Study On Dynamic Characteristics Of Piezoelectric Energy Harvester With Tristable Cantilever Structure

With the gradual maturity of wireless sensing technology and microelectronic system,the market demand increases year by year.In order to overcome the limitations of traditional power supply technology,the self power supply mode is adopted,and the external environment is used as the excitation source to supply power to the device.In order to collect vibration energy in the environment,piezoelectric vibration energy harvester has been widely studied.The piezoelectric vibration energy harvester based on linear vibration has the problems of narrow resonance frequency band and low output power.On the one hand,the energy harvester based on nonlinear vibration can realize multistability and reduce the barrier height,on the other hand,it can broaden the acquisition frequency band.Taking the nonlinear piezoelectric vibration energy harvester as the object,this paper discusses the effect of magnetic force on broadening the frequency band and improving the acquisition efficiency.At the same time,the collision structure parameters are optimized and the magnetic force is combined with the collision force to maximize the acquisition efficiency.The main research contents are as follows:Firstly,this paper extends the magnetizing current method to three magnets,calculates the magnetic force between magnets,and compares it with COMSOL simulation and experiment to prove the reliability and accuracy of this method.Secondly,the piezoelectric vibration energy harvester with magnetic force is modeled to obtain the distributed parameter model.Considering the relationship between the deflection angle of piezoelectric beam and the displacement of tip magnet,the accurate expression of magnetic force and tip displacement is obtained by using the magnetization current method.Then,the governing equations of the system are obtained by Galerkin discretization.According to the Routh Hurwitz criterion,the magnet arrangement parameters for the harvester to produce tristable state are determined.The optimal resistance value and the system damping ratio obtained from the experiment are substituted into the control equation.The asymptotic analytical solution and amplitude frequency response relationship of the system are obtained by using the improved multi-scale method.It is verified by the numerical solution.It is found that under certain external excitation conditions,The addition of magnetic force will broaden the frequency band of the system and obtain higher power output.Finally,considering the magnetic force,the collision structure is added,and the Hamiltonian principle is used to model the system.Under the determined magnet spacing,the best collision stiffness and collision spacing are matched,so that the system can realize large inter well vibration at small external excitation frequency.The research results of this paper improve the modeling of nonlinear piezoelectric vibration energy harvester and expand the application of harvester;The magnetizing current method is extended and applied to the calculation of the magnetic force between three magnets,which provides a theoretical basis for the accurate calculation of the magnetic force between magnets;Considering the vibration mode function of the segmented piezoelectric beam,the deflection angle is converted by using the first-order partial derivative of the deflection at the tip magnet,which is substituted into the magnetization current method to calculate the magnetic force,and the accurate distributed parameter model of the transverse vibration of the continuous system is obtained,which provides a reference for the modeling of the magnetic piezoelectric vibration energy harvester;The theoretical modeling of the magnetic piezoelectric vibration energy harvester based on collision is improved,and the optimal collision stiffness and collision spacing under each magnet spacing are obtained,which provides theoretical guidance for the theoretical modeling and experimental research of subsequent collision.