Limb-inspired bionic quasi-zero stiffness vibration isolator

Acta Mechanica Sinica - Vibration reduction has always been one of hot and important topics in mechanical engineering, especially for the special measurement instrument. In this paper, a novel...     

Nonlinear vibration isolation via a compliant mechanism and wire ropes

Nonlinear Dynamics - Nonlinear vibration isolation systems with both stiffness and damping nonlinearities are promising for a broad-band and high-efficient isolation performance. In this research,...     

Nonlinear vibration isolation of a viscoelastic beam

In this paper, the transmissibility of a viscoelastic beam supported by vertical springs is defined by proposing a new vertical elastic support boundary. By contrasting with the viscoelastic beam with rigid vertical supports and the rigid rod with vertical elastic support ends, the necessity of the transmissibility of an elastic structure with vertical elastic supports is proved. In order to approximately solve the steady-state responses of the nonlinear transverse vibration of the viscoelastic beam under periodic excitation, the harmonic balance method in conjunction with the pseudo arc-length method is adopted. The numerical results are calculated to confirm the approximate analytic results. The comparison between the rigid rod and the elastic beam shows that neglecting the bending vibration of the structures will underestimate the frequency range in which the elastic support produces an effective vibration isolation. On the other hand, the comparison between the rigid support and the spring support demonstrates that ignoring the elasticity of the support ends will create a false understanding of the force transmission of elastic structures. In general, this paper presents the necessity of studying the force transmission of elastic structures with elastic supports. Moreover, this paper will become the beginning of the study of the vibration isolation of the elastic structure.     

Nonlinear dynamic response of an isolation system with superelastic hysteresis and negative stiffness

Nonlinear Dynamics - The negative stiffness exhibited by bi-stable mechanisms together with the tunable superelasticity offered by shape memory alloy (SMA) wires can enhance the dynamic resilience...     

An improved quasi-zero stiffness vibration isolation system utilizing dry friction damping

Nonlinear Dynamics - Quasi-zero stiffness (QZS) isolators, a nonlinear vibration isolation technique, enhance the isolation performance, by lowering the natural frequencies of an isolation system...     

Force transmissibility of a two-stage vibration isolation system with quasi-zero stiffness

Nonlinear Dynamics - A quasi-zero stiffness (QZS) vibration isolator outperforms other passive control strategies in vibration attenuation especially in a low-frequency band, but it also has an...     

Nonlinear vibration energy harvesting with adjustable stiffness,damping and inertia

A novel nonlinear structure with adjustable stiffness, damping and inertia is proposed and studied for vibration energy harvesting. The system consists of an adjustable-inertia system and X-shaped supporting structures. The novelty of the adjustable-inertia design is to enhance the mode coupling property between two orthogonal motion directions, i.e., the translational and rotational directions, which is very helpful for the improvement of the vibration energy harvesting performance. Weakly nonlinear stiffness and damping characteristics can be introduced by the X-shaped supporting structures. Combining the mode coupling effect above and the nonlinear stiffness and damping characteristics of the X-shaped structures, the vibration energy harvesting performance can be significantly enhanced, in both the low frequency range and broadband spectrum. The proposed 2-DOF nonlinear vibration energy harvesting structure can outperform the corresponding 2-DOF linear system and the existing nonlinear harvesting systems. The results in this study provide a novel and effective method for passive structure design of vibration energy harvesting systems to improve efficiency in the low frequency range.     

Active vibration control of a nonlinear magnetic levitation system via Nonlinear Saturation Controller (NSC)

In this paper, a nonlinear saturation controller (NSC) is proposed to reduce the horizontal vibration of a magnetically levitated body described by a nonlinear differential equation. An approximate solution is obtained applying the multiple scales perturbation technique to analyze the nonlinear behavior of this model. Based on the quadratic coupling, the energy transfer between the main system and the controller is achieved by designing the natural frequency of the NSC to be close to one half of the natural frequency of the main system. Time histories of the main system and the controller are included to show the response with and without control. Validation curves are included to show the closeness between the perturbation solution and the numerical one. A comparison with previously published work is included.     

Nonlinear dynamic behavior of a bio-inspired embedded X-shaped vibration isolation system

To improve the vibration isolation performance and bandwidth, loading capacity and supporting stability of passive vibration isolation system by utilizing nonlinearity, a bio-inspired embedded X-shaped vibration isolation (BIE-XVI) structure is proposed considering muscle/tendon contractile functions, joint rotational friction and connecting rod mass simultaneously. Furthermore, the dynamic model with pure linear elements and geometric relationship are established and the nonlinear variation properties are investigated. The effects of the key parameters of the BIE-XVI structure on frequency response characteristics and vibration isolation range are analyzed thoroughly by incremental harmonic balance method in various working conditions. From the parametric investigations, it can be found that the sensitivities of the nonlinear resonance properties are markedly different with respect to the different structure parameters. For longer rod length, larger assembly angle and higher stiffnesses, the hardening nonlinearity is weakened, but the resonance peak does not necessarily decrease. Besides, the softening nonlinearity and hardening nonlinearity can be interconverted with changing isolated mass and excitation amplitude. The BIE-XVI structure can widen the isolation frequency range and reduce the resonance peak to improve the vibration isolation properties by adjusting/designing the structural parameters, which could realize quasi-zero-stiffness property for vibration isolation.

     

一种准零刚度系统隔振性能的几何参数优化分析

提出了一种采用菱形连杆组件作为负刚度机构的准零刚度隔振器(下文简称菱形准零刚度隔振器).通过静力学分析方法,建立了菱形准零刚度隔振器数学模型,并与其他调节变量较少的隔振器模型进行了对比;以被测量曲线在隔振器平衡位置处的曲率作为评价参数,研究了负刚度机构几何参数对系统刚度、阻尼非线性的影响,推导了利用几何参数进行隔振优化...     

Correction to: An improved quasi-zero stiffness vibration isolation system utilizing dry friction damping

Nonlinear Dynamics - Equation 7 should appear as follows     

介电弹性作动器主动隔振模糊控制试验研究

采用模糊控制策略,开展介电弹性作动器的主动隔振性能试验研究。基于介电弹性材料的Maxwell应力模型建立了作动器的力电耦合模型,分析了作动器的非线性特性;针对隔振系统设计了Mamdani型模糊控制器,建立了控制电压信号与振动响应之间的关系;在此基础上,开展了介电弹性作动器主动隔振试验研究,并与加速度反馈控制进行了对比。试验结果表明,在相同驱动电压的情况下,基于模糊控制策略的主动隔振性能要优于加速度反馈控制,且能够显著降低由于非线性驱动力导致的倍频响应幅值,有助于提高隔振系统的稳定性。     

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.

     

Nonlinear vibration analysis of a generally restrained double-beam structure coupled via an elastic connector of cubic nonlinearity

Nonlinear Dynamics - Double-beam structures are frequently encountered in various engineering applications. Their vibration behavior is attracting more and more research attention. The majority of...     

基于Hilbert-Huang变换理论的结构振动主动变刚度频率控制

在主动变刚度(AVS)控制策略的基础上,提出一种新的结构振动控制主动变刚度频率控制算法。首先利用Hilbert-Huang变换理论将地震信号分解为有限数量的固有模态函数(IMF),再对这些IMF求解瞬时频率,进而获得信号的时频谱。由地震信号的瞬时频率与结构固有频率构造AVS控制切换准则,当两者频率接近时,AVS装置改变结构的刚度以抑制地震激励下的结构响应。选取两个建筑结构的Benchmark模型作为算例给出仿真分析,结果表明该方法能有效地控制受控结构的地震响应。