Opportunities for electrically-based frequency tuning of piezoelectric vibration energy harvesters

This paper focuses on electrically-based solutions for tuning the resonant frequency of piezoelectric vibrations energy harvesters in order to compensate for aging or vibration frequency shifts. We present the theory behind electrical frequency tuning, and show that a strong electromechanical coupling associated with two-tuning electrical interfaces allow to reach relatively large frequency tuning ranges. Such solution requires the design of strongly coupled harvesters as well as the design of self-adaptive self-powered electrical interfaces, but, compared to other design approaches, requires much less volume and energy.