Mechanical overload protection strategies for energy harvesters with frequency up-conversion mechanism

Vibration energy harvesters utilising the frequency up-conversion mechanism have been effective in harvesting low-frequency ambient vibrations. However, the mechanical impact required for this process could also damage the devices when excessive load is applied. To address this issue, this paper presents novel protection strategies for energy harvesters with a frequency up-conversion mechanism, including a ring-type stopper within the resonant system and specially designed impact protection components (IPC) within the impact system. By applying these methods, the influence of excessive input excitation has been mitigated, and thus, the reliability and durability of the device have been improved. Finite element modelling has been employed to model the proposed protection methods, and then experiments have been conducted to verify and refine the modelling. Stress analysis is finally conducted based on the refined model to validate the effectiveness of the protection strategies. The results demonstrate that the proposed strategies are capable of protecting the harvesting system from excessive input excitations, which means the device functions effectively in the operating state and decelerates the growth rate of maximum stress and acceleration in the limiting state. This research contributes valuable insights into the development of effective protection strategies for energy harvesters with frequency up-conversion mechanisms, thereby improving their durability and performances in real-world applications.