| Energy harvesting is one of key technologies for the micromation and practical development of wireless sensor and communication node networks. Among all kinds of energy harvesters,the piezoelectric energy is the most promised one as they are high in energy densities and particularly attractive in MEMS for its relatively simple configuration. In order to improve power harvesting efficiency, two novel techniques for optimizing energy harvesting circuitry are investigated in the dissertation. In addition, two self-powered vibration damping system and a self-powered wireless sensor node for structural health monitor (SHM) are developed, which are the application of the piezoelectric energy harvesting.The main works and novel researched performed in this dissertation include:(1) Based on the constitutive equation of piezoelectric materials and the theory of mechanical vibration, the model of a cantilever bimorph with a proof mass attached to its end is established, which is used to determine the relationship between performance and physical and geometrical parameters.(2) A new technique for optimizing energy harvesting circuitry called enhanced synchronized switch harvesting (ESSH) is presented. Compared with the standard technique of energy harvesting, the new technique dramatically increases the harvested power by almost 300% at resonance frequencies in the same vibration condition (the gain also can be greatly increased using low losses components), and also ensures an optimal harvested power whatever the load connected to the microgenerator. Furthermore, the new technique (ESSH) in the paper can be truly self-powered, a self-powered circuit which implements the technique (ESSH) is proposed. In addition, the overall power consumption for the control circuitry is relatively constant (only about 121μW), which shows more attractive especially in the high excitation. Because the new technique (ESSH) in the paper can be truly self-powered, no external power supply is needed, making the system suitable for more application fields, especially in remote operation. Besides, a self-powered vibration damping system is proposed as the application of the ESSH technique. Experimental results show that a vibration damping of about -5 dB is achieved as a result of energy harvesting, in good agreement with the theory.(3) Another novel technique for optimizing energy harvesting circuitry called adaptive ESSH approach is presented. This technique is based on a control law which deals with the energy harvesting under multimode vibration. Compared with the ESSH technique of energy harvesting, the new technique improve efficiency harvesting efficiency when the piezoelectric energy harvester is excited under two-mode vibration. Furthermore, the new technique (adaptive ESSH) in the paper can be truly self-powered, a self-powered circuit which implements the technique (adaptive ESSH) is proposed. In addition, the overall power consumption for the control circuitry is relatively constant (only about 329μW). Besides, a self-powered multimode vibration damping system is proposed as the application of the adaptive ESSH technique.(4) A vibration damping system powered by harvested energy with implementation of the so called SSDV (Synchronized Switch Damping on Voltage Source) technique is designed and investigated. By supplying the energy collected from the piezoelectric materials to the switching circuit, a new low-power device using the SSDV technique is proposed. Compared with the original self-powered SSDI (synchronized switch damping on inductor), such a device can significantly improve its performance of vibration control. Its effectiveness in the single-mode resonant damping of a composite beam is validated by the experimental results. Besides, a self-powered self-sensing vibration damping system with implementation of the SSDI technique is designed and investigated. Its effectiveness in the single-mode resonant damping of a steel beam is validated by the experimental results. The experimental results show that -7.89dB attenuation for the first mode was achieved. The total power dissipation of the control circuit is only 0.322mW.(5) A wireless sensor based on the energy harvesting from vibrations is designed, which is composed of energy harvesting module and low-power wireless sensor module. Firstly, the structure and electrical interface of energy harvesting module are optimized to enhance the efficiency of transforming mechanical energy to electrical energy. Secondly, a balance technique is introduced during the design of the wireless sensor module, which can not only monitor the real-time structural strain but also be low-powered and meet the need of self-powered sensor node. Finally, an experiment is carried out to test the wireless sensor, which shows its good stability and reliability.
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