Impact Location in an Isotropic Plate without Training

Abstract

Unexpected impacts are a major concern in the aerospace industry that can result in hard-to-detect damage. Techniques have been developed to detect and locate impacts based on time difference of arrival of strain waves propagating to piezoelectric sensors. Current systems typically utilize data from 4 sensors to calculate an impact location and are dependent on the knowledge of the speed of wave propagation in the material or other training data. Training data, like wave propagation velocity, can vary with temperature changes or frequency generated requiring large databases of reference data that can be hard to collect.This paper presents a method of impact detection and location based on hyperbolic positioning, suitable for isotropic homogenous plates, that does not require training. A closed form solution to the underlying location equations is presented which works for general, non-specific, layouts of omnidirectional sensors without knowledge of the wave velocity in the structure. The lack of training data overcomes issues of variation in wave propagation velocity due to temperature changes or other properties. The paper outlines the mathematical formulation, system hardware design considerations, and experimental testing of the system. The calculation simultaneously produces impact location and wave velocity results.