Research On Design And Collection Efficiency Of Z-shaped Piezoelectric Vibration Energy Harvester

With the wide application of wireless sensing technology around the world,people are paying more and more attention to the power supply of wireless electronic devices.Mechanical vibration energy is easier to collect than other forms of energy,and is not affected by factors such as service environment and use time,so it has been widely studied by scholars at home and abroad;among them,the structure of piezoelectric energy harvesting is simple,and the higher force-electrical coupling effect can collect more energy,which has become the key research direction in the field of energy harvesting.At present,the vibrating bodies of the common piezoelectric vibration energy harvesters are mostly straight beams or L-beam structures,and there are few studies on Z-beam piezoelectric vibration energy harvesters.The nonlinear internal resonance of the Z-beam structure can realize broadband vibration,so that the energy harvester can collect energy in a wider frequency range.In this paper,combined with the piezoelectric theory and the nonlinear vibration theory of the structure,the electromechanical coupling governing equations of the Z-shaped nonlinear piezoelectric vibration energy harvester structure based on 1:2 internal resonance are established.The energy harvesting efficiency is studied by theoretical analysis and numerical simulation.At present,the vibrators of common piezoelectric vibration energy harvesters are mostly straight beams or L-beam structures.Z-shaped nonlinear piezoelectric vibration energy harvester can obtain higher acquisition efficiency compared with traditional straight beam or L-beam piezoelectric vibration energy harvester,and the nonlinearity comes from its own Z-shaped structure,without the need for magnetic nonlinearity.The Z-beam structure enables broadband vibration through the design of internal resonance,which can widen the bandwidth of energy harvesting.In this paper,the structural parameters of Z-shaped beams are designed to satisfy the frequency of the first twoorder bending modes by combining piezoelectric theory and nonlinear vibration theory,and the electromechanical coupling control equation system of Z-shaped nonlinear piezoelectric vibration energy harvester structure based on 1:2 resonance is established,and the energy harvesting efficiency is studied by theoretical analysis and numerical simulation.Construct the geometry vector of Z-beam structure under the global coordinate system,use Hamilton principle to derive the dynamic control equation and boundary conditions of Z-shaped nonlinear piezoelectric vibration energy harvester,and then solve the natural frequency and mode shape function of the system.The finite element simulation software is used to analyze the system mode,and the natural frequency and mode of the obtained system are compared with the theoretical calculation results,and the accuracy of the theoretical calculation results is verified.The effect of folding angle on the natural frequency of Z-shaped nonlinear piezoelectric vibration energy harvester is studied,and the natural frequency of the first-and second-order bending modes of the system meets the resonance condition within 1:2 by adjusting the folding angle of the Z-shaped beam.The nonlinear dynamic equations of the energy harvester are perturbed by multiscale method,and the influence of system parameters on the amplitude and bandwidth of energy harvester under the resonance condition of Z-type piezoelectric vibration energy harvester within 1:2 is explored.The results show that with the increase of the excitation amplitude,the amplitude and bandwidth of the system will increase,resulting in a very obvious nonlinear phenomenon,and the voltage amplitude generated on each section of the beam is different,compared with other beam segments,the III.beam produces the highest voltage amplitude,the I.beam is the lowest,so the Z-beam structure can significantly improve the energy harvesting efficiency compared with the traditional cantilever beam,and is more suitable for working in the working conditions of large excitation.In the case of first-order main resonance,when the excitation amplitude is fixed,with the increase of damping,the voltage amplitude and bandwidth collected by the system are reduced,and the fixed second-order mode damping adjusts the first-order mode damping,and the system amplitude-frequency response changes particularly significantly,that is,the effect of system energy acquisition can be improved by reducing the first-order mode damping.When the internal resonance is close to the tuning state,the amplitude of the second-order modal response gradually increases,the amplitude of the first-order modal response decreases,the degree of internal resonance detuning becomes larger,the energy transfer is relatively small,the amplitude of the second-order modal response gradually decreases,and the amplitude of the first-order modal response slowly increases,when the system is in the case of small detuning or detuning,the position of the output voltage maximum will be relatively offset,and the output voltage is the largest when fully tuned.The influence analysis of the tuning parameters proves that the amplitude and bandwidth of the system acquisition voltage can be obtained at full tuning,and the energy harvesting efficiency is the highest.When the external excitation amplitude is fixed at a certain value,the voltage amplitude generated on each section of the system beam increases with the increase of resistance,and because the external excitation amplitude is unchanged,the voltage amplitude of the system does not increase with the increase of resistance,which provides a reference for the system to select a suitable resistor to improve the efficiency of energy harvesting.Finally,an experimental platform is built to make a Z-beam test prototype,and the natural frequency and mode of the vibration of the model are analyzed experimentally to verify the reliability of the theoretical analysis.