A Public Blockchain-Enabled Wireless LoRa Sensor Node for Easy Continuous Unattended Health Monitoring of Bolted Joints: Implementation and Evaluation

With the advent of Internet of Things (IoT) a slow shift is happening from manual checks of capital intensive assets such as bridges, wind turbines, etc., where bolted joint is used as a main fastening method, towards unattended Structural Health Monitoring (SHM). Numerous approaches are proposed for monitoring the looseness of bolted joint assemblies, however, the majority of them can only be used for looseness detection purposes and not viable for monitoring since these approaches contain design impracticalities, not scalable or hard to implement outside of the laboratory environment. Furthermore, remote unattended monitoring is still very much in its infancy. Thus, to solve this issue, we propose a TenSense M20, a custom designed smart sensor node for continuous remote SHM of bolted joints. Complete node design is presented. Each aspect of the design is evaluated both by simulation and practical tests. Long Range (LoRa) is used as a means of wireless communication and the network can cover 3.8 km. The results show that TenSense M20 is able to precisely track the pre-tension force of a bolted joint with the approach being robust and scalable. Several transmission scenarios are analyzed and in the worst case scenario the node is estimated to last more than 5 years powered by several LiSOCl
₂
primary batteries. Received data is securely stored in a blockchain and is easily accessible for services targeting integration with a Smart City.