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Increasing demand in mobile, autonomous devices has made energy harvesting a particular point of interest. Systems that
can be powered up by a few hundreds of microwatts could feature their own energy extraction module. Energy can be
harvested from the environment close to the device. Particularly, the ambient mechanical vibrations conversion via
piezoelectric transducers is one of the most investigated fields for energy harvesting. A technique for optimized energy
harvesting using piezoelectric actuators called “Synchronized Switching Harvesting” is explored. Comparing to a typical
full bridge rectifier, the proposed harvesting technique can highly improve harvesting efficiency, even in a significantly
extended frequency window around the piezoelectric actuator’s resonance.
In this paper, the concept of design, theoretical analysis, modeling, implementation and experimental results using
CEDRAT's APA 400M-MD piezoelectric actuator are presented in detail. Moreover, we suggest design guidelines for
optimum selection of the storage unit in direct relation to the characteristics of the random vibrations.
From a practical aspect, the harvesting unit is based on dedicated electronics that continuously sense the charge level of
the actuator’s piezoelectric element. When the charge is sensed, to come to a maximum, it is directed to speedily flow
into a storage unit. Special care is taken so that electronics operate at low voltages consuming a very small amount of the
energy stored.
The final prototype developed includes the harvesting circuit implemented with miniaturized, low cost and low
consumption electronics and a storage unit consisting of a super capacitors array, forming a truly self-powered system
drawing energy from ambient random vibrations of a wide range of characteristics.
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