Study On The Performance Of Periodic Structure Piezoelectric Vibrators

With the widespread application of MEMS in industrial production and practical life,traditional energy supply methods are no longer meet the environmental needs of MEMS,and the piezoelectric energy harvester(PEH)is used to collect the vibration energy in the environment to provide real time energy for MEMS has become the key method to solve this problem.Most of the commonly used PEH are cantilever beams,which have considerable energy capture performance only when they are in resonance state.However,the frequency of vibration source in the environment is low,and the traditional frequency reduction methods also have many limitations.Aiming at the above problems,two kinds of periodic structure piezoelectric vibrators are proposed,and their theoretical modeling and simulation analysis are carried out.The results show that the periodic structure can not only improve the low-frequency energy capture performance of PEH,but also have good broadband capture performance.For the design of ultra-low frequency high performance piezoelectric cantilever beams in the future,this thesis has reference significance.The main research work of this thesis is as follows:(1)Combining the piezoelectric constitutive equation and Euler-Bernoulli beam theory,the output voltage expression of the piezoelectric beam under external harmonic excitation is deduced,and the relationship between the structural parameters of the cantilever beam and the output voltage is determined.It is pointed out that it is necessary for piezoelectric beams to produce resonance in ordinary environment,which provides theoretical basis for the study of periodic cantilever beams.(2)To establish the structural model and the theoretical model of two kinds of periodic structural piezoelectric beams,and analyzed by using Euler-Bernoulli hypothesis distributed parameter method.The vibration control equations of piezoelectric beams with periodic structures are established and solved.The first five modes of natural frequencies of piezoelectric beams are solved and compared by numerical simulation software and finite element software.The results show that the spiral beam has a lower natural frequency when the number of beams is low.When the number of beams increases to more than 8,the zigzag beam has lower natural frequency.However,the natural frequency ratio of each mode of the zigzag beam increase with the number of beams.The mode orders matching with the frequency of vibration sources in the environment are less,and the broadband energy capture performance is not as good as that of the spiral beam.(3)Analyze the influence of periodic structure on piezoelectric beam,the strength analysis,modal analysis and harmonic response analysis of piezoelectric beams with periodic structure are carried out respectively.Compared with the traditional single-segment piezoelectric beam,the carrying capacity of the spiral structure is better than that of the zigzag structure,but they are superior than that of traditional single-segment piezoelectric beam.At the same time,the mode shapes of the two periodic structures exhibit good energy capture characteristics,and their response voltage values are higher than those of the traditional single-segment piezoelectric beams,and there are multiple resonance response frequencies in general environment,which exhibit higher broadband energy capture performance.(4)The effects of the number and width of beam segments,the thickness ratio of piezoelectric layer to metal substrate,the external load resistance and the position of piezoelectric patch on the energy capture performance are investigated.The results show that increasing the width of the beam can improve the energy apture performance of the piezoelectric beam but increase its natural frequency.When the number of spiral beam segments is 7,the energy harvesting performance is best,and the zigzag beam energy harvesting performance increases with the number of beam segments.There is an optimum thickness ratio of 1.13 in both structures,which makes the energy capture performance of piezoelectric beams optimal,and the output voltage increases with the increase of the external load resistance.When the thickness of the piezoelectric layer is 0.3mm and the load resistance is 1 0~5Ω,the power reaches the maximum value.The response voltage of spiral piezoelectric beam is the highest when PZT are pasted on the second,third and fourth piezoelectric beams,and that of zigzag piezoelectric beams when PZT are pasted on the second beam to the last beam.