Design, development, and theoretical and experimental tests of a nonlinear energy harvester via piezoelectric arrays and motion limiters

This paper presents the design, development and test of a nonlinear piezoelectric energy harvesting array with wideband performance under directly and parametrically excited conditions; theoretical verifications of equation-type as well as finite-element-methods are also provided. The array, as the core element, consists of four cantilever beams with attached piezoelectric layers and individual tip masses; two pairs of motion limiters were designed to limit the cantilever motions. By introducing 1-pair motion limiters, a strong hardening frequency response extended the system resonance regime and generated an enhanced bandwidth; when the monotonically increased system response triggered engagement with 2-pair motion limiters, the operational bandwidth was even further extended and formed a fully merged resonance regime for energy harvesting purposes. With motion limiters, the directly excited device achieved a continuous operational frequency bandwidth from 5.7 Hz to 12.3 Hz, which is a frequency bandwidth increase of 240%; by introducing the nonlinear frequency response in parametric resonance to the proposed device, the operational frequency bandwidth is increased by 579%. The corresponding piezoelectric voltage output of the proposed device is compared with conventional no limiter and one limiter counterparts. Theoretical investigations using an equation for the motion of the system along with a time-integration solution, as well as a finite element method using ANSYS, have been carried out to verify the results, showing good agreement. The results reveal that the proposed device has potential for dealing with different excitation levels and low frequency applications while broadening the frequency bandwidth.