New insight into piezoelectric energy harvesting with mechanical and electrical nonlinearities

This letter investigates the piezoelectric energy harvesting system with mechanical and electrical nonlinearities. Through impedance model, nonlinear interface circuits for energy harvesting purpose can be simplified as an electrical impedance with real and imaginary parts. Their effects on the mechanical structure can be regarded as circuit-induced damping and stiffness. The resulted equivalent mechanical vibratory system allows us to analytically obtain the system responses under different excitation and loading conditions by harmonic balance method. Furthermore, it becomes possible to achieve a comprehensive comparison among different nonlinear interface circuits, including the standard energy harvesting circuit, synchronized electric charge extraction circuit, series synchronized switching on inductor circuit, parallel synchronized switching on inductor circuit and parallel synchronized triple bias-flip circuit. The results from the theoretical model and experiments together reveal that the nonlinearities play a significant role in the energy harvester's hysteresis region size, displacement amplitude, and piezoelectric voltage level. This investigation provides an insight into the design, optimization and implementation for the nonlinear energy harvester.