A Multidirectional Piezoelectric Vibration Energy Harvester With Direction-Dependent Dual Resonance.

A multidirectional base-mounted piezoelectric vibration energy harvester with a 2 mm ×2 mm ×20 mm polyurethane resonating beam, an 8.36-g tip mass, and a lead zirconium titanate (PZT) transducer was designed, fabricated, and tested. The harvester was shown to operate in any direction in a 2-D plane and produced as much as [Formula: see text] across a 50- [Formula: see text] load under harmonic base excitations with peak acceleration of 0.25 g at an angle of 45°. Experiments showed that, in some directions, the harvester had two resonant frequencies, one at 36.0 Hz and one at 38.5 Hz. Analysis shows that this phenomenon is caused by deviations in the shape of the polyurethane beam from the intended square cross section. This analysis is used to propose a method for designing harvesters with any two desired resonant frequencies. The possibility of using this design method to increase the harvester's bandwidth is discussed.