Experimental implementation of switching and sweeping tuneable vibration absorbers for broadband vibration control

This paper describes the laboratory implementation of two semi-active tuned vibration absorbers (TVAs): a switching TVA and a sweeping TVA. The two absorbers are designed to control the low frequency total flexural response of a cylindrical duct excited by a stationary broadband random force. The two TVAs are composed by a seismic mass mounted on a axial spring. Both TVAs are equipped with a relative displacement and relative velocity feedback control system, which is used to vary the characteristic stiffness and damping, that is the characteristic natural frequency and damping ratio, of the TVA. The switching TVA cyclically tunes its characteristic natural frequency and damping ratio to iteratively control the resonant responses due to three targeted flexural natural modes of the duct. Alternatively the sweeping TVA continuously varies its characteristic natural frequency and damping ratio within given ranges to blindly control the resonant responses due to the same three flexural natural modes of the duct. The paper presents both simulation and experimental results regarding the feedback loop used to iteratively or continuously tune the TVAs and about the reduction of vibration produced by the two semi-active TVAs. The simulation and the experimental results show that both TVAs effectively control the flexural response of the duct in the low frequency band, which is characterised by the resonances of the three targeted flexural natural modes of the duct.