Study On Piezoelectric Energy Harvester Based On Collision Mechanism

With the rapid development of wireless sensor nodes and micro electro mechanical systems,the traditional power supply technology has been difficult to meet the power demand.The use of piezoelectric energy harvesters to convert the vibration energy in the environment into electrical energy to power these sensor nodes and micro systems has become a research hotspot.However,since most of the vibration excitation in the environment has the characteristics of random and broadband,the traditional resonance type piezoelectric energy harvester is difficult to exert its effectiveness due to the narrow effective working frequency band.In response to this problem,this paper improves the structure of the traditional piezoelectric cantilever beam energy harvester,and proposes a piezoelectric energy harvester based on the impact mechanism.Orthogonal experiments and single-factor experiments are carried out on the prototypes produced,and the influence of the structure parameters and excitation parameters of the harvester on the output performance is studied.Aiming at the problem of low output voltage of the collector,a six times voltage rectifier energy management circuit is designed,and the boost effect of this circuit is simulated and experimentally analyzed.The main conclusions are as follows:1)With the help of COMSOL software,a simulation model of piezoelectric energy harvester based on collision mechanism is established.The transient analysis of the model shows that the time-domain waveform of the output voltage obtained is consistent with the experimental results.The influence of excitation acceleration and external load on the output performance of the collector is studied.As the excitation acceleration increases,the output voltage is also increasing.When the external load is large enough,the output voltage remains stable.2)The best parameter combination of substrate length,substrate width,substrate thickness and ball quality of the piezoelectric energy harvester based on impact mechanism proposed in this paper is L=120mm,S=16mm,H=2mm,m=1g.Among them,the quality of the ball has the greatest impact on the output of the harvester.The F ratio,significance level and contribution rate of this parameter can be obtained through the analysis of variance on the orthogonal experiment results,which are 13.2,5%,and 42%,respectively.With 80% of the maximum output voltage as the threshold,the frequency range of the proposed structure reaches 4Hz,which is four times that of the traditional resonant piezoelectric energy harvester,and the peak output voltage is increased by 10%.At the same time,the output voltage at higher than the first-order natural frequency is also improved.The single factor experiment results show that when the substrate thickness,excitation acceleration and external load increase,the output voltage also increases.There is no monotonic relationship between the changes of other parameters and the output voltage.3)The experimental results of the six times voltage rectifier circuit show that when the charging time is 80 S,the output voltage can reach 18.96 V,and the charging speed is0.237V/S.The feasibility of the six times voltage rectifier circuit as the energy management circuit of the proposed piezoelectric energy harvester based on the impact mechanism is verified.