Vibration Isolation Effect Research Articles

Wide quasi-zero stiffness region isolator with decoupled high static and low dynamic stiffness

Quasi-zero stiffness (QZS) isolators can achieve the two goals of relatively high static and low dynamic stiffness (HSLDS). However, the static and dynamic stiffness of most QZS isolators remains coupled, causing conflicts in optimizing these dual objectives, especially in the case of large displacement excitations and heavy loads, leading to limited performance. To overcome these limitations, this paper presents an isolator with an extended QZS region that allows for the independent design of HSLDS. The positive stiffness provided by the cantilever beam with curve fixture (CBCF) precisely counteracts the negative stiffness offered by a pair of inclined springs, thereby achieving continuous and extensive QZS characteristics from a point to a region. Dynamic equations are established based on the Lagrangian principle and swiftly solved utilizing the Runge-Kutta-4 method. The proposed isolator exhibits a low resonance frequency, and superior performance when exposed to large displacement excitations compared to alternative isolators. Both static and dynamic experiments confirm a QZS region of 0.023 m and resonance frequencies of below 1 Hz. The proposed isolator facilitates effective vibration isolation for ultra-low-frequency and large displacement excitations.

A novel vibration barrier for low-frequency surface waves in the ground

As for certain engineering scenarios, such as open-air quarries and underground pipeline areas, vibration barriers are in urgent need. However, their design and construction face various challenges, especially for attenuating surface waves with low frequencies. Inspired by the topography of hills and periodic phononic crystal structures, a novel vibration barrier consisting of periodic soil strips is proposed. Firstly, utilizing the finite element method and the theory of periodic structures, the dispersion band diagram is calculated for the periodic soil strips. The corresponding band gap mechanisms are discussed by the displacement field of modes in the lower boundary of band gaps. Besides, a simplified model and a theoretical expression are proposed to analyze the minimum frequency of the band gaps. Through frequency domain analysis, the influence of the damping of soil strips on isolation effects is examined, and the dissipated energy is also quantified using a spatial Fast Fourier Transform. Finally, a comparison of the isolation effect between soil strip barriers and typical trench barriers is conducted. The results show that periodic soil strips can exhibit several band gaps, within which surface waves (SWs) can be effectively isolated. Soil strip barriers exhibit similar or even better vibration isolation effects compared to trench barriers, especially for isolating low-frequency vibrations. This study enhances our understanding of surface wave mitigation using periodic barriers and provides fresh insights for designing seismic metamaterials.

Mechanical characteristics analysis of high dimensional vibration isolation systems based on high-static-low-dynamic stiffness technology

Large floating raft vibration isolation systems (FRVISs) based on high-static-low-dynamic stiffness (HSLDS) technology offer excellent low frequency vibration isolation performance with broad application prospects. However, the design process for these complex high-dimensional coupled nonlinear systems remains poorly developed, particularly when applied for ocean-going vessels that experience rolling and pitching motions. The present work addresses this issue by establishing a six-degree-of-freedom HSLDS vibration isolation model for FRVISs composed of eight isolators, and the model is applied to fully analyze the swing stability and multidimensional vibration isolation performance of these systems. The influence of nonlinearity on the mechanical properties of the vibration isolators is analyzed more clearly by assuming that each vibration isolator realizes nonlinear HSLDS characteristics in the z direction and linear characteristics in the x and y directions. The results demonstrate that the swing displacement responses of the system are greatly reduced under weak nonlinearity, which reflects the high static stiffness and high static stability characteristics of an HSLDS system. The multidimensional vibration isolation performance of the system is evaluated according to the impacts of nonlinearity, the installation height Hz of the isolators, and the relative position Dr of the two middle isolators. The results of analysis demonstrate that applying a value of Hz = 0 produces the best vibration isolation performance overall under strong nonlinearity by avoiding unnecessary secondary peaks in the force transmission rate under harmonic mechanical excitation and ensuring a maximum high-frequency vibration isolation effect. However, applying a weak nonlinearity is better than a strong nonlinearity if Hz is not zero. In contrast, Dr has little effect on the vibration isolation effect of the raft in the x, y, and z directions. Therefore, an equidistant installation with Dr = 0.5 would be considered ideal from the standpoint of installation stability.

Simultaneous vibration isolation and energy harvesting via a new negative stiffness system with inertial amplifier

The negative stiffness system provides significant vibration isolation. The conversion of mechanical energy from structural vibrations into electrical energy is an effective method of energy harvesting. In this paper, a new negative stiffness system (NSS) with inertial amplifier for vibration isolation and energy harvesting is established, whose main purpose is to achieve good vibration isolation effect while the system can achieve the purpose of energy harvesting. Inertial amplifiers are used to improve the dynamic effective mass of the system, thereby reducing the natural frequency of the system. Using the multi-scale method, the amplitude-frequency response equation of the system is derived and the amplitude-frequency characteristic curve is plotted. The Lyapunov exponent, the root mean square of the voltage of the piezoelectric system and the basin of attraction are introduced to analyze the energy harvesting performance of the system. Numerical results show that the inertial amplifier improves the vibration isolation capacity of the negative stiffness structure in the low-frequency band. There is a correlation between the basin of attraction, the Lyapunov exponent, and the root mean square of voltage.

Vibration transmission analyses of double-layer cylindrical shell with fully immersed elastic connections through experimental and analytical approaches

This paper investigates vibration transmission characteristics of the double-layer cylindrical shell with fully immersed elastic connections through experimental and analytical approaches. A test sample of the double-layer cylindrical shell connected by six vibration isolators is firstly manufactured and a forced vibration test is done with fully immersed interlayer. Meanwhile, a novel analytical approach is developed to calculate vibration responses of an unequal double-layer cylindrical shell with fully immersed elastic connections. The substructure receptance method and wave propagation method are combined in the coupling theoretical model. Springs are utilized to simulate elastic connections, that are considered as substructures. By comparing the achieved analytical and experimental vibration responses, good agreements are gained and the two approaches are demonstrated. Then the transmission characteristics are gradually analyzed with respect to the double-layer shell with elastic connections, double-layer shell with interlayer fluid and double-layer shell with fully immersed elastic connections. It is found that the interlayer water between the inner and outer shells plays a “short-circuit” role in vibration transmission, which greatly reduces the isolation performance of vibration isolators. Nevertheless, the fully immersed isolators with small stiffness still have the non-ignorable vibration isolation effect compared with the case of rigid connection.

Concept and behavior of a novel long-period isolation bearing with variable stiffness

To reduce the effect of train-induced vibration on the structure and improve the serviceability of structures, this study proposes a novel isolation bearing with a simple configuration and low cost, having a wide market prospect. Compared with bearing with constant stiffness, the novel bearing can achieve a broadband vibration isolation effect. Based on quasi-static tests, the behavior of the bearing is investigated, and the analytical hysteresis model of the bearing is derived and validated. Furthermore, comprehensive on-site assessments amidst multi-source traffic vibration scenarios are conducted to validate the vibration mitigation of the isolation bearing. The findings reveal that while at varying preloads and amplitudes, the hysteretic properties remain remarkably stable, except in the case of small amplitude cycles. The theoretical hysteresis model aligns closely with the test result, accurately capturing the cyclic behavior. The bearing significantly reduces the response of structures under multi-source transport vibrations.

Design and implementation of a precision levelling composite stage with active passive vibration isolation

The white-light-interference (WLI) three-dimensional topography fine detection has high requirements for the chip-loading stage on levelling and vibration isolation capacity, to ensure that the micro-meter-level structured chip is stably aligned with the WLI scanning head. To meet the high performance detection requirements, this paper designs a novel three-axis levelling and active-passive vibration isolation (LAPV) composite stage, in order to perform precision tilt levelling and wide-frequency-domain vibration isolation. The proposed LAPV stage integrates a modified quasi-zero-stiffness passive vibration isolation unit with an active actuation unit which consists of three voice coil motors (VCMs). It performs active-passive vibration isolation while ensuring a precision levelling. Considering the load bearing and motion vibration of the chip-loading stage, a miniaturized quasi-zero-stiffness mechanism having a specialized leaf spring structure is then designed to limit the vibration isolation operation to the vertical direction and coordinate the levelling motion of the tilt rotation direction, so as to establish a structural decoupling stage. Based on the dynamic and kinematic modelling analysis, a customized PID-Positive Position Feedback (PID-PPF) control scheme is implemented. Afterwards, an experimental verification is conducted. The obtained results show that the stage can achieve a precise levelling motion, reaching a levelling deviation of 33.2 μrad. Moreover, it also can achieve effective active-passive vibration isolation for various vibrations with different frequencies and amplitudes, and the vibration isolation rate can reach 90 %.

Research on vibration isolation optimization design technology for the articulated link mount of turbofan engine

As an important structure connecting the aircraft and the engine, the turbofan engine mount often adopts a hinged multi-link mechanism, and its dynamic performance directly affects the transmission of engine vibrations to the fuselage. To study and improve the vibration isolation performance of this type of mount system, this paper proposes an optimization strategy based on modal design ideas, which takes the minimum distance between the natural frequencies of the mount system and the excitation frequency as the optimization objective, seeks the parameter solution that maximizes the optimization objective, and uses genetic algorithms to carry out optimization analysis. The results show that through optimization analysis, the effective vibration isolation range of the system is increased by approximately 125% near the excitation frequency of the low-pressure rotor; at the excitation frequency of the low-pressure rotor, the system transfer rate is reduced by approximately 58.4%; after optimization, due to the overall frequency deviation of the installation section system from the excitation frequency, the impact of small perturbations of the main parameters on its transfer rate is generally lower, with a maximum decrease of approximately 17.3%, greatly improving the robustness of the system.

Design and performance of an ultrahigh vacuum spectroscopic-imaging scanning tunneling microscope with a hybrid vibration isolation system.

A spectroscopic imaging-scanning tunneling microscope (SI-STM) allows for the atomic scale visualization of the surface electronic and magnetic structure of novel quantum materials with a high energy resolution. To achieve the optimal performance, a low vibration facility is required. Here, we describe the design and performance of an ultrahigh vacuum STM system supported by a hybrid vibration isolation system that consists of a pneumatic passive and a piezoelectric active vibration isolation stage. We present the detailed vibrational noise analysis of the hybrid vibration isolation system, which shows that the vibration level can be suppressed below 10-8 m/sec/√Hz for most frequencies up to 100Hz. Combined with a rigid STM design, vibrational noise can be successfully removed from the tunneling current. We demonstrate the performance of our STM system by taking high resolution spectroscopic maps and topographic images on several quantum materials. Our results establish a new strategy to achieve an effective vibration isolation system for high-resolution STM and other scanning probe microscopies to investigate the nanoscale quantum phenomena.

Propagation Behavior of P1-Wave Passing through Fluid-Saturated Porous Continuous Barrier in Layered Saturated Soil

The fluid-saturated porous continuous barrier has a better vibration isolation effect than the single-phase solid continuous barrier, and layer-forming saturated soils will have an impact on the vibration isolation effect of the barriers due to their irregular layer-forming distribution. Based on Biot’s theory of saturated porous media and Snell’s law, a dynamic model of a fluid-saturated porous continuous barrier in layered saturated soil is established in this study. By introducing the potential function and using the continuous boundary condition of the interface between the saturated soil and the barrier, the analytical solution of the inverse transmission amplitude ratio of a P1-wave passing through the fluid-saturated porous continuous barrier in stratified saturated soil is obtained. The rationality of the proposed method is verified by comparing the solution of the P-wave model at the interface between the elastic medium and the saturated coarse particle interlayer. The differences in the propagation characteristics of fluid-saturated porous continuous barriers in layered saturated soils, homogeneous saturated soils, and layered single-phase soils are analyzed via numerical examples, and the influence of changes in the physical and mechanical parameters of the fluid-saturated porous continuous barriers on the reflectance amplitude ratios under the conditions of a layered saturated soil foundation are also analyzed. The results show that the presence of fluid in the stratified saturated soil model changes the trend of the reflection amplitude ratio with the incidence angle. The reflection amplitude ratio of the P2-wave and the SV-wave increases first and then decreases with the increase in the incident angle, while the reflection amplitude ratio of P1-wave decreases first and then increases. Barrier thickness and porosity change the energy distribution relationship at the interface; a relatively thicker barrier thickness and a higher porosity would result in a higher amplitude of barrier reflections.

Improving the performance of nonlinear isolator through triboelectric nanogenerator damper integrating energy harvesting

In order to solve the problem of integration of low-frequency vibration isolation and vibration energy harvesting, this paper proposes a novel nonlinear oscillator with triboelectric nanogenerator damper (NO-TENGD), which can realize different nonlinear characteristics of quasi-zero stiffness (QZS) and bistable by changing the length of rigid links. The mechanism of improving the isolation performance of NO-TENGD was analyzed and discussed with a dynamic model proposed, and the effects of excitation frequency, friction force, geometric parameters, and spring stiffness were studied. The damping can be increased by adjusting the pressure of TENGD, which can effectively suppress the resonance peak value of response amplitude and force transmissibility. The experimental results show that when the excitation frequency is larger, the amplitude response of NO-TENGD is smaller under frictionless condition, and the amplitude response of NO-TENGD under large friction condition is smaller than that under small friction one. NO-TENGD with QZS has a good vibration isolation effect, and the output power can light up 50 LED lights or electronic watches. Finally, NO-TENGD with QZS can achieve low frequency vibration suppression, and increasing damping can reduce the response amplitude and force transmissibility of the beam bridge in the resonance frequency range.

A novel three-dimensional isolation bearing for buildings subject to metro- and earthquake-induced vibrations: Laboratory test and application

The implementation of three-dimensional (3D) isolation technology effectively enhances the structural seismic resilience and mitigates the impact of vibrations induced by metro trains. However, the challenge remains to increase the vertical loading capacity of 3D isolation bearings while reducing their vertical stiffness and guaranteeing excellent stability. The 3D isolation bearing (3DIB) consisting of an improved laminated natural rubber bearing (LNR-400-imp) and spring bearings (SBs) built vertically in series were proposed in this study. Its design principle and working mechanism were introduced, and prototype specimens were designed and manufactured. The 3D mechanical performance of the 3DIB was investigated through horizontal and vertical tests. Furthermore, the earthquake and metro vibration isolation performances of the building installed with the 3DIB were analyzed using a case study. The results demonstrated that the 3DIB exhibited horizontal energy dissipation effect, and had stable vertical performance, higher vertical loading capacity, and lower vertical stiffness attributing to the improved LNR-400-imp and SBs. Specifically, the vertical stiffness of the 3DIB was about 1/14 of that of the traditional LNR-400-tra. The case study demonstrated that the 3DIB had remarkable earthquake and metro vibration isolation effects, behaving huge potentials in enhancing the seismic resilience of structures and mitigating the impact of metro vibrations. This study offers valuable insight and practical guidance for future research on 3DIB in the field of vibration isolation, contributing to the advancement of 3D isolation technology.

Design of a novel two-degree-of-freedom translational-rotation low-frequency vibration isolation platform

Multi-dimensional vibration isolation platforms often use parallel mechanisms to achieve multi-dimensional vibration isolation control. However, due to the high stiffness of the parallel mechanism, its own natural frequency is high, and it has good performance when applied to high-frequency vibration isolation, but it is hard to achieve low-frequency vibration isolation. This paper aims at the problem that the actual polishing and grinding equipment is often subjected to axial and circumferential low-frequency disturbances during operation, a novel C/2-(2-RRR) RR two-degree-of-freedom (2-DOF) translational-rotation low-frequency vibration isolation platform is proposed based on the singular configuration of planar 2-RRR mechanism. The coupling dynamic model of the vibration isolation platform is established, and the amplitude-frequency curve and force transmissibility curve are analyzed. The simulation analysis and prototype experiment are carried out by using the independent external excitation in both translational and rotational directions, and the corresponding linear system is compared to verify the effectiveness of the low-frequency vibration isolation of the two-degree-of-freedom vibration isolation platform.

Active vibration isolation by emulating the inerter through relative acceleration feedback

This study focuses on the realisation of a small-scale inerter by relative acceleration feedback and its use to isolate vibration. Two accelerometers attached to the two mechanical terminals of an electrodynamic force actuator are used to obtain the relative acceleration signal. This signal is then amplified by a constant gain and fed back to the two electrical terminals of the electrodynamic actuator as a voltage command. This sensor-actuator system is coupled to a two Degree-Of-Freedom (DOF) mechanical oscillator to study the feedback loop’s stability and the maximum achievable inertance effect. A fully coupled simulation model including the dynamics of the two inertial accelerometers and the electrodynamic actuator is developed. It is shown that, because of the active control system emulating an inerter, an antiresonance appears in the transfer admittance function of the two DOF mechanical system. Therefore, significant vibration isolation effect can be achieved in the narrow frequency band around the antiresonance. The antiresonance frequency is easily tuned by adjusting the feedback gain. The synthetized inertance is a complex frequency dependent function, which is predominantly real-valued in the frequency range between 5 and 1600 Hz. It is shown that it does not depend on the mechanical system properties, but only on the properties of the transducers used and the signal conditioning in the feedback loop. As a result, this frequency range can be adjusted according to a particular application.

The Vibration Isolation Properties of an Asymmetrical Quasi-Zero Stiffness Isolator with Geometrical Nonlinear Damping

This paper proposes a Quasi-Zero-Stiffness (QZS) vibration isolator with asymmetric stiffness and geometric nonlinear damping. The nonlinear stiffness and nonlinear damping characteristics of proposed model are studied. The motion equation of proposed system under force excitation is established, and its dynamic response is solved by the Harmonic Balance Method (HBM). In addition, the influence of nonlinear damping on force transmissibility is studied. The results indicate that the proposed isolator has a large equivalent damping ratio in the resonance region and a small equivalent damping ratio in the high-frequency region. Therefore, the proposed asymmetrical QZS isolator with nonlinear damping can supress the resonance in lowfrequency under force excitation and achieve a good highfrequency vibration isolation effect simultaneously than that with linear damping.

Experimental study and numerical analysis for vibration isolation performance on open trench and wave impeding block combined vibration isolation barrier

This paper presents a series of laboratory tests to investigate the vibration isolation performance of open trench and wave impeding block (WIB) combined vibration isolation barrier. To study the vibration isolation performance of open trench-WIB, design the 15 pairs of trials, including comparison with other vibration isolation methods, and the variation of vibration isolation performance with the depth, width, and thickness of open trench-WIB. The experiment is validated by FEM results with vibration isolation performance. The experimental results show that the vibration isolation effect of open trench-WIB combined vibration isolation barrier is better than that of the open trench at various excitation frequencies, and it is most obvious in the low frequency band. In addition, the effects of trench depth, wave barrier depth, barrier thickness, and barrier length on the vibration isolation performance of the open trench-WIB combined vibration isolation barrier are discussed. The research results are of great significance to guide the design of engineering vibration isolation.

Shaking table test of vertical isolation performances of super high-rise structure under metro train-induced vibration

Metro systems are integral to improving transportation efficiency and providing convenience to the public; however, they cause environmental vibrations. To analyze the metro vibration propagation law and vibration isolation performance of a 120 m super high-rise structure positioned directly above two metro tunnels, a shaking table test at a 1/30 scale ratio is conducted in this study. First, a model for the shaking table test is designed and manufactured, and measurements of metro train-induced ground vibrations obtained on site are input into the model. Subsequently, vertical vibration tests are performed on the models with and without laminated rubber isolation bearings. Finally, their dynamic characteristics, vibration propagation law, and vibration isolation effect are analyzed, and the vertical vibration isolation mechanism of the structure is discussed. The results indicate that the metro vibration exerts a resonance effect on non-isolated super high-rise structures, thus resulting in the progressive amplification of the metro vibration response along the floors of the structure. The vibration isolation layer formed by the laminated rubber isolation bearings significantly reduces the vertical modal frequency and increases the vertical damping ratio of the super high-rise structure, thus effectively attenuating the vertical metro vibration. Unlike the non-isolated structure, the vibration-isolated structure can avoid severe structural resonance responses in the dominant frequency band of the metro vibration. This study aims to offer insightful considerations for evaluating metro vibrations in super high-rise structures and may serve as essential reference for vertical vibration isolation.

Modeling of a Ti/NiTi spring-blade gear for space micro–vibration isolation

Space pointing mechanisms are crucial in space scientific experiments and observations. Since the precision of such mechanisms is highly susceptible to micro–vibrations due to environmental disturbances and inherent defects, isolating micro–vibrations is important. A low rotational stiffness spring-blade gear installed on the output shaft of the stepper motor can isolate micro–vibrations due to the motor’s discontinuous rotation. However, a quantitative performance description is still lacking. In this paper, a rotational stiffness model for the spring-blade gear made of titanium and nickel–titanium-based shape memory alloy is established and experimentally validated. A vibration transmissibility model is developed, revealing the relationships among the layout, material properties, structural parameters, external loads, rotational stiffness, and vibration transmissibility of the spring-blade gear. This paper can be used to design and optimize the spring-blade gear, predicting the isolation and suppression capability against micro–vibrations at different frequency ranges. The optimal gear structure can be obtained according to vibration isolation requirements, load, and installation constraints to achieve the predetermined vibration isolation effect. This study can ensure the space pointing mechanisms operate with high precision and stability by attenuating space micro–vibrations effectively, improving the quality of signal acquisition and observation accuracy.

An adaptive feed-forward active vibration isolation algorithm for input disturbance unbalanced MIMO systems

Multi-axis active vibration isolation systems often encounter order-of-magnitude differences in the perturbations in each input direction. This causes adaptive feedforward control systems to converge at a relatively slow rate, or possibly even diverge. To solve this problem, we propose an improved adaptive feedforward vibration isolation technique based on the classical FxLMS algorithm. Our approach constructs a weighted transformation matrix based on singular value decomposition, attenuates the uneven influence of the input perturbations, and effectively avoids the problems of slow convergence and poor stability faced by existing adaptive algorithms. This paper first describes the parameter update algorithm and the structure of adaptive feedforward algorithms. The convergence of the proposed algorithm is then analyzed, and the method for constructing the weighting matrix is introduced. Finally, the feasibility of the algorithm is verified using a multi-axis vibration isolation system simulation model. The simulation results show that the power spectrum of acceleration in the frequency domain from 0.1 to 100 Hz is attenuated by up to 70 dB under the condition of no excitation in a specific direction, demonstrating the vibration isolation effect of the algorithm. The relative deviation between the predicted and actual parameter error is no more than 6 %, which shows that the algorithm achieves good convergence. The proposed algorithm has potential applications in the active vibration isolation of space telescopes and high-precision optical equipment.

A Compliant Self-Stabilization Nanopositioning Device With Modified Active–Passive Hybrid Vibration Isolation Strategy

Micro/mini light-emitting diodes (LEDs) display panel inspection and repairs have a high demand for vibration isolating devices to protect industrial-level atomic force microscopes (AFM scanning head) against vibrations. The motivation of this work is to combine the advantages of both passive and active vibration isolation strategies to improve inspection performance. The developed self-stabilization device achieves this objective with a design that incorporates a suspension-type passive vibration isolation unit and integrates it with the modified active–passive hybrid (MAPH) vibration isolation strategy using piezoelectric ceramics (PZT) and voice coil motors (VCM) as compensators. First, the design, modeling, and optimization of a self-stabilization device are presented based on the MAPH vibration isolation strategy. To satisfy the requirements of vibration isolation performance and a lightweight design, a multiobjective optimization task was conducted. Next, a tailor-made double compensating PID controller was designed to allow this mechanism to run in the MAPH method to effectively isolate vibrations. Finally, a series of validation experiments, including passive vibration isolation performance tests and MAPH closed-loop tests, were applied. From 1 to 500 Hz, more than 98% frequency domain achieved a vibration isolation rate of 90%, the vibration amplification effect of the passive vibration isolation was significantly suppressed, the steady-state positioning accuracy reached <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm 0.1\;\mu$</tex-math></inline-formula> m, load capacity was up to 2.5 kg, the attenuation ratio of the disturbances reached up to 70%, and the heat of the VCM was effectively reduced. All results comprehensively confirmed that the developed compliant MAPH vibration isolation system has achieved a satisfactory self-stabilization function.