使系统的隔振效果有局限性,对较低频率振动,尤其是共振时的隔离效果很差。提出了将可调刚度的磁流变弹性体隔振器用于隔振系统中．通过改变隔振器的线圈电流大小来控制磁流变弹性体的剪切模量,进而调整隔振系统的刚度,使系统获得更宽的隔振频率范围。设计了隔振器的结构,基于SimuLink软件对系统的隔振效果进行仿真分析．表明了设计的有效性．     

Performance limit of a passive vertical isolator using a negative stiffness mechanism

A passive vibration isolator using a negative stiffness mechanism (NSM) is being considered for small precision instruments since it does not need any outer power supply and pressurized air, and its fundamental frequency can be lowered down to 0.5 Hz. Although the working principle of the NSM and its patents are well known, neither the isolation performance limit related to the lowest fundamental frequency nor its nonlinear behavior have been studied. This paper discusses the performance limit of the passive vertical isolator using the NSM and presents the design guidelines for the isolator based on that performance limit. First, a nonlinear dynamic model of the passive isolator is derived through solid approximations, and the fundamental frequency or performance limit is obtained using nonlinear analysis, which entirely explains the nonlinear behavior of the isolator. In addition, the approximate design equations of the isolator are derived to analyze its performance limit. Finally, an approximate expression of the lowest fundamental frequency of the isolator is derived using nonlinear analysis and design equations, which provide substantial design guidelines to improve isolator performance. This paper was recommended for publication in revised form by Associate Editor Seong-Wook Hong Dr. Ahn received B. S., M. S. and Ph. D. degrees from Seoul national university in 1995, 1997 and 2001, respectively. Dr. Ahn was a research associate of University of Virginia, USA and worked as a BK21 assistant professor at Seoul national university. Dr. Ahn is currently an assistant professor at department of mechanical engineering at Soongsil University. He is currently serving as an editor of the International Journal of Rotating Machinery. Dr. Ahn’s research interests are in the area of rotordynamics, control and mechatronics.