Electromagnetic vari-potential bi-stable energy harvester under low-amplitude excitation

Abstract

This study proposes a novel electromagnetic vari-potential bi-stable energy harvester (EM-VBEH). The potential barrier of the primary oscillator can be dynamically adjusted by an external spring-magnetic oscillator to form a vari-potential barrier effect (VPBE), which enables the harvester to achieves large amplitude inter-well motion under low-frequency and weak-amplitude excitation, significantly improving output power and bandwidth. A mathematical model of the EM-VBEH is established based on the dual-magnetic dipole theory. The VPBE is validated by tracking response trajectories on potential energy and restoring force surfaces, and the influence of system parameters on the dynamic potential barrier is quantitatively analyzed. Frequency and amplitude sweeping dynamics reveals rich nonlinear behaviors of the system, including intra-well harmonic, inter-well harmonic and subharmonic orbits, as well as chaotic motion. Compared to the traditional electromagnetic fixed-potential bi-stable energy harvesters (EM-FBEHs), the EM-VBEH exhibits significant advantages: the inter-well excitation threshold is reduced by 45 %, the inter-well bandwidth is expanded by over 1.65 times, and the maximum average power is increased by approximately 10 times under low-excitations. The performance of EM-VBEH is optimized by using genetic algorithm, and the maximum output power and half-power bandwidth are increased by 42.77 % and 19.58 %. The results of fixed-frequency and frequency-sweep experiments indicate that compared to the EM-FBEH, both the inter-well voltage and bandwidth of the EM-VBEH have multiple-fold increases under weak excitations. Simultaneously, the accuracies of the theoretical model and numerical simulations are validated. The proposed EM-VBEH provides an innovative solution for efficient and broadband energy harvesting from low-frequency, weak-amplitude vibrations.