Characterization of Piezoelectric Energy Harvesters Using Frequency-Weighted Impedance Method

This paper presents a frequency-weighted impedance method for the characterization of piezoelectric bending beam energy harvesters. The method uses the frequency response of the beam to determine the beam model parameters. Existing methods often need to measure the beam tip deflection for the characterization of the parameters. This requires the accessibility of the tip and advanced measurement tools, such as a laser vibrometer. However, in the proposed method only the knowledge of the base acceleration is adequate to determine the electromechanical coupling coefficient of the beam. Furthermore, the rest of parameters including mechanical damping ratio can be determined based on a pure electrical test. The proposed method is useful for the characterization of all types of piezoelectric energy harvesters, particularly the vacuum-packed ones in which the tip of the beam is inaccessible. The validity of the method is experimentally verified using a test setup including a vacuum-packed piezoelectric energy harvester. The measured parameters of the beam are compared with the bulk material parameters showing that the proposed method can accurately estimate the model parameters without using the information of the tip deflection and with an error less than 4%.