Versatile Sensor Node with Acoustic Data Communication Capabilities for FSAT Networks in Guided Wave-based Structural Health Monitoring Applications

Abstract

Correct evaluation of structural integrity and the ability to predict the remaining useful life of structures is of critical importance in numerous applications, particularly for aerospace industry. The development of Structural Health Monitoring (SHM) systems and their integration into real-world structures has become a necessity to provide a robust and cost-effective solution for structural assessment. Normally structure inspection is done periodically after weeks or months. For machines such as aircrafts or trains, they are taken out of service for structural integrity evaluation. Indeed, one main advantage of modern SHM systems is the continuous, autonomous monitoring of structures, even during service. Therefore, dense networks of ultrasonic transducers are distributed over structures to perform reliable damage detection and localization. Unfortunately, powering these poses many challenges in terms of cabling and added weight, besides to long latency times if a single central processing unit is charged of managing all transducers in the network. To solve this issue, new systems rely on specialized sensor nodes (SNs) and transducers, such as frequency steerable acoustic transducers (FSATs), which offer inherent directional capabilities for data actuation/ sensing. These SNs can drive high voltages and various types of signals to and from transducers conforming a SHM network. They also perform signal treatment tasks and lead communication protocols, such as on-off keying (OOK) or frequency shift keying (FSK), and even help identifying defective nodes within the network. Given the specificities of the FSATs, a matching SN is required to ensure reliable data exchange, even in cases in which traditional radiofrequency-based wireless communication is not possible. In this contribution, we address this need by presenting the design, implementation and test of a new, lightweight and low-cost SN, capable of driving voltage signals as high as 60 Vpp and powering both: commonly used piezoelectric transducers and the more specialized FSATs, and perform communication tasks, using a regular 5V USB port as power source. With this SN, the weight, latency and cable complexity of regular sensor networks are addressed, while disclosing novel opportunities for a higher level of automation and, hence, safer embedded SHM systems for ultrasonic inspection.