A piezoelectric energy harvester for human body motion subjected to two different transversal reciprocating excitations

Abstract. Harvesting energy from human body motion to supply electricity for wearable devices is focused on in this paper. Based on the fact that the frequency of human body motion is lower and the motions of different human body parts are variable, a piezoelectric energy harvester subjected to two different transversal reciprocating excitations is studied in this paper. Each excitation is treated as a transverse rheonomic constraint. The dynamics equation of the beam is established using the Hamiltonian principle. Expressing the transverse rheonomic constraint as a periodic function, closed-form solutions of the dynamics equation are obtained. And the characteristics of energy harvesters are investigated based on the closed-form solutions. The results show that the difference between the two excitations will certainly cause the energy harvester to generate more output power at lower frequencies of excitations, and the larger the difference, the more the output power will be generated. This unusual characteristic at the lower frequency enables the proposed harvester to be quite suitable to harvest energy from the motions of the human body.