Optimized Mechanical Performance of Cantilevered Vibration Energy Harvesters Using a Modal Approach

In order to improve the performance of cantilevered vibration energy harvesters, current methods normally vary their geometric dimensions and derive the maximum power outputs by running a full analysis. This paper attempts to optimize the structural performance of cantilevered vibration energy harvesters using a modal approach without carrying out full analysis. The effects of varying geometrical dimensions on the modal mechanical performance are analysed, which includes the analysis on rectangular cantilevered beams with and without extra mass, the convergent and divergent tapered cantilevered beams. The modal approach uses mass ratio and the modal electromechanical coupling coefficient to determine the electrical and mechanical modal performance of vibration energy harvesters. In particular, mass ratio depends on the modal participation factor, and it represents the influence of modal mechanical behaviour on the power density directly. The required modal parameters are derived using the finite element method and a distributed parameter electromechanical model is also used for comparison. The cantilevered beam designs using the modal approach can be used with different sizes with the power ranging from microwatts to milliwatts.