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On the Way to Autonomy: the Wireless-interrogated and Self-powered “Smart Patch” System

Systems and System Design

Autonomous Sensing

  1. Stephen C. Galea,
  2. Stephen Van der Velden,
  3. Scott Moss,
  4. Ian Powlesland

Published Online: 15 SEP 2009

DOI: 10.1002/9780470061626.shm093

Encyclopedia of Structural Health Monitoring

Encyclopedia of Structural Health Monitoring

How to Cite

Galea, S. C., Van der Velden, S., Moss, S. and Powlesland, I. 2009. On the Way to Autonomy: the Wireless-interrogated and Self-powered “Smart Patch” System. Encyclopedia of Structural Health Monitoring. .

Author Information

  1. Defence Science and Technology Organisation (DSTO), Air Vehicles Division, Melbourne, VIC, Australia

Publication History

  1. Published Online: 15 SEP 2009

Abstract

Composite patches bonded to defective aircraft structures are a recognized cost-effective repair or reinforcement technique for many types of structural problems, such as metallic cracking, repairing corrosion damage, and reducing fatigue strain at structural hot spots. However, certification concerns limit the application of composite bonded repairs in critical components. For certification and management of repairs to critical structure, the smart patch approach may be a useful approach from the airworthiness perspective in facilitating certification. The smart patch consists of a number of in situ sensors used to monitor the structural condition (health or well-being) of the patch system and the status of the remaining damage in the parent structure. In summary the smart patch is an in situ structural health monitoring (SHM) technology applied to a composite bonded repaired structure. The demonstration of the smart patch on an operational aircraft offers an excellent vehicle to demonstrate autonomous SHM technology in an operational environment.

This article describes the development, evaluation, and implementation of the self-powered wireless smart patch system, including issues such as system design, functionality and certification testing, and installation. This system had no primary power source (i.e., battery) and was powered instead by energy harvested from the local strain environment. It was wirelessly interrogated using a magnetic transceiver and employed piezoelectric elements for both powering and health monitoring functions. The article gives a brief overview of the various available power-harvesting techniques considered and discusses several key issues that arose when designing and developing the self-powered smart patch system, namely, (i) demand—power requirements, (ii) supply—energy generation from vibration or strain-based sources, and (iii) conversion—issues and efficiencies associated with energy conversion from mechanical to electrical energies. Flight data from the system and lessons learned during the program are also presented.

Keywords:

  • structural health monitoring;
  • condition-based maintenance;
  • composite bonded repairs;
  • composite bonded reinforcements;
  • smart patch;
  • power harvesting;
  • energy harvesting;
  • self-powered