## 5 Conclusions  
Magnetostrictive Energy Harvesting devices can be connected to a properly controlled AC-DC boost stage in order to increase their output voltage and manage the harvested power. This technique has the advantage to exploit these devices' internal inductors as a storage element.  
This paper discussed the experimental characterization of an AC-DC boost interface driven with a novel strategy able to self-adapt with respect to the input voltages. Indeed, because of typical applications of Vibration Energy Harvesters, the input source vibration may have fundamental frequencies changing over time without a deterministic behavior. By exploiting the Arduino code, an optimum set of control parameters has been found. A peak output voltage of about 3 V has been obtained with a peak input voltage of 220 mV at an input frequency of 80 Hz. The maximum achieved RMS output power is about 4 mW, with a voltage gain factor of about 19.  
Furthermore, the setup has been excited with an impulse-like random input voltage, representing a general VEH output voltage when the device undergoes randomic force profiles, and a 10 V open circuit output voltage has been achieved in steady-state conditions. Experimental tests have been compared with simulations of an LTspice model, showing a good agreement. Finally, the proposed technique has been compared in simulations with standard switching frequency techniques, which are often adopted for other types of VEHs. The comparison highlighted the drawbacks of such techniques when VEH based on magnetostrictive materials are adopted.  
In conclusion, this work can be considered as the proof of principle of a boost circuit for magnetostrictive VEH. Future works will include the verification of the performances with a real magnetostrictive VEH, which will have a dual function of input source voltage and storage inductor. Moreover, further investigation with other output electric loads will be addressed in future works.  
The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app13031606/s1](https://www.mdpi.com/article/10.3390/app13031606/s1)]([https://www.mdpi.com/article/10.3390/app13031606/s1](https://www.mdpi.com/article/10.3390/app13031606/s1)).  
Conceptualization, C.S.C., I.I., V.P.L. and D.D.; methodology, C.S.C. and D.D.; algorithm, D.D.; investigation, C.S.C., I.I., V.P.L. and D.D.; data curation, C.S.C.; simulation curation, C.S.C.; writing--original draft preparation, C.S.C. and D.D.; writing--review and editing, C.S.C., I.I., V.P.L. and D.D.; supervision, D.D. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The Arduino code is available in the attached Supplementary Materials.  
The authors declare no conflict of interest.  
The following abbreviations are used in this manuscript:  
\begin{tabular}{l l} WSN & Wireless Sensor Network \\ IoT & Internet of Things \\ PEI & Power Electronic Interface \\ EH & Energy Harvesting \\ SHM & Structural Health Monitoring \\ VEH & Vibration Energy Harvester \\ DCM & Discontinuous current Conduction Mode \\ CCM & Continuous current Conduction Mode \\ BCM & \"Critical\" Boundary current Conduction Mode \\ PWM & Pulse Width Modulation \\ DAQ & Data Acquisition \\ \end{tabular}