| Summary: | 博士 === 國立臺灣大學 === 應用力學研究所 === 101 === Nowadays with the world oil price soaring, the energy issue is becoming a significant topic and the possibility of harvesting ambient energy receiving much attention. In this dissertation, the main topic surrounds improving the piezoelectric energy harvesting device in several aspects and the final objective is to integrate it with low power consumption device, for example a wireless sensor network node to extend the battery lifetime and further supply the energy to device directly. Based on the high mechanical quality factor of the structure, the output power of the piezoelectric energy harvesting device will decrease rapidly when the exciting frequency is out of the resonant frequency range. The tunable resonant frequency technique is proposed to broaden the resonant frequency range and to increase the output power effectively. Then this technique is successfully combined with a wireless sensor module to transmit the radio frequency signal. To broaden resonant frequency another method is proposed, based on a bistable vibrating cantilever beam and a switching-type interfacing circuit. It is a new and interesting concept to combine these two techniques. The magnets are used to make mechanical behavior non-linear and increase the output power at non-resonance. The synchronized switching technique through zero-velocity detection can work well when system is driven in non-linear system. The experimental and simulation results through work-cycles discussion show good performance of combining these two techniques. Synchronized switching harvesting on an inductor have been verified to be a successful technique to increase output power in low-coupling system. In order to make use of the synchronized switching technique in the real application, the velocity control self-powered system is proposed. Unlike the conventional peak detector technique, the zero-velocity detection is used to make the switching time more accurate. The energy flow is separated into three paths to construct the above-mentioned velocity control self-powered synchronized switching system and the experimental results show good performance.
When the system is not low-coupled, the synchronized switching harvesting on an inductor technique will damp vibration. This technique is synchronized switching damping on an inductor. Based on the self-powered technique and zero-velocity detection used in energy harvesting, these techniques are further applied in structural damping to construct a self-powered synchronized switching damping system. The major advantage is that it is only necessary to sacrifice a small amount of damping performance to make the system fully self-powered. The theoretical analysis and experimental results of time domain comparison and frequency response testing show the limit and performance of this technique. The self-powered damping system is like a feedback loop system and when the displacement is over the limit the system will effectively damp the vibration.
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