Wideband Improvement by Switch Design Used in Mixed Parallel-Series Connection of Piezoelectric Energy Harvesters

The thesis is to study the mixed parallel-series connection of piezoelectric energy harvesters. Using the different connection of oscillators have different frequency response, so that to design energy harvesting system which can automatically switch connection of oscillators. With respect the traditional single connection of oscillators system, this smart switching system have more power boosting and broadband improvement. The proposed analytic estimates are validated numerically by PSpice circuit simulation. By numerical simulation to set up a design rule at this switching system. The design rule can effectively increase broadband improvement. There is also proposed fixed-load design. The fixed-load design for the practicality of the energy harvesters has a big breakthrough. Finally, though LabVIEW system development and design of the switching circuit to finish a mixed parallel-series energy harvesting system. This system can accurately measure the external vibration frequency and automatically switches to the optimal configuration. According to this system is based on the measurement of external vibration frequency to switch configuration of oscillators so author designed two different switching modes. The optimal switching mode has the best output power, but it calculation is more complicated. Another simple switching mode has a more convenient method to estimate the frequency interval. And its output effect no less than the optimal switching mode. The results appear in the experiment and simulation. Strong coupling harvesting system has a higher power boosting and broadband improvement in fixed-load design and simple switching mode; Medium coupling harvesting system, although there is no good power boosting but can has a good improvement of broadband. In case of four oscillators system, the smart switching harvesters has more than traditional array harvesters four times a broadband improvement in experimental results.