Designing a vibration energy harvester for several directions of excitation in planar motion

Harvesting energy from a mechanical vibration source is always challenging and comes with drawbacks, especially when the vibration input changes direction very often. This research proposes a novel design to harvest energy from a planar mechanical vibration source no matter its direction of oscillation. To achieve this, a spiral beam with a tip mass is designed to be flexible to various directions of the vibration input in a horizontal plane, which is orthogonal to the direction of gravity. An approximate analytical investigation is first performed. Numerical simulations are then conducted using commercial FEA software and the results are in good agreement with the analytical approach. Numerical simulations show that the tip mass acts symmetrically in the plane, although the system is not geometrically symmetric. To experimentally validate the proposed configuration, a 3D-printed prototype device was manufactured and attached to a shaker, which induced a vibrating motion for the tests. A piezoelectric patch was attached to the curved beam to generate electrical energy and measurements of produced open-circuit voltages were taken for different directions of the exciting vibration.