Shaped sensor for material agnostic Lamb waves direction of arrival (DoA) estimation

In this work, a sensor formed by clustering three ad-hoc shaped piezoelectric patches is proposed for guided waves direction of arrival (DoA) estimation in laminate composite and metallic structures. The irregular shaping of the transducer electrodes allows to simplify the signal processing procedures which are necessary to detect the wave DoA. The cluster is conceived so that there is a linear dependence between the difference in time of arrival (DToA) of the wavefront at two of the sensor patches and the DoA of the wavefront itself. The third piezoelectric patch is shaped so that the estimation of the DoA from the DToA can be performed without knowing the actual wave velocity. The transducer performance in terms of DoA estimation accuracy are evaluated through numerical simulations, in which the plate response to a point source is evaluated in the frequency domain using the Green's function approach. Results show that the standard deviation of the error in the estimation of the DoA is less than 2°. This device is meant as a basic building block for the development of passive sensor networks in smart structure applications.