Nonlinear damping in an energy harvesting device

Abstract

Energy harvesting from ambient vibration has attracted significant attention in recent years. Some interesting applications include low-power wireless sensors, harvesting power from human motion and large-scale energy harvesters. In order to increase the frequency range of the excitation amplitude over which the vibration energy harvester operates, various nonlinear arrangements have been suggested, particularly using nonlinear springs [1-5]. In contrast, it has recently been shown that the dynamic range of a vibration energy harvester can be increased using a nonlinear damper [5]. Nonlinear damping, particularly stiction, can, however, also be an unwanted problem in practical power harvesters. However, this paper considers the effect of stiction, as Coulomb damping, on the performance of such a vibration power harvester. A mechanical single degree-of-freedom nonlinear oscillator is considered, subjected to a harmonic base excitation. The relative displacement and the average harvested power are obtained for different sinusoidal base excitation amplitudes and frequencies, both analytically and numerically. The performance of the nonlinear harvester at different excitation levels is compared with a linear harvester, which has the same maximum relative displacement at resonance when driven at maximum amplitude. It is demonstrated that the nonlinear harvester can harvest much more energy, compared to the linear one, when driven below its amplitude threshold [5]. The effect of Coulomb damping, as a source of loss, is also investigated, for the harvesters with a linear damping and a cubic damping. It is shown that the Coulomb damping can reduce the amount of the harvested energy, particularly at low excitation amplitudes.