Development of Laser-powered Wireless Ultrasonic Device for Aircraft Structural Health Monitoring

In recent years, wireless sensor and sensing networks have emerged as a reliable method for structural health monitoring (SHM). Consequently, powering methods to these wireless sensors is one of important factors to consider for their practical applications. In many applications, wireless sensors must be operated in locations that are difficult or even impossible to access, and often these systems have desired operational lifespan that exceeds that of conventional batteries. Replacing the batteries is labor intensive and time consuming. Especially, it is very difficult or even impossible to replace batteries of embedded sensors in concrete or composite structures. Therefore, novel powering methods such as energy harvesting or wireless power transmission (WPT) are necessary in order to guarantee the long life-span for wireless sensors. In this study, we explored potential solutions to this challenge by collecting energy from a laser beam to power devices called a wireless ultrasonic device (WUD). The delivered light is captured by a GaInP photovoltaic cell which shows high spectral responsivity at 532 nm and collected a supercapacitor to supply the power to the sensor. The delivered light is captured by a GaInP photovoltaic cell which shows high spectral responsivity at 532 nm and collected a supercapacitor to supply the power to the sensor. Furthermore, one more smart component called fiber optic bolt is also developed using a large core hard polymer clad fiber (HPCF) to solve the line-of-sight issue. The WUD was developed using the MSP430FG4618 evaluation board and CC2500 radio and designed to include actuator and sensor interface to evaluate structural damages. The applicability of the proposed system to detect of various damage types such as crack and artificial corrosion is experimentally investigated. The results show that the proposed wireless sensing system gives good agreement with those of wired system and feasibility for implementation of the proposed system for SHM.