Analysis of spiral cantilever structures for hybrid vibration energy harvesters

The recent advancement of low power electronic circuits has boosted the importance of vibration energy as a viable source to power such devices. Vibration energy can be harvested using piezoelectric, electromagnetic, or triboelectric transductions. Piezoelectric energy harvesters typically use micro-scale cantilevered beams, but their fundamental frequency often exceeds the range of most mechanical vibrations. While increasing beam length can reduce the frequency, it may lead to impractical designs. Multi-cantilever beam systems offer an alternative by addressing these limitations while maintaining efficiency. This study explores the significance of various orthogonal spiral cantilevers as prominent structures for the design of a hybrid vibration energy harvesting using the piezoelectric-electromagnetic technique. As piezoelectric requires higher stress density, electromagnetic transduction requires a greater displacement to enhance the power output, the analysis is performed for the natural frequency, stress distribution and surface displacement of various beam structures, ensuring stable and efficient energy harvesting. All the structures are simulated in COMSOL Multiphysics and excited with a vibration force of 1g acceleration. Among the analyses on spiral cantilevers, orthogonal spiral cantilevers have shown the best response. The natural frequency of the structures has shown a decreasing trend which varied from 31Hz for structures with the number of beams (n) = 2 to 15.3Hz for structures with n=6. With a displacement of 0.307cms and maximum Von Mises stress of 3.83x106N/m2 orthogonal spiral structure with n=5, has proved to be the ideal candidate for VEH in this study. This study serves as the preliminary analysis for the use of spiral structures as prominent structures for developing VEHs, overcoming traditional limitations, and providing a robust solution for harvesting ambient vibrations.