An accurate localization system for Nondestructive testing based on magnetic measurements in quasi-planar domain G. Cerro a , L. Ferrigno a,⇑ , M. Laracca a,b , F. Milano a , P. Carbone c , A. Comuniello c , A. De Angelis c , A. Moschitta c a Department of Electrical and Information Engineering, University of Cassino and Southern Lazio, 03043 Cassino, Italy b Department of Medicine and Health Science, University of Molise, 86100 Campobasso, Italy c Department of Engineering, University of Perugia, 06125 Perugia, Italy article info Article history: Received 7 December 2018 Received in revised form 4 March 2019 Accepted 8 March 2019 Available online 11 March 2019 Keywords: Eddy current testing Localization system Magnetic measurement abstract Localization of eddy current probes in Nondestructive Testing allows merging the defect detection with the information about defect positions. Typically, this task requires the usage of additional and costly position measurement systems or software assisted handlers in controlled laboratory conditions. However, many of these tests require free hand movements of the eddy current probes. In addition, in many industrial applications low cost is a stringent requirement. This paper proposes a novel solution to address the considered issues. In particular, the paper describes the usage of a magnetic 2D wireless localization method, able to track the probe position during the execution of Nondestructive Tests. To the best of our knowledge, such approach is novel and promises to provide localization information in Nondestructive Testing by means of low-cost hardware. Moreover, it is characterized by a light compu- tational burden, since it reuses most of the equipment already needed for the test itself. Preliminary results, proving the suitability of a real time simultaneous testing and localization system, are reported in this paper. Ó 2019 Elsevier Ltd. All rights reserved. 1. Introduction Modern Industrial and Aerospace applications intensively adopt Nondestructive Testing (NDT) to assure the integrity and the health monitoring of components and systems. To date, Eddy Cur- rent Testing (ECT) is a widespread technique that can be adopted in several application cases where metallic or carbon fiber materials are involved [1–4]. As requested by product standards [1], a com- plete ECT analysis needs for the following three steps: detection, location, and characterization. The detection step is the capability to find out the flaw presence. The location goal is to find the area, on the material under test, where the defect is placed. Finally, the characterization phase is focused on the estimation of both the shape and size of the defect. This last step is very important since it could imply acceptance or rejection of a material under investigation. Nevertheless, the reliability of this phase is strictly related to the availability, with good precision, of the exact positions of the defect together with good detection systems [5–14]. As an exam- ple, if the defect is an inner linear crack with a length of some mil- limeters, it is crucial to reliably know the starting and ending points of the crack to define its effect on the health of the material. Similarly, if the defect is an inner hole or a bubble, it would be very important to define the exact region where the flaw is located. ECTs can be executed by automated movers or by human operators. In the former case, the eddy current probe is moved by an automated robotic arm or by a scanning system. Typically, these systems execute predefined paths with scanning resolutions lower than a fifth of millimeter. In the latter case, the human operator freely moves, by hand, the probe on the specimen under test, looking for the defect. Then, when he reaches the defect zone, he executes a path with shorter steps necessary to characterize the defect. In the case of automatic scanning systems, the accurate measurement of the probe position while testing is not a problem, as a set of high precision encoders is often placed in support of the handler. In the case of freehand movements, accurate probe positioning may become a complex problem. https://doi.org/10.1016/j.measurement.2019.03.022 0263-2241/Ó 2019 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail addresses: gianni.cerro@unicas.it (G. Cerro), luigi.ferrigno@unicas.it (L. Ferrigno), marco.laracca@unimol.it (M. Laracca), filippo.milano@unicas.it (F. Milano), paolo.carbone@unipg.it (P. Carbone), antonella.comuniello@studenti. unipg.it (A. Comuniello), alessio.deangelis@unipg.it (A. De Angelis), antonio. moschitta@unipg.it (A. Moschitta). Measurement 139 (2019) 467–474 Contents lists available at ScienceDirect Measurement journal homepage: www.elsevier.com/locate/measurement