Nonlinear Dynamics of a Softening-Hardening Oscillator for Energy Harvesting in Industrial Applications.

Recent research effort in exploiting the benefits of nonlinear dynamics for vibration energy harvesting has proven the validity of incorporating geometrical nonlinear elements on purpose to improve performance. Converting kinetic energy into usable electrical energy could be useful to provide a local, clean, and sustainable supply power to sensor nodes for data collection and health monitoring, avoiding wiring. This paper presents an investigation on the case where harmonic excitation at very low frequency is of interest, as this could be a common problem in industrial machines and their environment. The use of a softening-hardening suspension with tailored characteristics is proposed, to cope with the competing requirements of a high static stiffness and a low dynamic stiffness of the mechanical oscillator. Since the coexistence of low and high-energy orbits manifests, to induce the device to oscillate at the higher amplitude (and thus potentially harvest more energy), a feed-forward control strategy is proposed.