Experimental Model And Nonlinear Analysis Of Piezoelectric Laminated Plate Circular Vibration Energy Harvester

Vibration-based energy harvesting devices can generate enough power to sustain low-power electronic devices,such as wireless sensors.In this dissertation,a piezoelectric laminated plate circular vibration energy harvester is investigated.The experimental model method,system identification method of piezoelectric vibration energy harvester and solving methods of nonlinear dynamic system are studied.The dissertation is organized as following:Chapter 1 presents the purpose and significance of this dissertation and surveys the research status of linear or nonlinear piezoelectric laminated plate circular vibration energy harvester.The two non-parametric system identification methods based on time domain are discussed.The solving methods of periodic solution are summarized.The main contents and main innovations of this dissertation are listed at the end.Chapter 2 establishes the linear elastic model of the harvester and the expressions of electromechanical coupling coefficient and equivalent capacity coefficient are proposed.A parameter identification method of piezoelectric vibration energy harvester is also proposed.The nonlinear elastic restoring force of the laminated plate harvester is identified by a modified restoring force surface method.The harmonic balance method with the arc-length is introduced into the piezoelectric harvester.The semi-analytical results are in good agreement with the numerical and experimental results.The softening nonlinearity is discovered under small excitation and the hardening nonlinearity and softening nonlinearity are combined when the harvester is subjected to sufficient large excitation.Chapter 3 investigates the nonlinear characteristic of the laminated circular plate itself.The restoring force surface method and Hilbert transform method are applied to identify the laminated circular plate nonparametrically.The identification results show that the plate has combined softening and hardening nonlinearity characteristics.The elastic restoring force data and the stiffness function data are compared.The stiffness function data can better reflect the system nonlinear characteristics when the displacement is small.A modified hyperbolic tangent function is proposed to approximate the stiffness function data.The laminated circular plates with different diameter are also identified and the robustness of the results is verified.Chapter 4 proposes a non-parametric method to identify the laminated circular plate harvester based on the Hilbert transform method.Through the definition of analytic signal,two approaches,‘direct method' and ‘equivalent method' are proposed.The simulation example shows that the equivalent method has higher accuracy.A non-parameter identification method for multilayer piezoelectric harvester is proposed.The experimental identification results of laminated circular plate harvester resemble the combined softening and hardening nonlinearity characteristics.The time-varying functions of electromechanical coupling and equivalent capacity are also identified.With the retrogressed verification for the proposed method,energy harvesting is similar to damping effect in the system.Chapter 5 expands the HB-AFT method to piezoelectric vibration energy harvester system.The periodic solutions of the harvester with the complicated non-polynomial elasticity and damping restoring force are solved successfully.The Floquet theory with Hsu algorithm is applied to judge system stability of periodic solutions.The amplitude frequency response curve based on the modified hyperbolic tangent function model can exhibit the combined softening and hardening nonlinearity characteristics of the harvester more accurate.The amplitude frequency and phase frequency response of high-order harmonic,and the super harmonic resonance phenomenon are also studied.