Low-frequency Vibration Isolation Research Articles

Origami-inspire quasi-zero stiffness structure for flexible low-frequency vibration isolation

As an emerging technology, origami exhibits rich nonlinear static and dynamic properties. However, simulating creases remains a key challenge hindering practice application, especially for volumetric (deformable) origami. Inspired by the bistable behavior and axial-rotational coupling mechanism of triangulated cylindrical origami (TCO), this paper proposes a novel combined truss-spring structure with additional inertial mechanism (TCTS-RIM) for low-frequency vibration isolation. Unlike pure TCO, the TCTS-RIM uses elastic linkages to simulate all creases and modifies crease positions, enhancing physical realization in engineering applications and offering tunable stiffness and inertia on demand. Static analysis shows the modified truss-spring structure in TCTS-RIM has superior quasi-linear negative stiffness compared to pure TCO, which enables a very wide quasi-zero stiffness (QZS) range via linear spring compensation. The wide QZS range for different loads can be realized by setting appropriate structural parameters. From system dynamic equations, nonlinear inertia, nonlinear quadratic force, and nonlinear damping due to RIM are identified and discussed. The Alternating frequency–time harmonic balance method is used to obtain the displacement transmissibility, and its parametric influencing investigations verify that the proposed TCTS-RIM has excellent low-frequency vibration isolation performance and rich tunability. Comparative discussions show the wide QZS range significantly reduces the resonance frequency, broadens the isolation frequency band, and yields superior dynamic performance versus pure TCO isolators. Moreover, equivalent mass, anti-resonance and softening behavior induced by the rotational inertia mechanism further enhance low-frequency vibration isolation performance. An experimental prototype is built, and experimental results validate the correctness of the theoretical analyses. This work presents a simple mechanical implementation of volumetric origami, which may progress the engineering applications of origami and provide a viable approach to low-frequency vibration control.

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.

Chiral phononic crystal-inspired railway track for low-frequency vibration suppression

Chiral phononic crystals (CPCs) offer an advanced approach to vibration isolation by exploiting inertial amplification, establishing broad band gaps at low frequencies and outperforming conventional phononic designs. This study pioneers a CPC-inspired railway track that significantly enhances low-frequency vibration isolation through an orthogonal polarization coupling mechanism of the chiral subunit cell. Mechanical modeling and simulations have validated the causes of the enhanced performance and the tunability of crucial physical parameters across characteristic dimensions. Incorporating this structure within a coupled vehicle-floating slab track (FST)-tunnel system facilitates a comparative analysis against conventional steel spring FSTs. The CPC-inspired track system demonstrates enhanced isolation, significantly reducing vibrations within the 200 Hz range for both slab and tunnel structures, achieving a maximum insertion loss of 7.19 dB for the slab and 5.69 dB for the tunnel. Further evaluation of rail and slab displacements, alongside the wheel load reduction rate, underscores the operational safety of trains with the CPC-inspired system implemented. This pioneering exploration of CPC-inspired structures showcases the potential to significantly advance vibration control in urban rail infrastructure, providing a foundational reference for future research.

A novel adjustable magnetorheological fluid gradient material of low frequency vibration isolation: a theoretical and experimental study

In this paper, a novel adjustable magnetorheological fluid (MRF) gradient material for low-frequency control is proposed, and the vibration isolation performance of this gradient material is investigated theoretically and experimentally. The gradient material has an excellent ability to control the sound waves and vibrations. However, the currently prepared gradient material does not have the parameter adjustability. At the same time, the MRF can change its material parameters according to the external magnetic field. After applying the traveling magnetic field (TMF) to the MRF with continuously varying and adjustable magnetic induction strength, its material parameters will also be continuously varying and adjustable to constitute an adjustable gradient material. In order to investigate the vibration transfer characteristics of this adjustable gradient material, this paper establishes a micro-mechanical model of MRF and theoretically investigates and numerically calculates the mechanical impedance and vibration transfer characteristics of the adjustable gradient material through the machine-electric analogy theory. At the same time, experimental research was conducted by building an experimental platform to conduct experiments. The results show that the novel adjustable gradient material composed of a TMF and MRF has a good vibration suppression effect in the low-frequency range (10 ∼ 60 Hz) with the vibration level difference of up to 30 dB or more, which has a broad application prospect in the field of vibration control.

Machine Learning-Driven Design Optimization of Buckling-Induced Quasi-Zero Stiffness Metastructures for Low-Frequency Vibration Isolation.

Metastructures, artificial arrangements of micro/macrostructures, possess unique properties and are of significant interest in aerospace, stealth technology, and various other applications. Recent studies have focused on quasi-zero stiffness metastructures, providing an outstanding vibration isolation capability. However, existing methods are constrained to low preloads and lack the consideration of structural analysis, despite their intended use in practical structures. This study introduces metastructures with quasi-zero stiffness characteristics under high preloads by inducing local buckling. An optimization framework combining deep reinforcement learning and finite-element analysis is employed to derive an optimal model that considers both structural safety and quasi-zero stiffness characteristics. To validate the optimization results, quasi-zero stiffness metastructures are fabricated via 3D printing, and compression and vibration experiments are conducted. The fabricated metastructures exhibit quasi-zero stiffness characteristics under a high target preload along with outstanding vibration reduction performance, even in the low-frequency range.

Biomimetic dual-phase ceramic lattice architectures with enhanced mechanical and vibration isolation performances

Ceramic materials have broad application prospects for impact/perforation protection purposes due to their high strength, high hardness, and other characteristics. Nevertheless, the high brittleness, susceptibility to fracture, and difficulty in processing and forming limit the popularization of ceramic components. This paper proposed a novel silica gel-filled dual-phase ceramic lattice meta-structure based on a biomimetic biphasic design method to achieve the improvement of mechanical properties. Two configurations of dual-phase body-centered cubic (BCC) and face-centered cubic (FCC) ceramic lattice structures were designed and fabricated through DLP-based additive manufacturing and simple filling technology. Quasi-static compression and dynamic vibration testing were conducted. Comparisons between single-phase and dual-phase ceramic lattices were performed from the perspective of compression strength, fracture toughness, and vibration level difference. It was demonstrated that the addition of soft silica gel reduced the stress concentration at the connection of the lattice rod and effectively inhibited the crack propagation. The dual-phase BCC lattice structure exhibited a 3 times increase in toughness and a 4.2 times increase in compressive strength relative to the single-phase design. The toughness and compressive strength of the dual-phase FCC ceramic lattice were increased by 1.4 times. The introduction of the soft silica gel achieved a significant vibration isolation in the pre-resonance frequency band between 1000 Hz to 3000 Hz. This study provides a reliable method for constructing biomimetic dual-phase meta-structures with both load-bearing capacity and low-frequency vibration isolation capacity.

Low-frequency forbidden band characteristics of metamaterials based on combined resonant units

With a view to increasing the width of the local resonant band gaps and obtaining damping at low-frequency, a metamaterial structure with multiple resonant units and an adjustable band gap is proposed. The single-unit structure of the metamaterial consists of a main system and three resonant units. Simultaneously, the energy band structure and frequency response characteristics of the metamaterial are investigated with the finite element method and the dispersion equation. Further, the effects of natural frequency, mass of resonant units, mass ratio, and stiffness ratio on the energy band structure are demonstrated. Also, the effect of damping on the band gap in the metamaterial structure is examined. The low-frequency vibration isolation performance of the structure is verified on experimental platform. In conclusion, the designed metamaterial structure provides three adjustable band gaps in the low-frequency range with good vibration damping.

Linear and nonlinear stiffness compensation for low-frequency vibration isolation: a comparative study

Linear and nonlinear stiffness compensation for low-frequency vibration isolation: a comparative study

Vibration isolation by relative resonance perceived in combination of rigid bodies and elastic beams

This paper develops a novel low-frequency vibration isolation device based on rigid body dynamics called a Rigid Elastic Vibration Isolator (REVI). The REVI model is realized by coupling four elastic beams with two rigid bodies monolithically made using 3D printing. The system operates based on the vibration of the intermediate rigid bodies, which leads to the anti-resonance phenomenon at low frequencies. The dynamic analysis of the proposed REVI system has been meticulously investigated through analytical methods and real-world experimentation. The analytical method uses the Spectral element method to obtain the dynamic response, which is also validated by the experimental findings. Furthermore, the REVI transmittance sensitivity analysis was conducted by adjusting the rigid mass and system load and exploring methods for generating wide low-frequency bandgaps. The inclination angle of the REVI system is also varied, revealing the bandgap characteristics regarding negative transmittance level. The parametric study varying the geometric properties of the REVI system enhances our understanding of the bandgap and attenuation characteristics within the attenuation band. The REVI mechanism is practical and easily implemented, allowing for accurate and repeatable modeling. Moreover, the analytical observations assist in refining the shape of the REVI mechanism to achieve the necessary bandgap for the desired transmittance.

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.

Low-frequency vibration isolation via new wide range zero-stiffness isolator with multiple negative stiffness mechanisms

Low-frequency vibration isolation via new wide range zero-stiffness isolator with multiple negative stiffness mechanisms

A 3D-printed quasi-zero-stiffness isolator for low-frequency vibration isolation: Modelling and experiments

Quasi-zero-stiffness (QZS) isolators have shown great promise for low-frequency vibration isolation, thus outperforming conventional linear isolators. However, the hardening behavior typically exhibited in QZS isolators can deteriorate the isolation performance at high excitation amplitudes. To tackle this problem, utilizations of inherent material damping in soft resin offer a feasible way to counteract the hardening effect. This paper proposes a continuous QZS isolator, which can be readily fabricated by three-dimensional (3D) printing using soft resin. QZS properties are achieved by combining the snap-through behavior of inclined beams and the support of folded beams, acting as negative-stiffness (NS) and positive-stiffness (PS) elements, respectively. Analytical methods are developed for predicting the stiffness of the NS and PS elements of the design, whose efficacy is demonstrated numerically and experimentally through examining the static behavior. To evaluate the vibration isolation performance of the QZS isolator, a nonlinear single-degree-of-freedom (SDOF) model is proposed. The model incorporates cubic nonlinear damping in addition to classical viscous damping. The harmonic balance method (HBM) and the Runge-Kutta algorithm are employed to solve the equation of motion and to predict the velocity transmissibility. Parametric analyses are conducted to assess the effect of the excitation amplitude on isolation performance. The results show that an increased excitation level entails a down-shifting of the peak frequency in the transmissibility curve and that of the starting frequency of the effective isolation zone, resulting in enhanced isolation performance at large amplitudes. Numerical findings are further supported by dynamic experiments with varying excitation levels, demonstrating the validity of the proposed numerical model.

Tunable stiffness design of curved-crease origami and extended quasi-zero stiffness vibration isolator

A kind of origami tube based on the curved crease, which has a tunable stiffness, was designed, fabricated, tested, and extended to the concept of a quasi-zero stiffness (QZS) vibration isolator. The regulating function of crease stiffness on the overall origami stiffness without changes in the crease pattern was verified by single-crease models. With various opening ratios along the creases, three tubes composed of mirrored single-crease origami were designed, fabricated by 3D printing, and compressively tested. The test results present the potential of the approach of QZS. Further, the elastic-frictionless origami tubes were redesigned and simulated to obtain the target stiffness. The cubic term fitting of the load curve was adopted by the harmonic balance method to solve the steady-state vibration response, and then the simulation results obtained by the finite element method (FEM) were compared. The study shows that the designed elastic-frictionless isolator has a good low-frequency vibration isolation performance. The concept of the simple stiffness control method of curved-crease origami provides more practice options for high static and low dynamic stiffness systems.

A novel permanent magnet vibration isolator with wide stiffness range and high bearing capacity

Quasi-zero stiffness (QZS) vibration isolators have attracted extensive attention because of their excellent performance in low-frequency vibration isolation and high bearing capacity. However, its practical engineering application remains challenges due to the magnitude and adaptability of the negative stiffness. This paper proposes a permanent magnet type variable stiffness (PMVS) mechanism with a wide stiffness range from negative to positive. Based on the semi-analytical model of magnetic force, the QZS isolator composed of the spiral spring in parallel with the PMVS mechanism is developed, which has both stiffness adjustment and load adaptability. The nonlinear dynamic equation with 5th polynomial restoring force is established then solved by the harmonic balance method (HBM). The dynamic behaviours is investigated and validated through the experimental prototype and good isolation performance is observed. Building upon the wide stiffness adjustment and large magnitude of the PMVS mechanism. the proposed isolator achieves a stiffness range of 4.15–153.45 N/mm under a safe load up to 120 kg, which implies that the natural frequency of the isolator can reach an ultralow value of 0.93 Hz within the safe load (120 kg).

Low frequency vibration isolation characteristics and intelligent design method of hull grillage metastructures

In this paper, the wave propagation mechanics theoretical model of hull grillage metastructures with local resonators is established, and the intelligent design method of hull grillage metastructures is proposed based on deep learning. The flexural vibration isolation characteristics of periodic hull grillage structures and the proposed hull grillage metastructures are theoretically studied using the spectral element method. Numerical calculation and experimental tests of the flexural wave vibration transmission of hull grillage metastructures are conducted to validate the proposed theoretical model. In addition, the data set is constructed by using the wave mechanics theoretical model of hull grillage metastructures, and the forward prediction neural network model of vibration transmission characteristics as well as the inverse design neural network model of hull grillage metastructures are established. Results show that compared with periodic hull grillage structures, the proposed hull grillage metastructures possess significant low-frequency flexural wave vibration isolation characteristics which almost completely covers the low-frequency range from 27 Hz to 169 Hz. Both forward prediction and inverse design network models have good performance, which verifies the correctness of the intelligent design method based on deep learning, and provides a new direction for the structural design on demand of low-frequency vibration reduction of ship and offshore structures.

Active Control of Quasi-Zero-Stiffness Vibration Isolator with Variable Load

Quasi-zero-stiffness (QZS) isolator has great application potential in the field of low-frequency vibration isolation due to its high-static and low-dynamic (HSLD) nonlinear stiffness characteristic, but it is precisely this characteristic that makes it very sensitive to load changes. Once the load changes, causing it to deviate from the equilibrium position, it no longer qualifies zero-stiffness characteristic, and the vibration isolation capacity will be significantly decrease. To make the QZS isolator possess variable load capacity and be more suitable for engineering practice, an active QZS vibration isolator based on electromagnetic actuator is designed in this paper, which eliminates the influence of load changes through the active force of the electromagnetic actuator. First, the dynamic equation of the isolator is established by Newton–Euler method, and the dynamic characteristic of the isolator under standard load and load variations are analyzed through improved incremental harmonic balance (IHB) method based on discrete Fourier transform (DFT). Next, the improved particle swarm optimization (PSO) algorithm are employed to optimize the Proportion Integration Differentiation (PID) controller parameters. Then, the vibration isolation performance of QZS isolator in controlled and uncontrolled and linear systems in the same control state are compared in frequency domain and time domain, respectively. Finally, the performance of active QZS isolator under load variation is discussed. The results indicate that the isolation performance of the QZS isolator under active control is significantly better than in uncontrolled conditions and the controlled linear system. When the load changes, real-time compensation through the actuator output control force can also enable the QZS isolator to achieve a better vibration isolation performance.

A novel frog-like meta-structure with linkage mechanism for low-frequency vibration isolation

Structures with linkage mechanism, which could be widely seen in engineering, usually need to bear a certain load and exhibit ideal vibration isolation performance. One of the key factors affecting the mechanical and vibration properties is the connection behavior of the linkage mechanism. To clarify its influence on the vibration characteristics, a novel frog-like meta-structure by introducing a linkage mechanism into the conventional locally resonant metamaterial with a mass-spring resonator is proposed in the present paper, in which the linkage connection is considered as three types of hinged, fixed and elastic, respectively. The equivalent dynamic model of the meta-structure is established theoretically to calculate the effective material properties, which is then validated numerically through band gap and vibration analysis. The results show that the hinged linkage offers equivalent mass and free vertical displacement, while the fixed linkage provides supporting stiffness, shifting the band gap towards higher frequencies. An appropriate elastic connection can enhance the ‘spring-vibrator’ effect, which in turn can significantly expand the low-frequency vibration suppression range of the structure. Experiments are also conducted corresponding to the different linkage mechanisms, and the dynamic model is verified. This study could provide a new idea for promoting the application of the locally resonant meta-structure with a linkage mechanism in the field of low-frequency vibration isolation.

Modeling and Analysis of Bio-Inspired, Reconfigurable, Piezo-Driven Vibration Isolator for Spacecraft.

The positioning accuracy of spacecraft in orbit is easily affected by low-frequency micro-vibrations of the environment and internal disturbances caused by the payload. Inspired by the neck structure of birds, this study devised a piezo-driven active vibration isolation unit with high stiffness. First, a dynamic model and two-sensor feedback control method for the isolation unit were developed, and the isolation mechanism and anti-disturbance characteristics were analyzed. Further, the stability of the closed-loop was verified. Simulation models of serial and parallel systems based on the proposed vibration isolation unit were implemented to demonstrate its feasibility. The results indicate that the proposed isolation units can provide excellent low-frequency vibration isolation performance and inertial stability and that they can effectively resist the internal disturbance of the payload. Moreover, its performance can be further improved via serial or parallel reconfiguration that facilitates its adaptation to the varied isolation requirements of spacecraft.

Design and Analysis of a Novel Horizontal Large-Amplitude and Low-Frequency Vibration Isolator

Design and Analysis of a Novel Horizontal Large-Amplitude and Low-Frequency Vibration Isolator

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.