Extending the Frequency Bandwidth of a Tristable Electromagnetic Energy Harvester Through the Use of Stoppers

This study investigated a nonlinear tristable electromagnetic vibration energy harvester enhanced with adjustable mechanical stoppers. The stoppers were designed to limit yoke displacement and prevent sticking in the outer stable positions. The research aimed to extend the operational frequency bandwidth and improve the stability of energy conversion under variable excitation conditions. A comprehensive experimental setup based on a PXI measurement platform was developed to analyze the system’s electrical and mechanical responses. The study examined the influence of stopper spacing, vibration acceleration, and electrical load on the frequency–voltage characteristics and beam strain. The results showed that introducing adjustable stoppers eliminated the sticking phenomenon and broadened the effective operational bandwidth to a total range of 14 Hz under excitation frequencies between 10 and 50 Hz, while maintaining structural safety. The findings confirmed that the proper selection of stopper distance enabled adaptive tuning of the harvester’s dynamic behavior and power output, increasing the average voltage by approximately 50% compared with the configuration without stoppers. The proposed approach improved the autonomy and reliability of self-powered sensor nodes and other low-power electronic systems for Internet of Things (IoT) and condition monitoring applications.