Multi-modal vibration energy harvesting utilizing spiral cantilever with magnetic coupling

• This paper presents a multi-modal energy harvester to extract vibration energy from five frequency bands.
• The spiral-shaped configuration is shown to be beneficial to narrowing the band spacings.
• The frequency spacings can be further reduced under the magnetic coupling.

Most vibration energy harvesters use conventional cantilever configuration and typically perform well for a specific frequency at the first resonant mode, this makes the devices less effective in ambient vibrations with varying frequencies. This paper presents a multi-modal vibration energy harvester achieving multiple peaks in the frequency response and causing the possibility of widening the operation frequency range. A spiral-shaped cantilever with tip mass in the form of magnets coupling with a magnetoelectric (ME) transducer is adopted in this harvester. The spiral-shaped beam is shown to be conductive to presenting multi-modal responses and lowering the natural frequencies of the harvester. Furthermore, due to the magnetic coupling between the magnets and the transducer, the peak frequencies are tunable and the frequency spacing between the adjacent modes can be obviously reduced. The operating principle of energy conversion is based on the relative movement of the magnets and the transducer, and the effects of magnetic coupling working on the peak frequencies are experimentally determined. The experimental results indicate that the proposed harvester can obtain five obvious peak values in the range of 15–70 Hz, which are concentrated around 20.7, 26.1, 32.3, 42.2 and 63.7 Hz, respectively.