Asymmetry-enhanced performance in bistable energy harvesters: Experimental and numerical analysis

Abstract

Asymmetry in bistable energy harvesters, often arising from manufacturing imperfections, assembly misalignments, or operational factors, has traditionally been viewed as detrimental to energy conversion efficiency. This study challenges that perspective through a comprehensive experimental investigation demonstrating that controlled asymmetry can enhance energy harvesting performance. A custom-designed prototype was tested under multiple configurations, introducing asymmetry through magnet rotation and base tilting. Frequency-sweep and single-frequency tests showed that magnet rotation weakens magnetic attraction, while base tilt introduces a gravitational bias, together reshaping the potential landscape, lowering resonance frequencies, and even mitigating asymmetry effects. This tunability proved particularly effective at low excitation levels, where conventional bistable systems are less efficient. Moreover, certain asymmetric configurations exhibited higher power output and broader bandwidths than the symmetric case. State-space analyses, including experimentally constructed Poincaré maps, confirmed that asymmetry significantly influences dynamic behavior, stability, and energy distribution, providing additional tuning flexibility. Although excessive asymmetry may reduce performance at high frequencies, the results demonstrate that it is not a defect to be minimized but a strategic design parameter for achieving adaptive and efficient energy harvesting in practical applications.