Clusters of Shaped Ultrasonic Transducers for Lamb Waves’ DoA Estimation

Marco Dibiase,Luca De Marchi

doi:10.3390/app10228150

Abstract

The direction of arrival (DoA) estimation of Lamb waves is a fundamental task to locate acoustic events, such as those caused by impacts in plates or shells. To perform this task, a novel cluster of piezoelectric sensors is presented in this work. The designed cluster is composed by three irregularly shaped patch transducers (P1, P2 e P3). This is in contrast with the approaches that are typically presented in literature which are based on isotropic piezo-disks. In our approach, the transducers are shaped with a procedure based on the Radon Transform, so that the difference in time of arrival (DToA) of the Lamb waves at patches P1 and P2 is linearly related to the DoA, while P3 is designed so that it is possible to perform the estimation of DoA without knowing the actual wave velocity. The numerical validation shows that the performance in the DoA estimation achieved by means of the proposed cluster compares favorably with respect to clusters of conventional sensors, even in the case of noise-affected measurements.

Highlights

Structural Health Monitoring (SHM) systems [1], i.e., inspections systems based on permanently installed sensors, have been intensively investigated in recent years, due to the high potential that they have in reducing maintenance costs in a wide range of industrial application fields.In particular, an increasing demand to develop SHM systems comes from the automotive and aerospace industries [2]
We further investigate the concept of direction of arrival (DoA) detection via difference in time of arrival (DToA) estimations, by analyzing how beneficial the adoption of clusters constituted by irregularly shaped piezoelectric transducers can be
The DoA estimation is performed by measuring the differences in time of arrival (DToAs) of the wave fronts between the sensors that belong to the cluster that is composed by three piezo patches

Summary

Introduction

Structural Health Monitoring (SHM) systems [1], i.e., inspections systems based on permanently installed sensors, have been intensively investigated in recent years, due to the high potential that they have in reducing maintenance costs in a wide range of industrial application fields. The DToAs, i.e., the time delays, can be estimated with conventional cross-correlation procedures (i.e., the optimal method for measurements that are affected by additive white Gaussian noise NWG with zero mean [11]) This cluster typology allows for estimating the DoA with minimum amount of data to acquire (only three signals) and reduced computational cost (only two time delays estimations). In the proposed approach, the sensors are shaped with a procedure based on the Radon Transform (RT) and its Inverse (IRT)

Minimization of Uncertainty in Doa Estimation

The Radon Transform as Sensor Shape Design Tool

Numerical Results and Discussion

Conclusions