Design and optimization of secondary shock type piezoelectric system

Two models for energy harvesting system imparting rotational energy to piezoelectric materials are presented in order to compare the effects of applying identical amounts of energy to a cantilever beam by strain-changing and shock application. For a piezoelectric system given a high impulse with low displacement, higher power outputs were generated at lower resistive loads. Conversely, for a system with high displacement at a low impulse, power output was higher at high resistive loads. At matched impedance, the secondary shock system generated higher power output than the hitting system did at low resistive load. Optimized response of secondary shock system was obtained at a frequency of 60 Hz with a low resistive load of 1 k Ω. The generated output power was measured 124 mW, which corresponds to power density of 140 mW/cm3 for entire cantilever beam and power density of 342 mW/cm3 for only piezoelectric material volume. For a system without a secondary impulse at low resistive loads (1 k Ω), the optimizing frequency was between 20 and 30 Hz, with an output power of 22 mW, which corresponds to a 25 mW/cm3 power density for entire cantilever beam and power density of 60 mW/ cm3 for only piezoelectric material volume.