DEVELOPMENT OF A METHOD FOR THE IDENTIFICATION OF PIEZO-PROPERTIES FROM THE FRF OF A CANTILEVER HARVESTER

The Frequency Response Function (FRF) between the generated voltage and the base acceleration of a cantilever harvester depends on a set of mechanical and electrical parameters and in particular on the piezo constant. A mathematical expression of the FRF can be derived.

Cantilever harvester

If an experimental FRF is available, it can be fitted by means of the mathematical model.

Measured FRF

Since all the other parameters are known (or can be measured), the optimization algorithm implemented in MATLAB tries different values of the  constant to minimize the difference between the experimental and the calculated FRF.

Optimum fitting process

The experimental FRF can be measured using two approaches: impulsive excitation by means of a hammer; harmonic excitation by means of an electrodynamic shaker.

Impulsive excitation with hammer

Harmonic excitation with shaker

The best results were obtained by means of impulsive excitation.

The piezoelectric constant of the piezoelectric layer was measured with an error < 5%.