Dynamic analysis of viscoelastic tuned mass damper system under harmonic excitation

Tuned mass dampers (TMDs) are proposed as a solution to reduce the involuntary tremor at the upper limb of a patient with postural tremor. The upper limb is modeled as a three-degrees-of-freedom rotating system in the vertical plane, with a flexion-extension motion at the joints. The measured extensor carpi radialis signal of a patient is used to excite the dynamic model. We propose a numerical methodology to optimize the parameters of the TMDs in the frequency domain combined with the response in the time domain. The objective function for the optimization of the dynamic problem is the maximum angular displacement of the wrist joint. The optimal stiffness and damping of the TMDs are obtained by satisfying the minimization of the selected objective function. The considered passive absorber is a cantilever beam–like TMD, whose length, beam cross-sectional diameter, and mass position reflect its stiffness for a chosen additional mass. A parametric study of the TMD is conducted to evaluate the effect of the TMD position along the hand segment, the number of TMDs, and the total mass of TMDs. The sensitivity of the TMD to a decrease of its modal damping ratio is studied to meet the range of stainless steel. TMDs are manufactured using stainless steel beams of the same length (9.1 cm) and cross-sectional diameter (0.79 mm), for which the mass (14.13 g) position is adjusted to match the optimal frequency. Three TMDs holding a mass of 14.13 g each cause 89% reduction in the wrist joint angular displacement.

Section: Introductionmentioning

confidence: 99%

Upper limb involuntary tremor reduction using cantilever beam TMDs

Gebai

Cumunel

Hammoud

et al. 2022

“…The popularity of a TMD stems from its efficiency, reliability and ease of incorporation in the primary system without requirements of any considerable system modifications. Various forms of robust TMDs are evolving day-to-day encountering a wide range of structural applications such as TMD inerter (Marian and Giaralis, 2014), pounding TMD (Wang et al, 2017), viscoelastic TMD (Dai et al, 2019), frictional TMD (Jiang et al, 2019) and TMD with large mass ratio (Angelis et al, 2012). In its traditional passive form, a TMD is basically a linear spring–mass–dashpot vibration absorber system in different configurations such as a sliding mass block, a simple pendulum or its various other arrangements (Debnath et al, 2016; Gewei and Basu, 2010; Li et al, 2010; Saaed et al, 2015; Zhao-Dong et al, 2020; Zuo, 2009).…”

Section: Introductionmentioning

confidence: 99%

A novel tuned mass-conical spring system for passive vibration control of a variable mass structure

Chakraborty

Ghosh²,

Ray-Chaudhuri

2021

This article presents the design of a tuned mass damper with a conical spring to enable tuning to the natural frequency of the system at multiple values, as may be convenient in case of a system with fluctuations in the mass. The principle and design procedure of the conical spring in the context of a varying mass system are presented. A passive feedback control mechanism based on a simple pulley-mass system is devised to cater to the multi-tuning requirements. A design example of an elevated water tank with fluctuating water content, subjected to ground excitation, is considered to numerically illustrate the efficiency of such a tuned mass damper associated with the conical spring. The conical spring is designed based on the tuning requirements at different mass conditions of the elevated water tank by satisfying the allowable load bearing capacity of the spring. Comparisons are made with the conventional passive tuned mass damper with a linear spring tuned to the full tank condition. Results from time history analysis reveal that the conical spring-tuned mass damper can be successfully designed to remain tuned and thereby achieve significant response reductions under stiffening conditions of the primary structure, whereas the linear spring-tuned mass damper suffers performance degradation because of detuning, whenever there is any fluctuation in the system mass.

“…The TMD is composed mainly of a mass suspended on spring elements and viscous dampers. When the structure vibrates, the TMD vibrates in the opposite phase which results in a restoring force (Batou and Adhikhari, 2019; Dai et al, 2019; Ghassempour et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Mitigation of vibrations in sandwich-type structures by a controllable constrained layer

Orłowska

Gałęzia

Świercz

et al. 2020

This study presents and tests a method for semi-active control of vibrations in sandwich-type beam structures. This method adapts a strategy called prestress accumulation release. The prestress accumulation release strategy is based on structural reconfiguration: it uses short time, impulsive and localised changes of actuator properties (such as stiffness or damping), which are applied to a part of the system in the moments, when its strain energy attains a local maximum. The method has been earlier applied as a global control scheme to mitigate the fundamental vibration mode of a cantilever beam (by stiffness control) and in the task of mitigating the first four modes of a frame structure (by damping control). This study proposes a prestress accumulation release strategy and tests its effectiveness for the case of a three-layered sandwich structure, with the internal layer fabricated from a material with dissipative characteristic locally controllable through the material damping coefficient. In contrast to the earlier research, the control is applied thus at the level of material characteristics instead of a discrete set of dedicated actuators. Based on the finite element method, a numerical experiment involving a passively damped, as well as prestress accumulation release-controlled, three-layered cantilever beam excited by initial displacements was performed. The effectiveness of the approach was studied for a broad range of internal layer damping parameters. The presented results revealed a high potential of the prestress accumulation release strategy in semi-active damping of vibrations of sandwich-type structures.