A Nonlinear Method for Harvesting Mechanical Energy from Vibrations

A novel pendulum-generator system taking advantage of parametric resonance is proposed as an alternative way of energy harvesting in civil engineering application. A mass or length augmentation coefficient is introduced to consider the inertia effect of the generator. Theoretical analysis of the nonlinear behavior of the device is performed. It is found that there exists an optimal as well as an upper bound of equivalent viscous damping of the electrical load. The average electro-mechanical output power characteristics in terms of excitation frequency and total equivalent damping are developed for the case of parametric excitations. Two typical working modes, i.e. fixed amplitude of either displacement or acceleration of the external excitation source, are considered. Numerical results show that the output power reaches the maximal value when the equivalent damping is between 70.7∼80.9% of the upper bound of the equivalent damping. It is also shown that the proposed device may collect more energy from the source than its linear counterparts at lower frequencies.