Adaptive Vibration Absorber Research Articles

Investigation of Macroscopic Mechanical Behavior of Magnetorheological Elastomers under Shear Deformation Using Microscale Representative Volume Element Approach.

Magnetorheological elastomers (MREs) are a class of smart materials with rubber-like qualities, demonstrating revertible magnetic field-dependent viscoelastic properties, which makes them an ideal candidate for development of the next generation of adaptive vibration absorbers. This research study aims at the development of a finite element model using microscale representative volume element (RVE) approach to predict the field-dependent shear behavior of MREs. MREs with different elastomeric matrices, including silicone rubber Ecoflex 30 and Ecoflex 50, and carbonyl iron particles (CIPs) have been considered as magnetic particles. The stress-strain characteristic of the pure silicon rubbers was evaluated experimentally to formulate the nonlinear Ogden strain energy function to describe hyper-elastic behavior of the rubbery matrix. The obtained mechanical and magnetic properties of the matrix and inclusions were integrated into COMSOL Multiphysics to develop the RVE for the MREs, in 2D and 3D configurations, with CIP volume fraction varying from 5% to 40%. Periodic boundary condition (PBC) was imposed on the RVE boundaries, while undergoing shear deformation subjected to magnetic flux densities of 0-0.4 T. Comparing the results from 2D and 3D modeling of isotropic MRE-RVE with the experimental results from the literature suggests that the 3D MRE-RVE can be effectively used to accurately predict the influence of varying factors including matrix type, volume fraction of magnetic particles, and applied magnetic field on the mechanical behavior of MREs.

Shunted piezoelectric patch adaptive vibration absorber set to maximise electric power absorption: A comparison between parallel and series RL-shunts

This paper presents a comparative study on two types of shunted piezoelectric patch adaptive vibration absorbers, which can be bonded in batches on thin-walled structures to control the broad-band resonant response of low order flexural modes. The self-contained control units are formed by a thin piezoelectric patch connected either to a series or to a parallel resistive-inductive (RL) network. The two components of the shunt are adapted online in such a way as to maximise the time-averaged electric power absorbed by the shunt, which corresponds to minimising the time-averaged total flexural response of the hosting structure. The study considers a practical demonstrator formed by a thin rectangular plate with five piezoelectric patches connected to digital RL-shunts, which is excited in bending by a stationary white noise point force. The aim of the paper is to contrast the tuning and vibration control properties of the series and parallel RL shunts. More specifically, the online implementation of a recursive two-paths tuning strategy along R-constant and L-constant paths with an extremum seeking gradient search algorithm is analysed first for the two types of shunts. Then, the vibration control performance produced by the two types of shunts is investigated for the case where they are tuned to control the resonant response of the first flexural mode of the plate.

Stability control of high-speed bogies using an adaptive vibration absorber

In this paper an active bogie stability scheme combining a dynamic vibration absorber (DVA) and an actuator is proposed for high-speed trains, and a control strategy is presented by transforming the actuating force into a virtual part of hybrid DVA whose characteristic frequency and damping can be adjusted. Firstly, a simplified model of the lateral bogie dynamics is established for control system design, and the optimal value of the characteristic frequency and damping of the hybrid DVA are theoretically investigated from the perspective of bogie stability. Then the strategy of active stability is introduced by using the idea of adaptive vibration absorber, and a method for auto-tuning the optimal value of the DVA suspension is proposed. To realize this auto-tuning strategy a method to detect the bogie instability and its frequency is presented. At last, the feasibility of the adaptive vibration absorber is verified by comparing it to a passive one using a co-simulation model of a railway vehicle, and the effect of time delay in the control system on bogie stability is also analyzed.

An adaptive and space-energy efficiency vibration absorber system using a self-sensing and tunable magnetorheological elastomer

Vibration monitoring and buffering is an important technical task in many industrial fields, such as bridges, machine tools and other specific applications. Recently, a magneto-rheological elastomer (MRE) has been utilized in an intelligent vibration absorber system with tunable stiffness, which can reversibly regulate its resonant frequency in real time to effectively prevent the resonance of the mechanical system. However, this MRE must be integrated with a vibrational sensor and equipped with an external magnetic field (e.g., electromagnetic coils or permanent magnets). Thus, the overall system is usually bulky and energy-intensive, which severely limits its broad application potential. In this work, we present an MRE-based tunable vibration absorber (MRE-TVA) with an elaborate 3-layered architecture integrated with a self-sensing triboelectric nanogenerator (TENG) sensor. The inner two-layer MRE structure exhibits variable stiffness, while the outer layer of the negative Poisson's ratio structure can confine the deformation of the inner MRE layers and form a contact-separation TENG sensor with the MRE, where the sensor can recognize external vibration information in a timely manner. In particular, the TENG sensor enables sensitive identification of the abnormal state of resonant excitation and other mechanical disturbances through dual logic judgment control based on vibration frequency and amplitude. For energy-space efficiency, a bistable permanent magnet controlled by a pulse current is integrated to generate a desirable magnetic field for modulation of the MRE stiffness. Compared with traditional electromagnetic coils, the energy and space utilization rates are increased by 94.25% and 75%, respectively. This combination of self-sensing and vibration damping systems achieves high energy-space efficiency, which will enable the intelligent health monitoring of bridges and other autonomous, smart, and long-term engineering tasks.

Active shaping of a bi-stable potential: Exploring nonlinear coupling to a stiff externally-excited oscillator

The ability to actively shape the potential energy function of a bi-stable oscillator without the use of feedback control offers key advantages in the design of adaptive morphing structures, mechanical switches, vibration absorbers, and energy harvesters. In this paper, we propose an approach based on nonlinearly coupling the bi-stable (low-frequency) oscillator to a stiff (high-frequency) linear oscillator, which, in turn, is excited harmonically near its resonant frequency. We show that active and controlled shaping of the potential energy function can be achieved by changing either the magnitude and/or the frequency of the high-frequency harmonic input. Pronounced shape changes are achieved even for relatively small levels of the input excitation; levels that are much lower than those needed when the bi-stable oscillator is directly subjected to the high-frequency excitation. The study also reveals an interesting phenomenon where the effective potential energy function of the slow dynamics can transition from the bi- to the mono-stable type and vise versa by simply changing the initial conditions of the externally-excited stiff oscillator.

The Modeling of Magnetorheological Elastomers: A State‐of‐the‐Art Review

The magnetorheological elastomers (MREs) are novel multifunctional materials wherein their viscoelastic properties can be varied instantly under an application of applied magnetic field. Due to their field‐dependent stiffness and damping properties, MREs are widely used in the development and design of MRE‐based adaptive vibration isolators and absorbers and also biomedical engineering. Moreover, MREs due to their inherent magnetostriction effect have enormous potential for the development of soft actuators. The dynamic behavior of MREs is affected by various material parameters (e.g., matrix and particle types, particle concentration, additives) as well as mechanical and magnetic loading parameters (e.g., frequency, amplitude, temperature, magnetic flux density). Understanding and predicting the effect of materials and loading parameters on the response behavior of MREs are of paramount importance for the design of MRE‐based adaptive structures and systems. This review paper mainly aims to provide a comprehensive study of material constitutive models to predict the nonlinear magnetomechanical behavior of MREs. Particular emphasis is paid to physics‐based models including continuum‐ and microstructure‐based models. Moreover, phenomenological models describing the dynamic magnetoviscoelastic behavior of MREs as well as the effect of temperature on the magnetomechanical behavior of such materials are properly addressed.

Design and experiment of an adaptive dynamic vibration absorber with smart leaf springs

An adaptive dynamic vibration absorber (ADVA) is designed for low-frequency vibration suppression. The leaf springs are applied as the tuning stiffness elements. The principle of variable stiffness is analyzed to obtain the effective range of the first natural frequency variation. A classic simply supported manipulator is selected as the controlled system. The coupled dynamic model of the manipulator-ADVA system is built to obtain the maximum damping efficiency and the vibration absorption capacity of the designed ADVA. An experimental platform is set up to verify the theoretical results. It is revealed that the ADVA can adjust the first natural frequency on a large scale by changing the curvature of the leaf springs. The amplitude of the manipulator is reduced obviously with the installation of the designed ADVA. Finally, based on the short-time Fourier transformation (STFT), a stepwise optimization algorithm is proposed to achieve a quick tuning of the natural frequency of the ADVA so that it can always coincide with the frequency of the prime structure. Through the above steps, the intelligent frequency tuning of the ADVA is realized with high vibration absorption performance in a wide frequency range.

Analyzing the influence of the core pre-structure on the dynamic response of a magnetorheological elastomer sandwich structure

Recently, vibration control has been useful in various engineering fields such as aerospace, adaptive dynamic vibration absorbers, and infrastructure. Magnetorheological elastomer (MRE) is an interesting material for controlling and suppressing undesirable vibrations through the application of a magnetic field. The present study aims at analyzing the pre-structure of the magnetorheological viscoelastic core in the dynamic response of an MRE-sandwich structure. The forced vibration tests were performed under a non-homogenous magnetic field to evaluate the dynamic properties of the MRE-sandwich structure in a frequency bandwidth range of 0–250 Hz. Experimental results show that the proposed MRE-sandwich structures are capable of eliminating unwanted resonances due to induced magnetic field intensity in the activated region, especially at the fundamental mode. Moreover, results highlight that an oriented pre-structure in an MRE-sandwich has an attenuation effect on vibrations in the low frequency range. Additionally, the external magnetic field increased the structural vibrations damping capability by approximately 200%. In addition, the oriented pre-structures of the MRE core were also used to dissipate vibration. Consequently, they could potentially be used in vibration attenuation applications such as stop operations in dynamic structures.

Adaptive Electromagnetic Vibration Absorber for a Multimode Structure

All structures experience vibrations due to external dynamic force excitations, such as earthquakes and wind loadings. At resonance, the impact of this natural dynamic force on structures may lead to structural failures. Hence, an absorber is mounted to absorb vibrations from the primary system. Unfortunately, passive tuned mass absorbers can only target a single frequency. Since structural buildings possess multiple modes, an adaptive or tune-able vibration absorber is needed to attenuate the vibration in a multi-degree of freedom (MDOF) system. In this work, an adaptive electromagnetic vibration absorber (AEMVA) is proposed to eliminate the effects of vibrations and is dynamically tuned using electromagnets. By varying the current supplied to the coil, the stiffness of the AEMVA can be adjusted, resulting in a varying absorber frequency. A mathematical description of the AEMVA on a three-story prototype model building is also presented. The three-story benchmark model was used to demonstrate the effectiveness of AEMVA in absorbing multiple vibration modes, both analytically and experimentally. It is shown that 68.81 %, 50.49 %, and 33.45 % of vibration amplitude reductions were achieved at the first, second, and third modes, respectively.

Mathematical Modeling and Experimental Evaluation of an Air Spring–Air Damper Dynamic Vibration Absorber

Nowadays, vibration control is one of the limitless and major operating parameters in science and technology. The most promising and adaptive dynamic vibration absorber (DVA) with an air spring–air damper assembly is designed with a facility to change the spring rate and damping in the system to control the vibration. To optimize and effectively controlling the resonant amplitude ratio efficiently, a Maxwell-type air damper mathematical model is formulated for an SDOF vibrating system subjected to sinusoidal base excitation for better performance of DVA. Insight into the physics of such systems was carried out by mathematical modeling, design, and development of an air spring–air damper system for the SDOF vibrating system. Experimental investigation of an air spring–air damper for the primary mass displacement amplitude to optimize and effectively control the vibration. It will provide a compact and right platform for DVA among the current potential market and provide the major attention of the control community as a platform for the development of low-frequency nonlinear devices.

Design and control of adaptive vibration absorber for multimode structure

In this study, we used two tunable vibration absorbers composed of shape memory alloy to reduce vibration of a platform structure. The natural frequency of the shape memory alloy absorber can be tuned online using a fuzzy logic controller to change the axial force of the shape memory alloy wires through phase transformation. In addition, we employed the finite element method to analyze the dynamic characteristics of the multimode platform structure and to evaluate the effectiveness of the shape memory alloy vibration absorber in terms of platform vibration attenuation. Experimental testing of the platform structure was conducted to verify its modal characteristics. By setting the two shape memory alloy tunable vibration absorbers on two adjacent sides of the platform at 90 degrees to each other and offset from the platform’s center axes, it is shown that all six modes can be covered for vibration absorption. The experiments show that the vibration due to all six mode modal excitations can be attenuated by more than 7.49 dB using the shape memory alloy tunable vibration absorber. Specifically, at the fourth, fifth, and sixth resonant modes, an average of 16.68 dB vibration suppression is observed. Overall, an average of 12.69 dB vibration suppression is achieved for resonant excitation of the entire platform structure when using the designed shape memory alloy tunable vibration absorber.

Design and Development of Self Adaptive Dynamic Vibration Absorber

Design and Development of Self Adaptive Dynamic Vibration Absorber

Toward an adaptive vibration absorber using shape-memory alloys, for civil engineering applications

This article explores the capabilities of a novel adaptive vibration absorber for civil engineering structures, with regard to frequency self-tuning, based on the temperature modulation of shape-memory alloy restitution elements. This real-time temperature modulation of shape-memory alloys, through Joule effect, enables to control the elastic modulus of these elements, by inducing thermal martensitic transformations, and allows for the adaptation of the stiffness of the absorber, in order to be continuously tunable for a wide frequency range. A series of simulations are performed, using numerical models of a lively footbridge, to give an additional insight into the high potentialities of this adaptive control approach in the mitigation of vibrations in civil engineering structures.

Adaptive dynamic vibration absorber based on a new type of smart material

Adaptive dynamic vibration absorber based on a new type of smart material

Transient vibration analytical modeling and suppressing for vibration absorber system under impulse excitation

The impulse excitation of mechanism causes transient vibration. In order to achieve adaptive transient vibration control, a method which can exactly model the response need to be proposed. This paper presents an analytical model to obtain the response of the primary system attached with dynamic vibration absorber (DVA) under impulse excitation. The impulse excitation which can be divided into single-impulse excitation and multi-impulse excitation is simplified as sinusoidal wave to establish the analytical model. To decouple the differential governing equations, a transform matrix is applied to convert the response from the physical coordinate to model coordinate. Therefore, the analytical response in the physical coordinate can be obtained by inverse transformation. The numerical Runge-Kutta method and experimental tests have demonstrated the effectiveness of the analytical model proposed. The wavelet of the response indicates that the transient vibration consists of components with multiple frequencies, and it shows that the modeling results coincide with the experiments. The optimizing simulations based on genetic algorithm and experimental tests demonstrate that the transient vibration of the primary system can be decreased by changing the stiffness of the DVA. The results presented in this paper are the foundations for us to develop the adaptive transient vibration absorber in the future.

Adaptive Piezoelectric Absorber for Active Vibration Control

Passive vibration control solutions are often limited to working reliably at one design point. Especially applied to lightweight structures, which tend to have unwanted vibration, active vibration control approaches can outperform passive solutions. To generate dynamic forces in a narrow frequency band, passive single-degree-of-freedom oscillators are frequently used as vibration absorbers and neutralizers. In order to respond to changes in system properties and/or the frequency of excitation forces, in this work, adaptive vibration compensation by a tunable piezoelectric vibration absorber is investigated. A special design containing piezoelectric stack actuators is used to cover a large tuning range for the natural frequency of the adaptive vibration absorber, while also the utilization as an active dynamic inertial mass actuator for active control concepts is possible, which can help to implement a broadband vibration control system. An analytical model is set up to derive general design rules for the system. An absorber prototype is set up and validated experimentally for both use cases of an adaptive vibration absorber and inertial mass actuator. Finally, the adaptive vibration control system is installed and tested with a basic truss structure in the laboratory, using both the possibility to adjust the properties of the absorber and active control.

An adaptive piezoelectric vibration absorber enhanced by a negative capacitance applied to a shell structure

Piezoelectric shunt damping is a well-known technique to damp mechanical vibrations of a structure, using a piezoelectric transducer to convert mechanical vibration energy into electrical energy, which is dissipated in an electrical resistance. Resonant shunts consisting of a resistance and an inductance connected to a piezoelectric transducer are used to damp structural vibrations in narrow frequency bands, but their performance is very sensitive to variations in structural modal frequencies and transducer capacitance. In order to overcome this drawback, a piezoelectric shunt damping technique with improved performance and robustness is presented in this paper. The design of the adaptive circuit considers the variation of the host structure’s natural frequency as a project parameter. This paper describes an adaptive resonant piezoelectric vibration absorber enhanced by a synthetic negative capacitance applied to a shell structure. The resonant shunt circuit autonomously adapts its inductance value by comparing the phase difference of the vibration velocity and the current flowing through the shunt circuit. Moreover, a synthetic negative capacitance is added to the shunt circuit to enhance the vibration attenuation provided by the piezoelectric absorber. The circuitry is implemented using analog components. Validation of the proposed method is done by bonding the piezoelectric absorber on a free-formed metallic shell.

Design and test of an adaptive vibration absorber based on magnetorheological elastomers and a hybrid electromagnet

The focuses of this study are to design an adaptive-tuned vibration absorber based on a smart materials known as magnetorheological elastomers and to test its dynamic performance. A primary system replicating a miniature cryogenic cooler (i.e. mass and shape) was designed and fabricated in order to test the effectiveness of the vibration absorber. A hybrid magnetic system (electromagnet and permanent magnets) was also designed and fabricated in order to actuate the magnetorheological elastomers as an adaptive stiffness element in the vibration absorber. The vibration testing was conducted on both the primary system and vibration absorber individually in order to characterize the behavior and verify the design constraints. Further testing was performed on a 2-degrees-of-freedom system to measure and assess the feasibility of the magnetorheological elastomer material for use in an application requiring an adaptive vibration absorber. The results show that by using a hybrid design for the electromagnet within the vibration absorber, the stiffness of the magnetorheological elastomer material can be increased and decreased above its nominal value, therefore demonstrating the feasibility of this design as an alternative adaptive vibration absorber.

Numerical Investigation of an Adaptive Vibration Absorber Using Shape Memory Alloys

The tuned vibration absorber (TVA) is a well-established passive vibration control device for achieving vibration reduction of a primary system subjected to external excitation. This contribution deals with the non-linear dynamics of an adaptive tuned vibration absorber (ATVA) with a shape memory alloy (SMA) element. Initially, a single-degree of freedom oscillator with an SMA element is analyzed showing the general characteristics of its dynamical response. Then, the analysis of an ATVA with an SMA element is carried out. Initially, small amplitude vibrations are considered in such a way that the SMA element does not undergo a stress-induced phase transformation. Under this assumption, the SMA influence is only caused by stiffness changes corresponding to temperature-induced phase transformation. Afterwards, the influence of the hysteretic behavior due to stress-induced phase transformation is considered. A proper constitutive description is employed in order to capture the general thermomechanical aspects of the SMAs. The hysteretic behavior introduces complex characteristics to the system dynamics but also changes the absorber response allowing vibration reduction in different frequency ranges. Numerical simulations establish comparisons of the ATVA results with those obtained from the classical TVA.

Improved Active Vibration Isolation Systems

The control force, feedback gain, and actuator stroke of several active vibration isolation systems were analyzed based on a single-layer active vibration isolation system. The analysis shows that the feedback gain and actuator stroke cannot be selected independently and the active isolation system design must make a compromise between the feedback gain and actuator stroke. The performance of active isolation systems can be improved by the joint vibration reduction using an active vibration isolation system with an adaptive dynamic vibration absorber. The results show that the joint vibration reduction method can successfully avoid the compromise between the feedback gain and actuator stroke. The control force and the object vibration amplitude are also greatly reduced.