Wireless sensor system for infrastructure health monitoring

In this thesis, radio frequency identification (RFID)-based wireless sensor system for infrastructure health monitoring (IHM) is designed and developed. It includes mountable semi-passive tag antenna integrated sensors capable of measuring critical responses of infrastructure such as dynamic acceleration and strain. Furthermore, the system is capable of measuring structural displacement. One of the most important parts of this system is the relatively small, tunable, construction material mountable RFID tag antenna. The tag antenna is electronically integrated with the sensors. Leading to the process of developing tag antenna integrated sensors having satisfactory wireless performance (sensitivity and read range) when mounted on concrete and metal structural members, the electromagnetic performance of the tag antenna is analyzed and optimized using both numerical and experimental procedures. Subsequently, it is shown that both the simulation and the experimental measurement results are in good agreement. The semi-passive RFID-based system is implemented in a wireless IHM system with multiple sensor points to measure dynamic acceleration and strain. The developed system can determine the natural frequencies of infrastructure and identify any state changes of infrastructure by measuring natural frequency shifts. Enhancement of the spectral bandwidth of the system has been performed under the constraints of the RFID hardware. The influence of the orientation and shape of the structural members on wireless power flow in the vicinity of those members is also investigated with the RFID reader-tag antenna system in both simulation and experiments. The antenna system simulations with a full-scale structural member have shown that both the orientation and the shape of the structural member influence the wireless power flow towards and in the vicinity of the member, respectively. The measurement results of the conducted laboratory experiments using the RFID antenna system in passive mode have shown good agreement with simulation results. Furthermore, the system’s ability to measure structural displacement is also investigated by conducting phase angle of arrival measurements. It is shown that the system in its passive mode is capable of measuring small structural displacements within a short wireless distance. The benchmarking of the developed system with independent, commercial, wired and wireless measurement systems has confirmed the ability of the RFID-based system to measure dynamic acceleration and strain. Furthermore, it has confirmed the system’s ability to determine the natural frequency of an infrastructure accurately. Therefore, the developed system with wireless sensors that do not consume battery power in data transmission and with the capability of dynamic response measurement is highly applicable in IHM

UHF RFID-based low-power wireless sensor development for infrastructure health monitoring : issues in metallic environments

This paper investigates the critical issues of developing ultra-high frequency (UHF) radio frequency identification (RFID)-based low-power wireless sensors for infrastructure related metallic environments. Our studies show that the readability of tag antennas is considerably affected by the dimensions of the metallic mounts. Simulation results show that the surface current density distribution on the mount has a direct correlation with the measured readability. It is also shown that the wireless power flow towards the mounted tag antenna is significantly affected by the orientation of the metal mounts resulting in variable incident power. Furthermore, the studies show that the tag antennas de-tune considerably, due to the different shapes of the metal mounts. Both transmit and receive mode simulation results are in good agreement with the experimental measurements

RFID-based passive wireless displacement measurement of metal structures in infrastructure health monitoring

In this paper, radio frequency identification (RFID) -based passive wireless displacement measurement for infrastructure health monitoring is studied. An ultra-high frequency (UHF) RFID section consisting of two antennas is used to measure the displacement of metal structures in which the tag antenna is mounted on metal. It is shown that displacement measurement resolutions of 1 mm and 5 mm can be achieved within λ and 6λ starting distances, respectively, between antennas (Australian UHF RFID frequency band) by changes in the received phase. It has also been shown that displacement measurement resolution of 1 mm can be achieved within λ starting distance using the frequency domain phase difference of arrival (FD-PDoA) method with compensation for reader inaccuracy

Wireless system with a RFID tag antenna for infrastructure health monitoring

In this paper, a wireless system with radio frequency identification (RFID) tags is proposed for infrastructure health monitoring. In the process of developing sensor integrated RFID tags, a novel tag antenna is designed and its electromagnetic performance has been investigated when it is mounted on selected concrete and metal blocks. Read range analysis of RF section of the system is carried out for the above cases. The optimized RF section with the designed RFID tag antenna has shown desired performance in complex physical environment. It has the potential to be used in mountable sensor integrated RFID tag wireless systems

Measurement system with a RFID tag antenna mounted on structural members for infrastructure health monitoring

In this paper, a radio frequency identification (RFID)-based wireless system for infrastructure health monitoring is studied. Ultra high frequency (UHF) RFID section with two different patch antennas is designed and investigated with the tag antenna mounted on concrete and metal structural members. The tag antenna is designed to be compatible with a new generation RFID chip and to be used to develop a sensor integrated RFID tag. Changes of the electromagnetic performance of the tag antenna are observed with an analysis of achievable read ranges with selected RFID hardware. The optimized tag antenna has shown satisfactory tolerance in the studied cases where the antenna system have the potential to be used in the development of the proposed RFID-based wireless infrastructure health monitoring system

Investigation of UHF power flow in the vicinity of a steel I-beam for optimization of its health monitoring using wireless sensor integrated RFID tag antenna system

In this paper the results of investigation of ultrahigh frequency power density in the vicinity of a steel I-beam using radio frequency identification (RFID) antenna system are presented. Simulation results show that the I-beam has different influence upon the amount power of incident on a tag antenna on its different locations along the beam. Furthermore, they show that suitably designed tag antennas can increase the power density in their locations in the inner surface of the I-beam. The measurement and simulation results are in good agreement. These findings have important implications for infrastructure health monitoring of complex-shaped structures using passive or semi-passive RFID-based sensory systems

Measurement system with accelerometer integrated RFID tag for infrastructure health monitoring

This paper presents a measurement system for measuring dynamic acceleration of infrastructure remotely using semi-passive radio-frequency identification (RFID) tag. This measurement is critical to the vibration-based method for infrastructure health monitoring. Design considerations of accelerometer integrated ultrahigh-frequency RFID tag and dynamic acceleration measurements through an RFID wireless link are discussed. Measurement results of the system for a structural specimen have shown that it is capable of acquiring data which provides the information of natural frequency of the structural specimen. Moreover, the system can distinctively identify the state changes of the structural specimen by natural frequency shifts. These results are benchmarked against the results obtained with two commercial systems. It is shown that the standard deviation of the measurement of the natural frequency is ±0.01 Hz which is very close to the standard deviation of the commercial measurement systems