Archery-inspired catapult mechanism with controllable energy release for efficient ultralow-frequency energy harvesting

Ultralow-frequency (< 5 Hz) vibration energy is abundant in the environment, but its efficient utilization is still highly difficult due to the frequency-mismatch problem encountered by the vibratory energy harvesters and the slow rotation of rotary energy harvesters (REHs). To solve this issue, we developed herein a high-performance REH (named AI-REH) based on the archery-inspired catapult mechanism, which breaks through the limitation of the slow vibration source to the REH rotation speed through an innovative magnetic coupling strategy between the vibration source and the AI-REH. By employing an accumulator spring as the energy reservoir, the AIREH also realizes the accumulation and controllable release of ultralow-frequency vibration energy via the interaction between the magnetic coupling and the elastic force. High-speed kinetic energy can thus be acquired for efficiently powering the rotor, contributing to significantly accelerated rotor speeds and enhanced electric outputs. Compared with the traditional counterpart, the AI-REH achieves 3.6-fold increase in rotor speed, 3.5fold increase in output voltage and 3.0-fold increase in output power under an ultralow-frequency vibration of 4 Hz. A power backpack was also constructed and tested, which demonstrates the superior capability of the AIREH in harnessing real ultralow-frequency amplitude-varying vibration energy. The AI-REH proposed in this study provides a new pathway for efficiently exploiting environmental ultralow-frequency vibration energy toward self-sufficient systems with various purposes.