Analytical and experimental investigation of a flexible bistable energy harvester in rotational environment

As one of the basic motion forms, rotational motion exists widely in nature and artificial mechanical structures, such as joint rotation, gear transmission and bearing rolling. Energy harvesting technology based on rotational motion has drawn much concern recently. One of the key issues in rotational energy harvesting is the mismatch between the operating frequencies and the excitation frequencies. Conventional resonance-based linear energy harvesters perform well only near their resonant frequencies, and their performance degrades sharply while the external excitation frequencies diverge from their resonant frequencies. To solve this problem, in this paper, a flexible bistable energy harvester in rotational environment with time-varying potential wells is proposed. It mainly contains a generating beam with a tip magnet and a tuning beam with a middle magnet. Under the effects of the centrifugal force, its configuration and nonlinear characteristics change with different rotational speeds. A distributed-parameter electromechanical model is derived, and numerical simulation and experiments are accomplished. The effects of rotational speed and initial magnetic spacing on the dynamic characteristics of the harvester are studied. Analytical and experimental investigations indicate that the proposed harvester performs well in terms of operating bandwidth and is suitable for broadband rotational energy harvesting.