Piezoelectric vibration energy harvesting and its application to vibration control

Vibration-based energy harvesting using piezoelectric materials have been investigatedby several research groups with the aim of harvesting maximum energy and providingpower to low-powered wireless electronic systems for their entire operational life. Theelectromechanical coupling effect introduced by the piezoelectric vibration energyharvesting (PVEH) mechanism presents modelling challenges. For this reason, there hasbeen a continuous effort to develop different modelling techniques to describe thePVEH mechanism and its effects on the dynamics of the system. The overall aims ofthis thesis are twofold: (1) a thorough theoretical and experimental analysis of a PVEHbeam or assembly of beams; (2) an in-depth analytical and experimental investigation ofthe novel concept of a dual function piezoelectric vibration energy harvester beam/tunedvibration absorber (PVEH/TVA) or "electromechanical TVA" and its potentialapplication to vibration control. The salient novel contributions of this thesis can besummarised as follows:o An in-depth experimental validation of a PVEH beam model based on the analyticalmodal analysis method (AMAM), with the investigations conducted over a widerfrequency range than previously tested.o The precise identification of the electrical loads that harvest maximum power andthat induce maximum electrical damping.o A thorough investigation of the influence of mechanical damping on PVEH beams.o A procedure for the exact modelling of PVEH beams, and assemblies of suchbeams, using the dynamic stiffness matrix (DSM) method.o A procedure to enhance the power output from a PVEH beam through theapplication of a tip rotational restraint and the use of segmented electrodes.o The theoretical basis for the novel concept of a dual function PVEH beam/TVA, andits realisation and experimental validation for a prototype device.A thorough experimental validation of a cantilever piezoelectric bimorph energyharvester without a tip mass is presented under random excitation. The study provided adeep insight into the effect of PVEH on the dynamics of the system for variations inelectrical load. An alternative modelling technique to AMAM, based on the DSM, isintroduced for PVEH beams. Unlike AMAM, the DSM is exact, since it is based on theexact solution to the bending wave equation. It also readily lends itself to the modellingof beams with different boundary conditions or assemblies of beams of different crosssections.AMAM is shown to converge to DSM if a sufficiency of modes is used.Finally, an in-depth theoretical and experimental investigation of a prototype PVEHbeam/TVA device is presented. This device comprises a pair of bimorphs shunted byR-L-C circuitry and can be used as a tuned mass damper (TMD) to attenuate a vibrationmode of a generic structure. The optimal damping required by this TMD is generatedby the PVEH effect of the bimorphs. Such a device combines the advantages ofconventional mechanical and electrical TVAs, overcoming their relative disadvantages.The results demonstrate that the ideal degree of attenuation can be achieved by theproposed device through appropriate tuning of the circuitry, thereby presenting theprospect of a novel class of "electromechanical" tuned vibration absorbers.