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

Fatigue cracks need to be monitored in fracture critical elements. Previous research by the PI produced an RFID (radiofrequency identification) sensor prototype that can accurately measure tens of micro-strains in laboratory. The antenna sensor was made on a glass microfiber-reinforced polymer substrate. Although accurate for strain measurement and detection of fatigue cracks in laboratory testing, the sensor performs less satisfactorily in field conditions since the substrate material (RT/duroid® 5880) is susceptible to thermal effect. Approach and Methodology: An innovative, 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 resonant 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. Overall Objectives: This project aims to develop and validate a new antenna sensor prototype that has significantly improved thermal stability than previous versions. In addition, an integrated dual-mode prototype will be developed to allow the sensor operation to benefit from battery power, when available, in active mode. A small circuit with a credit-card size solar panel and a rechargeable coin cell battery will be designed. If the battery is charged by solar power, the sensor operates in the active mode, providing stronger response to the reader. When the battery is drained up, the sensor automatically falls back to the passive mode, i.e. receiving operational energy completely from reader interrogation. Scope of Work in Year 1: (1) Select a new substrate material that provides steady performance under temperature changes, (2) Redesign an RFID antenna sensor and characterize its performance in temperature chamber, and (3) Validate the sensor performance in both tensile, compressive, and crack tests. Scope of Work in Year 2: (1) Test the performance of the new antenna sensor in application settings and compare it with the pervious sensor prototypes and metal foil gages, (2) Extend the wireless interrogation distance by an integrated dual mode sensor design, and (3) Characterize the strain sensing performance of the dual-mode sensor with tensile tests.

Project

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