Open source - low cost wireless sensor network for SHM applications

This work presents the design of a complete open source - low cost wireless sensor network (WSN) that is specifically intended for SHM applications where sensing low frequency low amplitude accelerations with high resolution is essential, as well having a flexible system, free of cables that complicate its installation in the case of short-term measurement campaigns. The platform consists of a Low Noise, Low Drift, Low Power 3-Axis Accelerometer used to collect the data from the structure, a mid-range inertial measurement unit (IMU) used to calibrate the sensor, an ultra-low power Microcontroller used for in loco sampling, transmitting and saving raw data into a microSD card, an RF module for wireless connectivity and a GPS for synchronization through different sensors and track the position of each sensor. Further, TDMA (Time Division Multiple Access) method is used to reduce collisions and improve energy efficiency; data compression algorithm to reduce the bandwidth required for transmission and storage and try to reduce as much as possible data switching activity; error detection bits are also inserted to detect and correct any corrupted data. Recover of the corrupted transmission data that are not resolvable by recover bit is possible in 1-view-mode (real time visualization of only one sensor) or in offline-data-collection mode. The implemented system is evaluated through a testbed application. Sensor data are compared to the one collected through a high-speed camera and analyzed by video recognition technique.