An asymmetric bistable vibro-impact DEG for enhanced ultra-low-frequency vibration energy harvesting

In order to enhance the performance of bistable energy harvesters with dielectric elastomers (DEs) under ultra-low frequency vibrations, this paper proposes an asymmetric bistable vibro-impact dielectric elastomer generator (ABVI DEG), which mainly consists of a vibro-impact (VI) DEG, two identical pre-compressed springs, two pairs of undeformed springs, and a base. Two kinds of dynamics models of the proposed energy harvester under ultra-low frequency harmonic excitations are developed, and the instantaneous impact model is selected due to its computational efficiency and accuracy. The instantaneous impact model is extended by a series of impact experiments and validated by comparing the dynamical responses of the proposed energy harvester obtained from the two kinds of dynamics models. On this basis, the dynamical behavior and the energy harvesting (EH) performance of the proposed energy harvester under ultra-low frequency harmonic excitations are studied for the initial conditions of the system, different bistable potential wells, and various parameters, which include the pre-stretched ratio of the membranes and the distance between the two membranes. A further comparative study demonstrates the superiority of the proposed energy harvester under the ultra-low frequency harmonic excitation. This work not only provides an insight into dynamical behavior of the proposed ABVI DEG, but helps guide the design and optimization of the proposed EH system in the ultra-low frequency vibration environment.