Development of a dual-DOF vibration energy harvester using a foldable spring pendulum mechanism

The novelty of this design is that it changes the traditional idea of an unchangeable pendulum length to achieve folding and stretching through the shear fork structure. The concept of spring as the modulation mechanism of the vibration energy harvester is introduced to complete the dynamic change of the pendulum length and realize the dual degrees of freedom output of the roll and heave motions. The spring mechanism integrated into the design, including tension and torsion springs, not only realizes the flexible expansion of the structure but also significantly enhances the ability of the vibration energy harvester to capture external vibration energy through the unique energy storage and release mechanism. The vibration energy harvester has been designed, mathematically simulated, constructed, and experimentally tested with good results, characterized by dual mode state, low-frequency characteristics, and high-power output. Experimental results show that the prototype can achieve an average power output of 5.47 W at an excitation frequency of 0.8 Hz, corresponding to a normalized power output of 377.42 W g⁻² and a normalized power density of 26.25 W g⁻² kg⁻¹.