**Structure Design and Electro-mechanical Performance Analysis of Vibration Piezoelectric Composite Energy Harvester**

Author:Lu Qing Qing

Supervisor:liu yan ju

Database:Doctor

Degree Year:2019

Download:59

Pages:145Size:6914K

Keyword:Composites，dynamic response，piezoelectric materials，Vibration Energy Harvester

In recent years,the fast development of the wireless sensor networks has significantly driven the wide applications on the road and bridge infrastructure,environmental monitoring,various large equipment and aerospace.At the same time,with the low power consumption tendency of the various sensors,wireless transmission devices and other microelectronic devices,looking for some new energy supply ways to break through the network life limit caused by the traditional chemical batteries,which is one of the key factors to determine the development of wireless sensor technology in the future.The technology of piezoelectric vibration energy harvesting has many advantages,such as simple structure,high energy conversion efficiency,green environmental protection and sustainable development,so it has been drawn more attention by some researchers.By using positive piezoelectric effect to convert the abandoned mechanical energy exist in the environment into electric energy,and this technology has great potential to realize the self-power supply of the wireless sensor network nodes and extend the lifespan of the rechargeable battery in the future.In this thesis,the structural design and dynamic response of the piezoelectric energy harvester are presented.By establishing the electro-mechanical model,the relationship between the structural parameters,material parameters,boundary conditions and the external excitation conditions and the dynamic response,energy generation characteristics of the system is analysed.The responses of the linear piezoelectric energy harvesting device and the frequency bandwidth expandation of the nonlinear energy harvesting system are studied.This thesis will provides theoretical guidance and technical supports for the design and optimization of the piezoelectric energy harvesting system.The main work is list as follows:Firstly,the structural design and modeling of the dynamic response tuning characteristic of the variable stiffness composite material for linear piezoelectric vibration energy harvesting system is introduced.The elastic layers in the traditional piezoelectric energy harvesting structure are replaced by the variable stiffness composite,and the variable stiffness characteristics of the shape memory alloy-epoxy(SMA-epoxy)composites with temperature control is used to adjust the resonance frequency of the system.The stiffness model of SMA-epoxy composites was established and the effect of temperature was simulated.The output voltage of the SMA-epoxy composites piezoelectric energy harvester are simulated through the numerical calculation.Finally,the vibration test of the SMA-epoxy piezoelectric energy harvester under thermal environment condition,including the power spectral density function and the output voltage test.The simulation and experimental results show that the resonance frequency can be controlled by the temperature of the variable stiffness composite piezoelectric energy harvester.Secondly,the structural design of the multi-layer piezoelectric through the thickness and the electro-mechanical model of the energy harvester were presented.The power generate efficiency can be improved through embedded more PZT layers into the composites laminates.The electro-mechanical model of the multi-layer piezoelectric energy harvester(MPEH)is here established based on the use of the Euler-Bernoulli beam theory.The fundamental natural frequency and the power output of the MPEH beam are then extracted,and the performance of the MPEH is discussed based on simulations and experimental data.A parametric analysis of the voltage density and resonant frequencies is also performed versus different stacking sequences of the MPEHs and PEHs leading to different specific flexural stiffness(i.e.,normalized by the mass of the beams).The specimen of the MPEH is fabricated through integrated molding method of the CFRP and PZT layers.The dynamic responses and the output power performance of the MPEH are tested through vibration experiments.The comparisons between the MPEH and the classic PEH are conducted through the experiments.From the simulations,experimental data and the parametric analysis we can demonstrate that the MPEHs can generate significantly more power than the PEHs configurations.The comparison between the MPEH and a classical PEH configuration shows that the MPEH can provide an output voltage 2 times higher of the PEH system with the same load resistance.Thirdly,the effect of the stacking sequences on the piezoelectric energy harvester with symmetry angle composites laminates is conducted.With variable stacking sequences can obtain laminates with through-thickness Poisson’s ratios exhibiting negative Poisson’s ratio or near zero values,and this part is evaluated by using classical laminate theory.Six stacking sequences with different through-thethickness Poisson’s ratios are then selected to fabricate composite beams with PZT layers.The statics characteristic of the composites piezoelectric energy harvester are obtained based on the simulation and three-points bending experiment.The vibration experiments are finally conducted to discuss the dynamic property and the voltage output.The test results show the effect of the stacking sequences effect on the performance of the composites piezoelectric energy harvester.The numerical simulations and experiments results show that the piezoelectric energy harvester with near zero Poisson’s ratio can generate the highest power compared to the other configurations.The maximum voltage output of the near zero Poisson’s ratio laminates can be 1.625 times than the positive one.In the last part,in order to overcome the narrow bandwidth of the linear piezoelectric energy harvester,a novel nonlinear piezoelectric energy harvesting system is designed to expand the working bandwidth.The dynamic analysis model of the magnetic induced nonlinear piezoelectric energy harvester are established and the vibration modes and frequency response at different space distance are predicted.The model of the magnetic induced nonlinear energy harvesting system is developed using the Hamilton principle,and the influence of the magnetic force is taken into account.Based on the numerical calculation program,the dynamic response and the output voltage of the nonlinear piezoelectric energy harvester with different spacing distance are presented.Then the sweep vibration experimental validation(forward and backward sweep)with different excitation level are conducted to obtain the electromechanical performance of the magnetic induced nonlinear piezoelectric energy harvester.Through the comparisons between the simulation and experimental results,the power output and the working bandwidth performance of the E-shape system are achieved.The voltage response of the magnetic induced nonlinear system show excellent power generation property and the working bandwidth of the system obtained significantly improve.