NONLINEAR DYNAMICS CHARACTERISTICS OF TUMBLER-INSPIRED ELECTROMAGNETIC ENERGY HARVESTERS

Ocean wave energy, as a prominent renewable source, possesses the potential to be harnessed for the generation of electricity, specifically catering to the power requirements of wireless sensors. It will be the key promoting the digital evolution of the marine environmental monitoring systems. However, the low-frequency and large randomness characteristics restrict the efficient harvesting of ocean waves. The tumbler structure has ultra-low frequency vibration characteristics that are different from traditional structures, and it is sensitive to low-frequency excitation, which can absorb surrounding vibration energy. In this paper, we design a tumbler-inspired electromagnetic energy harvester with a Halbach array, aiming to enhance the performance of low-frequency wave energy harvesting by constructing magnetic nonlinear forces. The theoretical model of the harvester is established according to the Lagrange’s equation. The analytical responses of the tumbler's swing angle and the harvester's voltage are derived by the harmonic balance method. The analytical solution is compared with the numerical solution. Moreover, simulations are conducted to investigate the effect of different excitation conditions such as excitation amplitude and frequency on the dynamic response characteristics of the system. Finally, a prototype of the tumbler-inspired electromagnetic energy harvester was fabricated, and an experimental platform was built. It verifies the correctness of the theoretical model. Both the simulation and experimental results show that the harvester exhibits the hardening stiffness characteristic through introducing magnetic nonlinearity. This characteristic is beneficial to enhance the low-frequency energy harvesting efficiency. The harvester exhibits diverse dynamic behaviors such as periodic motion, quasi-periodic motion, and chaotic motion with the change of the excitation amplitude and frequency. In addition, low frequency and large excitation are more likely to cause chaotic motion, which is beneficial to energy harvesting effect. This study provides a theoretical support for the design and application of the tumbler mechanism in low-frequency ocean wave energy harvesting.