A Sensorless Self-Tuning Resonance System for Piezoelectric Broadband Vibration Energy Harvesting

This article presents a broadband piezoelectric vibration energy harvesting system. It can actively tune its resonant frequency to match the frequency of the ambient vibration excitation. The energy harvester is comprised of a movable mass attached to a piezoelectric cantilever beam. And a microstepper is employed to adjust the position of the mass for regulating the resonant frequency. Furthermore, in this article, a new method is proposed for the online dynamic detection of the piezoelectric transducer (PZT) vibration statement without any additional sensors. A circuit is proposed to detect the ambient vibration excitation frequency deviation against the resonant frequency only by measuring the phase difference between the open-circuit voltage and the short-circuit current of the PZT. Experimental results indicate a frequency broadening rate of up to 60.56%, while the maximum extraction efficiency is 84.8%. It can harvest vibration energy and self-power the system in a wide broadband ambient excitation vibration frequency for the wireless sensor network nodes.