Analysis On The Nonlinear Multi-field Coupling In Piezoelectric Compound Structures And Experimental Study On Piezoelectric Energy Harvesters

Due to their excellent electromechanical (EM) coupling, piezoelectric compoundstructures (PCS) have been widely applied in acoustical wave devices like piezoelectricenergy harvesters, piezoelectric transformers and piezoelectric resonators, etc. Progressin this field has greatly promoted the more in-depth development of the modernintelligent structural control and wireless energy supply. Because there existscomplicated multi-field coupling in PCS and this coupling gradually appears stronglynonlinear with the miniaturization and integrated circuit developments of microelectronicdevices, solving those physical quantities in PCS becomes very difficult. In thisdissertation, dynamic equations of PCS are established from the three-dimensionalelectroelastic theory together with the introduction of nonlinear deformation. Then,in-depth studies are conducted on the linear and nonlinear characteristics of severaltypical piezoelectric acoustic wave devices. A few new conclusions are drawn from theanalysis. Finally, some experimental studies are focused on piezoelectric energyharvestors with the results in agreement with our previous theoretical analysis. Theimportant research achievements are as follows:(1) A novel torsion-type low-frequency piezoelectric energy-harvesting structure isput forward, which can effectively extract energy from low-frequency ambient vibrations.The structure/circuit coupling model of such harvesters is established. The effects ofvarious system parameters on harvester performances are clarified in detail.(2) Several typical nonlinearly-dynamic model of piezoelectric energy harvesters areestablished by introducing nonlinear deformation of PCS. Considering that thepolarization voltage and boundary charge are caused by two deformations, bending andin-plane stretching, the voltage and charge caused only by bending are distinguished fromthe remainders. Then the output voltage and current of the energy-harvesting structure areredefined in terms of the identified polarization voltage and boundary charge by bending.Moreover, the nonlinearly-dynamic behaviors of several typical piezoelectric energy-harvesting structures in the vicinity of resonance are analyzed. Themulti-valuedness and jumping of output power are revealed, and the important influencesof system parameters on the nonlinear region of harvesters are clarified, which are usefulin harvester design.(3) A nonlinearly-dynamic model of5-layer piezoelectric transformers is establishedand the nonlinearly-dynamic behavior of the piezoelectric transformer structure in thevicinity of resonance is analyzed. The multi-valuedness and jumping of output/inputvoltage ratio are revealed, and the important influences of system parameters on thenonlinear region of transformers are clarified, which are useful in transformer design.(4) An experiment model is established for a piezoelectric bimorph harvester. In themodel, a linear vortex sensing circuit is applied to catch the displacement maximums viathe EM similar relationship in a linear EM system. Then, a differential full-wave rectifiedmicrocontraller is self-designed to periodically control the switch in series with the SSHI.The voltage reversal has been successfully achieved through the controlled SSHI at thedisplacement maximums. Finally, the experiments on the nonlinear coupling betweenpiezoelectric structure and energy-storage circuit are conducted. Experiment results hasverified our previous theoretical analysis.In summary, we presents a torsion-type low-frequency energy harvesting structure.The linear and nonlinear characteristics of piezoelectric harvesters and piezoelectrictransformers are investigated in depth through the integrated analysis withharvesting-structure/storage-circuit full coupling. A few meaningful conclusions havebeen drawn in the dissertation. The achievements not only are of important guidingsignificance for the optimal design of piezoelectric harvesters and transformers, but alsohave a larger role in promoting further cross-discipline and the integration.