Exploring the benefits of an asymmetric monostable potential function in broadband vibration energy harvesting

Abstract

This letter explores the benefits offered by an asymmetric monostable potential function over the conventional symmetric linear and bistable potential functions in broadband vibration energy harvesting. Multi-stable harvesters such as the bistable and tristable harvesters provide an order of magnitude higher power than the linear harvesters while undergoing inter-well oscillations. However, when the excitation noise levels are insufficient to trigger inter-well oscillations, such harvesters provide very low power output. We propose a monostable configuration with an asymmetric potential energy function that is capable of providing a high energy output starting from excitation levels as low as 0.005 g2/Hz (g denotes acceleration due to gravity). The superior performance of the proposed asymmetric configuration over the conventional linear and bistable configurations is demonstrated through experiments, considering a band-limited white noise excitation. The experimental results also indicate that the asymmetric configuration delivers higher power at lower strain levels than the bistable configuration, mitigating the burden on the piezoelectric transducer. Thus, the asymmetric configuration offers a two-fold advantage in energy harvesting, leading to an increase in both the power output and the lifetime of the piezoelectric transducer.