Battery-free Antenna Sensors for Strain and Crack Monitoring of Bridge Structures

Fatigue cracks need to be monitored in fatigue critical elements. Previous research by the principal investigator (PI) produced an RFID (radiofrequency identification) sensor prototype that can accurately measure tens of micro-strains in laboratory. The antenna sensor was made of a glass microfiber-reinforced polymer substrate. Although accurate for strain measurement and detection of fatigue cracks, the sensor performs less satisfactorily in field conditions since the substrate material (RT/duroid® 5880) is susceptible to thermal effect. In addition, a wireless interrogation distance by a general-purpose commercial RFID reader is limited to the order of meter, which is not desirable with the operation of an unmanned aerial vehicle (UAV). The commercial reader also weighs over 30 N and costs approximately $30k. A fundamentally new, battery-free, wireless strain/crack sensor is proposed for bridge monitoring. Unlike conventional smart sensors with wireless transmission of digitized data, the proposed sensor makes use of the strain-dependent (transducer-like) behavior of electromagnetic (EM) waves in an antenna. Upon illumination by a wireless reader that is carried by a human inspector or an aerial robot, the antenna sensor scatters an EM signal back to the reader. The radiation parameters of the antenna sensor, such as resonance frequency and backscattered power level, can be wirelessly interrogated by the reader. When bonded to a base structure to be monitored, a thin planar antenna sensor is deformed as the structure is loaded or experiences cracking. The deformation in a properly designed antenna can cause a significant and observable change of antenna radiation parameters. This project aims to develop and validate a light antenna sensor (1 kg) with new substrate materials that can be accurately interrogated at a desirable distance (over 30 m) in field applications, and develop and test a customized RFID reader that costs less than $3k for effective monitoring of bridges. The focus of the first year will be to: (1) Select a new substrate material (e.g. Taconic RF-35TC – a ceramic-filled fiberglass material) that provides steady performance under temperature changes, (2) Redesign an RFID antenna sensor and characterize its performance in temperature chamber or under tension tests, and (3) Validate the sensor performance with field testing of a few bridges near Atlanta.


Subject/Index Terms

Filing Info

  • Accession Number: 01646007
  • Record Type: Research project
  • Source Agency: Inspecting and Preserving Infrastructure through Robotic Exploration University Transportation Center
  • Contract Numbers: 69A3551747126
  • Files: UTC, RiP
  • Created Date: Sep 14 2017 11:10AM