Design and Optimization of a Novel Multimodal Piezoelectric Energy Harvester With Asymmetrically Branched Beams Operating in <i>d</i>15 Mode

Abstract To extend the operational bandwidth of traditional piezoelectric energy harvesters (PEHs) from ambient vibrations, a novel multimodal PEH with asymmetrically branched beams operating in d15 mode is proposed. The proposed PEH can fully utilize d15 mode piezoelectric patches to capture the torsional deformation energy from the main beam, which is induced by asymmetrically branched beams under unidirectional excitation. Furthermore, the proposed PEH exploits the multiple modes induced by asymmetrically branched beams to efficiently enlarge its bandwidth. The electromechanical coupling model is first established, and then, an optimization model is proposed with the maximum bandwidth as the design objective. By solving the proposed optimization model, the multiple optimized configurations can be obtained and form a larger design domain, thereby achieving increased bandwidth and energy harvesting over a wider frequency range. The present numerical results are in agreement with the experimental results, validating the accuracy of the proposed theoretical model. This article can provide a basis for multiobjective optimization of PEHs.