Electromechanical modelling of piezoelectric vibration energy harvester with a novel dynamic magnifier

Abstract

Abstract In piezoelectric energy harvesting devices, the relative displacement between the two ends of the harvester beam decides the output power from the piezoelectric patch. A novel four bar mechanism with a helical spring is used as a dynamic magnifier to improve the relative displacement and thereby the output power from the harvester. This dynamic magnifier is placed between the base excitation location and the composite harvester beam to form two degrees of freedom (2DOF) piezoelectric energy harvester. Electromechanical coupled analytical equations for the voltage and output power are derived using a lumped electromechanical model. The model is developed assuming linear transverse vibrations of the harvester. A dynamic magnifier is fabricated for the required frequency range and the suitable dimensions of the harvester beam are estimated using commercially available software. Experiments are conducted for base excitation amplitude of 0.05 mm and the performance of the proposed 2DOF harvester is studied for the output voltage and power. The proposed 2DOF harvester has shown 110 % improvement in output power in first mode and 270 % improvement in second mode compared to the conventional single degree of freedom (SDOF) cantilevered harvester for given identical input conditions. The measured frequencies and output power are validated with analytical solutions and are found to be in good agreement. Further, the effect of mass ratio, stiffness ratio and base excitation amplitude on the output voltage and power is investigated using analytical expressions.