The performance of piezoelectric cantilever beam energy harvesters subjected to base excitation is considered in this work. Based on the linear assumption, a theoretical model is developed to predict the mechanical and electrical responses of the harvester and in comparison to other theoretical models, more accurate mode shape functions are used for the structural part of the harvester. The model is validated against experimental measurements and parameter studies are carried out to investigate the maximum power output in different situations. In some applications, like powering tyre pressure monitoring sensors (TPMS), energy harvesters are subjected to large amplitude shocks and high levels of acceleration, which can cause large bending stresses to develop in the beam, leading to mechanical failure. In this work, a bump stop is introduced in the energy harvester design to limit the amplitude of vibration and prevent large amplitude displacement. A theoretical model is developed to simulate the energy harvester impacting a stop, and the model is used to investigate how the electrical output of the harvester is affected by the stop. The work demonstrates how the model can be used as a design tool for analysing the compromise between the electrical output and structural integrity. Nonlinear behaviour of the energy harvester is observed to have a significant effect on the resonance frequencies when the harvester is subjected to large amplitude base accelerations. To correctly predict the behaviour of the harvester, piezoelectric material nonlinearity and geometric nonlinearity are incorporated in the theoretical model. It is found that the nonlinear softening effect is dominated by the material nonlinearity, while the geometric nonlinearity is less significant. The nonlinear energy harvester model is used in conjunction with the bump stop and results obtained using the linear and nonlinear models are compared to experimental measurements to investigate the importance of using a nonlinear model. The inclusion of nonlinear behaviour is shown to improve significantly the accuracy of predictions under some circumstances. The energy harvester models developed in this work are used to simulate the electrical power generated in a TPMS application, where the harvester embedded in the tyre is subjected to large radial accelerations as the tyre rolls along the road. The simulated results are compared to reported experimental work and agreement is found between the results.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:549881 |
| Date | January 2011 |
| Creators | Mak, Kuok Hang |
| Publisher | University of Nottingham |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://eprints.nottingham.ac.uk/12534/ |
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