A Wireless, Multi-Channel Printed Capacitive Strain Gauge System for Structural Health Monitoring
Structural health monitoring of soft structural textiles plays a key role within the space industry to ensure the safety and integrity of space habitats, parachutes, and decelerator systems. Strain monitoring could be an effective means to evaluate structural integrity, but conventional monitoring systems are not suitable because they are intended for large, rigid structures. To overcome the limitations of rigid sensors, we recently proposed using printed capacitive strain gauges (CSGs) on flexible substrates to monitor the structural health of soft structure materials. Here, we present a strategy and implementation of a wireless, multi-channel readout system for distributed monitoring of soft structural textiles with printed CSGs. The system is comprised of localized sensor motes and a wireless Bluetooth hub. The sensor mote employs a relaxation oscillator frontend to convert capacitance to frequency with a high dynamic range using only three interface wires per mote. The mote’s high dynamic range ensures compatibility with various gauge designs and accommodates significant process variation associated with printed gauges. Each hub enables users to read 8 channels of data wirelessly at a sampling rate of 100Hz and can be scaled to higher channel counts through the use of additional hubs. The sensor motes and wireless hub are miniaturized to accommodate flexible substrates, such as a Kevlar strap. The system is tested and exhibits excellent linearity and dynamic range.
Ranganatha, Kshama L.; Novich, Kaelee; Phero, Timothy; Fujimoto, Kiyo T.; Litteken, Doug; Estrada, Dave; . . . and Johnson, Benjamin C. (2021). "A Wireless, Multi-Channel Printed Capacitive Strain Gauge System for Structural Health Monitoring". 2021 IEEE Sensors. https://doi.org/10.1109/SENSORS47087.2021.9639749