Real-Time Vibratory Strain Sensing Using Passive Wireless Antenna Sensor

A wireless vibratory strain sensing system, which consists of a passive wireless sensor and a dynamic wireless interrogator, is presented in this paper. The wireless sensor utilizes a microstrip patch antenna as the strain sensing element since its resonant frequency is a function of the tensile strain it experiences. A dynamic wireless interrogator that is based on the principle of frequency modulated continuous wave radar and permits real-time monitoring of the antenna resonant frequency was designed and validated. The principle of operation of the dynamic wireless sensing system was first described, followed by the description of the design and implementation of the antenna-sensor node as well as the wireless interrogator. After calibrating the antenna-sensor response using static tensile tests, vibratory tensile tests were carried out by subjecting the test specimen to sinusoidal tensile loading at different frequencies. Antenna strain sensing accuracy was evaluated by comparing the strain readings from the antenna-sensor and the reference foil strain gauge. It reveals that the antenna-based strain sensing system has good dynamic strain tracking ability.