Design And Experimental Research Of A Frequency Self-Matching Vibration Energy Harvester For Rotational Application

One of the ideal solutions for the self-powering of integrated microsystems in rotating systems is the vibration energy harvester based(VEH-based)rotational energy harvesting techniques,which has been a popular research topic in recent years.However,there is an application problem of frequency mismatch with the VEH,and solving the mismatch between operating frequency and excitation frequency is one of its main research missions.The frequency matching method based on the frequency self-matching technology has the features of wide frequency matching range,high accuracy and no manual intervention,which is one of the effective technical schemes to solve this problem.According to the above scientific and technological problems,this paper carries out the research on the frequency self-matching mechanism of rotational self-tuning VEH.Mechanisms for frequency self-matching of the VEH under rotational excitation are studied;a self-matching method is proposed to adjust the equivalent stiffness of the piezoelectric beam by the rigid-flexible coupling effect while adjusting the effective length of the piezoelectric beam by the centrifugal force effect,and a corresponding frequency self-matching vibration energy harvester(FSM-VEH)with a new structure is designed;a theoretical model of the FSM-VEH is established,taking into account the rigid-flexible coupling effect and the centrifugal force effect.The simulation results show that the new structure can achieve self-matching within a certain continuous rotational frequency range;by optimizing the mass of the frequency tuning Mass(FTM),the mass and length of the additional mass(AM),the rotation radius,and the length and width of the piezoelectric beam,the output voltage,output power,and effective operating bandwidth of the FSM-VEH can be effectively increased,with the optimized maximum of 22.6～32.4 V,33.5～40.6 m W and 30.7 Hz(15.6～46.3 Hz),respectively.Based on the results of theoretical analysis and parameter optimization,an experimental prototype was fabricated,and an experimental platform was built for the experimental study of the FSM-VEH.The experimental results show that the frequency self-matching principle and its new structure are efficient;with parameter optimization,the peak-to-peak output voltage,output power and effective operating bandwidth can reach 54～78 V,1.27 m W and 5.16 Hz(9.67～14.83 Hz),respectively.The part of the experiment that does not match with the theory is further investigated,and the analysis results show that the damping-enhanced amplitude effect produced by the damping excitation force needs to be considered when modeling the relationship between output voltage,output power and rotation speed;and the effect of the AM needs to be further considered when modeling the centrifugal force effect in the case of a large AM mass.This paper analyzes and verifies the effectiveness of the proposed frequency self-matching method and its new structure from the theoretical and experimental perspectives;it enriches the VEH frequency self-matching method;the parameter analysis method and experimental research method developed during the research can provide new ideas for the research of the VEH frequency matching problem.In the future device research,the investigation of structures with non-linear spring properties and the development of silicon micromachining technology with equal scale reduction of device size are the keys to the practicalization of the FSM-VEH.