Abstract
This paper designs an underwater magnetic nonlinear piezoelectric energy harvester (PEH) based on the principle of vortex-induced vibration (VIV). The equivalent stiffness of the magnetic nonlinear PEH is significantly changed by varying the relative position of the magnet. It is observed that the proposed PEH displays hardening behavior and softening behavior due to the impact of magnetic forces, which greatly increase the performance of the magnetic nonlinear PEH. The analysis of the results shows that the open-circuit voltage (VRMS) of the hard stiffness system is increased from 9.43 V to 10.31 V, the frequency band is widened by 36.8%, and the efficiency is higher at high flow rates. The initial vibration velocity of the soft stiffness system is reduced. When the water velocity is 0.2 m/s, its VRMS is 10 times that of the classical configuration. Both numerical simulations and experiments prove that the soft stiffness system is more suitable for applications in low-speed water environments. This proposed design can provide the groundwork to promote the performance of the conventional PEH, further enabling to realize self-powered systems.