Electrical power generation characteristics of piezoelectric generator under quasi-static and dynamic stress conditions.

The electrical characteristics of a piezoelectric power generator are investigated under quasi-static (duration > 100 ms) and dynamic (stress duration < 10 ms) stress applications. The electromechanical model of piezoelectric generator is presented and used to explain the effects of the two stress conditions. A computer simulation of the piezoelectric generator is used to compare the theoretical and experimental results. The simulation predicts that a quasi-static stress will produce a bidirectional generator output voltage, and a dynamic stress will produce a unidirectional output voltage. The simulation also predicts that, when equal stresses are applied to the generator, the dynamic stress will generate a 10X higher output voltage than the quasi-static stress, contradicting results reported by other investigators. The output voltage is different for the two cases because of the generator's resistive capacitive (RC) time constant. The dynamic stress is applied in a time that is less than the generator's RC time constant, and the quasi-static stress is applied in a time greater than the generator's RC time constant. The piezoelectric capacitance has enough time to charge in the quasi-static case, resulting in the lower output voltage. The simulation results are experimentally verified for leaded zirconia titanate PZT 5H and PZT 5A materials. Simulated and experimental results are shown to be in good agreement.