Sebastián P. Machado

Non-resonant energy harvester with elastic constraints for low rotating frequencies

This paper presents a non-resonant piezoelectric energy harvester (PEH) which is designed to capture energy from low frequency rotational vibration. The proposed device works out of the plane of rotation where the motion of a mass-spring system is transferred to a piezoelectric layer with the intention to generate energy to power wireless structural monitoring systems or sensors. The mechanical structure is formed by two beams with rigid and elastic boundary conditions at the clamped end. On the free boundaries, heavy masses connected by a spring are placed in order to increase voltage generation and diminish the natural frequency. A mathematical framework and the equations governing the energy-harvesting system are presented. Numerical simulations and experimental verifications are performed for different rotation speeds ranging from 0.7 to 2.5 Hz. An output power of 125 μW is obtained for maximum rotating frequency demonstrating that the proposed design can collect enough energy for the suggested application.

Rotations of the Parametric Pendulum Excited by a Reciprocating Motion with a View on Energy Harvesting

In this article the nonlinear dynamics of a parametric pendulum considering a reciprocating excitation is addressed. The interest in the study of this kind of forcing lies in its wide use in machines and industrial equipment including a crank-rod mechanism. The work aims at the further development of pendulum devices for energy harvesting. In this context, the study is focused on pendulum rotations, which are highly energetic. Although reciprocating excitation is similar to the classic sinusoidal excitation, a different and more complex rotational behavior is observed and more rotating attractors are found as new rotation zones arise in the space of forcing parameters. It is shown that the existence of these additional rotating attractors, which depend on crank-rod ratio and the amount of damping, increases the possibilities of energy extraction.