## 5 Conclusions  
In summary, the S-type bistable generator beam is proposed, and energy harvesters using this beam in two typical environments (the up-and-down vibration excitation and the wind-induced vibration excitation) are designed, prototyped, and tested in order to assess its suitability for energy harvesting from broadband vibrations. Here are some important conclusions:  
1. This research paper proposes an S-type generator beam which can fully utilize materials and avoid premature fatigue failure caused by stress concentration. Under the same excitation conditions, the peak stress of the S-type generator beam is 34.3% lower than that of the cantilever beam (in the optimal working condition), indicating the advanced technology of the S-type generator beam in improving material fatigue failure.  
Figure 10: The output performance through a rectifier circuit.  
Figure 9: The output performance of the harvester at different circuit load conditions: **(a)** The up-and-down vibration excitation; **(b)** The wind-induced vibration excitation.  
2. The S-type generator beam has good energy capture performance in low-frequency environments. A collector using S-type bistable generator beam was tested in two typical environments. When the environmental excitation frequency rises to the third natural frequency (the third mode, 7.45 Hz) of the generator beam, the motion process of the beam breaks through the potential energy barrier and produces intrawell motion (penetration). The peak output voltage in the two environments is 14,350 mV and 17,630 mV, respectively.
3. The S-type generator beam has a high energy capture efficiency. Within the experimental range, when the external resistance of the circuit is 22 k\(\Omega\), the energy collector in both environments reaches the optimal power output state, which is 0.534 mW and 0.545 mW, respectively. At this time, the AC-to-DC bridge circuit sends power to a 470 uF capacitor, and the energy collector is better in the wind environment than in the up-down vibration environment.  
Conceptualization, N.W.; methodology, N.W.; software, N.W.; validation, N.W.; formal analysis, C.X.; investigation, C.X.; resources, J.F.; data curation, C.X.; writing--original draft preparation, N.W.; writing--review and editing, N.W.; visualization, J.F.; supervision, J.F.; project administration, J.F.; funding acquisition, J.F. All authors have read and agreed to the published version of the manuscript.  
This research was funded by National Science Fund for Distinguished Young Scholars grant number [51925802]; the National Natural Science Foundation of China grant number 11972123; 52108448] and The APC was funded by [11972123].  
Not applicable.  
The introduction data supporting this manuscript are from previously reported studies and datasets, which have been cited. The processed data are available from the corresponding author upon request. The test raw data used to support the findings of this study are available from the corresponding author upon request.  
The authors would like to thank the National Science Fund for Distinguished Young Scholars (Grant No. 51925802), and the National Natural Science Foundation of China (Grant No. 11972123; Grant No. 52108448) and the for their financial support.  
We declare that we do not have any commercial or associated interest that might represent a conflict of interest in connection with the work submitted.