Modal Interaction and Energy Harvesting Response of a Bi-Directionally Excited Piezoelectric Vibration Energy Harvester

Piezoelectric energy harvesting is a promising approach for powering nano- to microwatt-scale electronic devices using ambient vibrations. While most conventional energy harvester designs consider uni-directional excitation, real-world environments often involve multi-directional excitations. In this work, the dynamic and electrical response of a piezoelectric energy harvester (PEH) beam is investigated under bidirectional excitation. Experimental setup is developed such that transverse excitation to the energy harvester is provided by an electrodynamic shaker and axial excitation applied through a smart miniature shaker. A coupler is incorporated into the assembly to transmit axial motion from a miniature shaker to the energy harvester, which introduces an additional resonance mode that modifies the system’s response. The coupler is therefore included in the simulation models. The findings demonstrate that when bidirectional excitation is precisely tuned, can alter system dynamics and significantly improve the energy harvesting potential. It is observed that the voltage improvement compared to unidirectional excitation is 181.15% at the axial /transverse frequency ratio (A/T ratio)= 1.0 and 365.17% at the A/T ratio = 2.0. This work underscores the need to consider both structural interactions and multi-axis vibration inputs when designing and optimizing PEH systems for real-world applications.