Electromagnetic three-dimensional vibration energy harvester based on an oblique cross-spring vibrator structure

This paper presents an electromagnetic three-dimensional vibration energy harvesting device that uses an oblique cross-spring vibrator structure to collect low-frequency vibration energy. The oblique cross-spring structure allowed the center vibrator to vibrate in any direction. Together with six-directional coils, this configuration senses and harvests environmental vibrations across all directions and levels. First, the dynamics of the oblique cross-spring vibrator structure were analyzed and a finite element simulation was performed for the magnet arrangement and mode shape of the structure. A prototype is designed, fabricated, and experimentally verified. The results showed that the efficiency of the three-dimensional energy output was higher under the same excitation, which was 2.7 times higher than that of the unidirectional output. The unidirectional output power with load is 0.94 mW at 11 Hz under 0.3 g base excitation. The highest total output power of the prototype was 50 mW when it was fixed to the leg at a running speed of 8 km/h. Consequently, the energy harvesting scheme proposed in this study has a considerable low-frequency output effect, which provides a novel means of improving the electrical performance of energy harvesting systems for self-powered IoT and sensor devices.