A pendulum-type annular dielectric elastomer generator for multi-directional ultra-low-frequency vibration energy harvesting

Currently, dielectric elastomer generators (DEGs) demonstrate high energy density, rapid response, and simple structure in the field of energy harvesting (EH). However, the efficient multi-directional dielectric EH in complex vibrational environments, particularly at ultra-low frequencies (0-3 Hz), remains a significant challenge. To solve this issue, a pendulum-type annular DEG (PA-DEG) is designed in this paper to harvest multi-directional ultra-low-frequency vibrational energy. The PA-DEG consists of an annular dielectric elastomer membrane (DEM) that can be deformed by a pendulum structure, which swings under multi-directional vibrations. The dynamics model of the proposed PA-DEG under multi-directional vibrational excitations is established and verified through experiments. The PA-DEG under vibrational excitations exhibits rich dynamical behaviors resulting from the DEM's resonance, the pendulum's response and the system's 1:2 internal resonance, which are revealed through numerical simulations. Moreover, the electrical model of the PA-DEG is established to study its potential for ultra-low-frequency EH under different vibration directions. It is found that the PA-DEG can harvest ultra-low-frequency vibrational energy, whose EH performance is significantly influenced by the excitation parameters and the structural parameters. A comparative study between the PADEG and the system without a pendulum swing is further conducted under swept frequency excitation. Research results show that the PA-DEG can achieve higher output power within an ultra-low-frequency range with the help of the pendulum, thus demonstrating its superiority in high-performance ultra-low-frequency multi-directional vibration energy harvesting.