Comparison Study on Two-DOF Broadband Energy Harvester for Varied Tram Vibration Frequency

Abstract Vibration energy is widespread in tram systems with high density, and it is a prevalent option of passive energy generation to enable self-powering wireless sensors for structural health monitoring. This paper presents a broadband vibrational energy harvesting device design that utilizes a varied frequency from a tram vehicle using a 2-degree-of-freedom vibrational system combined with electromagnetic energy conversion. Specifically, this paper will compare the power output for two design configurations: open-end and closed-end designs. For each design, a stepwise optimization process is applied to determine (1) mechanical parameters for frequency tuning to adjust to the trams’ operational conditions, and (2) electromagnetic parameters for the whole system design to maximize power output. That is, the first step optimization will determine mechanical design parameters for frequency tuning: masses (m1, m2) and spring constants (k1, k2, k3). The second step will use these parameters as initial guesses and present electrical parameters (number of coil turns, external resistor) to maximize the power output in the frequency band of interest. The design results indicate that the 2-degree-of-freedom closed-end has a preferable performance in terms of broadband vibration energy harvesting with higher average power as well as manufacturability within design constraints.