Asymmetry-enhanced performance in bistable energy harvesters: An experimental study

Asymmetries in bistable energy harvesters — arising from manufacturing tolerances, assembly misalignments, or operational conditions — are traditionally viewed as detrimental to performance. This study challenges that as- sumption through a comprehensive experimental investigation, demonstrating that controlled asymmetries can, under specific conditions, enhance energy harvesting. A prototype system was tested with asymmetry introduced via magnet rotation and shaker base tilting. We explored a wide range of configurations, excitation levels, and initial conditions. Results show that rotating the magnet weakens the magnetic attraction, shifting the resonance frequency downward. While base tilting utilizes gravitational effects to modify the magnetic interaction, further reducing its strength. Although pronounced asymmetries reduce power output at higher frequencies, they can significantly improve performance at lower frequencies, depending on system dynamics and excitation. Monostable and chaotic responses were also characterized numerically and experimentally. Overall, the findings reveal that asymmetry, when properly controlled, is not a flaw but a tunable design parameter to optimize bistable energy harvester performance.