Vibration Isolation Mechanism Research Articles

Design and experimental study of a planar piezoelectric actuator with resonant actuation

Planar piezoelectric actuators, which can achieve high-precision motions over a wide range, have been widely applied in high-end equipment fields. However, the existing planar piezoelectric actuators can no longer meet the high actuation characteristics required for the rapidly development of these fields, which include large travel, high resolution, fast speed, planar three degrees of freedom (3-DOF) and a compact structure. A planar piezoelectric actuator with resonant actuation is proposed and tested in this work. The actuator consists of four symmetrically configured uniform bending-bending hybrid piezoelectric units, which coordinate to achieve large travel and planar 3-DOF characteristics. A vibration isolation mechanism adopting thin beam structure with low stiffness in coupling directions is designed to achieve vibration isolation among the units. The actuator can operate in high frequency resonance mode and low frequency stepping mode, allowing for the achievement of high-speed and high-resolution characteristics. A prototype is fabricated and tested. A compact structure measuring 53 mm × 53 mm × 13 mm and weighing only 30.2 g has been achieved. The maximum linear and rotary speeds have been tested to be over 400 mm/s and 13 rad/s, respectively. The linear and rotary resolutions are 0.42 μm and 12.9 μrad, respectively. The proposed actuator achieves characteristics of large travel, high resolution, fast speed, 3-DOF and a compact structure.

Vibration filtering effect of a novel three-dimensional isolation bearing on metro vibration isolation

Three-dimensional (3D) isolation bearings are effective means to reduce the adverse effects of metro vibrations on structures. The current research focuses on the relationship between the vertical stiffness and metro vibration isolation performance of bearings, but neglects the vibration filtering effect resulting from the inherent resonance and material damping effect of them. In this study, a novel 3D isolation bearing was proposed, composed of spring bearings (SBs) and laminated nature rubber bearings (LNR) vertically in series (denoted as 3DSL), and not only its vertical stiffness but also vibration filtering effect on metro-induced vibration isolation performance were fully studied. The design principle and vibration isolation mechanism of the 3DSL were described, followed by the design and test of three specimens. After that, a case study was conducted to investigate the influence of the 3DSL's filtering effect on metro vibration isolation. The results indicated that the 3DSL exhibited high vertical loading capacity and low vertical stiffness. Furthermore, it was found that the vibration amplitude was slightly amplified in the low-frequency range (1–50 Hz), while significantly reduced in the high-frequency range (50–200 Hz) due to the vibration filtering effect of the 3DSL. Altogether, these results demonstrated that the excellent metro vibration isolation performance of the 3DSL was attributed to the low vertical stiffness and vibration filtering effect. It is recommended to consider both the reduction of vertical stiffness and vibration filtering effect of 3D isolation bearings when designing isolation systems for metro vibrations.

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.

Design and correlation analysis of quasi-zero stiffness passive vibration isolation air spring

Vibration isolation systems are widely used in high-end automobile manufacturing, precision instrument processing, building and bridge seismic resistance, ship machinery noise reduction and other engineering fields, with good development prospects. At present, the existing vibration isolation systems on the market are mainly divided into active and passive vibration isolation systems. Passive vibration isolation does not require external energy input. Its structure is simple and the control scheme is easy to implement. However, passive vibration isolation performs well in high frequency vibration but not in low frequency. As a new nonlinear low-frequency vibration isolation technology, the quasi-zero stiffness vibration isolation system has changed the traditional concept of linear system vibration isolation. In addition, compared with traditional spring, air spring as a new type of elastic vibration isolation mechanism has many excellent performances, such as high fatigue resistance and high stiffness. Therefore, this paper uses air spring to design a passive vibration isolation quasi-zero stiffness air spring structure with good vibration isolation effect, simple structure and low cost in both low-frequency and high-frequency vibration.

Research on seismic performance of new bridge pier seismic reduction isolation system based on shaking table test

In view of the current poor seismic performance of bridges, this paper started with the vibration isolation and reduction mechanism of the bearing, and deduced the coordination relationship between the stress and the deformation of the bearing under the vibration isolation and vibration reduction working conditions. Combined with the shaking table test, the defect that the traditional rubber bearing has poor seismic isolation effect was analyzed. Based on this, a base-bearing double reduction system was proposed and its vibration reduction and isolation effect was compared with the traditional bearing. The shaking table test results showed that, compared with the traditional bearing, the proposed vibration reduction system had better energy dissipation effect and could weaken the apparent cracking damage of the pier under the action of earthquake. Under the 125 m/s2-750 m/s2 peak acceleration excitation of the EI-Centro wave, the proposed vibration reduction system could greatly reduce the displacement variation of the upper main beam by 20 %-47 %. Moreover, the results of dynamic amplification factor measured at the corresponding height of the two types of piers also verified that the proposed base-bearing double vibration reduction system had greater competitiveness when the peak acceleration of seismic waves was less than 500 m/s2.

Investigation of Geotechnical Seismic Isolation Bed in Horizontal Vibration Mitigation

Recently, a ground-borne vibration mitigation solution using rigid wave impeding blocks embedded in the foundation bed of buildings/embankments has emerged as a passive vibration isolation mechanism, wherein energy dissipation due to material damping was often ignored. The present study aims to examine the performance of a flexible foundation bed composed of a sand-rubber mixture (SRM) for ground-borne vibration isolation, referred to as geotechnical seismic isolation (GSI) bed, an emerging trend in low-cost earthquake mitigation studies. Field investigation consisting of vibration measurement on a model footing resting on a GSI bed with SRM and SRM-geogrid composite subjected to horizontal sinusoidal vibration of frequency 10 to 30 Hz with acceleration amplitude of 0.18 g to 0.33 g were undertaken. Further, a three-dimensional finite-element analysis of a model footing resting on a GSI bed made of geogrid reinforced SRM composite is presented. The strain-dependent nonlinear response of soil and SRM were accounted for using suitable hypoelastic and hyperelastic constitutive formulations, respectively. For the GSI bed, SRM with 10% to 50% rubber content and biaxial geogrids were studied. The numerical simulation and field study results were found to be comparable with a nominal difference that verifies the adequacy of the developed numerical modeling procedure. It was observed that GSI (30% rubber content) effectively reduced the vibration acceleration amplitude of the model footing above 40% and 55% for without and with geogrid reinforcement, respectively. Overall, the field experimental and numerical results demonstrate the proposed geogrid reinforced GSI bed as an effective ground vibration mitigation solution for typical industrial environments.

Recent Advances in Quasi-Zero Stiffness Vibration Isolation Systems: An Overview and Future Possibilities

In recent decades, quasi-zero stiffness (QZS) vibration isolation systems with nonlinear characteristics have aroused widespread attention and strong research interest due to their enormous potential in low-frequency vibration isolation. This work comprehensively reviews recent research on QZS vibration isolators with a focus on the principle, structural design, and vibration isolation performance of various types of QZS vibration isolators. The negative-stiffness mechanism falls into two categories by different realization methods: passive and active/semi-active negative-stiffness mechanisms. Representative design, performance analysis, and practical application are elaborated for each category. The results show that passive vibration isolation systems have excellent low-frequency vibration isolation performance under specific payload and design parameters, whereas active/semi-active vibration isolation systems can better adapt to different environmental conditions. Finally, the development trends and challenges of QZS vibration isolators are summarized, and the solved and unsolved problems are highlighted. This review aims to give a comprehensive understanding of the QZS vibration isolation mechanism. It also provides guidance on designing new QZS vibration isolators for improving their vibration isolation performance and engineering applicability.

Curved surface-based vibration isolation mechanism with designable stiffness: Modeling, simulation, and applications

This article develops a novel curved surface-based vibration isolation mechanism for the parametric design of stiffness characteristics, which consists of double linking rods, a coil spring, roller cam followers and curved surfaces. The general modeling derived from Lagrangian dynamics provides design guidance for implementing on-demand stiffness characteristics, such as quasi-zero stiffness, or absolute-zero stiffness in its special situation. The design methodology is then utilized to isolate severe vibrations. In theory, deterministic averaging is applied to predict the dynamical responses to harmonic excitations and evaluate its dynamical characteristics and transmissibility. An experimental platform is built, and vibration tests are conducted to verify the isolation performance. Systematic investigation uncovers prominent design of stiffness and an excellent ultralow frequency performance for vibration isolation.

Vibration suppression of omni-directional mobile robots for inspecting outdoor infrastructure facilities

Infrastructure facilities have been deteriorating and require a vast number of inspections conducted by skilled engineers. Inspection robots are required because of a shortage of skilled engineers. In order to improve the inspection efficiency of outdoor infrastructure facilities, an omni-directional mobile robot that can move freely in all directions has been investigated. However, it is necessary to design a vibration isolation mechanism because the accuracy of the positional inspection of underground objects is adversely affected by vibration in an outdoor environment. We have constructed an experimental setup to evaluate the vibration properties of the wheel. The acceleration characteristics due to the difference between the direction of movement and the speed of the omni-wheel have been evaluated. It was confirmed that periodic vibration occurred by each moving direction of the Omni wheel.

A theory for bistable vibration isolators

Bistable structures have been widely used for vibrational energy harvesting, the corresponding potential vibration isolation application has also received attention recently. This paper presents a general theory for bistable vibration isolators (BVIs) and reveals the bistable vibration isolation mechanism. The nonlinear restoring force and potential energy are obtained through analyzing the general model of BVIs with “three-spring” quasi-zero stiffness (QZS) model. The generalized force and displacement transmissibilities of BVIs are deduced. The theoretical and numerical transmissibilities are calculated. A feasible model of BVIs is applied to quantitatively verify the advantages of BVIs in vibration isolation. The results demonstrate that BVIs can provide negative and softening stiffness characteristics to broaden the isolation band, and a shallower potential barrier and intrawell oscillation are beneficial to vibration isolation. BVIs should be carefully designed to avoid the interwall oscillation to ensure a considerable vibration isolation performance due to the effects of initial equilibrium position. This paper provides a guideline for the design, analysis, and optimization of BVIs.

Filtering property of periodic pile barriers under moving loads

The attenuation property of periodic pile barriers for elastic-wave propagation in certain direction induced by stationary loading sources has been extensively investigated. However, the corresponding studies under moving-load excitations are rather limited due to the complexity caused by the time-varying feature of the induced wave-propagation directions. To address this issue, this paper investigates the vibration isolation performance of periodic pile barriers under moving loads. Using the periodic structure theory, a novel method for deriving the attenuation zones of periodic pile barriers under harmonic moving loads is proposed, which allows calculation of the directional attenuation zones (DAZs) for waves propagating in different directions. This is realized by combining the moving-load speed line with the dispersion properties of periodic pile barriers. A simplified numerical model is also developed to analyze the dynamic responses of the periodic pile barriers in frequency domain. The responses of periodic pile barriers under different moving loads are also conducted in time domain to validate the theoretical predictions. The two-dimensional (2D) Fourier transform in both time and space domain is used to study the filtering property of periodic pile barriers under harmonic moving loads and to reveal their vibration isolation mechanism. It is found that different from the stationary loading situation, for which the induced elastic waves mostly propagate in one certain direction, the filtering property of periodic pile barriers under moving loads is related to its dispersion properties along each possible wave-propagation direction. Besides, the attenuation zones for the moving loads are dependent not only on the dispersion properties of the periodic pile barriers, but also on the loading itself, namely the velocity and excitation frequency of the moving load.

Oscillations simulation of the vibration protection suspended load with a movable base

Reducing the vibration effects on a human operator of a construction, road or handling machine is an urgent task, since the vibration loads produced by the internal combustion engine, vehicle engine interacting with the support surface microrelief, as well as the machine working attachment, adversely affect the machine operator and increase the machine parts and assemblies wear. The operator may develop occupational diseases caused by vibrations. In this regard, the research objective is to develop the mathematical apparatus simulating the dynamic processes of the passive vibration protection systems oscillations at the design stage. Therefore, the problem developing a mathematical model that makes it possible to study the oscillations of a single degree of freedom passive vibration protection systems with any given static characteristic, was solved. On the basis of the dynamic equations of a single translational degree of freedom vibration system describing the vibration protection suspended operator’s seat, the mathematical model solving the differential equation of the system oscillations taking into account the spring loaded mass displacements damping and three-segment static characteristics of the vibration isolation mechanism with limiters was simulated using the package Simulink of MATLAB system. An example of using the developed mathematical model for modelling vibrations of a spring-loaded mass under the sinusoidal external influences is given. The preset vertical displacements of the machine base, i.e. its base chassis act as the external influences. The examples of the obtained simulation results, namely the vertical displacements and accelerations of the spring-loaded mass are presented. The maximum accelerations of the spring-loaded mass were found out to significantly increase, when the machine base forced displacements amplitude exceeds by half of the horizontal section of the quasi-zero static characteristic of the vibration protection suspension.

Analysis of mechanical characteristics and development of vibration isolation mechanism for ground application of marine terrain measurement system

Analysis of mechanical characteristics and development of vibration isolation mechanism for ground application of marine terrain measurement system

Optimal design of 6-DOF vibration isolation platform based on transfer matrix method for multibody systems

The structure parameters of 6-degree of freedom (DOF) vibration isolation platform have a significant effect on its performance. To make the designed vibration isolation platform perform well, non-dominanted sorting genetic algorithm version II (NSGA-II) was applied to optimize its structure based on the transfer matrix method for multibody systems. Firstly, the Jacobian matrix of 6-DOF vibration isolation platform was solved based on kinematics. Secondly, the transfer equation of 6-DOF vibration isolation system was established by the linear transfer matrix method for multibody systems. And the formula of its natural frequency was derived according to the boundary conditions of the system. Thirdly, the manipulability index was constructed based on a dimensionless Jacobian matrix. And a new performance index function was established considering the influence of dynamic isotropic and legs mass. Fourthly, genetic algorithm (GA) and NSGA-II were used to optimize the structure of the 6-DOF vibration isolation platform under the same conditions, respectively. It showed that NSGA-II had higher optimization efficiency, better calculation accuracy and shorter optimization time than that of GA. Finally, NSGA-II was adopted for multi-objective optimization design of 6-DOF vibration isolation platform based on the constraint conditions. Optimal Pareto solutions were obtained, which provides structural parameters for subsequent design work. Therefore, the proposed optimization method and the performance index in this paper provide a theoretical basis for the optimal design of relevant vibration isolation mechanism.

Development of engineering calculation methods of a vibration isolation mechanism with stiffness compensation of the main elastic element

The design and verification calculation of the vibration-isolating mechanism of a pneumatic riveting hammer with stiffness compensation of the main elastic element is devoted. Graphs of the frequency response and amplitude-stiffness characteristics are given. Conclusions about the effectiveness of the vibration-isolating mechanism are made.

Experimental Characterization of the Temperature Influence on the Stiffness and Damping of a Field-Cooled Superconducting Magnetic Suspension

Superconducting magnetic levitation has been used in contactless mechanical components for different applications like bearings or positioning devices. This technology is currently being investigated for its potential use as a vibration isolation and thermal disconnect passive mechanism to support the focal plane array of the ESA ATHENA scientific telescope. Although it is well known that superconducting levitation properties depends on temperature, theoretical models have difficulties with complex bearing geometries or capturing inhomogeneity in material properties. In addition, experimental studies focused on the characterization of the mechanical properties of superconducting magnetic bearings are scant and mostly carried out with zero-field-cooled thrust bearing configurations. In order to increase the maturity of the technology for its potential use in space applications, further experimental research of the superconducting levitation properties at different temperatures is required. In this paper, we present the results of an experimental study of the levitation mechanical properties of a journal superconducting suspension in a high vacuum and temperatures from 90 to 12 K. Axial stiffness quadratically increases at lower temperature and linearly in the radial direction. However, the hysteresis loss factor decreases when decreasing the temperature for both axial and radial directions of displacement. These results demonstrate that the temperature influence on superconducting levitation systems is significant, and thus, mechanical engineers must consider it for design of superconducting levitation systems subjected to temperature variations.

Emergence of Pseudo-Phononic Gaps in Periodically Architected Pendulums

Rejection of unmitigated vibrational disturbances represents an ongoing dilemma in complex linkage systems. In this work, we present an inherent and self-reliant vibration isolation mechanism in architected periodic chains of serially pivoted pendulums. Absorption of external excitations is achieved by virtue of Bragg-type band gaps which stem from the emergent chain dynamics. Owing to its coupled dynamics, the self-repeating cell of a Phononic Crystal (PC) is not trivial and cannot be readily identified from the periodic arrangement by inspection. As such, this work entails the extraction of a "pseudo" unit cell of an equivalent PC lattice from the derived motion equations of a finite chain, which departs from traditional wave dispersion methods. The model presented herein comprises a chain of linked pendulums with periodic variations of inertial/geometrical properties, carrying a payload at one end. We ultimately show evidence of forbidden wave propagation in prescribed frequency regimes, reminiscent of band gaps in PC lattices. The presented framework can be invaluable in applications that require vibration reduction in the delivery of payloads including gantry cranes, robotic arms and space tethers.

Vibration Isolation Mechanism of Concrete Piles for Rayleigh Waves on Sand Foundations

To study the propagation characteristics of Rayleigh waves and the isolation mechanism of a single-row of piles by isolation effects, in this paper we draw a two-dimensional contour map ofζ(normalized acceleration amplitude relative to a measure close at the vibration source) using a vibration test carried out on a sand foundation. In this experiment, we study, in addition to the free field and the single pile cases, settings with two and three piles. The result shows that the vibration caused by the point source in the free field excites Rayleigh waves in a radial direction along the surface of the foundation. Meanwhile, the vibrations of the points along the propagation path on the surface of the foundation are gradually weakened. There is a steady transition when theζdrops to 0.6 and a placid decline whenζdecreases to less than 0.25. The vibration-shielded region, the strengthened region, and the strengthened strips will appear on the surface of the foundation. The vibration-shielded region is located behind the piles, and the region presents a trumpet-shaped area that takes the pile as the vertex. Increasing the quantity of piles contributes to increasing the vibration isolation effect, not only that involving the degree of isolation but also for the area of the shielded area. The vibration-strengthened regions include the diffraction regions at the pile corners on both sides of the single-row of piles and the scattering region at the gaps of the piles. In addition, the composite regions are located among the vibration source and the scattering and diffraction-strengthened regions. Increasing the number of piles has little influence on the scattering and diffraction-strengthened regions but can significantly enhance the vibrations of the composite regions. In general, the vibration-strengthened strips are connected with the scattering-strengthened regions. However, in the test of a single pile, the pile is connected to the diffraction-strengthened regions near its two anterior angles.

Structural Design and Isolation Characteristic Analysis of New Quasi-Zero-Stiffness

This project aimed to design a new type of vibration isolation mechanism with quasi-zero-stiffness (QZS) and analyze the QZS systems’ characteristics by computation and numerical simulation. First, the force–displacement and stiffness–displacement relational expressions of the QZS systems were established based on the study of system force and stiffness characteristics. Second, the nonlinear dynamic equations of the system under the excitation of harmonic force and harmonic displacement were established, and the effect of damping ratio, excitation amplitude, and nonlinear term under the transmissibility mechanism system was analyzed by the average method. Finally, the response time and stability of the QZS vibration isolator were analyzed under different circumstances through numerical simulation. The excitation amplitude, damping ratio, and nonlinear term have a great influence on the transmissibility of the system. In addition, under three different working conditions, the mechanism can have good vibration isolation characteristics and can meet the requirement of low-frequency vibration isolation. A novel type of the QZS systems has been investigated, and it is found that the influence of the excitation amplitude and the nonlinear term are just the same on the system transmissibility through the statics and dynamics calculations. Meanwhile, when damping ratio was increased, the transmissibility of the QZS systems could be reduced. The numerical simulations show that the system has faster response and smaller amplitude for sine wave, single shock, and multi-frequency excitations, which is more suitable for low-frequency vibration isolation.

Dynamics and performance evaluation of an asymmetric nonlinear vibration isolation mechanism

In this work, the dynamics and performance of a harmonically excited asymmetric nonlinear vibration isolation mechanism is investigated using the multi harmonic balance method (MHBM). Asymmetry in the system is introduced in the form of a constant load along with the harmonic excitation. Instead of a truncated cubic nonlinear system considered in the previous works, the fully nonlinear system without any approximation is considered in this study. The MHBM framework considered in this paper is a systematic and computationally efficient method to generate periodic solutions of any order, continue their branches, identify stable, and unstable branches along with the types of bifurcations. Dynamics of the system is investigated with forcing frequency and forcing amplitude as the parameters. With an increase in the value of the constant load, the response diagram shows double folding with softening and hardening behavior and multiple jumps, disappearance of certain types of bifurcations, loss of stability of the periodic solutions, existence of higher order periodic solutions, and chaotic solutions. The transmissibility plots in the presence of the constant load show substantial deterioration in the vibration isolation capability of the isolation system. A comparison of the fully nonlinear system and the truncated cubic system is performed at the end to show that the solutions are qualitatively same but quantitatively different which is an important aspect in practical applications of isolation systems.