Shape optimization of railroad vibration energy harvester for structural robustness and power generation performance

This paper presents design optimization of a stiffness component in a vibration energy harvester - diaphragm spring - for structural robustness and reliable power generation in railroad vehicle monitoring applications. Power generation is usually sufficient under the high impact loading of railroad operating conditions, but a highly durable harvester design has been a challenging issue. This paper performs a practical shape optimization of the diaphragm spring considering realistic vibrational loading conditions. In this study, we build the power spectrum density (PSD) of acceleration loading based on a railroad system design standard and use it for maximum stress estimation. A separate electromagnetic analysis has been conducted to determine the vibrational amplitude for the required power generation. A new conceptual diaphragm spring model has been chosen to minimize any unnecessary parasitic motion that could cause asymmetric spring deformation and excessive stress. The shape optimization on the new conceptual spring model has been conducted to obtain the new design that reduces the magnitude of stress concentration by 16% while satisfying the required vibration amplitude for energy harvesting.