Active feedforward control of flexural waves in an Acoustic Black Hole terminated beam

Abstract

Acoustic Black Holes (ABHs) are structural features that are typically realised by introducing a tapering thickness profile into a structure that results in local regions of wave-speed reduction and a corresponding enhancement in the structural damping. In the ideal theoretical case, where the ABH tapers to zero thickness, the wave-speed reaches zero and the wave entering the ABH can be perfectly absorbed. In practical realisations, however, the thickness of the ABH taper and thus the wave-speed remain finite. In this case, to obtain high levels of structural damping, the ABH is typically combined with a passive damping material, such as a viscoelastic layer. This paper investigates the potential performance enhancements that can be achieved by replacing the complementary passive damping material with an Active Vibration Control (AVC) system in a beam-based ABH, thus creating an Active ABH (AABH). The proposed smart structure thus consists of a piezo-electric patch actuator, which is integrated into the ABH taper in place of the passive damping, and a wave-based, feedforward AVC strategy, which aims to minimise the broadband flexural wave reflection coefficient. To evaluate the relative performance of the proposed AABH, an identical AVC strategy is also applied to a beam with a constant thickness termination. It is demonstrated through experimental implementation, that the AABH is able to achieve equivalent broadband performance to the constant thickness beam-based AVC system, but with a lower computational requirement and a lower control effort, thus offering significant practical benefits.

A Partitioned Vibration Absorber with Acoustic Black Hole Features

“…Existing researches on ABH are grooming in the past few decades, including many aspects such as theoretical analyses [3][4][5][6][7][8], experimental researches [9][10][11][12], structural design [13][14][15][16][17], optimization [18][19][20] and some burgeoning engineering applications such as vibration and noise reduction and energy recovery [21][22][23][24][25]. The most recent evaluations of the state-of-the-art in ABH research as well as some prospective applications were provided by Pelat et al [26] and Zhao et al [27] However, in the majority of the researches mentioned above, ABH is embedded into a structure via thinned thickness..…”

Control of vibration in a plate using active acoustic black holes

“…An active solution to this problem has been presented for an active ABH (AABH) beam termination in [17], where it has been shown that a feedforward wave-based control strategy can be applied to control the reflection coefficient of the AABH. For a plate with embedded ABHs, the reflection coefficient with respect to structural waves is less obviously defined and, therefore, previous research on ABHs embedded in plates has focused on different structural metrics, such as surface mobility [1,9] and mean-squared acceleration/velocity [5,6,18].…”

“…To increase the low frequency performance of an ABH and also increase its potential adaptability, an active solution has been proposed in which an active vibration control system is integrated into an ABH beam termination [18]. This active ABH (AABH) utilises a feedforward wave-based control strategy, which can control the reflection coefficient in the beam using a piezoelectric patch actuator attached to the ABH taper.…”

“…The AABH beam termination is shown to offer significant augmentation of the low frequency control performance compared to the passive ABH, but also compared to a constant thickness beam with an identical active termination. In addition, it is shown that the AABH has both lower power and computational requirements compared to the active termination applied to a constant thickness beam [18].…”

Zero reflections by a 1D Acoustic Black Hole termination using thermally controlled damping

“…The Acoustic Black Hole (ABH), which is currently the subject of extensive research [1,2,3,4], is a response to this challenge. Its usual implementation in a one dimensional (1D) system consists in locally thinning the thickness of a beam according to a power-law profile and coating it with a visco-elastic layer [5,6].…”