CEE Distinguished Speaker Series 2026 by Professor Hoon Sohn from Korea Advanced Institute of Scienc

Low-cost and high-accuracy displacement sensor for civil infrastructure structural health monitoring 

Structural displacement is a critical physical quantity for monitoring civil infrastructure. The importance of this measurement has driven the development of numerous dedicated sensors and sensing technologies. This study presents a novel, cost-effective, and high-accuracy displacement sensor. Its architecture comprises an integrated frequency-modulated continuous-wave (FMCW) radar, a microelectromechanical systems (MEMS) accelerometer, a microcontroller unit (MCU), a wireless data transmission module, and a power supply unit. Through the synergistic fusion of data from the FMCW radar and MEMS accelerometer, the sensor attains exceptional displacement measurement performance with an accuracy better than 0.1 mm. Significant cost reduction was realized by leveraging a readily available FMCW radar chip, prevalent in autonomous vehicle systems, alongside an off-the-shelf MEMS accelerometer, projecting a unit cost under $1,000. Acquired and processed data are wirelessly disseminated to a range of client devices, such as mobile phones, laptops, and desktop computers, via diverse wireless protocols including Wi-Fi, LTE, and LoRa. The sensor operation is facilitated by a flexible power system, drawing energy from either a rechargeable lithium battery or an integrated solar panel, enabling fully self-contained and autonomous operation. The utility of this sensor spans multiple critical applications, encompassing: (1) continuous monitoring of road and rail bridges for early warning of collapses and impending hazards, (2) automated in-situ evaluations for bridge rating, (3) spatio-temporal displacement characterization utilizing distributed and non-dedicated telecommunication cables, and (4) structural integrity testing of a real nuclear power plant.