Torsional vibration energy harvesting through transverse vibrations of a passively tuned beam

The paper highlights the potential of harvesting vibration energy from mechanical systems in the form of electrical power to activate remote electronic devices. The principal idea is based upon the resonant response of a lightweight oscillator subjected to applied external excitation, coupled with an electrodynamic transducer (e.g. piezoelectric material, inductive coils). As far as the mechanical system is concerned, the aim is to maximize the harvested energy when an attachment vibrates with relatively high amplitudes. This means that the system natural frequency should be close to the expected dominant frequency of the applied (host) vibrations. However, in practice the dominant vibration frequency varies either within a limited range due to system uncertainties or across a large band due to the fundamental operation of the host structure, such as in rotational power transmission systems with speed variations. Recently, the introduction of nonlinearities has been proposed in order to compensate for small-scale frequency shifts. Nevertheless, in most cases one cannot fully bypass the necessary tuning effects, attributed to linear stiffness components in system dynamics. In this paper, a rotational vibration energy harvester is outlined, based upon a beam attachment, coupled with an electromagnetic transducer. The stiffening effect due to centrifugal action is utilized in order to passively tune the attachment to the dominant frequency of the rotational host structure. A reduced order model of the harvester is presented and its power extraction potential is assessed.