Design And Analysis Of Energe Harvestin With Bistable Piezoelectric Cantilever Beam For Duffing Oscillator

Recently,collecting energy from the environment is one of the most popular research topics.The energy harvester with bi-stable piezoelectric cantilever beam has attracted many attentions among others due to its simplicity.However,at present,the collection technology of chaotic vibration energy has not yet been reported.Chaotic vibration is a special kind of vibration between periodic vibration and random vibration.Therefore,the study and development of the energy harvester for chaotic oscillator are high significant.In this thesis,energy harvester with bi-stable piezoelectric cantilever beam for Duffing oscillator is studied addressing the problem including the influence of harvester on the motion of the oscillator,the mechanism of energy harvesting of energy harvester excited by chaotic vibration and optimal design of a bi-stable piezoelectric cantilever beam and so on.It is found that the average output power,one of most used index for energy harvesting,can not be utilized to describe the energy efficiency completely when the vibration is chaotic.As a supplement,interwell hopping frequency ratio is proposed to measure the energy efficiency from the perspective of energy storage,The main research work and conclusions in this thesis are as follows:1.The dynamic model of Duffing oscillator is established by using the Newton's second law,and the vibration characteristics of the oscillator are analyzed as the frequency and amplitude of external excitation is varied.Considering the quality distribution characteristics of the cantilever beam and treating it as an Euler-Bernoulli beam,the oscillator with a cantilever beam and itself are regarded as a system of two degrees of freedom,and Language equations are used to establish the dynamic model in which electronic system and the mechanical system is coupled Furthermore,the chaotic vibration characteristics of the oscillator with a cantilever beam are analyzed.The result shows that the installation of the energy harvester does not have influence on the chaotic vibration of the oscillator.Using the chaotic vibration as the excitation of the cantilever beam,it is found that periodic motion does not appear but chaotic motion.2.The reason for the bi-stable characteristics in the energy harvester is analyzed in detail.The shortage of index which is commonly used to measure the effectiveness of energy harvesting has been analyzed.A new index,named as interwell hopping frequency ratio,is proposed for the storage of energy collected.The results of simulation show that the higher the interwell hopping frequency ratio of the cantilever beam,the better the energy storage.3.With two design objectives,one is the global maximum average output power,the other one is interwell hopping frequency ratio over 95%,the value combinations of the magnet spacing and the load resistance are determined using Monte Carlo method.The procedure of optimization ensures that parameters determined can not only maximize the conversion of electric energy,but also store the energy efficiently.The method and results presented in this thesis will be helpful for design of the energy harvester with bi-stable piezoelectric cantilever beam for chaotic oscillator,and it has a certain reference value for broadening the application of energy harvester.