Modeling of plucking piezoelectric energy harvesters with contact theory

Non-harmonic excitations are widely available in the environment of our daily life. We could make use of these excitations to pluck piezoelectric energy harvesters. Plucking piezoelectric energy harvesting could overcome the frequency gap and achieve frequency-up effect. However, there has not been a thorough analysis on plucking piezoelectric energy harvesting, especially with good understanding on the plucking mechanism. This paper is aimed to develop a model to investigate the plucking mechanism and predict the responses of plucking piezoelectric energy harvesters under different kinds of excitations. In the electromechanical model, Hertzian contact theory is applied to account for the interaction between the plectrum and piezoelectric beam. The plucking mechanism is clarified as a cantilever beam impacted by an infinitely heavy mass, in which the multi-impact process prematurely terminates at separation time. We numerically predict the plucking force, which depends on piezoelectric beam, Hertzian contact stiffness, overlap area and plucking velocity. The energy distribution is investigated with connected resistor.