Nonlinear Mechanism Study Of Multi-Degree-of-Freedom Linkage Characteristic Energy Harvester In Low-Frequency Vibration Environments

In order to meet the needs of self-powered in the fields of wireless sensor equipment,health monitoring,and home safety monitoring,to reduce the pollution of chemical fuels to the environment,it is in line with the concept of sustainable development.At present,capturing energy in low-frequency vibration environment is a hot research field of energy harvesting.When the external excitation reaches a certain degree,the natural frequency is the same as the external excitation frequency,and the piezoelectric energy harvester produces a wider working bandwidth.Using nonlinear magnetic force to improve the bandwidth of the working frequency band is the most reliable means.In this thesis,a new type of piezoelectric energy harvester device is proposed based on the cantilever beam piezoelectric energy harvester,achieve self-powered.The innovation of the design of the energy harvester is that it can realize multi-degree-of-freedom linkage characteristics and time-varying potential energy wells.Firstly,by reading the research and development status at home and abroad,a piezoelectric energy harvester device with multi-degree-of-freedom linkage characteristics is proposed.Multi-degree piezoelectric energy harvester has the characteristics of simple structure,light weight,large output voltage and power.Based on the single-degree-of-freedom and two-degree-of-freedom structures,this thesis establishes a nonlinear magnetic model of a multi-degree-of-freedom linkage piezoelectric energy harvester.According to the vibration theory and the characteristics of piezoelectric materials,the electromechanical coupling equations,kinetic energy and potential energy mathematical models of three piezoelectric cantilever beams are established respectively.Then,the simulation analysis of piezoelectric energy harvester is carried out by Matlab software.The potential energy models of three piezoelectric cantilever beams are studied respectively,and the changes of potential energy wells of three piezoelectric cantilever beams are analyzed.At the same time,the amplitude-frequency characteristics of multi-degree-offreedom linkage piezoelectric cantilever beam are also studied,including output voltage,output displacement and phase diagram.Finally,the parameters of piezoelectric energy harvester are studied by experimental verification.The amplitude-frequency characteristics of single-beam piezoelectric energy harvester and double-beam piezoelectric cantilever beam are studied.The analysis results show that the working frequency band of piezoelectric cantilever beam is narrow.When the excitation frequency of excitation source deviates from the natural frequency,the voltage decreases.On this basis,a multi-degree-of-freedom piezoelectric energy harvester is established.The multi-degree-of-freedom piezoelectric energy harvester improves the bandwidth of its working frequency band and output power.The results show that the study the characteristics of piezoelectric energy harvester,the forward and reverse sweep curves,fixed frequency curves and different power characteristic curves under different excitation levels,different longitudinal distances,different lateral distances and different longitudinal magnet masses are respectively made.With the increase of the external excitation level,the generated mean square voltage increases.With the increase of transverse distance and longitudinal distance,the generated mean square voltage decreases.With the increase of the quality of the longitudinal magnet,the total power increases continuously.