A resonant frequency self-tunable rotation energy harvester based on magnetoelectric transducer

This paper presents a passive self-tuning energy harvester based on magnetoelectric (ME) transducer for potential powering the wireless sensors in rotational applications. The harvester has two cylindrical magnets arranged on the free end of a cantilever beam, and two hollow magnets with ME transducers inside their cavities are located symmetrically beside the beam and enfaced with the cylindrical magnets. With the beam radial-oriented, the harvester rotates around a horizontal axis, and the alternation of the gravity component causes the magnets on beam to move relative to the transducers, which induces the electrical power generation. Due to the axial tensile stress caused by the centrifugal force, the resonant frequency is tuned to track the rotation frequency over a wide frequency range, which enables the harvester a broad working bandwidth. Furthermore, the attractive magnetic forces between the magnets lower the initial resonant frequency of the beam and enlarge the vibration amplitude. Consequently, the electrical output performances over the target frequency range (below 20 Hz) are improved. A prototype is fabricated and tested. The experimental results are in agreement with the theoretical predictions. The prototype generates a maximum power of 517 μW at a rotation frequency of 9.8 Hz, corresponding to a half-power bandwidth of 13.5 Hz.

► The resonant frequency of the energy harvester is self-tuned to track and match the rotation frequency over a wide frequency range.
► A magnetic force technique is employed to lower the initial resonant frequency of the cantilever beam and enlarge the vibration amplitude.
► The ME transducers are optimally biased by employing an inverse pre-bias magnetic field.
► The maximum output power on load achieves 517 μW at a rotation frequency of 9.8 Hz, and the corresponding half-power bandwidth achieves 13.5 Hz.