Tuned Vibration Absorber Research Articles

Tunable vibration absorber for improving milling stability with tool wear and process damping effects

This paper deals with the problem of chatter suppression in milling process in order to achieve higher precision, better surface quality and larger material removal rate (MRR). The peripheral milling process is modeled as a two degrees of freedom system and the effects of tool wear and process damping are considered. It is shown that when regenerative chatter develops, both tool wear and process damping act as stabilizing factors. For larger values of depth of cut and consequently higher MRR, tunable vibration absorbers (TVA) (in x–y directions) are designed to improve stability. An optimal algorithm is developed which determines the optimum values for absorbers' parameters. The effects of tool wear, process damping and absorbers on the frequency response of the system and on the stability lobe diagram of the process are investigated. It is shown that the deigned absorber set is robust against parametric uncertainties associated with the dynamic model.

The Nonlinear Tuned Vibration Absorber

The objective of this paper is to introduce a new nonlinear dynamical absorber, the nonlinear tuned vibration absorber, through a rigorous nonlinear extension of the tuning rule for the linear tuned vibration absorber. This nonlinear tuning methodology combined with the increased suppression bandwidth brought by the intentional use of nonlinearity leads to the development of an absorber that is effective in wide ranges of frequencies and motion amplitudes. The results are illustrated using a one-degree-of-freedom primary system.

Suppression of Bending Vibration of Drill-Strings via an Adjustable Vibration Absorber

Vibration control of the drilling process in the gas and oil industries is of great importance. Applying an effective control system diminishes both costs and process time and increases work efficiency. Typically, the drill string vibrates in a combination of three distinct modes of transverse, torsional, and axial vibrations. Due to the importance of torsional vibration and the associated stick-slip phenomenon, many works have been devoted to this area. However, transverse vibration is another major source of vibration arisen from the long length of the drill string structure. In this paper, a tunable vibration absorber as a semiactive controller is designed to suppress the transverse vibration. After modeling the drill string as an Euler-Bernoulli beam and formulating the problem, the optimum specifications of the absorber, such as spring stiffness, absorber mass, and its position, are determined using an algorithm based on the mode summation method. The effect of bit rotational speed under the non-resonance and resonance condition is studied. It is shown that the best position of the absorber depends on the spring stiffness and bit rotational speed.

CIP 부피비에 따른 이방성 MRE의 전단계수 변화율

MRE(magneto-rheological elastomers) is a material which shows reversible and various modulus in magnetic field. Comparing to conventional rubber vibration isolator, MREs are able to absorb vibration of broader frequency range. These characteristic phenomena result from the orientation of magnetic particles named carbonyl iron powder(CIP) in rubber matrix. In this paper, simulation on variation rate of shear modulus for anisotropic MRE due to volume fraction of CIP and an effective permeability model was applied to predict the field-induced shear modulus of MREs. Also, the variation rate of shear modulus for anisotropic MRE was derived using magneto-mechanical theory. Based on Maxwell-Garnett mixing rule, the increment of shear modulus was calculated to evaluate the shear modulus of MREs with column structure of CIP due to induced current. The simulation results on variation rate of shear modulus can be applied to the variable mechanical system of MRE such as tunable vibration absorber, stiffness variable bush and mount.

Self-Tuning Multimodal Piezoelectric Shunt Damping

Piezoelectric shunt damping is a well known structural vibration control technique that consists in connecting an electrical circuit to a piezoelectric transducer attached to the structure. In the case of a resonant shunt, the network consisting of an inductor-resistor network when combined with the capacitive nature of the piezoelectric transducer impedance can be designed to act as a tuned vibration absorber. This paper discusses a method for the design and online adaptation of multimodal piezoelectric resonant shunts. The method presented in this work is different from previously multi-modal shunting methods (current blocking and current flowing) and implements the shunting network with a reduced number of discrete electrical components besides allowing for online tuning of the shunting parameters. The mathematical model of a structure with bonded piezoelectric transducers connected to a general electrical network is reviewed and the coupled equations of motion of a simply supported beam with piezoelectric elements and passive shunt networks are derived. The design of the multimodal shunt network is presented based on passive filter synthesis methods. The multimodal self tuning piezoelectric damper is demonstrated experimentally as a two-mode system applied to add damping to a cantilevered beam.

Energy dissipation characteristics of particle sloshing in a rotating cylinder

A study on the energy dissipation characteristics of granular materials flowing/sloshing in a rotating container is presented here. The objective is to develop a configuration for control of excessive structural oscillations, similar to those of tuned vibration absorbers and tuned sloshing absorbers. The effectiveness of energy dissipation through granular flow is primarily determined experimentally. A computational model is developed to understand the flow behavior and energy dissipation in this system. A promising kinematic match of the particle behavior is demonstrated between the numerical predictions and the experimental observations. The use of the granular flow in a rotating drum for vibration control is being investigated for the first time.

An investigation and modelling of energy dissipation through sloshing in an egg-shaped shell

Sloshing absorbers work on a similar principle to that of tuned vibration absorbers. A sloshing absorber consists of a tank, partially filled with liquid. The absorber is attached to the structure to be controlled, and relies on the structure's motion to excite the liquid. Consequently, a sloshing wave is produced at the liquid free surface possessing energy dissipative qualities to suppress excessive vibrations of the structure. The hen's egg has evolved to dissipate vibration energy rapidly to protect its contents. An uncooked hen's egg's capability to rapidly dissipate potentially harmful energy, is due to sloshing of its contents. Hence, there may be lessons to learn from the natural design of an egg which could be employed in the engineered (artificial) design of a sloshing absorber. The primary objective of this work is to identify the physical events responsible for effective energy dissipation in an eggshell, at different fill levels. A secondary objective is to demonstrate the suitability of the Smoothed Particle Hydrodynamics (SPH) method for numerical predictions in such an unusually shaped shell. Through numerical predictions, the possibility of modifying the egg's design to further encourage dissipation patterns is explored briefly. Simple experiments are also presented to check the validity of the numerical predictions.

Tuned vibration absorber for suppression of hand-arm vibration in electric grass trimmer

Prolonged use of electric grass trimmer exposes the user to the risk of hand-arm vibration syndrome. A simple approach for the suppression of hand-arm vibration in electric grass trimmer is presented. The proposed system is a tuned vibration absorber (TVA). Modal analysis and operating deflection shape analysis of the electric grass trimmer were carried out and a TVA was designed and fabricated for testing. The results indicated that minimum vibration level was related to the position of the TVA on the shaft of electric grass trimmer. The TVA was found to have best performance with 95% reduction on the acceleration level at position 0.025L. The results from modal analysis and operating deflection shape revealed that the presence of TVA has successfully reduced the large deformations of the handle where the node was shifted nearer to the handle location. The effect of TVA was also evaluated during field test involving grass trimming operation and subjective rating. The results indicated that average reduction of frequency-weighted rms acceleration in the Z h- axis was 84% and 72% in X h- axis for the cutting operation. For the no cutting operation, the reduction is 82% in Z h- axis and 67% in X h- axis. The presence of TVA in the electric grass trimmer has amplified the vibration level in Y h- axis by 19% (no cutting) and 21% (cutting). From the field test, subjective rating of vibration perception consistently rate better for controlled electric grass trimmer. Relevance to industry The tuned vibration absorber when installed to the electric grass trimmer attenuated the vibration total value by 67%. This significantly reduces the risk of hand-arm vibration syndrome.

Self-sensing tunable vibration absorber incorporating piezoelectric ceramic–magnetostrictivecomposite sensoriactuator

A novel self-sensing tunable vibration absorber (SSTVA) is developed for activeabsorption of vibrations in vibrating structures. The SSTVA consists of a piezoelectricceramic–magnetostrictive composite sensoriactuator suspended in a mounting frame by twoflexible beams connected to the axial ends of the sensoriactuator. The sensoriactuatorserves to produce an axial force for tuning of the natural frequency of the SSTVA, togather the signals associated with structural vibrations and to provide a lumped dampedmass for the SSTVA. By monitoring the sensoriactuator output voltage whileadjusting its input magnetic field (or electric current), the natural frequencyof the SSTVA is tuned to the targeted resonance frequency of a structure. Inthis paper, the working principle, design prototype and operating performanceof a 62.5 Hz SSTVA are reported. A high tunability of the natural frequency of20% and a good sensing capability of vibrations comparable to a commercialaccelerometer are obtained, together with a high absorbability of vibrations of ∼ 4 dB in a steel-plate–neoprene resilient mount structure.

The design of an active–adaptive tuned vibration absorber based on magnetorheologicalelastomer and its vibration attenuation performance

This paper presents an active–adaptive tuned vibration absorber (AATVA) which is basedon magnetorheological elastomer (MRE). A voice coil motor is attached to a conventionalMRE adaptive tuned vibration absorber (ATVA) to improve its performance. In this study,two feedback types of the activation force were analyzed and the stability condition wasobtained. In order to eliminate the time delay effect during the signal processing, aphase-lead compensator was incorporated. Based on the analysis, an MRE AATVAprototype was designed and its dynamic properties were experimentally investigated. Theexperimental results demonstrated that its resonant frequency could vary from 11 to18 Hz and its damping ratio decreased to roughly 0.05 from 0.19 by adding theactivation force. Besides, its vibration reduction abilities at the first two resonantfrequencies of the experimental platform could reach 5.9 dB and 7.9 dB respectively.

A Novel Semiactive Variable Stiffness Device and Its Application in a New Semiactive Tuned Vibration Absorber

An innovative design for a semiactive variable stiffness (SAVS) device is presented in this paper. This beamlike device is capable of altering its stiffness in a smooth manner between minimum and maximum levels by using the variations of moment of inertia of an area as it rotates around a normal axis passing through its centroid. Analytical expressions for the stiffness of the proposed device have been derived. As an application of the SAVS device in engineering, a semiactive tuned vibration absorber (SATVA) is developed that is capable of real-time retuning and operates effectively in broadband frequency excitations. A single-degree-of-freedom (SDOF) system coupled with the SATVA is considered. The excitation force is assumed to arise from a rotating unbalance whose frequency varies with a constant acceleration and then reaches a steady-state operating condition. The absorber stiffness is varied to tune the absorber’s natural frequency to the forcing frequency in real time. The effectiveness of SATVA is evaluated by comparing the system’s responses with those of the system with passive vibration absorber. The results show the salient features of the proposed SATVA in transient response reduction compared with the traditional passive vibration absorber.

Enhancement of Optical Adaptive Sensing by Using a Dual-Stage Seesaw-Swivel Actuator with a Tunable Vibration Absorber

Technological obstacles to the use of rotary-type swing arm actuators to actuate optical pickup modules in small-form-factor (SFF) disk drives stem from a hinge’s skewed actuation, subsequently inducing off-axis aberrations and deteriorating optical quality. This work describes a dual-stage seesaw-swivel actuator for optical pickup actuation. A triple-layered bimorph bender made of piezoelectric materials (PZTs) is connected to the suspension of the pickup head, while the tunable vibration absorber (TVA) unit is mounted on the seesaw swing arm to offer a balanced force to reduce vibrations in a focusing direction. Both PZT and TVA are designed to satisfy stable focusing operation operational requirements and compensate for the tilt angle or deformation of a disc. Finally, simulation results verify the performance of the dual-stage seesaw-swivel actuator, along with experimental procedures and parametric design optimization confirming the effectiveness of the proposed system.

Design of a Torsional Dynamic Absorber Using Magnetorheological Elastomers for Powertrain Vibration Control

This paper presents the design of torsional adaptive tunable vibration absorber (ATVA) using magnetorheological elastomers (MREs) for vibration reduction of powertrain systems. The MRE used for the ATVA development consists of a silicone polymer, silicone oil and magnetic particles with the weight fractions are 60%, 20%, 20%, respectively. Experimental testing is conducted to measure MRE Young’s modulus and damping ratio. With the MRE, a dynamic absorber design is proposed for powertrain vibration reduction and the parameters of magnetic circuit such as the number of turns of coils can be determined. Also, the mechanical parameters of the dynamic absorber are designed. In addition, the ATVA effectiveness is investigated through simulations, which is useful to optimize ATVA parameters to develop the ATVA.

Application of time delay resonator to machine tools

Undesirable vibration can negatively affect the performance of machineries. In case of a machine tool, it negatively affects machining accuracy and tool life. Performance may be improved at the design stage by increasing machine stiffness. However, this is difficult to accomplish with existing machines. This paper implements a delay resonator (DR) on model of a typical machine tool to minimize relative vibration between the cutting tool and workpiece during machining process. The DR is a tunable vibration absorber which converts a conventional passive absorber into a marginally stable resonator. This structure absorbs all the vibratory energy at its point of attachment. A strategy called “Stability charts” is used not only to resolve the stability question but also to find out gain and time delay of the absorption. Results show that relative motion between cutting tool and workpiece is reduced significantly.

Suppressing harmonic vibrations of a miniature cryogenic cooler using an adaptive tunable vibration absorber based on magneto-rheological elastomers

This paper presents dynamic performances of an adaptive tunable vibration absorber (TVA) designed to suppress the main harmonic disturbance of a miniature linear cryogenic cooler, which is being used in space applications such as an observation satellite. The adaptive TVA employs a magneto-rheological elastomer (MRE) for a variable stiffness element. This study first investigates the shear modulus change of MRE samples with respect to the magnetic flux density, which varies through the alignment of particle chains. The MRE with the maximal shear modulus change is mounted for the TVA on a prototype cooler, which emulates the characteristics of a miniature cryogenic cooler. Using the test setup, a series of vibration tests are performed to evaluate the performance and efficacy of the MRE TVA and its re-tuning ability. The experimental results show that the MRE TVA is able to robustly suppress the vibration of the cooler even when the frequency of resonant vibration is changed up to 87% from its initial frequency.

An adaptive tuned vibration absorber based on variable mass

The tuned vibration absorber (TVA) has been a device that is widely used to control the vibration of engineering structures and machines. However, the TVA works as a notch filter and only performs well when its natural frequency is identical to the excitation frequency. In order to obtain a wider band, some adaptive tuned vibration absorbers (ATVAs) were designed by modifying the stiffness or the damping of the TVA, but so far the design of ATVA by modifying the mass is seldom reported. In this paper, a novel ATVA based on variable mass (VM) is suggested by introducing a VM element into the TVA. The VM is implemented by a liquid tank with a mass that can be adjusted by changing the quantity of the liquid content. The frequency band of the VM ATVA is continuous and wider. The methods of extending the absorber band are discussed. Then, a little bottle is used to construct a VM ATVA. The performance of the constructed VM ATVA in vibration reduction in a primary system is investigated, and the band of the VM ATVA is predicted. The test results show that the designed VM ATVA attenuates the vibration in the primary system over a wider band of approximately 1.35 Hz. This indicates that the VM ATVA can be used as an effective, wideband vibration absorber

Optimum Design of a Tuneable Vibration Absorber with Variable Position to Suppress Vibration of a Cantilever Plate

Tuneable vibration absorbers (TVAs) are used as semi-active controllers to reduce the undesirable vibrations in applications such as electrical transmission lines, machining processes, gas turbines, engines, and bridges. In this paper, the application of a TVA to suppress vibration of a cantilever plate is presented. The TVA, including mass, spring, and damper elements, is attached to the cantilever plate under harmonic excitation. In addition, the effect of the spring mass is considered in this analysis, which cannot be neglected in the small-scale problems. After the formulation of the problem, the optimum specifications of the absorber, including the spring stiffness and its position, are determined using an algorithm based on mode summation method. Using a numerical algorithm, the spring stiffness of the absorber and its best position are found for different values of excitation force position and frequency.

Boundary value problem analysis of a tuned vibration absorber having non-linear springs

Non-linear dynamics of a two degrees-of-freedom (TDOF) tuned vibration absorber system using non-linear spring is studied as a boundary value problem. Five different combinations of linear and non-linear springs have been comprehensively analysed. For the different cases, a comparative study is made varying the forcing frequency. Another comparison is made for response versus time for different spring types at three important forcing frequencies. Analysis shows that the response of the system is changed because of the spring non-linearity; the change is different for different cases. Numerical simulation shows that the systems exhibit quasi periodic motion and instability.

Design and Control of a Real-Time Variable Modulus Vibration Isolator

A magnetorheological elastomer (MRE-based semi-active (SA) vibration isolator is developed and tested in real-time with a SA controller, illustrating the feasibility of MRE-based isolators. While several researchers have applied MREs to tunable vibration absorbers (TVAs), little work has been done using MREs in primary isolation systems. Further, in cases where TVAs were developed, few SA controllers were implemented in proof of concept experiments. This article presents a magnetically biased MRE-based vibration isolator, which enables the device to have a fail-safe operation in the event of a power failure. To test the effectiveness of the MRE isolator, a SA controller is developed to minimize the payload velocity. A comparison by simulation of variable modulus and damping systems is also presented. Finally, experimental results are given, showing that the MRE isolator and SA controller system reduce resonances and payload velocities by 16-30% when compared to passive systems.

An adaptive tunable vibration absorber using a new magnetorheological elastomer forvehicular powertrain transient vibration reduction

During the transient stage of acceleration, the powertrain experiences a period of high levelvibration because the engine speed passes through one or several powertrain naturalfrequencies. This paper presents a concept design of an adaptive tuned vibration absorber(ATVA) using a new magnetorheological elastomer (MRE) for powertrain transientvibration reduction. The MRE material used to develop the ATVA is a new one, which issynthesized from a highly elastic polymer and carbonyl iron particles of 3–5 and40–50 µm. Under a magnetic field of 0.3 T, the MRE material has a giant increase, which is morethan two orders, in both the storage and loss moduli. To facilitate the ATVAdesign, effective formulae for the storage modulus and loss factor were derived asexplicit functions of the applied magnetic field density. With the derived formulae,ATVA parameters such as the stiffness and damping coefficients were convertedeffectively from the magnetic field density. Thus, the ATVA frequency can betuned properly according to the excitation frequency. Numerical simulations of apowertrain system fitted with the ATVA were conducted to examine the ATVAproposed design. By using the MRE-based ATVA, the powertrain natural frequenciescan be actively tuned far away from the resonant area of excitation frequency.Also, the time histories of powertrain frequencies depending on the magneticfield density before and after installing the ATVA have been compared to showthat the resonant phenomena have been dealt with completely. As a result, thepowertrain transient vibration response is significantly suppressed. In addition, theeffect of the ATVA’s moment of inertia, stiffness and damping on the ATVA’seffectiveness during the transient stage was investigated to choose the ATVA’soptimal parameters. The MRE-based ATVA will be a novel device for powertrainvibration control not only for the steady stage but also for transient vibration.