Tuned Vibration Absorber Research Articles

Potential reduction of the inertial mass of tuned vibration absorbers by means of mechanical impedance matching

In this paper, a new technology for vibration isolation based on impedance matching using a linear magnetic gear is presented. Using that operational principle, a prototype of an Impedance Matching Tuned Vibration Absorber (Z-TVA) is designed, manufactured and tested. An inertial mass is coupled to the fast-moving stage of the linear magnetic gear, increasing its motion proportionally to the square of the gear ratio, and therefore its effectiveness as a vibration absorber.A theoretical model is postulated and validated with tests at a component level, demonstrating a promising solution for drastically reducing the required mass and installation and maintenance cost. A potential reduction of the required mass of a vibration absorber of more than an order of magnitude is predicted.

Effects of modal energy scattering and friction on the resonance mitigation with an impact absorber

A linear vibration absorber can be tuned to effectively suppress the resonance of a particular vibration mode. It relies on the targeted energy transfer into the absorber within a narrow and fixed frequency band. Nonlinear energy sinks (NES) have a similar working principle. They are effective in a much wider frequency band but generally only in a limited range of excitation levels. To design NES, their working principle must be thoroughly understood. We consider a particular type of NES, a small mass undergoing impacts and dry friction within a cavity of a base structure (vibro-impact NES or impact absorber). The nonlinear dynamic regimes under near-resonant forcing and resulting operating ranges are first revisited. We then investigate how off-resonant vibration modes and dissipation via impacts and dry friction contribute to the vibration suppression. Moreover, we assess the effectiveness of the impact absorber for suppressing multiple resonances in comparison to a linear tuned vibration absorber (LTVA) and a pure friction damper with the same mass.

Structural modification based analysis and design of tuned mass dampers

This article discusses the design of tuned vibration absorber for structures. A central notion in the identification of the parameters of a tuned mass damper (TMD) absorber for MDOF systems is that of modal mass of the original structure. The modal mass, as it is well known, is associated with the mode of vibration of the original structure whose frequency is required to be absorbed. The estimation of the modal mass can be achieved by either using a mass, stiffness, and damping model of the structure or, for an existing in service structure, from experimental modal analysis. In both of the above cases inaccuracies are introduced due to modeling errors and experimental noise. This article sets the theory of TMD in the context of structural modification. This enables the design of TMD by using only the frequency response function of the primary system without taking into consideration the original mass or modal mass. The theory developed herein is for one degree of freedom undamped primary vibrating system. The proposed structural modification based methodolgy of designing TMD is demonstrated on a specific single degree of freedom vibrating system.

Nonlinear magnetic vibration absorber for passive control of a multi–storey structure

A nonlinear magnetic vibration absorber is presented and used to control vibration of a three–storey structure. A distinctive feature of the absorber concerns its versatility for tuning the linear and nonlinear stiffness coefficients, depending on simple geometric design parameters such as the distance between fixed magnets and the moving one. In particular, the absorber can be set either as a nonlinear tuned vibration absorber, a nonlinear energy sink, or a bistable tuned vibration absorber, according to whether the linear stiffness term is positive, vanishing, or negative. The response of the primary structure and the vibration mitigation are investigated in the cases of impulsive shock, free vibration with imposed initial displacement, and single frequency excitation. Significant reductions of the primary structure vibrations are obtained for the three cases investigated, showing the ability of using a vibration absorber only relying on magnetic forces for passive control. The detailed comparisons of the absorbers performance show that, in this case study, no general guidelines can be easily deduced for selecting one of the three tunings for a nonlinear absorber. Depending on the excitation, the vibratory levels, and the frequency content of the excitation, the three configurations show advantages and drawbacks that are discussed.

Theoretical and experimental investigation of a tunable vibration absorber with liquid elastic chamber

This paper presents a novel Tunable Vibration Absorber with Liquid Elastic Chamber (TVA-LEC) for structural vibration suppression. It is formed by covering a rigid cylindrical chamber with two rubber membranes that act as springs and filling the chamber with incompressible liquid. Compared to conventional TVAs, the TVA-LEC is cost and weight efficient when it is integrated to the liquid network of a primary structure, such as oil pipelines inside aircraft wings, by utilizing the existing liquid as the mass of the TVA. A single-degree-of-freedom (SDOF) analytical model is developed for the proposed device with discussions on the tuning of its natural frequency. It is revealed that the natural frequency of the TVA-LEC can be tuned by regulating the liquid mass. The analytical model is validated by experimental tests in which the TVA-LEC is installed on a cantilever beam and the liquid mass is adjusted. The natural frequency of the TVA-LEC device shifts from 16.99 Hz to 21.99 Hz by adding liquid, which agrees well with the analytical prediction.

A fully passive nonlinear piezoelectric vibration absorber.

The objective of this study is to develop the first fully passive nonlinear piezoelectric tuned vibration absorber (NPTVA). The NPTVA is designed to mitigate a specific resonance of a nonlinear host structure. To avoid the use of synthetic inductors which require external power, closed magnetic circuits in ferrite material realize the large inductance values required by vibration mitigation at low frequencies. The saturation of an additional passive inductor is then exploited to build the nonlinearity in the NPTVA. The performance of the proposed device is demonstrated both numerically and experimentally.This article is part of the theme issue 'Nonlinear energy transfer in dynamical and acoustical systems'.

Designing an attachable and power-efficient all-in-one module of a tunable vibration absorber based on magnetorheological elastomer

This study designs an all-in-one module of a tunable vibration absorber (TVA) using magnetorheological elastomer (MRE) considering easy installation in a plug-and-play concept on an actual industrial plant. The proposed system is designed to overcome several limitations on a typical system composed of an electromagnet and MRE TVA, such as environmental robustness, bulky size, high power consumption and complex installation on an actual plant. The designed TVA module contains sensors for MRE tuning control feedback, an energy-efficient magnetic field density generator, MRE and absorber mass. A novel but simple magnetic field generator is proposed using a small brushless DC gimbal motor and permanent magnets to reduce unnecessary energy consumption for long-term operation. The TVA module is designed so that it can be easily attached to an existing target system, such as a linear compressor. Using the embedded sensors in the module, it can automatically tune the MRE stiffness adaptively to the disturbance vibration on the target system. The prototype performance is validated with experiments showing that it can provide approximately 94% of stiffness change and 58% of vibration suppression for disturbance in the frequency range of 51.6–71.9 Hz.

Reducing variable frequency vibrations in a powertrain system with an adaptive tuned vibration absorber group

Based on a multiple degrees of freedom dynamic model of a vehicle powertrain system, natural vibration analyses and sensitivity analyses of the eigenvalues are performed to determine the key inertia for each natural vibration of a powertrain system. Then, the results are used to optimize the installation position of each adaptive tuned vibration absorber. According to the relationship between the variable frequency torque excitation and the natural vibration of a powertrain system, the entire vibration frequency band is divided into segments, and the auxiliary vibration absorber and dominant vibration absorber are determined for each sensitive frequency band. The optimum parameters of the auxiliary vibration absorber are calculated based on the optimal frequency ratio and the optimal damping ratio of the passive vibration absorber. The instantaneous change state of the natural vibrations of a powertrain system with adaptive tuned vibration absorbers is studied, and the optimized start and stop tuning frequencies of the adaptive tuned vibration absorber are obtained. These frequencies can be translated into the optimum parameters of the dominant vibration absorber. Finally, the optimal tuning scheme for the adaptive tuned vibration absorber group, which can be used to reduce the variable frequency vibrations of a powertrain system, is proposed, and corresponding numerical simulations are performed. The simulation time history signals are transformed into three-dimensional information related to time, frequency and vibration energy via the Hilbert-Huang transform (HHT). A comprehensive time-frequency analysis is then conducted to verify that the optimal tuning scheme for the adaptive tuned vibration absorber group can significantly reduce the variable frequency vibrations of a powertrain system.

Switching and sweeping vibration absorbers: Theory and experimental validation

This paper investigates the principal properties of time varying operation modes for tuneable vibration absorbers mounted on distributed structures to reduce vibrations produced by stationary broad frequency band disturbances. The study considers a practical application where an electro-mechanical tuneable vibration absorber, comprising a seismic coil-magnet linear transducer, is fixed on a thin walled circular duct flexible structure. The absorber is commanded to either periodically switch or continuously vary the stiffness and damping of the elastic suspension holding the moving magnet. As a result, the tuneable vibration absorber fundamental natural frequency and damping ratio are respectively switched or swept to cyclically reduce the resonant response of multiple flexural natural modes of the duct structure. The study analytically shows, and confirms with simulations and experiments, that the vibration control produced by a simple “blind sweep” operation mode of the tuneable vibration absorber does not differ significantly from the (sub)optimal performance attainable via a switching operation mode.

A tunable dynamic vibration absorber for unbalanced rotor system

A tunable dynamic vibration absorber for unbalanced rotor system which is made up of coil springs and magnetic spring is presented. The structure of the absorber is introduced and the stiffness tuning mechanism of the magnetic spring is explained. A finite element model of the rotor-absorber system was built and the influencing factors to the appearance of the absorber were studied numerically. Finally, experiments were carried out to verify the numerical results, and PID control strategy was tested. The numerical and experimental results show that the present absorber is effective for vibration suppression of an unbalanced rotor system, and the control strategy is effective.

A tuned vibration absorber constituted of shape memory alloy wires for vibration reduction of platform structures: design and implementation

Machinery can suffer from mechanical vibrations since resonance may be generated from time-varying external excitations under different operation conditions. These detrimental vibrations may significantly influence the device's performance, effectiveness and reliability in operation. In this paper, an innovative, simple and high-efficiency tuned vibration absorber (TVA) consisting of shape memory alloy (SMA) wires, which is referred to a wire-type tuned vibration absorber (WTVA), is proposed to reduce the induced vibration. Experiments are carried out using a six-degree-of-freedom platform which is designed to simulate the frame of precision machinery in practical applications. With the equivalent stiffness of SMA wires adjusted by the controlled electric current, the frequency tunability of WTVA can be achieved. When the natural frequency of WTVA tuned in with the disturbance frequency, the experimental results demonstrate that the efficiency in vibration reduction of the platform is drastically increased even with considerable weight difference between WTVA and the platform. Moreover, the tunable frequency span also increases greatly due to the new design of WTVA and the material characteristics of SMA wires.

Seismic Energy Assessment of Buildings with Tuned Vibration Absorbers

Seismic analysis and energy assessment of building installed with distributed tuned vibration absorbers (d‐TVAs) are presented. The performance of d‐TVAs is compared with single tuned vibration absorber (STVA) installed at the top of the building. The placements of the d‐TVAs are based on the modal properties of the uncontrolled and controlled buildings. The governing equations of motion of the building with the STVA and d‐TVAs are solved by employing Newmark’s integration method. Various energies under earthquake ground excitations are computed to study the effectiveness of using the STVA and d‐TVAs. It is concluded that the use of the d‐TVAs is the most competent because it effectively dissipates the seismic energy, and they are convenient to install requiring reduced space, as are placed at various floors.

Vibration Reduction for a Flexible Arm Using Magnetorheological Elastomer Vibration Absorber

The application of the magnetorheological elastomer (MRE) to nonlinear vibration control for a flexible arm is investigated in this paper. A semiactive control method is suggested to reduce vibration via the internal resonance and the MRE. To establish a vibration energy transfer channel, a tuned vibration absorber based on the MRE is developed. Through adjusting the coil current, the frequency of the vibration absorber can be readily controlled by the external magnetic field, thereby maintaining the internal resonance condition with the flexible arm. By the perturbation analysis, it is proven that the internal resonance can be successfully established between the flexible arm and the MRE vibration absorber, and the vibration energy of the flexible arm can be transferred to and dissipated by the MRE vibration absorber. Through numerical simulations, virtual prototyping simulations, and experimental investigation, it is verified that the proposed method and the suggested MRE vibration absorber are effective in controlling nonlinear vibration of the flexible arm.

Control of a magnetorheological tuned vibration absorber for wind turbine application utilising the refined force tracking algorithm

This work covers selected control issues, including refined force tracking algorithm formulation, concerning the wind turbine tower-nacelle laboratory model equipped with a magnetorheological damper based tuned vibration absorber. The objective of the current research is a development and experimental implementation of the control algorithm that couples basic adaptive stiffness solution with stock magnetorheological damper force tracking concept to obtain a quality tower vibration reduction system. The experiments were conducted assuming monoharmonic, horizontal excitation applied to the assembly modelling the nacelle. The frequency range comprised the neighbourhood of the first bending mode of the tower-nacelle system. The results proved the effectiveness of the adopted algorithm referring to other high-performance solutions.

Adaptive tuned vibration absorber based on magnetorheological elastomer-shape memory alloy composite

Abstract Shape memory alloy (SMA) is an attractive smart material which could be used as stiffness tuning element in adaptive tuned vibration absorber (ATVA). The sharp modulus change in SMA material during phase transformation creates difficulties for smooth tuning to track forcing frequency to minimize vibrations of primary system. However, high hysteresis damping at low temperature martensitic phase degrades performance of vibration absorber. This paper deals with the study of dynamic response of system in which SMA and magnetorheological elastomer (MRE) are combined together to act as a smart spring- mass-damper system in a tuned vibration absorber. This composite is used as two way stiffness tuning element in ATVA for smooth and continuous tuning and to minimize the adverse effect at low temperature by increasing equivalent stiffness. The stiffnesses of SMA element and MRE are varied respectively by changing temperature and strength of external magnetic field. The two way stiffness tuning ability and adaptivity have been demonstrated analytically and experimentally. The experimental results show good agreement with analytical results. The proposed composite is able to shift the stiffness consequently the natural frequency of primary system as well as reduce the vibration level of primary system by substantial mount.

Vibration Control Design for a Plate Structure with Electrorheological ATVA Using Interval Type-2 Fuzzy System

This study presents vibration control using actively tunable vibration absorbers (ATVA) to suppress vibration of a thin plate. The ATVA is made of a sandwich hollow structure embedded with electrorheological fluid (ERF). ERF is considered to be one of the most important smart fluids and it is suitable to be embedded in a smart structure due to its controllable rheological property. ERF’s apparent viscosity can be controlled in response to the electric field and the change is reversible in 10 microseconds. Therefore, the physical properties of the ERF-embedded smart structure, such as the stiffness and damping coefficient, can be changed in response to the applied electric field. A mathematical model is difficult to be obtained to describe the exact characteristics of the ERF embedded ATVA because of the nonlinearity of ERF’s viscosity. Therefore, a fuzzy modeling and experimental validations of ERF-based ATVA from stationary random vibrations of thin plates are presented in this study. Because Type-2 fuzzy sets generalize Type-1 fuzzy sets so that more modeling uncertainties can be handled, a semi-active vibration controller is proposed based on Type-2 fuzzy sets. To investigate the different performances by using different types of fuzzy controllers, the experimental measurements employing both type-1 fuzzy and interval type-2 fuzzy controllers are implemented by the Compact RIO embedded system. The fuzzy modeling framework and solution methods presented in this work can be used for design, performance analysis, and optimization of ATVA from varying harmonic vibration of thin plates.

Sweeping shunted electro-magnetic tuneable vibration absorber: Design and implementation

This paper presents a study on the design and implementation of a time–varying shunted electro–magnetic Tuneable Vibration Absorber for broad–band vibration control of thin structures. A time–varying RL–shunt is used to harmonically vary the stiffness and damping properties of the Tuneable Vibration Absorber so that its mechanical fundamental natural frequency is continuously swept in a given broad frequency band whereas its mechanical damping is continuously adapted to maximize the vibration absorption from the hosting structure where it is mounted. The paper first recalls the tuning and positioning criteria for the case where a classical Tuneable Vibration Absorber is installed on a thin walled cylindrical structure to reduce the response of a resonating flexural mode. It then discusses the design of the time–varying shunt circuit to produce the desired stiffness and damping variations in the electro-magnetic Tuneable Vibration Absorber. Finally, it presents a numerical study on the flexural vibration and interior sound control effects produced when an array of these shunted electro–magnetic Tuneable Vibration Absorbers are mounted on a thin walled cylinder subject to a rain–on–the–roof stochastic excitation. The study shows that the array of proposed systems effectively controls the cylinder flexural response and interior noise over a broad frequency band without need of tuning and thus system identification of the structure. Therefore, the systems can be successfully used also on structures whose physical properties vary in time because of temperature changes or tensioning effects for example.

Multi-objective Optimal Design of Vibration Absorber with Simple Cell Mapping Algorithm

In this paper, we investigate a multi-objective optimal design of a tuned vibration absorber for a two degrees-of-freedom linear system, in which we take white Gaussian noise as the excitation. We use the simple cell mapping method to obtain solutions to the multi-objective optimization problem. We optimize tuned vibration absorbers in two different configurations. As our objective, we take various features of the response of the power spectrum density function. Our results show that the primary mass vibration with the optimally designed absorber has a lower peak power spectrum value. In addition, the two natural frequencies of the optimized system are further apart than in the non-optimized system, which implies that the absorber has a wider effective region in the frequency domain.

Flutter Control of a Two-Degrees-of-Freedom Airfoil Using a Nonlinear Tuned Vibration Absorber

The influence of a nonlinear tuned vibration absorber (NLTVA) on the airfoil flutter is investigated. In particular, its effect on the instability threshold and the potential subcriticality of the bifurcation is analyzed. For that purpose, the airfoil is modeled using the classical pitch and plunge aeroelastic model together with a linear approach for the aerodynamic loads. Large amplitude motions of the airfoil are taken into account with nonlinear restoring forces for the pitch and plunge degrees-of-freedom. The two cases of a hardening and a softening spring behavior are investigated. The influence of each NLTVA parameter is studied, and an optimum tuning of these parameters is found. The study reveals the ability of the NLTVA to shift the instability, avoid its possible subcriticality, and reduce the limit cycle oscillations (LCOs) amplitude.

Responses of Multiple Nonlinear Tuned Vibration Absorbers under Harmonic Excitation

In this paper, a system consisting of multiple perfectly tuned identical translational vibration absorbers, having both hardening and softening springs, attached to a main mass under harmonic excitation is considered. The existence of absorbers’ synchronous and non-synchronous responses is checked. The method of averaging is employed to reach to the averaged autonomous equations of motion that describe the dynamics of the absorbers. A graphical method is then employed to check the existence of different responses of the absorbers. It is found that for absorbers with hardening springs, only one synchronous response of the absorbers occurs and no other responses take place. However, for the case of absorbers with softening springs, other responses were found to exist. These include multi-valued synchronous responses and a jump instability. These findings are in agreement with those of another study by the author where a similar system was considered using different approach.