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Nonlinear Piezoelectric Transducers for Kinetic Energy Measurement and Broadband Energy Harvesting
Last modified: 2017-05-26
Abstract
The increasing demand for completely self-powered devices and autonomous sensor nodes has caused an increase of research
efforts into smart power harvesting devices. Energy can be harvested from different sources, in particular we will focus here on
mechanical vibrations. A common approach is based on vibrating mechanical bodies that collect energy through the adoption of
self-generating materials in order to charge a battery and to supply a specific sensor. The device proposed in this work performs
contemporaneously all the following three features: it is able to store the converted energy (kinetic source) in a capacitor
(devices behave in a nonlinear manner due to the use of a mechanical stopper that allows to increase the bandwidth of the device
[1]), it is able to measure energy of external vibrations [2], it is also suitable to transmit information. It is worth noting that the
device operates passively on ambient vibrations with no required external power or control system. The proof of concept has
been implemented considering a commercial piezoelectric cantilever (Midè Volture V25W [3]) and a suitable conditioning
electronic (see Fig.1a). The piezoelectric device is able to collect energy from mechanical vibrations and on the top of the
cantilever tip has been placed a mass in order to increase the sensitivity of the transducer. The piezoelectric output is rectified by
a full wave bridge, in which one of the diodes is a LED. The bridge output is represented by a capacitor where the energy
collected by the piezoelectric harvester is stored. The LED light signal is also connected to an optical fiber in order to transmit
pulses when the led diode is on; in fact, when the vibration amplitude is higher than diode threshold value, there is a spike in the
transmitted voltage. The number of pulses and in particular the total lighting time are related to the vibrations amplitude (σ) and
then, to the external energy; in this contest the transducer acts not only as energy harvester but also as a passive sensor of energy
(see Fig.1b). The activity includes mechanical transducers and integrated prototypes based on PiezoMUMPs technology.
efforts into smart power harvesting devices. Energy can be harvested from different sources, in particular we will focus here on
mechanical vibrations. A common approach is based on vibrating mechanical bodies that collect energy through the adoption of
self-generating materials in order to charge a battery and to supply a specific sensor. The device proposed in this work performs
contemporaneously all the following three features: it is able to store the converted energy (kinetic source) in a capacitor
(devices behave in a nonlinear manner due to the use of a mechanical stopper that allows to increase the bandwidth of the device
[1]), it is able to measure energy of external vibrations [2], it is also suitable to transmit information. It is worth noting that the
device operates passively on ambient vibrations with no required external power or control system. The proof of concept has
been implemented considering a commercial piezoelectric cantilever (Midè Volture V25W [3]) and a suitable conditioning
electronic (see Fig.1a). The piezoelectric device is able to collect energy from mechanical vibrations and on the top of the
cantilever tip has been placed a mass in order to increase the sensitivity of the transducer. The piezoelectric output is rectified by
a full wave bridge, in which one of the diodes is a LED. The bridge output is represented by a capacitor where the energy
collected by the piezoelectric harvester is stored. The LED light signal is also connected to an optical fiber in order to transmit
pulses when the led diode is on; in fact, when the vibration amplitude is higher than diode threshold value, there is a spike in the
transmitted voltage. The number of pulses and in particular the total lighting time are related to the vibrations amplitude (σ) and
then, to the external energy; in this contest the transducer acts not only as energy harvester but also as a passive sensor of energy
(see Fig.1b). The activity includes mechanical transducers and integrated prototypes based on PiezoMUMPs technology.