A Circular Eccentric Vibration Absorber with Circumferentially Graded Acoustic Black Hole Features

A previously proposed planar axisymmetric dynamic vibration absorber (DVA), with embedded acoustic black hole (ABH) features, has been shown to suffer from the very selective coupling with the host structure, thus compromising its vibration reduction performance. To tackle the problem, an eccentric ABH-based circular DVA whose thickness profile is tailored according to a circumferential gradient variation is proposed in this paper. This new configuration preserves the ABH profile in the radial direction alongside a continuous variation along the circumferential direction and breaks the axisymmetry of the original DVA design at the same time. While the former permits the ABH features to fully play out in a continuous manner, the later entails a more effective coupling with the host structure. These salient properties have been demonstrated and confirmed both numerically and experimentally by examining a benchmark plate structure. For analyses, a coupling model embracing the host structure and the add-on DVAs is established which allows the calculation of the coupling coefficient, a vital quantity to guide the DVA design. Studies demonstrate the advantages of the proposed DVA over existing designs for the same given mass. The enriched structural coupling and the enhanced modal damping, arising from the eccentric and circumferentially graded ABH design, are shown to be the origin of such improvement. All in all, the physical process underpinning the dynamic absorber principle and waveguide absorber from the host structures is simultaneously consolidated, thus leading to superior broadband structural vibration suppression.

Optimization design for multiple dynamic vibration absorbers on damped structures using equivalent linearization method

The dynamic vibration absorber and tuned mass damper are widely used to suppress harmful vibration of the damped structures under external excitation. The multiple dynamic vibration absorbers have more benefit than the single dynamic vibration absorber. The multiple dynamic vibration absorbers are portability and easy to install because its size is significantly reduced compared to an individual damper. This paper proposes a design method to obtain optimal parameters of multiple dynamic vibration absorbers attached on damped primary structures by using the least squares estimation of equivalent linearization method. An explicit expression of damping ratio and tuning parameters of multiple dynamic vibration absorbers are determined for minimizing the maximum displacement of the primary structures based on the fixed-point theory. The new contribution is provided a reliable theoretical basis for optimizing parameters of the multiple dynamic vibration absorbers that are attached on the damped primary structures. The numerical results reveal the effectiveness of the proposed optimal parameters of multiple dynamic vibration absorbers in reduce vibration of damped primary structures. In the practical applications, this research results allow to divide a large dynamic vibration absorber into many equivalent small dynamic vibration absorbers, which are convenient for manufacturing and installing on the damped primary structures such as high buildings and cable-stayed bridges.

Optimisation of absorber parameters in the case of stochastic vibrations in a bridge with a deck platform for servicing pipelines

The paper focuses on the problem of optimising the cooperation between a dynamic vibration absorber (DVA) and a structure. The authors analyse a road beam bridge equipped with a working platform (deck) used to service pipelines installed on the structure. The paper studies the problem of choosing the optimal parameters for damping absorbers that reduce the random vibration of a beam subjected to a random sequence of moving forces with a constant velocity. The stochastic properties of the load are modelled by means of a filtering Poisson process. A single-degree-of-freedom (SDOF) absorber model with a multi-degree-of-freedom (MDOF) primary structure model are is considered.

Modelling of SMA Vibration Systems in an AVA Example

Vibration suppression, as well as its generation, is a common subject of scientific investigations. More and more often, but still rarely, shape memory alloys (SMAs) are used in vibrating systems, despite the fact that SMA springs have many advantages. This is due to the difficulty of the mathematical description and the considerable effortfulness of analysing and synthesising vibrating systems. The article shows the analysis of vibrating systems in which spring elements made of SMAs are used. The modelling and analysis method of vibrating systems is shown in the example of a vibrating system with a dynamic vibration absorber (DVA), which uses springs made of a shape memory alloy. The formulated mathematical model of a 2-DOF system with a controlled spring, mounted in DVA suspension, uses the viscoelastic model of the SMA spring. For the object, a control system was synthesised. Finally, model tests with and without a controller were carried out. The characteristics of the vibrations’ transmissibility functions for both systems were determined. It was shown that the developed DVA can tune to frequency excitation changes of up to ±10%.

Design and Implementation of Passive Dynamic Vibration Absorber for Vibration control of rotating mass unbalanced Air Blower

Frequently it is found in the industry that unbalances of the rotating components generate vibration due to centrifugal force. Here an attempt has been made to reduce vibrations caused by unbalance in the impeller of the Air Blower. The Dynamic Vibration Absorber (DVA) device is designed in such a way that optimal tuning damping factor and mass ratio were found as same as that obtained by using higher order of perturbation method. The designed DVA brings Vrms values within the limit set by ISO 10816-3 for Unlimited Long-Term Operation Allowable. More than 50% appreciable vibration reduction was measured in radial horizontal and vertical direction both at the motor drive and non-drive end.

Effect of delayed resonator on the vibration reduction performance of vehicle active seat suspension

The combination of dynamic vibration absorber and partial state feedback with time-delay is called delayed resonator. In order to suppress the seat vibration caused by uneven road surface and improve ride comfort, the delayed resonator is applied to the seat suspension to realize active control of the seat suspension system. The dynamic model of the half-vehicle suspension system is established, and the time-delay differential equation of the system under external excitation is solved by the precise integration method. The root mean square of the time-domain vibration response of seat displacement, seat acceleration and vehicle acceleration are selected as the objective function. Then, the optimal time-delay control parameters are obtained by particle swarm optimization algorithm. The frequency sweeping method is used to obtain the critical time-delay value and time-delay stable interval of the system. Finally, an active seat suspension model with delayed resonator is established for numerical simulation. The results show that the delayed resonator can greatly suppress the seat vibration response regardless of the road simple harmonic excitation or random excitation. Compared with dynamic vibration absorber, it has a better vibration absorption effect and a wider vibration reduction frequency band.

Vibration Control of Time-Varying Delay under Complex Excitation

The existing available research outcomes on vibration attenuation control for time-delay feedback indicate that, for the delay dynamic vibration absorber with fixed time-delay control parameters, under harmonic excitation, a good vibration attenuation control effect occurs on the vibration of the main system. However, the effect is not obvious for complex excitation. Aiming at the above problems, in a short time interval, a harmonic excitation with the same displacement size as the complex excitation was established. Then, by calculating its equivalent amplitude and equivalent frequency, a harmonic equivalent method for complex excitation was proposed in this paper. The time-delay parameters were adjusted according to the equivalent frequency of harmonic equivalent excitation in real time; therefore, a good vibration attenuation control effect was obtained through the delay dynamic vibration absorber in the discrete time interval. In this paper, research on a time-varying delay dynamic vibration absorber was conducted by taking the two-degree-of-freedom vibration system with a delay dynamic vibration absorber as an example. The simulation results show that the proposed control method can reduce the vibration of the main system by about 30% compared with the passive vibration absorber. This can obviously improve the performance of the time-delay dynamic vibration absorber. It provides a new technical idea for the design of vehicle active frame system.