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

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.