Two-dimensional periodic actuators for frequency-based beam steering

Abstract

The paper investigates innovative designs of piezoelectric actuators for structural healthmonitoring (SHM). Periodic configurations are proposed as an effective means to provideactuators and sensors with strong, frequency dependent directional characteristics, whichallow beam steering through a sweep of the excitation frequency. The concept has thepotential to enable in situ monitoring of critical components through strongly focusedactuation (and/or sensing) and directional scanning capability, which may be achieved withvery limited hardware requirements. Beam steering is achieved by exploiting interferencephenomena generated by the spatial periodicity of the array and the simultaneousactivation of its components. Such interference phenomena produce waves withfrequency dependent directional characteristics, which allow directional scanning tobe performed simply through a frequency sweep. The need for beam-formingalgorithms and associated hardware is thus avoided. The concept is illustrated byconsidering 2D arrays of point sources of various topologies. The case of a thinmembrane supporting the propagation of SV waves is first presented to provide asimple frame work of analysis. The case of Lamb waves in a thin plate is thenconsidered to demonstrate the validity and the practicality of the proposed approach.