Good Vibration Isolation Performance Research Articles

Design of hyperbolic quasi-zero stiffness metastructures coupled with nonlinear stiffness for low-frequency vibration isolation

Quasi-zero stiffness (QZS) metastructures with simple structures exhibit a high low-frequency vibration isolation performance, but the bearing capacity and working regions are limited due to the linear positive stiffness elements. In this study, a novel hyperbolic QZS metastructure coupled with nonlinear stiffness is designed by combining a pair of cosine-shaped beams and arc-shaped beams for low-frequency vibration isolation. Finite element models (FEM) and experimental analysis are utilized to examine the static characteristics of the metastructure, revealing a wide QZS region and significant load-bearing capacity. The metastructure can achieve effective vibration isolation properties through reasonably designing the unit cells. The influence of geometrical parameters on the QZS region is investigated to optimize and realize desirable QZS features. The dynamic equation and response of the vibration isolation system are determined using the harmonic balance method. Moreover, the corresponding displacement transmissibility is confirmed by numerical simulation. The results of the dynamic sweep frequency experiment further verify the validity of the theoretical analysis model. The hyperbolic QZS metastructure system possesses good vibration isolation performance due to the introduction and compensation of a nonlinear positive stiffness arc beam element. The proposed hyperbolic QZS metastructure provides a significant route for the stiffness compensation of metastructures.

Dynamic analysis of a novel multilink-spring mechanism for vibration isolation and energy harvesting

Due to technical limitations, existing vibration isolation and energy harvesting (VIEH) devices have poor performance at low frequency. This paper proposes a new multilink-spring mechanism (MLSM) that can be used to solve this problem. The VIEH performance of the MLSM under harmonic excitation and Gaussian white noise was analyzed. It was found that the MLSM has good vibration isolation performance for low-frequency isolation and the frequency band can be widened by adjusting parameters to achieve a higher energy harvesting power. By comparison with two special cases, the results show that the MLSM is basically the same as the other two oscillators in terms of vibration isolation but has better energy harvesting performance under multistable characteristics. The MLSM is expected to reduce the impact of vibration on high-precision sensitive equipment in some special sites such as subways and mines, and at the same time supply power to structural health monitoring devices.

Integrated vibration isolation and actuation via dual nonlinear stiffness regulation

Integrating vibration isolation and actuation is superior, enabling enhanced vibration isolation performance while attaining controllable load position and attitude. Herein, a novel actuatable quasi-zero stiffness (QZS) vibration isolator (AQVI) is proposed and systematically investigated. The stiffness nonlinearization for QZS is fulfilled by paralleling nonlinear electromagnetic negative and positive stiffness structures. This configuration gives rise to an interesting behavior, that is, the rated load and equilibrium position are tailorable via dual nonlinear stiffness regulation, rendering the load actuatable without a trade-off with the QZS characteristic. The comprehensive static investigation is implemented to fully reveal and verify the dual nonlinear stiffness regulation mechanism. Dynamic governing equations are derived and solved in the cases of dwell and actuation, and it is found that the AQVI is capable of isolating broadband vibrations and tracking prescribed trajectories. Finally, an experimental apparatus is built to evaluate the vibration isolation performance and examine the effectiveness of the load actuation. The sweep excitation test demonstrates that the AQVI has good vibration isolation performance, exemplified by a low resonant frequency of 2.5 Hz and a small isolation starting frequency of 3.6 Hz. The load actuation test validates that the AQVI under open-loop control is competent to actuate the load following the desired trajectory while retaining excellent vibration attenuation. The proposed AQVI provides a novel paradigm for devising QZS isolators that are insensitive to the load and working point, shedding promising light on applications requiring integrated vibration isolation and actuation.

Performance of rubber-concrete composite periodic barriers applied in attenuating ground vibrations induced by metro trains

Recently, the use of periodic vibration isolation barriers (PVIBs) has emerged as a significant method for attenuating environmental vibrations along the propagation path. Previous studies have indicated that periodic infilled trenches and piles can effectively isolate low-frequency surface waves. However, a considerable number of these periodic structures require full-size shipments or cast-in-place construction, thus increasing the shipment difficulty or construction period. In addition, few experimental studies have reported on the performance of PVIBs under underground excitation. To solve these problems, this study proposes a novel periodic composite rubber-concrete barrier (PCRCB) with prefabricated assembly characteristics. A laboratory test was performed, in which the calculated frequency band gap (FBG) and attenuation zones of the optimised PCRCB were validated under ground-borne and underground hammering excitations. Then, a numerical model was developed to analyse the vibration mitigation effect of the optimised PCRCB considering the metro train loads. The results of the laboratory study demonstrated that the depth of the impact load affects ground vibration attenuation. The optimised PCRCB has been proven to exhibit good vibration isolation performance. The results of the numerical study demonstrate that the vibration mitigation effect of the PCRCB on the ground surface is good under underground metro train loads. The insertion loss (IL) increases, but its value is less than 2 dB, with the ratio of burial depth to tunnel base depth increases from 1 to 2 times. Accordingly, the ratio of the burial depth to the tunnel base depth is recommended to be 1 in the vibration isolation project of an underground metro train.

Theoretical modeling and analysis of a quasi-zero-stiffness vibration isolator equipped with extensible and axially magnetized negative stiffness modules

Quasi-zero-stiffness (QZS) isolation systems have demonstrated good performance in low-frequency vibration isolation fields. However, the existing QZS isolation systems with traditional negative stiffness elements cannot support high payloads under miniaturization and simplification. To give some beneficial insights into high loading capacity, optimized structure, and good vibration isolation performance, a novel axially magnetized negative stiffness module (MNSM) is proposed based on the concepts of modularity and expansibility. Concretely, an axially magnetized negative stiffness unit (MNSU) is designed as the fundamental building block of MNSM, and the proposed MNSM can be composed of different axially magnetized negative stiffness units (MNSUs) for diversified requirements. To effectively investigate the characteristics of the MNSU, a computationally high efficient equivalent surface current method is developed. As a result, two types of MNSUs with optimized parameters are achieved, and their design procedures are presented respectively. To verify the benefits of the MNSMs, the designed QZS isolator is theoretically modeled and solved with the average method and then verified through the Runge–Kutta method. Through analyzing the isolation systems with MNSMs under different nonlinearities and dynamic parameters, the results indicate that the proposed MNSMs can endow the QZS vibration isolator with a lower resonant frequency, a wider isolation frequency range, and a smaller transmissibility. Additionally, it is also demonstrated that there is an inverse relationship between the complexity of the MNSM structure and the sensitivity of the isolation system.

Analytical modeling of a device for vibration isolation and energy harvesting using simply-supported bi-stable hybrid symmetric laminate

The bi-stable hybrid symmetric laminate (BHSL) has been investigated for vibration isolation and energy harvesting, by taking advantage of its bi-stable characteristic. A device using simply-supported BHSL is proposed to integrate these two functions. This device is called the quasi-zero-stiffness (QZS) vibration isolator with a piezoelectric element (PE). An equivalent theoretical model is developed based on the restoring force-displacement curve of BHSL. The approximate analytical solutions and direct numerical solutions are obtained by the harmonic balance method and the Runge-Kutta method, respectively. Displacement transmissibility is utilized to quantify the vibration isolation performance of this vibration isolator. The influences of the excitation amplitude, the length of BHSL, the width of BHSL and the load resistance are analyzed. The results show that adjusting these parameters can improve the vibration isolation performance and energy harvesting performance. The QZS vibration isolator with PE achieves the goal of higher power density under a low-frequency and low-amplitude excitation and simultaneously has a good vibration isolation performance.

Design of micro-vibration suppression platform based on piezo-stack array intelligent structure

Micro-vibration seriously affects the precision and stability of precision mechanical systems. Aiming at the micro-vibration existing in the semiconductor package positioning system, this paper first designed an active-passive integrated actuator (APIA) based on piezo-stack array, which compensated the mechanical error through the piezo-stack array to improve its positioning accuracy. Based on the APIA, a 6-PUU parallel micro-vibration suppression platform (MVSP) was designed, in which the two APIAs were combined into one and installed on the lower platform along the tangential distribution of the circle, and then the kinematic model of the platform was established. Finally, the PID control algorithm was used to conduct vibration isolation experiments on the MVSP. The experimental results showed that the MVSP had good vibration isolation performance for micro-vibration, the vibration isolation frequency band was above 5 Hz, and the attenuation of micro-vibration signals was between 18% and 64%.

Tilt Active Vibration Isolation Using Vertical Pendulum and Piezoelectric Transducer with Parallel Controller

Tilt vibrations inevitably have negative effects on some precise engineering even after applying horizontal and vertical vibration isolations. It is difficult to adopt a traditional passive vibration isolation (PVI) scheme to realize tilt vibration isolation. In this paper, we present and develop a tilt active vibration isolation (AVI) device using a vertical pendulum (VP) tiltmeter and a piezoelectric transducer (PZT). The potential resolution of the VP is dependent on the mechanical thermal noise in the frequency bandwidth of about 0.0265 nrad, which need not be considered because it is far below the ground tilt of the laboratory. The tilt sensitivity of the device in an open-loop mode, investigated experimentally using a voltage controller, is found to be (1.63±0.11)×105 V/rad. To compensate for the hysteresis nonlinearity of the PZT, we experimentally established the multi-loop mathematical model of hysteresis, and designed a parallel controller consisting of both a hysteresis inverse model predictor and a digital proportional–integral–differential (PID) adjuster. Finally, the response of the device working in close-loop mode to the tilt vibration was tested experimentally, and the tilt AVI device showed a good vibration isolation performance, which can remarkably reduce the tilt vibration, for example, from 6.0131 μrad to below 0.0103 μrad.

Design of quasi-zero stiffness joint actuator and research on vibration isolation performance

This paper proposes a new QZS joint actuator, which uses a torsion electromagnetic spring (TES) that can generate negative stiffness in parallel with a flexible rod with positive stiffness to obtain QZS characteristics with high static and low motion. In this paper, the expression of TES magnetic moment and stiffness is obtained by static analysis, the simulation is carried out by ANSYS Maxwell finite element software and the effect of TES structure parameters and current on its negative stiffness characteristics is analyzed. Then the dynamic model of QZS joint actuator is established, and the amplitude-frequency response function and torque transmissibility analytical expression are obtained by harmonic balance method, the good vibration isolation performance of QZS joint actuator is revealed. Finally, the stiffness and vibration isolation performance experiments are carried out with the QZS joint actuator to verify the correctness of the theoretical analysis, which indicates that it has a wide range of application background and research significance.

Semi-Active Predictive Control of Isolated Bridge Based on Magnetorheological Elastomer Bearing

Time-delay of magnetorheological elastomer bearing (MRB) can bring structural response menace to bridges. This paper investigates a bridge pier-bearing semi-active-coupling control method based on model predictive control (MPC). The presented strategy takes the structure prediction model to predict the state responses of the controlled plant in a period of future time. Then, the control law can be determined by solving a finite horizon optimization problem. The peak shearing force of pier top, the displacement and the acceleration of beam are chosen as control goals, and the vibration isolation rate is applied to characterize the vibration isolation effect. It is noted that MPC method naturally takes the time-delay and uncertain interference into consideration, and significantly improves the control performance of the system. Finally, the numerical example is described and the seismic response of isolated bridge based on MRB is analyzed. The simulation results show that predictive control can be used to control the time-delay of bridge system in different degrees. The best control performance is at 0.4 s. Even if the time-delay reaches 2 s, it is still good. Therefore, the control method significantly reduces the adverse effects of time-delay on the system, and has a good vibration isolation performance.

Design and analysis of an active‐controlled hydraulic low‐frequency vibration isolator

This study proposes an active-controlled hydraulic low-frequency vibration isolator. The vibration isolator can achieve large equivalent mass and quasi-zero dynamic stiffness by combining the fluid inerter with the hydraulic active compensation. Thus, good vibration isolation performance at ultra-low frequency can be realised. The model for the dynamics of the device is set up. The principle of low-frequency vibration isolation is explicated. The natural frequency and its influencing factors are analysed. Finally, preliminary experimental research works are carried out. The results indicate that low-frequency vibration can be effectively isolated by the device proposed in this study.

Characteristic analysis of a quasi-zero-stiffness vibration isolator

The frequency range over which a linear passive vibration isolator is effective, is often limited by the stiffness required to support a static load. And this can be improved upon by employing nonlinear negative stiffness elements to get a low dynamic stiffness. In this paper, a quasi-zero-stiffness (QZS) system comprising an air spring with positive stiffness and Euler buckled beams with negative stiffness is studied. Compliant mechanisms are also introduced into the QZS system to achieve quasi-zero-stiffness characteristics under a variable load. Static mechanical characteristics of the system are analyzed by the FEM, and load-displacement curves and stiffness-displacement curves of the system under different working conditions are given. The natural frequency and the response curve of the system are obtained through dynamic analysis. It is concluded that the system has good vibration isolation performance in low frequency range.

Dynamic modeling and experimental analyses of Stewart platform with flexible hinges

A new dynamic model of the Stewart platform with flexible hinges is proposed based on the Kane equation combined with the principle of virtual powers. Firstly, the model and coordinates introduced are described. Specifically, the velocity and acceleration of each part are obtained through kinematics analysis. Secondly, balance equations are subsequently formulated using the principle of virtual powers. Noting that the vibration amplitude of satellites is very small in the space microgravity environment, a linearly simplified form of the dynamic equation of the Stewart platform with flexible hinges is obtained. Finally, the validity of the equations is experimentally and numerically verified, and it is also demonstrated that the proposed platform possesses a good vibration isolation performance. All the results presented in this paper lay the foundation for further study on vibration control using a Stewart platform.

A six degree of freedom passive vibration isolator with quasi-zero-stiffness-based supporting

A six degree of freedom nonlinear passive vibration isolator is proposed based on Stewart platform configuration with the quasi-zero-stiffness structure as its legs. Due to the high static stiffness and low dynamic stiffness of each leg, the proposed six degree of freedom system can realize very good vibration isolation performance in all six directions while keeping high static load-bearing capacity in a pure passive manner. The mechanic model of the proposed six degree of freedom isolator and the dynamic equation of the isolator are established successively. Theoretical analysis on cross coupling stiffness reveals that the system can demonstrate quasi-zero-stiffness property in all six degree of freedom. Moreover, an analysis on stability shows that the condition of structural parameters for the isolator to realize quasi-zero-stiffness is also the stability boundary of the system. A series of numerical simulations on displacement transmissibilities in coupled degree of freedoms, the coupling effects of transmissibility, and a dynamic response in random excitation are carried out to show the effectiveness of the proposed six degree of freedom isolator, as well as the influence of structural parameters on vibration attenuation performance. Considering its high performance in a simple passive manner, it can be foreseen that the proposed six degree of freedom isolator will be applied in various engineering practices with multi-degree of freedom vibration isolation.

Effect of periodic pile row in subway vibration Isolation

At present measures for reducing vibration by subway are mainly from vibration source, path and building, where vibration isolation on path is an important one. This article studies the effect of periodic pile row in subway vibration Isolation for a planned building close to a subway in Beijing based on phonon crystal theory. First test the vibration of surface field and get the vibration characteristic frequency. Second calculate the attenuation zone of periodic pile row which contains the vibration characteristic frequency, and get the parameter combination of the pile. Third A track-tunnel-soil-building 3D finite element model was established by software ANSYS. Input the force of vibration source calculated by the model of vehicle and guideway coupling. Then use the finite model to calculate the effect of the periodic pile row. The result shows that the working frequency of the periodic pile row is higher than 12Hz. The Damping capacity of the largest Z vibration level is 4.13dB on the first floor, and the Damping capacity becomes greater with the increase of the floor. Periodic pile row based on phonon crystal has a wide vibration isolation frequency and a good vibration isolation performance.

A 6DOF passive vibration isolator using X-shape supporting structures

A novel 6 degree of freedom (6-DOF) passive vibration isolator is studied theoretically and validated with experiments. Based on the Stewart platform configuration, the 6-DOF isolator is constructed by 6 X-shape structures as legs, which can realize very good and tunable vibration isolation performance in all 6 directions with a passive manner. The mechanic model is established for static analysis of the working range, static stiffness and loading capacity. Thereafter, the equation of motion of the isolator is derived with the Hamilton principle. The equivalent stiffness and the displacement transmissibility in the six decoupled DOFs direction are then discussed with experimental results for validation. The results reveal that (a) by designing the structure parameters, the system can possess flexible stiffness such as negative, quasi-zero and positive stiffness, (b) due to the combination of the Stewart platform and the X-shape structure, the system can have very good vibration isolation performance in all the 6 directions and in a passive manner, and (c) compared with the simplified linear-stiffness legs, the nonlinearity of the X-shape structures enhance the passive isolator to have much better vibration isolation performance.

An Application of Oil-Hydraulic Actuator for Active Suspension of Railway Vehicle. Experimental Study with Actual-Size Vehicle Model on Test Stand.

Active suspensions have been studied to improve the ride quality of railway vehicles. In many cases, pneumatic actuators were employed in those studies. This paper deals with the application of oil-hydraulic actuators, which are expected to have stronger control effect on the running vibration. This is examined experimentally by using an actual-size vehicle model on a test stand. The LQG control law, in which state variables are estimated from measurable accelerations on actual railway vehicles, is adopted. The LQ control law, in which state variables are measured accelerations and their integrated quantities, is also adopted. The results show that both controllers have good vibration isolation performance in both harmonic and random excitations. The control force and the stability are improved by decreasing the lateral damping in parallel with the actuator in the secondary suspension. In this case, it is confirmed that the relative displacement between the car body and bogie does not increase.