Parametric excitation has been investigated for several years as an effective way to drive a structure parametrically into large distinctive responses. However, parametric resonance requires a minimum threshold of excitation to be triggered. To reduce the threshold, we propose a two-degree-of-freedom vibration system. This system consists of two perpendicular beams each with a tip magnet placed so the same poles face each other. The repulsive magnetic force couples the motion of the two beams. By decreasing the distance between the magnets, the threshold value for parametric excitation decreases. In addition, the repulsive magnetic force decreases the first resonance frequency of the vertical beam and thus its principal parametric resonance. Lowering the threshold excitation and parametric resonance frequency are two unique properties that make the device ideal for energy harvesting at low frequencies.
Wei Yang and Shahrzad Towfighian, "Parametric resonance of a magnetically coupled harvester," Proc. SPIE 10595, Active and Passive Smart Structures and Integrated Systems XII, 105952V (Presented at SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring: March 09, 2018; Published: 15 March 2018); https://doi.org/10.1117/12.2301384.
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