Innovative mechanical sensors architectures and their physics applications

Vibrations measurement is relevant in many applications, since the acquired signals contain direct and indirect information on the dynamic behavior and on the health state of systems, in connection to external forcing. Although generally spread over a large band, the low-frequency signal content (1 mHz–10 Hz), the so-called slow-motion, contains the most relevant part of information, as in the case of large structures, like buildings or bridges, subject to environmental and anthropic forcing. For this reason, despite the large present scientific and technological research efforts aiming at implementing suitable typologies of sensors, the low-frequency band is still only partially covered by sensors, due to the difficulty of satisfying the stringent requirements on their mechanical oscillators, like low resonance frequency, high directivity and low intrinsic noise. The Folded Pendulum, a classical mechanical oscillator, whose monolithic architecture has been reinvented for the design of low-frequency mechanical oscillators, may represent an interesting solution. In this work, we present and discuss theoretical properties and experimental applications of the Folded Pendulum mechanical oscillator, highlighting its peculiar characteristic for its use as an instrument for low-frequency measurements.