Modular Vibration Control Unit Formed by an Electromagnetic Proof-Mass Transducer and Sweeping Resistive–Inductive Shunt

Abstract

This paper presents a vibration control unit formed by an electromagnetic proof-mass transducer connected to a sweeping resistive–inductive (RL)-shunt, which can be used to control broadband flexural vibrations of thin structures. The shunt is composed of a resistor and an inductor in series, whose values vary harmonically in time. The design and practical implementation of an electromagnetic transducer and harmonically varying shunt is first discussed. The unit is then tested on a thin-walled cylinder exposed to a broadband disturbance, considering two operation modes: fixed and sweeping RL-shunts. The former mode sets the unit to control the resonant response of a target flexural mode of the cylinder. The latter mode sets the unit to control the resonant responses of multiple modes of the cylinder with natural frequencies confined in a target frequency band. The study demonstrates the practical feasibility of a unit, which sweeps the natural frequency and the damping ratio of the transducer between 36 Hz and 187 Hz and between 4% and 60%. Also, it shows the unit generates broadband control of the flexural vibration of a cylinder, with reductions of the peak responses of the natural modes resonating in frequency band of the sweep comprised between 2 and 13 dB.

Tuning of a shunted electromagnetic vibration absorber based on the maximisation of the electrical power dissipated

“…As discussed in Turco et al., 33 and shown in Figure 1(c), the combined resistive-inductive effects of the coil and of the shunt circuit, which is composed of a resistance Rs and an inductance Ls connected in series, generate equivalent mechanical stiffness and damping effects. These two effects can be modelled as a mechanical network formed by a spring kes=ψ2Les and damper ces=ψ2Res in series, which is connected in parallel with the mechanical spring ka and damper ca of the transducer.…”

“…Conversely, for progressively lower values of the shunt inductance, the fundamental resonance frequency of the transducer tends to increase. As discussed in Turco et al., 33 eventually, a negative inductance should be implemented, which compensates the inherent inductance of the coil to bring the resonance frequency beyond the limit of about 100 Hz. Moving to the effect produced by the shunt resistance, the solid blue lines show that, as the shunt resistance is increased, the resonance peak is progressively rounded.…”

“…21–26 In particular, electro-mechanical TVAs formed by a coil-spring-magnet linear transducer connected to a resistive-inductive (RL) shunt were investigated in several works. 27–33 As shown in Turco et al., 32,33 the coil-spring-magnet transducer can be regarded as mechanical system formed by a seismic mass mounted on a spring-damper in parallel, where the damping arises from the Couette air damping that develops in the tiny air gap between the coil and magnet. 34 Also, the RL shunt produces an equivalent mechanical effect, which can be represented by a spring-damper in series, which, in turn, is connected in parallel with the spring-damper of the transducer.…”

“…34 Also, the RL shunt produces an equivalent mechanical effect, which can be represented by a spring-damper in series, which, in turn, is connected in parallel with the spring-damper of the transducer. Therefore, as shown in Turco et al., 32,33 the RL parameters can be suitably set to generate variable stiffness and damping effects such that the shunted electromagnetic TVA can be continuously adapted to track both the optimal frequency ratio normalνa and damping ratio ζa necessary to control the resonant response of the hosting mechanical system.…”

Comparison of smart panels for tonal and broadband vibration and sound transmission active control

“…In parallel, passive and semi-active tuneable vibration absorbers (TVAs) have been employed to solve particular problems, such as the control of tonal disturbances or the control of the resonant response of specific flexural modes of thin structures [14,15]. In particular, semiactive TVAs formed by either electromagnetic proof-mass transducers [16,17] or piezoelectric patch transducers [18][19][20] connected to electrical shunts have been used to develop adaptive TVA systems, which can track the frequency of the tonal excitation or can trace the resonance frequencies of structures subject to significant variations of the working conditions (e.g. tensioning effects, temperature variations, etc.…”