Integration of Tapered Beam and Four Direct-Current Circuits for Enhanced Energy Harvesting From Transverse Galloping

To improve the performance of energy harvesting from transverse galloping, structural and circuit designs are integrated. Tapered energy harvesters due to more uniform strain distribution with the standard direct current (dc), synchronous charge extraction (SCE), parallel or series synchronized switch harvesting on inductor (P-SSHI or SSSHI) circuit are adopted. An electromechanically coupled distributed parameter model considering the exact modal shape of the tapered beam attached with the bluff body, is established. The electromechanical coupling coefficient and piezoelectric capacitance are related to the tapered ratio. The proposed model is reduced to the model for the uniform beam via setting the tapered ratio to null. The Hopf bifurcation, beam displacement, and harvested power are generalized to the same expressions for different dc circuits. The modal shapes of the tapered beam and the analytical responses of the harvested power processed through the four the dc circuits, are respectively confirmed via the finite element method, Simulink simulation, and wind tunnel experiment. As the tapered ratio increases, the modified frequencies increase greatly and the tip displacements decrease sharply for all the four circuits. The SCE circuit provides the highest onset speed due to large electrical damping. Additionally, the maximum power of the two SSHI circuits is detected to be the upper boundary of those yielded by the four circuits, and the S-SSHI circuit gives lower displacement. The comparison data show that the harvested power and the energy conversion efficiency can be enhanced by appropriate tapered and circuit designs.