Abstract
Over the past years, there are growing interests on scavenging energy from ambience for portable and low-power electronic devices. Among these low-power electronic devices, wireless sensor networks combined with piezoelectric power harvesting devices are the most promising scenario which using piezoelectric cantilever beam structure excited by ambient vibrations to convert mechanical vibration power to electric power and power the wireless sensors. It is known that the environmental excitation frequency will not be always the same as the resonant frequency of the cantilever beam. However, the cantilever beam excited under resonant frequency will have the highest energy output. In this paper, bimorph and sandwich type structure with frequency tuning circuit is proposed to shift the resonant frequency of the piezoelectric cantilever beam in real-time to match the environmental excitation frequency in order to increase the power efficiency and harvest more energy. For the bimorph and sandwich laminated PZT cantilever beam, there will be 2 layers and 3 layers of PZT layers, and one for the PZT layers will be used to control the beam resonant frequency by connecting to different electrical loading impedance. The exciting frequency will be monitored by a low-power micro-processor usually used on wireless sensors. The design and fabrication of the bimorph and sandwich beam structure with and without frequency tuning circuit will all be evaluated and detailed in this paper.
Published Version
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