Wideband energy harvesting using nonlinear energy sink with bio-inspired hexagonal skeleton structure

Inspired by human fitness push-ups, a bio-inspired hexagonal skeleton structure is proposed to design wideband energy harvesters using nonlinear energy sink. The hexagonal skeleton structure consists of two symmetrical bionic arms as skeleton, a horizontal spring as muscle and two platforms (upper and lower) as the back of human body and the ground. The lower platform is supported by linear springs, and the upper platform is supported by the bio-inspired hexagonal skeleton structure as nonlinear energy sink. Magnets are attached to the upper and lower platforms respectively. The piezoelectric beam is fixed on the upper platform. The dynamic equations of the wideband energy harvesting via bio-inspired nonlinear energy sink structure are established for theoretical analysis, which is verified by both simulations and experiments. The effects of nonlinearity, equivalent mass of the upper platform, parameter of BNES and acceleration level are discussed with the perspective of optimizing the magnitude and bandwidth of the output voltage and power. The harvester can cover a broad low-frequency range of 5–15 Hz, and convert the hybrid vibration into electricity effectively. The maximum output power of the electromagnetic units can reach 0.18 mW and 0.63 mW respectively, and the maximum output power of the piezoelectric unit can reach 0.1 mW as a supplement to the power at the low excitation level of 0.08 g (g = 9.8 m/s²). This means that the wideband energy harvester using nonlinear energy sink with bio-inspired hexagonal skeleton structure should be a viable solution for the hybrid, low-frequency, and broadband vibration energy harvesting. © 2022 Elsevier B.V.