An experimentally validated model for geometrically nonlinear plucking-based frequency up-conversion in energy harvesting

Abstract

It is well known that plucking-based frequency up-conversion can enhance the power output in piezoelectric energy harvesting by enabling cyclic free vibration at the fundamental bending mode of the harvester even for very low excitation frequencies. In this work, we present a geometrically nonlinear plucking-based framework for frequency up-conversion in piezoelectric energy harvesting under quasistatic excitations associated with low-frequency stimuli such as walking and similar rigid body motions. Axial shortening of the plectrum is essential to enable plucking excitation, which requires a nonlinear framework relating the plectrum parameters (e.g. overlap length between the plectrum and harvester) to the overall electrical power output. Von Kármán-type geometrically nonlinear deformation of the flexible plectrum cantilever is employed to relate the overlap length between the flexible (nonlinear) plectrum and the stiff (linear) harvester to the transverse quasistatic tip displacement of the plectrum, and thereby the tip load on the linear harvester in each plucking cycle. By combining the nonlinear plectrum mechanics and linear harvester dynamics with two-way electromechanical coupling, the electrical power output is obtained directly in terms of the overlap length. Experimental case studies and validations are presented for various overlap lengths and a set of electrical load resistance values. Further analysis results are reported regarding the combined effects of plectrum thickness and overlap length on the plucking force and harvested power output. The experimentally validated nonlinear plectrum-linear harvester framework proposed herein can be employed to design and optimize frequency up-conversion by properly choosing the plectrum parameters (geometry, material, overlap length, etc) as well as the harvester parameters.

Electrode Coverage Optimization for Piezoelectric Energy Harvesting from Tip Excitation

“…The maximum electromechanical coupling coefficient was obtained with an electrode coverage of 42%, but the strain distribution in this case is different from that of cantilever beams. Du et al provided an analysis of the electrode coverage for cantilever beams, showing the optimal coverage percentage of 44% [ 23 ], but the external force in this study is a uniformly distributed force along the beam length direction, which is different from the normally used base excitation [ 24 ] or tip excitation [ 25 , 26 ].…”

Development of Piezoelectric Harvesters with Integrated Trimming Devices

“…When the frequency of ambient vibrations is very low (e.g., in energy harvesting from human motion) the tip mass able to trim the harvester would be impractically large. Therefore, several frequency-up strategies have been proposed: they are based on specific devices like a flexible stopper [8], a non-linear plectrum [9], or a pendulum magnetically coupled with the harvester [10].…”

Multi-dimensional constrained energy optimization of a piezoelectric harvester for E-gadgets

“…This energy is then released as the beam freely vibrates at its natural frequency. This technique was mainly implemented via impact interaction ( Abedini and Wang, 2019 ; Chen et al, 2017 ; Dauksevicius et al., 2019 ; Rui et al., 2021 ), contact plucking ( Kathpalia et al, 2017 ; Kuang and Zhu, 2017 ) and magnetic contactless plucking ( Chen et al, 2019 ; Kuang et al., 2016 ; Xue and Roundy, 2017 ).…”