Dynamic Characteristics of Coupled Dual-Oscillator Piezoelectric Vibration Energy Harvester with External Magnet

Magnetic nonlinearity and multi-oscillator coupling are commonly employed to improve the performance of energy harvesters. This study integrates both mechanisms to propose a nested dual-oscillator coupled piezoelectric energy harvester with an external magnet, investigating both repulsive and attractive interactions between the two oscillators. The influence of parameters on static/dynamic characteristics and harvesting performance is analyzed. For the repulsive-type harvester, the response under weak excitation is characterized by small-amplitude in-phase motion within potential wells; under strong excitation, one oscillator exhibits a large-amplitude response while the other remains nearly quiescent, and non-periodic responses may occur. Large magnet spacings effectively enhance the bandwidth and output power. The attractive-type harvester primarily shows in-phase periodic motion, though non-periodic behavior may appear under strong excitation. Small moving-magnet spacing combined with large external-magnet spacing can significantly boost bandwidth and power output. In both configurations, performance declines as the external-magnet spacing exceeds an optimal range. The repulsive-type harvester features a wider potential well, performing well under weak excitation, whereas the attractive-type, with vibration modes aligned to the potential well profile, is more likely to generate large-amplitude responses under strong excitation. Experimental results show excellent agreement with simulation data, confirming the reliability of the proposed design.