An Autonomous Wireless Sensing System for Long-Term Structural Health Monitoring Applications

Structural health monitoring (SHM) of civil infrastructure is among many areas with a need for low-cost autonomous wireless sensors capable of operating without any required maintenance for an extended period of time. This paper describes an autonomous wireless sensing system for long-term SHM applications developed by Green SHM Systems. The wireless sensing system contains a set of sensing modules and at least one base station. Each sensing module incorporates a microcontroller, nonvolatile memory, a transceiver and a set of sensors including digital accelerometer, tilt, temperature and strain sensors. The sensing modules are powered by a combination of batteries and energy harvesting devices. The module operates in two modes - active mode and sleep mode. Low power consumption in sleep mode, along with power management capabilities and the use of energy harvesting allows the sensing module to provide a very long service life. When used as part of a typical SHM application with short active mode sessions, it is estimated that the sensing module can be self-sufficient for at least 25 years without any required maintenance including battery replacement. Each base station incorporates a microcontroller, non-volatile storage, and a transceiver. The base station can be powered from a wired power line and/or a battery. The base station controls sensing modules and collects data from the modules via wireless channels. The base station communicates with a remote data center via a wireless channel or a wired data line. The autonomous wireless sensing module and the base station are designed as a platform for long-term monitoring applications. Different sensors and energy harvesting devices can be integrated both with the sensing module and the base station. Experimental results on the use of wireless sensing systems for vibration monitoring of bridges and tall buildings are provided.