Showing papers on "Dynamic Vibration Absorber published in 2008"
TL;DR: In this article, the authors developed an adaptive tuned vibration absorber (ATVA) based on unique characteristics of magnetorheological elastomers (MREs), whose modulus can be controlled by an applied magnetic field.
210 citations
TL;DR: In this article, magnetorheological elastomers (MREs) are used as field-dependent springs within three vibration absorber configurations, and to determine their vibration absorption characteristics.
Abstract: The purpose of this work is to use magnetorheological elastomers (MREs) as field-dependent springs within three vibration absorber configurations, and to determine their vibration absorption characteristics. Magnetorheological elastomers are fabricated from silicone gel and iron microparticles, and implemented as tunable springs in three vibration absorber configurations, which excited the MREs in shear, squeeze mode, and compression. Each vibration absorber configuration exploits different magneto-mechanical properties, achieving very different results. The MRE iron concentration is varied to find the largest natural frequency shift for the squeeze-mode absorber due to an applied magnetic field. Absorbers with MREs containing 35% iron by volume exhibits the largest natural frequency shift, 507%. MREs containing 35% iron are placed into shear and longitudinal mode vibration absorber devices, which exhibit 470% and 180% frequency increases, respectively.
153 citations
Book•
03 Dec 2008
TL;DR: In this article, a comparison of passive, active and hybrid control methods for wind-excitation control in Civil Structures is presented, based on a Lumped Modeling Approach.
Abstract: About the Authors. Preface. Acknowledgements. 1 Active Damping. 1.1 Introduction. 1.2 Structural Control. 1.3 Plant Description. 1.4 Equations of Structural Dynamics. 1.5 Collocated Control System. 1.6 Active Damping with Collocated System. 1.7 Decentralized Control with Collocated Pairs. 2 Active Isolation. 2.1 Introduction. 2.2 Relaxation Isolator. 2.3 Sky-hook Damper. 2.4 Force Feedback. 2.5 Six-Axis Isolator. 2.6 Vehicle Active Suspension. 2.7 Semi-Active Suspension. 3 A Comparison of Passive, Active and Hybrid Control. 3.1 Introduction. 3.2 System Description. 3.3 The Dynamic Vibration Absorber. 3.4 Active Mass Damper. 3.5 Hybrid Control. 3.6 Shear Control. 3.7 Force Actuator, Displacement Sensor. 3.8 Displacement Actuator, Force Sensor. 4 Vibration Control Methods and Devices. 4.1 Introduction. 4.2 Classification of Vibration Control Methods. 4.3 Construction of Active Dynamic Absorber. 4.4 Control Devices for Wind Excitation Control in Civil Structures. 4.5 Real Towers Using the Connected Control Method. 4.6 Application of Active Dynamic Absorber for Controlling Vibration of Single-d.o.f. Systems. 4.7 Remarks. 5 Reduced-Order Model for Structural Control. 5.1 Introduction. 5.2 Modeling of Distributed Structures. 5.3 Spillover. 5.4 The Lumped Modeling Method. 5.5 Method of Equivalent Mass Estimation. 5.6 Modeling of Tower-like Structure. 5.7 Modeling of Plate Structures. 5.8 Modeling of a Bridge Tower. 5.9 Robust Vibration Control for Neglected Higher Modes. 5.10 Conclusions. 6 Active Control of Civil Structures. 6.1 Introduction. 6.2 Classification of Structural Control for Buildings. 6.3 Modeling and Vibration Control for Tower Structures. 6.4 Active Vibration Control of Multiple Buildings Connected with Active Control Bridges in Response to Large Earthquakes. 6.5 Vibration Control for Real Triple Towers Using CCM. 6.6 Vibration Control of Bridge Towers Using a Lumped Modeling Approach. 6.7 Conclusion. References. Index.
152 citations
TL;DR: In this paper, a nonlinear energy sink (NES) was used to suppress the vibrations in a 2D forced linear system with a single nonlinear vibration absorber, which was compared to the best-tuned linear one and excitation zones of preference of the nonlinear absorber.
102 citations
TL;DR: In this paper, the application of tuneable vibration absorbers (TVA) for suppression of chatter vibrations in the boring manufacturing process is presented, where the boring bar is modeled as a cantilever Euler-Bernoulli beam and the TVA is composed of mass, spring and dashpot elements.
90 citations
TL;DR: In this article, a damped mass-spring absorber system that is attached continuously along the beam length is considered to attenuate structural waves in beams, which can also be designed to be effective over a broad frequency range by using a high damping loss factor and multiple tuning frequencies.
84 citations
TL;DR: In this paper, the optimum parameters of a dynamic vibration absorber of non-traditional form have been derived for suppressing vibration of a single degree-of-freedom system due to ground motion, and the reduction of transmission of motion from the support to the mass of the structure is compared for the cases of using the traditional and the proposed dynamic absorbers.
80 citations
TL;DR: In this article, the performance of the tuned rail absorber on vibration reduction is investigated. But, it is found that a large active mass used in the absorber is beneficial to increase the decay rate of rail vibration.
54 citations
TL;DR: In this article, the authors describe how to design an optimal system of viscoelastic absorbers for a known material, through a model using four fractional parameters, and a real example, of the design of a system of six VAs for mitigation of the response to fluid-structure instability in a hydroelectric generator system, is presented and discussed.
Abstract: So-called vibration absorbers, which might more appropriately be called vibration neutralizers, are mechanical devices designed to be attached to another mechanical system, or structure, called the primary system, for the purpose of controlling, or reducing, the vibration (and consequent sound production) of machines, structural surfaces and panels. The cheapest and easiest way to construct a vibration absorber is by incorporating a viscoelastic material, functioning as both the resilient and the energy dissipating component. The viscoelastic material acts as a damped spring. This article sets out to describe how to design an optimal system of viscoelastic absorbers for a known material, through a model using four fractional parameters. A real example, of the design of a system of six viscoelastic vibration absorbers for mitigation of the response to fluid-structure instability in a hydroelectric generator system, is presented and discussed.
54 citations
TL;DR: In this article, the ant colony optimization was used to solve the optimization problem of two different types of dynamic vibration absorbers (DVA), namely the vibrating blade DVA and the multi-mode DVA.
52 citations
Patent•
29 Jul 2008TL;DR: In this article, a disk drive includes a disk base, a disk, an actuator arm actuatable over the disk, and a motor, which is operable to rotate the disk.
Abstract: A disk drive includes a disk drive base, a disk, an actuator arm actuatable over the disk, and a motor. The motor is operable to rotate the disk, and is coupled to the disk drive base. During operation of the disk drive, the motor emits vibrations at a source vibration frequency. A vibration absorber is coupled to the disk drive base, the vibration absorber including a cantilever beam having a fixed end and a free end.
TL;DR: In this article, a coupled acoustic system of a cylindrical combustor and an absorber cavity has been investigated experimentally in hot-fire and cold-flow tests and the general behavior of the coupled system is explained based on an analytical one-dimensional analysis of the problem.
Abstract: The coupled acoustic system of a cylindrical combustor and an absorber cavity has been investigated experimentally in hot-fire and cold-flow tests. The addition of an absorber volume to the combustor is shown to result in eigenfrequencies of the coupled system systematically different from that of a pure cylindrical resonance volume. The general behavior of the coupled system is explained based on an analytical one-dimensional analysis of the problem. Numerical simulations in two dimensions result in very good agreement with experimental observations. A three-dimensional simulation of a cylinder equipped with 40 absorbers demonstrates the relevance of the reported phenomena for rocket engines equipped with absorber rings. Experimental data on the damping behavior of an absorber are given and the damping of absorbers is discussed based on the numerically obtained acoustic eigenmodes of the coupled system.
TL;DR: This paper describes a theoretical and experimental study to show how an electrical damper or an electrical dynamic absorber, implemented using an electromagnetic actuator and an accelerometer, can control vibration transmission through a vibration isolator.
Abstract: This paper describes a theoretical and experimental study to show how an electrical damper or an electrical dynamic absorber, implemented using an electromagnetic actuator and an accelerometer, can control vibration transmission through a vibration isolator. The electrical damper is realized by feeding back the equipment velocity to the actuator with constant gain. The electrical dynamic absorber is realized by feeding back the equipment acceleration through a second-order low-pass filter. Because it is found that the plant on a flexible base is asymptotically similar to that on a rigid base, the optimal parameters of the control filter are determined analytically, independent of the base dynamics. Experimental results show that the electrical dynamic absorber has a similar performance to the electrical damper. The maximum reduction in transmitted vibration achieved was about 38 dB for both methods. It is also shown that the electrical dynamic absorber is more robust to undesirable dynamics outside the control bandwidth. Another advantage of the electrical dynamic absorber is that it does not require an integrator to transform acceleration into velocity.
TL;DR: In this paper, a non-model based groundhook control (displacement-based on-off control or "on-off DBG") was used to control the damping of the TVA.
TL;DR: In this paper, the design and application of active interfaces and semi-active vibration absorbers that can be used to reduce annoying vibration or noise levels are discussed. But the simulation results are compared with experimental measurement results, which agree very well.
TL;DR: In this article, the dynamic damping of magnetorheological elastomer (MRE) was studied and analyzed and the influences of different test conditions including test strain amplitude, test frequency and test magnetic field were deeply studied.
Abstract: Magnetorheological elastomer (MRE) is a new kind of smart materials, its dynamic mechanic performances can be controlled by an applied magnetic field. MRE is usually used as a stiffness-changeable spring in the semi-active vibration absorber. In order to get perfect vibration control effect, low dynamic damping of MRE is need. But the dynamic damping of MRE was not studied deeply in the past. The dynamic damping of MRE was studied and analyzed. The influences of different test conditions including test strain amplitude, test frequency and test magnetic field were deeply studied. MRE sample and pure silicone rubber sample were prepared and tested under different conditions. The test results show that the main source of dynamic damping is the friction between iron particles and rubber matrix. And the friction is mainly influenced by the strain amplitude and test magnetic field.
TL;DR: In this article, the response properties of a single-degree-of-freedom system under dual harmonic excitation are analyzed to provide some principles for the choice of time span and step in the simulations.
TL;DR: In this paper, an equivalent mechanical model is employed to study structure-tuned liquid damper (TLD) systems and evaluate the performance of TLDs having rectangular, vertical cylindrical or horizontal-cylindrical tank shapes, which are placed at the top of a structure.
Abstract: An equivalent mechanical model is employed to study structure-tuned liquid damper (TLD) systems and evaluate the performance of TLDs having rectangular, vertical-cylindrical or horizontal-cylindrical tank shapes, which are placed at the top of a structure. TLD performance is evaluated in terms of effective damping, efficiency and robustness. This theoretical study is limited to small response amplitude such that the natural frequency and the effective mass of the TLD can be assumed to remain constant, while the damping of the TLD can be expressed in terms of equivalent amplitude-dependent viscous damping. The tuning ratio, the structural response amplitude, the mass ratio and the liquid depth are varied to investigate their effects on TLD performance. Performance charts are developed and subsequently utilized to present findings from this study. It is found that small liquid depth ratio and large mass ratio lead to a more robust structure-TLD system with small relative motion occurring between the structure and the vibration absorber. Comparisons of TLD performance, corresponding to the different tank geometries investigated, are made. Copyright © 2008 John Wiley & Sons, Ltd.
TL;DR: In this paper, a self-tuning vibration absorber including a carrier rod assembly having operatively connected with a mounting mechanism for mounting the rod assembly to a primary system and a hollow shafted motorized tuning mechanism was presented.
Abstract: A self-tuning vibration absorber including a carrier rod assembly having operatively connected thereto a mounting mechanism for mounting the carrier rod assembly to a primary system and a hollow shafted motorized tuning mechanism for tuning a phase difference between vibration of the primary system and vibration of the carrier rod assembly to 90 degrees, the carrier rod assembly further including a detecting mechanism for detecting the vibration of the primary system and the vibration of the carrier rod assembly, and a controller in electrical connection with the detecting mechanism and the tuning means for controlling the tuning mechanism based on the vibration of the primary system and the vibration of the carrier rod assembly detected. A method of vibration dampening, a method of controlling a self-tuning vibration absorber, and a method of reducing hunting motion in railcars.
TL;DR: In this article, the frequency and dynamic response of a damped Duffing system attached to a parametrically excited pendulum vibration absorber is analyzed. And the results are compared with a similar application of a pendulum absorber for a linear primary system.
Abstract: In this work we study the frequency and dynamic response of a damped Duffing system attached to a parametrically excited pendulum vibration absorber. The multiple scales method is applied to get the autoparametric resonance conditions and the results are compared with a similar application of a pendulum absorber for a linear primary system. The approximate frequency analysis reveals that the nonlinear dynamics of the externally excited system are suppressed by the pendulum absorber and, under this condition, the primary Duffing system yields a time response almost equivalent to that obtained for a linear primary system, although the absorber frequency response is drastically modified and affected by the cubic stiffness, thus modifying the jumps defined by the fixed points. In the absorber frequency response can be appreciated a good absorption capability for certain ranges of nonlinear stiffness and the internal coupling is maintained by the existing damping between the pendulum and the primary system. Moreover, the stability of the coupled system is also affected by some extra fixed points introduced by the cubic stiffness, which is illustrated with several amplitude-force responses. Some numerical simulations of the approximate frequency responses and dynamic behavior are performed to show the steady-state and transient responses.
TL;DR: In this paper, the optimal stiffnesses and damping coefficients of a two-degree-of-freedom (2DOF) system acting as a dynamic vibration absorber (DVA) on a beam structure were investigated.
Abstract: This paper deals with the problem of finding the optimal stiffnesses and damping coefficients of a two degree of freedom (2DOF) system acting as a dynamic vibration absorber (DVA) on a beam structure. In this sense, a heuristic criterion for the optimization problem will be developed to contemplate this particular type of DVA. Accordingly, it is planned to minimize the amplitude of vibration in predetermined points of the main structure. Two optimizations will be proposed for two DVAs of 1DOF to compare their performances with the optimized 2DOF system. A simulated annealing algorithm is used to obtain the DVA’s optimal parameters for minimum amplitude in a given point of the beam. The best configuration depends on the location of the absorbers on the beam and, for a fixed location, on the distribution of the stiffness constants.
TL;DR: In this paper, the authors investigated the efficacy of a dynamic vibration absorber (DVA) in suppressing friction-induced instability in a two-degree-of-freedom model, incorporating tangential and normal mode-coupling along with the velocity-weakening friction characteristic.
Abstract: The present article investigates the efficacy of a dynamic vibration absorber (DVA) in suppressing friction-induced instability. A two-degree-of-freedom model, incorporating tangential and normal mode-coupling along with the velocity-weakening friction characteristic (the so-called Stribeck effect), represents the minimal phenomenological model of the primary system. The DVA is aligned at an angle to the direction of sliding. A method of selecting the best parameters of the DVA is discussed. The design criteria are based on minimal detuning and maximum stability and robustness against all possible parametric perturbations. Robustness of the design is analysed using the e-pseudospectra of the Jacobian matrix.
TL;DR: In this article, it is proved that if damping in a vibrating beam structure is negligible, a translational dynamic absorber used in combination with a rotational dynamic absorbber can absorb both translational and rotational motions for part of a vibration beam subjected to harmonic excitation.
Abstract: One drawback of the traditional dynamic vibration absorber is that it can only absorb the vibration of a continuous structure such as a beam at the point to which it is attached. In this article, it is proved that if damping in a vibrating beam structure is negligible, a translational dynamic absorber used in combination with a rotational dynamic absorber can absorb both translational and rotational motions for part of a vibrating beam subjected to harmonic excitation. An analytical model based on Euler-Bernoulli beam theory is constructed for a beam under partially distributed loading, and it is proved theoretically that the two absorbers can not only absorb vibration in the unforced portion of the beam, but can also isolate vibration in the portion under direct excitation. Two numerical examples are given for illustration, and some useful applications of the absorbers are discussed.
TL;DR: In this article, the possibility of making a rectangular cutout in a plate for the purposes of employing this cut-out as a dynamic vibration absorber was explored, and numerical predictions were presented in the form of design charts to indicate the conditions under which vibration control may be possible.
TL;DR: In this paper, the nonlinear dynamics of an autoparametric vibration absorber of pendulum type is considered and conditions of existence of periodic motions in the case of monoharmonic excitation are considered.
Abstract: The nonlinear dynamics of an autoparametric vibration absorber of pendulum type is considered. The conditions of existence of periodic motions in the case of monoharmonic excitation are considered. A comparison of the vibration quenching qualities of the autoparametric absorber and a “classical” (linear) dynamic vibration absorber is presented.
Patent•
05 Mar 2008TL;DR: In this paper, an active tuned vibration absorber is disclosed for reducing vibrations in a structure, and a control system for generating an actuator driving signal for driving the actuator using the first and second measurement, wherein the control system is operable to generate the actuators driving signal to conform to a target relationship.
Abstract: An active tuned vibration absorber (100) is disclosed for reducing vibrations in a structure, the vibration absorber comprising: a mount (104) for attachment to the structure; a moveable mass (106); a spring arrangement (108) connected between the mass and the mount; an actuator arrangement (110) for applying a force between the mass and the mount; a first sensor (112) for providing a first measurement indicative of a force exerted between the structure and the mount; a second sensor (114) for providing a second measurement indicative of an acceleration of the structure at or proximate to the mount; and a control system (116) for generating an actuator driving signal for driving the actuator using the first and second measurement, wherein the control system is operable to generate the actuator driving signal to cause the first measurement and second measurement to conform to a target relationship.
TL;DR: In this paper, a 3DOF model was proposed for a real helicopter, where the freedom of the fuselage is added and the periodic forces are applied to the blade by aerodynamic force.
Abstract: Currently, some kinds of helicopters use pendulum absorbers in order to reduce vibrations. Present pendulum absorbers are designed based on the antiresonance concept used in the linear theory. However, since the vibration amplitudes of the pendulum are not small, it is considered that the nonlinearity has influence on the vibration characteristics. Therefore, the best suppression cannot be attained by using the linear theory. In a helicopter, periodic forces act on the blades due to the influences of the air thrust. These periodic forces act on the blades with the frequency which is the integer multiple of the rotational speed of the rotor. Our previous study proposed a 2-degree-of-freedom (2DOF) model composed of a rotor blade and a pendulum absorber. The blade was considered as a rigid body and it was excited by giving a sinusoidal deflection at its end. The present paper proposes a 3DOF model that is more similar to the real helicopter, since the freedom of the fuselage is added and the periodic forces are applied to the blade by aerodynamic force. The vibration is analyzed considering the nonlinear characteristics. The resonance curves of rotor blades with pendulum absorbers are obtained analytically and experimentally. It is clarified that the most efficient condition is obtained when the natural frequency of the pendulum is a little bit different from the frequency of the external force. Various unique nonlinear characteristics, such as bifurcations, are also shown.
TL;DR: In this paper, a novel active electromagnetic vibration absorber (AEMVA) is developed for suppression of steady-state response to a harmonic excitation, a proportional and derivative feedback control is equivalent to a time-delayed control.
Abstract: A novel active electromagnetic vibration absorber (AEMVA) is developed. It is shown that for suppression of steady-state response to a harmonic excitation, a proportional and derivative feedback control is equivalent to a time-delayed control. The study of the stability issue focuses on a conflicting goal of achieving the marginal stability of the time-delayed vibration absorber and the stability of the combined system. The achievability of the ideal performance of the time-delayed vibration absorber is investigated. An experimental study is conducted to test the proposed AEMVA. An online tuning algorithm is proposed. The experimental results show that with the proposed tuning strategy, the AEMVA can maximize the vibration suppression while maintaining the system stability. Copyright © 2008 John Wiley & Sons, Ltd.
Patent•
17 Oct 2008TL;DR: In this paper, a hand-held power tool with at least one vibration absorbing element has at least 1 degree of freedom of movement along a line of action, which is defined as the angle not equal to zero with the line-of-action.
Abstract: A hand-held power tool, in particular an impact driver, an impact drill, or a rotary hammer, is proposed, which has a drive unit and/or output with at least one line of action, which produces at least oscillations along the line of action. In order to reduce these oscillations, the hand-held power tool is equipped with at least one vibration absorber unit. The vibration absorber unit has at least one mobile vibration absorbing element, which has at least one degree of freedom of movement. This degree of freedom of movement encloses at least one angle not equal to zero with the line of action.