Vibration Attenuation Performance Research Articles

Experimental study on driver seat vibration characteristics of crawler-type combine harvester

To improve the driving comfort of combine harvesters, driver seat low-frequency vibration and related driver ride-comfort problems were investigated on a Chinese CFFL-850 crawler-type full-feed combine harvester based on ISO2631. Driver vibration and driving seat transmission characteristics were measured under the following conditions: no-load idling, driving on the road, driving in the field, and simulated harvesting. The root mean square values composite vibration under four conditions were 3.63 m/s2, 2.35 m/s2, 3.34 m/s2, and 2.67 m/s2, respectively. For the same condition, the maximum root mean square scores of vibration component on driver whole-body occurred in the seat support surface (test point 1) and vertical direction (Z direction), which were 3.56 m/s2, 2.05 m/s2, 3.15 m/s2, and 2.43 m/s2, respectively. The test point 2 to test point 1 vertical-transfer function curve trends were nearly identical. Nearly all of the transfer coefficients were greater than 1 in the range of 1-50 Hz, therefore, the seat vibration attenuation performance was poor. Based on the analysis results, the driver seat structure was altered and a verification test was performed. The test results indicated that after an X-damping mechanism was installed, vibration acceleration, on the surface of the seat support under the road-driving conditions, decreased from 2.35 m/s2 to 1.68 m/s2. Under the simulated harvesting condition, the vibration acceleration decreased from 2.56 m/s2 to 1.46 m/s2. Nearly all of the seat vertical transfer coefficients were less than 1 within the frequency range of 1-80 Hz, therefore the dynamic comfort of the seat was ameliorated after structural improvement. Keywords: crawler-type combine harvester, driver seat, vibration characteristics, ride comfort, damping, structure optimum DOI: 10.25165/j.ijabe.20191202.3657 Citation: Xu L Z, Chai X Y, Gao Z P, Li Y M, Wang Y D. Experimental study on driver seat vibration characteristics of crawler-type combine harvester. Int J Agric & Biol Eng, 2019; 12(2): 90–97.

Reducing Uncertainty in Shunt Damping by Model-Predictive Product Stiffness Control in a Single Point Incremental Forming Process

The stiffness of metal formed products strongly affects the dynamic behavior of structures in which they are integrated. Forming processes underlie short and long-term variations which cause the stiffness to be uncertain.In the application of resonant shunted piezoelectric transducers for vibration attenuation, uncertain stiffness may cause significant reduction in the vibration attenuation performance due to imprecise tuning. In the past, large efforts were made to control one or more geometrical feature of products while weightier features that cause uncertainty have not been addressed.In this paper, a single point incremental forming process of a membrane-like spring element on a servo press with a 3 degrees of freedom drive system is investigated. This spring element is used in a beam support for lateral vibration attenuation with resonant shunted transducers as well as axial buckling stabilization.To reduce uncertainty caused by process variations, an offline closed-loop control of product stiffness is presented. Different product and forming criteria are integrated into a control approach based on an optimization routine. By making use of a model-based prediction of the product properties, the approach shows how to realize a multi-objective control.

A novel energy sink with piecewise linear stiffness

In this paper, a nonlinear energy sink with piecewise linear stiffness spring is proposed, and the fundamental characteristics of the nonlinear energy sink are investigated. Firstly, the structure of the piecewise linear stiffness spring is proposed and nonlinearity of the spring is analyzed. Then, the dynamic model of the primary vibration system with the nonlinear energy sink is built, and the responses and vibration suppression effects are studied by numerical simulations. Finally, the effectiveness of the NES is proved by experiment. The results show that the piecewise linear stiffness spring is effective; its structure is simple, compact and adjustable; the vibration attenuation performance of nonlinear energy sink is very good under moderate exciting force.

Hybrid Active Wave/Mode Control of Space Prestressed Taut Cable Net Structures

The space environments and special mission demands require large-scale and high shape accuracy cable net structures. The vibration control is an essential issue for shape control and performance conservation of large flexible cable net structures. This paper investigates the hybrid active wave/mode control of space prestressed taut cable net structures. First, the traveling wave dynamic model of cable net structures is explored by elemental waveguide and propagation equations of cables together with force balance conditions and compatibility conditions of joints. Then, the active wave control model is established by using the assumption forms of wave controllers to adjust the mechanical boundaries of the controlled joints. Finally, the hybrid active wave/mode control model is proposed by constructing the mapping relationship between wave control force, modal damping and natural frequencies. The proposed control method is verified by a planar cable net structure and the results show that the hybrid active wave/mode control can give a better broadband vibration attenuation performance for space prestressed taut cable net structures.

Vibro-acoustic metamaterial for longitudinal vibration suppression in a low frequency range

This study proposes a theoretical model of a vibro-acoustic metamaterial for longitudinal vibration suppression in a low frequency range and computationally and experimentally demonstrates the vibration attenuation performance of the proposed metamaterial. The vibro-acoustic coupling analysis is performed on a theoretical model in which a discrete vibration system and a short-length duct are periodically repeated. The transfer matrix method and the Bloch–Floquet theorem were developed to calculate the Bloch phase of a unit cell of the proposed vibro-acoustic metamaterial. Its stop band predicted from the Bloch phase commenced at 0 Hz and coincided with the frequency range of low transmissibility (<1). The effects of unit cell parameters on the upper limit frequency of the stop band are discussed, and the dispersion relation and effective mass density curves of the proposed vibro-acoustic metamaterial explain its underlying physics. The developed theoretical approach is extended to vibro-acoustic metamaterials including a continuous vibration system, instead of a discrete vibration system, for actual application. Finite element analysis and experiments on the extended vibro-acoustic metamaterials were performed to validate the vibration attenuation performance of the proposed metamaterial, which can be used to suppress longitudinal vibration waves transmitted between two mechanical parts.

A six degree of freedom passive vibration isolator with quasi-zero-stiffness-based supporting

A six degree of freedom nonlinear passive vibration isolator is proposed based on Stewart platform configuration with the quasi-zero-stiffness structure as its legs. Due to the high static stiffness and low dynamic stiffness of each leg, the proposed six degree of freedom system can realize very good vibration isolation performance in all six directions while keeping high static load-bearing capacity in a pure passive manner. The mechanic model of the proposed six degree of freedom isolator and the dynamic equation of the isolator are established successively. Theoretical analysis on cross coupling stiffness reveals that the system can demonstrate quasi-zero-stiffness property in all six degree of freedom. Moreover, an analysis on stability shows that the condition of structural parameters for the isolator to realize quasi-zero-stiffness is also the stability boundary of the system. A series of numerical simulations on displacement transmissibilities in coupled degree of freedoms, the coupling effects of transmissibility, and a dynamic response in random excitation are carried out to show the effectiveness of the proposed six degree of freedom isolator, as well as the influence of structural parameters on vibration attenuation performance. Considering its high performance in a simple passive manner, it can be foreseen that the proposed six degree of freedom isolator will be applied in various engineering practices with multi-degree of freedom vibration isolation.

Decentralized vibration control of a voice coil motor-based Stewart parallel mechanism: Simulation and experiments

In pursuit of a better working performance of the precise instruments equipped in spacecraft, vibration control systems are essential for preventing them from being disturbed. This paper studies the decentralized vibration control problems of a voice coil motor-based Stewart parallel mechanism. The Newton–Euler Method is used to formulate the dynamical equations of the Stewart platform in joint space. The decentralized control theory is employed to design the controller for the linearized system. A prototype of the voice coil motor-based Stewart platform was designed and tested to validate the vibration attenuation performance of the decentralized system. The effectiveness of active vibration isolation system is revealed by both the simulation and real-time experiments.

On the impact of damping on the dispersion curves of a locally resonant metamaterial: Modelling and experimental validation

Recently, locally resonant metamaterials have come to the fore in noise and vibration control engineering, showing great potential due to their superior noise and vibration attenuation performance in targeted and tunable frequency ranges, referred to as stop bands. Damping has an important influence on the performance of these materials, broadening the frequency range of attenuation at the expense of peak attenuation. As a result, understanding and including the effects of damping is necessary to more accurately predict the attenuation performance of these locally resonant metamaterials. Classically, these often periodic structures are analysed using a unit cell modelling approach to predict wave propagation and thus stop band behaviour, discarding damping. In this work, a unit cell method including damping is used to analyse the complex dispersion curves of a locally resonant metamaterial design. The wave solutions in and around the stop band frequency range are compared to those of the unit cell method discarding damping. The influence on the dispersion curves of damping in resonator and host structure is discussed and the obtained dispersion curves are validated through an experimental dispersion curve measurement based on an Extended Inhomogeneous Wave Correlation method using Scanning Laser Doppler Vibrometry for a metamaterial plate manufactured at a representative scale. Excellent agreement is obtained between the numerically predicted and experimentally retrieved dispersion curves.

Development of a Vibration Attenuation Track at Low Frequencies for Urban Rail Transit

AbstractRailway‐induced vibrations at low frequencies have become an important environmental issue with the rapid development of urban rail transit. In this study, a new vibration attenuation track (VAT) capable of passively mitigating vibrations at low frequencies is developed based on an integrated theoretical and experimental study. The full‐scale VAT is built which incorporates a floating slab track (FST) and the attached dynamic vibration absorbers (DVAs) with key parameters determined by the fixed‐point theory and modal analysis technique. The vibration attenuation performance of the VAT is investigated under train dynamic loads by establishing a three‐dimensional coupled dynamic model of a metro vehicle‐VAT‐subgrade system, and is further elucidated and validated by carrying out full‐scale dynamic tests under different harmonic loadings. Computational and experimental results both show that vibrations of the track are effectively absorbed by the attached DVAs leading to a significant reduction of the subgrade vibrations at the low frequency of 9–16 Hz.

Development of an MR seat suspension with self-powered generation capability

This paper proposes a self-powered magnetorheological (MR) seat suspension on the basis of a rotary MR damper and an electromagnetic induction device. By applying the self-powering component to the MR seat suspension, the operation cost of the semi-active seat is much cheaper because no external energy is required to control the MR damper. In this paper, the structure, design and analysis of the seat suspension were presented following the introduction section. The property tests of the self-powered seat suspension were conducted using an MTS machine. A robust control algorithm was developed to control the self-powered MR seat suspension and the vibration attenuation performance of the seat suspension was tested under two different vibration excitations, i.e. harmonic excitation and random excitation. The testing result verifies that the self-powered MR seat suspension under proper control can improve the ride comfort for passengers and drivers.

Force transmissibility of floating raft systems with quasi-zero-stiffness isolators

In view of the excellent performance of a single quasi-zero-stiffness (QZS) device in vibration attenuation, this paper presents a study on a vibration isolation floating raft system constructed with a double-layer QZS mechanism. A QZS device is a typical nonlinear isolator, hence the floating raft system is a coupled highly nonlinear isolation system. To understand the behaviors and its performance in vibration attenuation, an analytical approach is developed to describe the characteristics including the mathematical relationship between amplitude–frequency, force transmissibility, and the effects of the mass ratio and damping ratios on attenuation performance. The outcomes show that the two-degree-of-freedom QZS–QZS system is superior for vibration isolation when compared to the traditional linear system and the two other types of QZS systems. The effective vibration isolation frequency region of the QZS–QZS system is expanded to the low-frequency region by 72%. The QZS system is sensitive to the damping ratio, which decreases the resonance peak significantly. The mass ratio is a crucial design parameter in low-frequency vibration isolation design.

Evidence of multimodal vibration damping using a single piezoelectric patch with a negative capacitance shunt

In this work, a piezoelectric patch shunted with a negative capacitance circuit has been used to simultaneously damp several modes of a square aluminum plate at low frequencies. The active nature of such electromechanical system leads to regions of instabilities in which the highest vibration attenuation performance appears in the softening region. Once the geometry is fixed, the system has two degrees of freedom, dominated by the electrical parameters of the circuit: the resistance and the negative capacitance. We tune both the value of the negative capacitance, in order to place the structure close to the instability in the softening region, and the resistance of the circuit in such that control the losses of the system. This work shows an optimal design to simultaneously damp several modes with non-zero electromechanical coupling factors using a single shunted patch at low frequencies. The problem is solved numerically and tested experimentally with good agreement. The results show the possibility of controlling the modal response of the system, opening prospects to improve the acoustic comfort with systems using piezoelectric shunted damping circuits with small additional mass with a high tunability by only adjusting the properties of the shunt.

Vibration attenuation of high dimensional quasi-zero stiffness floating raft system

This paper investigates the vibration attenuation performance of a floating raft system with quasi-zero stiffness (QZS) isolators. A high dimensional mathematical model of the floating raft system with 12 degrees of freedom (DOF) is established for dynamics analysis. The harmonic balance method is adopted to obtain the analytical solution of the high dimensional and coupled system, which permits the study of the nonlinear characteristic and mechanism of the QZS system. The results show that the QZS –QZS system has the lowest force transmissibility and the lowest frequency band for vibration isolation, which is a promising candidate for low frequency vibration isolation even in high dimensional systems. The vibration isolation region of the QZS-QZS system extends to low frequency by 80% compared with the 1 DOF linear system. The force transmissibility of the QZS-QZS system is four times lower than that of the corresponding linear system in vibration isolation region. Amplitudes of the transmitted forces in the x, y, and z directions are 9.8%, 9.8%, and 0.4% of the corresponding excitations.

State observation–based control algorithm for dynamic vibration absorbing systems featuring magnetorheological elastomers: Principle and analysis

Based on state observation, a rapid, stable, and effective control algorithm for magnetorheological elastomer (MRE)–based dynamic vibration absorbers (DVAs) applied to automobile powertrain mount systems is proposed and investigated in this article. The state-space model for powertrain mount systems with MRE-based DVAs is established using the rank criterion method for observable systems. According to the principle of system reconfiguration, a full state observation model using an adaptive Kalman filter with Sage–Husa noise estimator is developed. With the state vectors estimated by the Kalman filter, the phase difference between the displacement of the dynamic mass of the MRE-based DVA relative to the powertrain and the absolute displacement of the powertrain is updated continuously based on Simpson’s rule. By adjusting the applied current to the MRE-based DVA with fuzzy logic control corresponding to the cosine value of the phase difference, the natural frequency of the MRE-based DVA could track the excitation frequency of the powertrain well, which results in vibration attenuation of the powertrain mount system. With consideration of excitation noise, time delays, and parametric uncertainties, the simulation experiments of vibration attenuation performance of the MRE-based DVA for the powertrain mount systems when under time-varying excitation are carried out to verify the effectiveness and the stability of the proposed algorithm with fuzzy steps. The simulation results show that when using the proposed algorithm with fuzzy steps, the MRE-based DVA could attenuate the powertrain vibration rapidly and effectively, and the vibration attenuation performance will not be influenced by noise, time delays, and parametric uncertainties.

Effect of shelf aging on vibration transmissibility of anti-vibration gloves.

Anti-vibration gloves have been used in real workplaces to reduce vibration transmitted through hand-held power tools to the hand. Generally materials used for vibration attenuation in gloves are resilient materials composed of certain synthetic and/or composite polymers. The mechanical characteristics of the resilient materials used in anti-vibration gloves are prone to be influenced by environmental conditions such as temperature, humidity, and photo-irradiation, which cause material degradation and aging. This study focused on the influence of shelf aging on the vibration attenuation performance of air-packaged anti-vibration gloves following 2 yr of shelf aging. Effects of shelf aging on the vibration attenuation performance of anti-vibration gloves were examined according to the Japan industrial standard JIS T8114 test protocol. The findings indicate that shelf aging induces the reduction of vibration attenuation performance in air-packaged anti-vibration gloves.

Magnetic Nonlinear Energy Sink for Vibration Attenuation of Unbalanced Rotor System

A novel nonlinear energy sink (NES) consisting of permanent magnetic springs and coil springs is proposed, and the vibration attenuation performance of the NES for unbalanced rotor system is investigated. Firstly, the nonlinearity of the magnet spring is analyzed and the structure of the NES is introduced. Then, the dynamic model of the rotor system with the NES is built, and the responses and stabilities of the system are studied by applying Complexification-averaging method. The strongly modulated responses (SMR) behavior, which is the most important performance characteristic of the NES, is analytically studied by combining Complexification-averaging method and multiscale method and numerically verified by Runge-Kutta method. The results show that the NES is effective in attenuating the vibration of unbalanced rotor, and the SMR occurrence range can be broadened by increasing the nonlinearity of the NES. And also, the NES has better performance over a wider frequency range than the linear absorber.

Fingers vibration transmission performance of vibration reducing gloves

Vibration attenuation performance of vibration reducing (VR) gloves is, invariably, measured at the palm using the method described in ISO 10819 (2013). The standardized method, however, does not address the glove performance in terms of fingers vibration, which is substantially different from that of the palm. An investigation was conducted to enhance the understanding of fingers vibration transmission properties of 4 different types of VR gloves (air, gel, hybrid and leather) using 4 male subjects in the laboratory. Three different finger adapters, each containing a miniature three-axis accelerometer, were designed and assessed for measurements of vibration responses at the fingers of the gloved hand. Vibration responses of the VR gloves were measured at the middle phalanges of the index and middle fingers using two Velcro finger adapters under the standardized vibration spectra and the spectra of 3 different hand tools, namely a road breaker, a nutrunner and an orbital sander. Vibration transmissibility of the gloves was also measured at the palm using the standardized palm adapter. The frequency response functions (FRF) obtained for the fingers of the gloved hand were used to estimate vibration transmission performances of the gloves at the index and middle fingers. The results show that only the air and hybrid VR gloves provide some attenuation of vibration transmitted to the index finger compared to the bare hand, while nearly all the gloves amplify vibration of the middle finger. The vibration attenuation was evident at the palm for the air and hybrid gloves above 40 Hz. The gel and leather gloves revealed nearly unity transmissibility in most of the frequency range. Only the hybrid glove passed the criteria of ISO 10819 (2013) to be designated as an anti-vibration (AV) glove, although it amplified vibration transmitted to the middle finger, particularly in the H-frequency range (200–1250 Hz). Fairly good agreements (−11%–13%) were obtained between the measured and estimated fingers vibration responses for all the gloves using the FRF method under the vibration spectra of the selected tools.Relevance to industry:Vibration is transmitted to the hand-arm system of operators using power tools and occupational exposure to hand transmitted vibration (HTV) arising from hand-held power tools has been related to an array of disorders. Vibration reducing (VR) gloves are viewed as one of the simple methods to protect workers from hand-arm vibration syndrome (HAVS). The international standard on the assessment of VR gloves addresses only the transmission of vibration to the palm, even though the vibration responses of fingers are substantially different. This study explored both the palm and fingers vibration transmissibility characteristics of VR gloves and proposed a method for assessing the vibration reduction performance of the glove under vibration spectra of different tools. The results of the study are thus considered to provide guidance towards enhanced screening criteria for AV gloves, and for selection of gloves for different tools.

Principle, modeling, and control of a magnetorheological elastomer dynamic vibration absorber for powertrain mount systems of automobiles

This article proposes and validates the principle of a new magnetorheological elastomer (MRE) dynamic vibration absorber (DVA) for powertrain mount systems of automobiles. The MRE DVA consists of a vibration absorption unit and a passive vibration isolation unit. The vibration absorption unit composed of a magnetic conductor, a shearing sleeve, a bobbin core, an electromagnetic coil, and a circular cylindrical MRE is utilized to absorb the vibration energy, and the passive vibration isolation unit is used to support the powertrain. The finite element method is employed to validate the electromagnetic circuit of the MRE DVA and obtain the electromagnetic characteristics. The theoretical frequency-shift principle is analyzed via the established constitutive equations of the circular cylindrical MRE In order to demonstrate how the parameters of the MRE influence the vibration attenuation performance, the MRE DVA is applied to a powertrain mount system to replace the conventional passive mount. The frequency-shift property of the vibration absorption unit and the vibration attenuation performance of the MRE DVA on the powertrain mount system are experimentally tested. To validate and improve the vibration attenuation performance for the semi-active powertrain mount systems, an optimal variable step algorithm is proposed for the MRE DVA and numerical experiments are carried out.

Embedded Acoustic Black Holes for semi-passive broadband vibration attenuation in thin-walled structures

We explore the use of structure-embedded Acoustic Black Holes (ABH) to design thin-walled structural components exhibiting broadband vibration attenuation characteristics. The ABH is a geometric taper with a power-law profile fully integrated into the structural component and able to induce a smooth and progressive decrease of both the velocity and the wavelength of flexural waves. Previous studies have shown these characteristics to be critical to enable highly efficient vibration attenuation systems. The performance of ABH thin-walled structures is numerically and experimentally evaluated under both transient and steady state excitation conditions. Both numerical and experimental results suggest that the proposed approach enables highly efficient and broadband vibration attenuation performance.

Carbonyl iron powder surface modification of magnetorheological elastomers for vibration absorbing application

With excellent characteristic of magnetic-control stiffness, magnetorheological elastomer (MRE) is well suited as a spring element of vibration absorber. To improve the vibration attenuation performance of MRE vibration absorbers, this paper expects to improve the mechanical strength and reduce the loss factor of MRE by interface modification. The surface of carbonyl iron powder (CIP) was modified with silica coating by a simple and convenient approach. Several MRE samples, with different proportions of modified CIPs were fabricated under a constant magnetic field. The morphology and composition of modified CIP were characterized by scanning electron microscope and Fourier transform infrared spectra. The results indicated that the modified CIPs were coated with uniform and continuous silica, which can make a better combination between particle and matrix. The tensile strength, magnetorheological properties and the damping properties of the MRE samples were tested by material testing machine and rheometer. The experimental results demonstrated that the loss factor of the MRE which incorporated with modified CIPs decreased markedly, and the tensile strength of such material has been much improved, at the same time this kind of MRE kept high MR effect. It is expected that this MRE material will meet the requirements of vibration absorber.