Passive Isolation System Research Articles

Application of one-dimensional periodic layers with elastomeric seismic isolators for three-dimensional isolation

Three-dimensional (3D) seismic isolation is an appealing idea to protect structures and their components from earthquake-induced horizontal and vertical ground motions. Past attempts to develop 3D isolation systems were ineffective due to their complexity and reliability issues. One-dimensional periodic material-based isolation systems (1D-PIS) have been extensively researched for applications as raft foundations due to their simple and construction-friendly unit cell designs. These systems aim to attenuate seismic excitations in both horizontal and vertical directions. However, the effectiveness of 1D-PIS in mitigating 3D excitations may be limited due to the potential mismatch between the frequency content of horizontal and vertical vibrations. The present study proposes to combine a conventional horizontal isolation system with a 1D-PIS in the vertical direction to achieve a simple, passive, and efficient three-dimensional isolation system for structures and components. The 1D-PIS is strengthened by incorporating steel shims within the rubber layers and implementing steel casings at its periphery, enabling its utilization as an isolated system. Small-scale experimental and numerical investigations were conducted on strengthened 1D-PIS to study its isolation characteristics in the vertical directions. The study reveals that infinite boundary conditions required for the efficacy of 1D-PIS were achieved through lateral restraint provided by steel shims and steel casings. Notably, the individual isolation characteristics of the conventional and the 1D-PIS are not compromised in the combined isolation system. Nonlinear time history analysis on a prototype combined isolation system confirms its effectiveness in attenuating the seismic response under simultaneous horizontal and vertical ground motions.

Research on a Bridge Hybrid Isolation Control System Based on PID Active Control and Genetic Algorithm Optimization

A bridge hybrid isolation system, integrating both active and passive control strategies, is proposed and investigated to enhance seismic performance. The system is modeled as a two-layer structure, with the upper layer subjected to active control via a Proportional–Integral–Derivative (PID) controller, and the lower layer employing a conventional passive base isolation system. The displacement response of the superstructure is minimized by the control forces generated by the PID controller, which also accounts for the reaction forces transmitted to the lower isolation layer. To optimize the controller’s performance, a genetic algorithm is implemented for real-time tuning of the PID parameters. Numerical simulations, conducted using the Newmark method, are employed to assess the influence of active control on the lower isolation system. The results reveal that, while active control increases the peak displacement of the superstructure to some extent, it significantly prolongs the structural period, thus enhancing the system’s overall seismic resilience and stability.

Hybrid vibration isolator based on piezoelectric actuator and metal rubber and its adaptive control method

To achieve vibration isolation across the entire working frequency range, this paper proposes a novel hybrid vibration isolator combining metal rubber and piezoelectric actuators, along with an adaptive active control algorithm. The passive isolation system allows for manual adjustment of stiffness and damping based on the preload, overcoming the issue of fixed stiffness and damping in traditional passive isolation units. For the active isolation system, an improved Filtered-x Normalized Least Mean Squares with adaptive step size active control algorithm is proposed, overcoming the problem of narrow frequency range applicability in traditional active control algorithms. A hybrid model of electromechanical coupling and hysteresis for the piezoelectric actuator is developed for the secondary path in the algorithm. Experimental results confirm that the hybrid isolator possesses vibration isolation capabilities within the 5–500 Hz working frequency range, with vibration suppression at the first and second resonance frequencies improved by 98.9% and 92.2%, respectively, compared to the passive system. Additionally, the hybrid isolator effectively suppresses complex multifrequency signals and demonstrates robustness and adaptability. This research provides advanced technological means to address complex vibration problems, and establishes both theoretical and practical foundations for multi-degree-of-freedom vibration isolation.

Adaptive Passive Seismic Isolation System for Mitigating the Acceleration Response of Floor-Mounted Equipment

Adaptive Passive Seismic Isolation System for Mitigating the Acceleration Response of Floor-Mounted Equipment

Improvement of ride quality for a wheel loader with semi-active cab isolation system via fuzzy self tuning of PID controller

Improving driver ride comfort of a wheel loader is important to avoid potential health hazards from the whole-body vibration. A fuzzy self-tuning of PID controller is designed to control the damping coefficient of Semi-active cab isolation system (SCIS) for a wheel loader. A dynamic model of a wheel loader is establish under survey conditions for analysis and evaluation. The r.m.s acceleration responses of the vertical driver's seat and pitch angle of vehicle body according to ISO2631-1 (1997-E) are chosen as objective functions. The effectiveness of the proposed control strategy is analyzed through simulations involving excitations for a random road profile in time domain. The proposed SCIS is simulated and analyzed by Matlab/Simulink software in comparison with a passive cab isolation system (PCIS) under survey conditions. The achieved results indicate that ride comfort effectiveness of a wheel loader with SCIS is better than PCIS under survey conditions. In addition, the study results are the initial basis for optimizing controller parameters.

Overview of Onera acoustic active control activities in helicopter cabin

Within a helicopter cabin, passengers are in close proximity to disturbing sources that contribute to interior noise: main and tail rotors, engines, main gearbox and aerodynamic turbulence. These sources generate bending vibrations of the entire tail boom, induced vibrations in the cabin at blade passing frequencies, transient vibrations of rotor blades and structure borne noise induced by gear meshing within gearboxes. Conventional passive systems, as trim panels or passive anti-resonance isolation systems, are still the main way to control the cabin noise. Nevertheless, (semi) active control techniques have been the subject of numerous studies for decades, especially to improve the performance of passive concepts in low frequencies. Unfortunately, many turned out to be unreliable or completely inapplicable because problems of robustness, time convergence of algorithms, but also a difficult identification of optimal locations for actuators and sensors or a high added mass and electrical power. The objectives of this paper is to describe in details the research projects in active noise control carried out at Onera since the 1990s, i.e. from numerical modeling and laboratory tests to flight tests in helicopter cabin. This overview will feed into the reflection on the renewal of active vibro-acoustic control within different laboratories.

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.

Experimental Study on the Active Control and Dynamic Characteristics of Electromagnetic Active–Passive Hybrid Vibration Isolation System

Targeting the problems of conventional active–passive hybrid vibration isolation systems, such as low output force, poor bearing capacity, large power loss and inability to withstand strong impacts, this paper proposes an active–passive hybrid vibration isolation system combining an electromagnetic actuator, rubber passive vibration isolator and magnetorheological damper. The overall design of the hybrid vibration isolation system is first introduced. Then, a two-dimensional electromagnetic frequency-domain simulation is carried out on the electromagnetic actuator to obtain the output characteristics. A three-dimensional modeling is conducted to simulate the electromagnetic–mechanical coupling in the time–frequency domain to obtain nephograms of the magnetic flux diffusion distribution and power loss. Then, a dynamic stiffness test is carried out on the rubber vibration isolator to obtain the dynamic stiffness characteristics and the damping angle curve. At the same time, an adaptive suppression filtered-x least mean square (ASFXLMS) algorithm is proposed to adjust the update of the control weight coefficients to ensure that the current signal does not exceed the effective operating range of the actuator when the electromagnetic actuator is subjected to strong external disturbances. Finally, a hybrid vibration isolation system-based active vibration isolation experimental platform is built, and multifrequency line spectra active–passive vibration isolation experiments are carried out. The results demonstrate that the hybrid vibration isolation system has good control effects in the time–frequency domain and shows good robustness when subjected to impact.

A Hybrid Vibration Isolator Based on Elastomeric and Electromagnetic Restoring Force

The protection of structures and machines from ground vibrations is a deeply felt and widely studied problem. These vibrations are typically generated by the operation of machines, vehicular traffic, seismic events, shocks, explosions, etc., and are generally characterized by frequencies that are not known a priori, making the use of passive isolation systems problematic. Just away from the source, ground vibrations have a predominantly horizontal component. To meet the conflicting requirements of passive isolation systems, which should have higher stiffness when the structure is at rest and lower stiffness when the ground forces it to vibrate, active or semi-active isolation systems can be adopted. In the following article, the possibility of adopting a hybrid isolator is evaluated; it consists of shear-stressed elastomeric pads coupled with an electromagnetic actuator; the latter consists of three coils, two of which are connected to the ground and the other one to the body to be isolated. This kind of isolator has the same flexibility and adaptability as the active ones, with the advantage of ensuring its functioning even in the absence of an external energy source. Its flexibility is due to the presence of a smart element that allows one to tune the characteristics of the isolator to consider the instantaneous isolation requirements. The proposed solution allows one to modify the isolation system’s characteristics in a sufficiently wide range of displacements equal to that defined by the maximum allowed deformation of the elastomeric pads. This paper reports the description of the isolation system and an analytical model to describe its restoring force; then, an experimental setup is adopted to identify the parameters of the analytic model; finally, several simulations are reported to compare the analytical and the experimental trends of the restoring force and to characterize the isolator.

Passive Isolator Design and Vibration Damping of EO/IR Gimbal Used in UAVs

One of the most critical factors affecting the quality of the images captured by the surveillance systems used in the unmanned aerial vehicles is the vibrations transmitted from the aircraft to the gimbal. The gimbal used in unmanned aerial vehicles is essential equipment, holding the camera steadily and accurately and pointing it in the desired direction. Within the scope of this article, a passive vibration isolation system design has been made for the two-axis electro-optical gimbal used in the mini unmanned aerial vehicle. By choosing the spring-damper system among different methods, the design that isolates the harmonic vibration from the platform on a single axis has been made using the analytical method. The analytical method was used to create a design that isolates the harmonic vibration from the platform along a single axis. In addition, the part named 'Pan Yoke', which contains this damper system, was designed with a computer-aided design program, and natural frequency values were checked with Ansys modal analysis. The frequency of the vibration transmitted from the air vehicle to the gimbal and the natural frequency of the designed part have been determined to be close to each other, at around 200 Hz. The natural frequency values of this part were optimised with various design changes and topology optimisations to prevent the part from resonating.

Dynamic Research on Low-frequency Vibration Isolation Tables

In the paper, an establishment of dynamic characteristics of tabletops of the newly-developed optical tables is being discussed upon. Low-frequency vibration isolation systems are reviewed. Theoretical and experimental tests have been performed. Dynamic models of an optical table on a vibrating platform at different excitations have been developed, the dynamic displacement and the resonance frequencies of the system have been established and vibration transmissibility curves have been presented. The obtained dynamic characteristics of the mechanical passive low-frequency vibration isolation system show that such a system is able to isolate the vibrations effectively. The results of the performed experimental tests confirm the data of the theoretical research.

Design of a compliant lever-type passive vibration isolator with quasi-zero-stiffness mechanism

This paper focuses on design and analysis of a hybrid passive vibration isolation system that uses both compliant lever-type and quasi-zero-stiffness (QZS) mechanisms. By using the lever-type mechanism, an inertial coupling induced antiresonance frequency is generated and the effective mass of the system is increased, which improve low-frequency vibration isolation performance. The QZS mechanism is used to provide very low stiffness, which in turn lowers the resonance and antiresonance frequencies of the system. Hence, the lower limit of the isolation bandwidth can be significantly reduced. After examining the system analytically, a finite element model is formed. Finally, the design is manufactured and tested. The tests validate the analytical and numerical calculations, thereby confirming that lower limit of the isolation frequency range can be substantially decreased by adjusting the effective mass and the effective stiffness of the system.

Modeling and characteristics study of double-diamond bionic vibration isolation system with inerter

An integrated and bionic passive vibration isolation system is proposed based on the double-diamond bionic structure and inerter to solve the problems of poor low-frequency vibration isolation performance, narrow vibration isolation frequency band, and big additional mass of current passive vibration isolation system. To analyze the low-frequency vibration isolation performance and the valuable frequency band, the nonlinear dynamic model of the system is established, then the system transmission characteristics and stability are studied. It is found that the system can reduce the amplitudes of resonant peaks, broaden the valuable frequency band, and the system stability is excellent. Seen from the performance analysis, the introduction of the inerter with smaller additional mass makes the system have better vibration isolation performance and wider effective vibration isolation frequency band. The proposed system provides a new solution for vibration control in practical engineering.

Band-stop characteristics of a nonlinear anti-resonant vibration isolator for low-frequency applications

In order to broaden the vibration attenuation bandwidth of passive isolation systems in low-frequency applications, a nonlinear anti-resonant vibration isolator was studied by coupling a lever-type vibration isolator with a nonlinear vibration absorber. By appropriately designing the structural parameters, a wider double-attenuation stop-band emerges from the coupling of the levered mass and the absorber mass. Theoretical results show that the bandwidth of the proposed NL-AVI is much wider than that of an existing lever-type vibration isolator. A parametric influence investigation shows that the transmissibility and width of the stop band can be flexibly designed with structural parameters. The cubic nonlinearity of the vibration absorber has the effect of shifting the anti-resonant frequency and the resonant peak to higher frequencies, thereby increasing the stop band width. The proposed nonlinear anti-resonant vibration isolator provides a distinctive mechanical mechanism for realizing a combination of band transmissibility and width in the vibration attenuation characteristics and has been successfully validated by experimental prototypes for their advantageous performance in low-frequency vibration isolation.

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.

Seismic collapse probability and life cycle cost assessment of isolated structures subjected to pounding with smart hybrid isolation system using a modified fuzzy based controller

The possibility of pounding on isolated structures with surrounding moat walls is one of the concerns in the design of isolation systems, especially in pulse-type near-field earthquakes. This paper puts forward the seismic probability assessment of structures equipped with passive and smart hybrid isolation systems by considering pounding possibilities. This investigation is performed on isolated structures equipped with a high damping rubber bearing (HDRB) considering stiff moat walls around the structure. In the Hybrid isolation system, magnetorheological dampers (MR) are considered an adaptive dissipation energy device along with isolators using an optimized novel interval Type-2 fuzzy logic controller with adaptive red-zone function (IT2FS + RZF) to reduce pounding possibilities. The fragility curves of the building for various cases are determined using incremental dynamic analysis (IDA), and possible damage costs are evaluated by using exceedance probability in each damage level. This study concludes that the collapse probability of the isolated structures with restrains at the code-based distance is over the acceptable limit of ASCE 7–22. The smart additional damping system with the proposed controller reduces the possible damage cost of the building by about 64 % compared to the uncontrolled system and puts the collapse probability of the structure in the acceptable range.

Evaluating the use of variable curvature frictional isolators to mitigate the adverse effects of internal lateral impacts

Under high magnitude ground motions, excessive base displacement can generate internal lateral impacts between inner sliders and restraining rims of frictional isolators. This study aims to evaluate the use of variable curvature frictional isolators to mitigate the adverse effects of these internal impacts. One specific geometry of the sliding surface was studied, obtained by revolving an ellipse around a vertical axis. Due to the shape of the sliding surface, the pendular force transmitted by the bearing exhibits a smooth hardening behavior. A physical model for dynamic analysis of base-isolated structures equipped with variable curvature frictional bearings is presented. This numerical model accounts for effects such as large deformation, P-Δ, sticking, uplift, and lateral and vertical impact behavior. The impact parameters of the physical model were calibrated using a Finite Element Model subjected to dynamic loads. A three-dimensional model of a base-isolated structure was developed to characterize the dynamic behavior of an adaptive passive isolation system under different base displacement demands. Finally, a nonlinear reinforced concrete frame equipped with isolators with spherical or elliptical sliding surfaces was examined to determine the average reduction in the Engineering Demand Parameters affected by internal impacts. On average, reductions of 44%, 11%, 8%, and 6% in the maximum response of the base shear, first inter-story drift, second inter-story drift, and third inter-story drift are obtained by replacing classical Friction Pendulum System (FPS) devices with variable curvature isolators.

Experiment and analysis of active vibration isolation system based on rigid pedestal using SDOF actuator

This paper is about the active-passive isolation system based on single degree of freedom electromagnetic actuator and focuses on different control effect of different measure points. In view of this problem, the authors analyze the vibration characteristics of the active and passive vibration isolation systems of electromagnetic airbags under single and multi-vibration isolators. Then they decompose the rigid pedestal vibration into two orthogonal components, the vertical translation and the fix axis rotation. After that compare simulation and experiment results in terms of the control effect when the single active-passive isolator location varies. Finally, the authors draw a conclusion about the reason why the rigid pedestal vibration can be globally controlled by arranging more than 3 active-passive isolations and design a multiple isolator system experiment to verify.

Hybrid isolation system with wire‐rope isolators and magnetorheological dampers for the isolation of blast‐induced vibration

The aim of this research is to improve the isolation performance and energy dissipation characteristics of the widely used passive isolation (PI) system with wire-rope isolators (WRIs) under the excitation of various blast-induced vibration loads through the use of a semi-active control system. A hybrid isolation (HI) system composed of WRIs and an innovative magnetorheological (MR) damper equipped with a motion controller is proposed, which can protect sensitive equipment and nonstructural elements by attenuating their dynamic response. The designs of the MR damper's magnetic circuit and control system were validated by establishing an electromagnetic field finite element model and a motion controller simulation model, respectively. A series of quasi-static and shock table tests were conducted on models using three types of isolation: (1) a PI with WRIs, (2) an HI without a motion controller, and (3) an HI alone. The results show that the proposed MR damper can effectively restrain the tensile vibration of WRIs, significantly increase the isolation rate, and provide greater energy dissipation in HI systems with different weights of static loading subjected to various blast-induced vibration loads.

Numerical studies regarding the behaviour a large span roof under seismic load when using anti-seismic devices

Abstract The study presents the data obtained on a large span structure equipped with passive seismic isolators, placed at roof level, when subjected to multiple seismic loads. Three distinct passive isolation systems are taken into consideration to reduce the seismic response of the structure. The first case uses Friction Pendulum Systems (FP), the second uses a combination of High Damping Rubber Bearing (HDRB) and low friction pot-bearing systems, and the third implies the use of Lead Rubber Bearings (LRB) and low friction pot-bearing systems. Using seven sets of accelerograms, recorded and generated, the values for the main seismic response parameters are extracted in to underline the efficiency of the proposed systems. The results obtained in terms of natural vibration period, accelerations, bending moment, base shear are compared.