Design and manufacture of an optimised side-shifted PPM 2 EMAT array for use in mobile robotic localisation

Ross McMillan, Rory Hampson, Morteza Tabatabaeipour, William Jackson, Dayi Zhang, Konstantinos Tzaferis, Gordon Dobie

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)
8 Downloads (Pure)


Guided wave Electro Magnetic Acoustic Transducers (EMATs) offer an elegant method for structural inspection and localisation relative to geometric features, such as welds. This paper presents a Lorentz force EMAT construction framework, where a numerical model has been developed for optimising Printed Circuit Board (PCB) coil parameters as well as a methodology for optimising magnet array parameters to a user’s needs. This framework was validated experimentally to show its effectiveness through comparison to an industry built EMAT. The framework was then used to design and manufacture a Side-Shifted Unidirectional Periodic Permanent Magnet (PPM) EMAT for use on a mobile robotic system, which uses guided waves for ranging to build internal maps of a given subject, identifying welded sections, defects and other structural elements. The unidirectional transducer setup was shown to operate in simulation and was then manufactured to compare to the bidirectional transmitter and two-receiver configurations on a localisation system. The unidirectional setup was shown to have clear benefits over the bidirectional setup for mapping an unknown environment using guided waves as there were no dead spots of mapping where signal direction could not be interpreted. Additionally, overall package size was significantly reduced, which in turn allows more measurements to be taken within confined spaces and increases robotic crawler mobility.
Original languageEnglish
Article number2012
Pages (from-to)1-18
Number of pages18
Issue number4
Early online date10 Feb 2023
Publication statusPublished online - 10 Feb 2023

Bibliographical note

Funding Information:
This research was funded by EPSRC “Delivering Enhanced Through-Life Nuclear Asset Management” (EP/R004889/1) and EPSRC “UK Research Centre in Non-Destructive Evaluation (RCNDE)” (EP/L022125/1).

Publisher Copyright:
© 2023 by the authors.


  • guided waves
  • ranging and mapping
  • shear horizontal
  • unidirectional


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