Passively-switched vibrational energy harvesters

Vibrational energy harvesters capture mechanical energy from ambient vibrations and convert the mechanical energy into electrical energy to power wireless electronic systems. Challenges exist in the process of capturing mechanical energy from ambient vibrations. For example, resonant harvesters may be used to improve power output near their resonance, but their narrow bandwidth makes them less suitable for applications with varying vibrational frequencies. Higher operating frequencies can increase harvesters’ power output, but many vibrational sources are characterized by lower frequencies, such as human motions. This work presents the design, modeling, optimization, and demonstration of a new class of resonant vibrational energy harvesters that passively switch among dynamics with different characteristic frequencies to adapt to low-frequency excitations and changing vibrational environment. The passively-switched harvester consists of a driving beam that couples into ambient vibrations at low frequencies and a generating beam that converts mechanical energy into electrical energy at high frequencies. The interaction between the driving beam and the generating beam enables multiple characteristic dynamics of the system, namely coupled-motion dynamics and plucked dynamics. When the system passively switches between coupled-motion harvesting and plucked harvesting, its operational range is increased. The system is simulated in the time domain using a lumped element model that predicts power output. Based on the model, a