For the IoT Bridge Pilot the Årsta Railway Bridge was instrumented with two wireless nodes. Each of them is equipped with an accelerometer to record vibrations during a train crossing. The nodes measure vertical and horizontal accelerations at 50Hz.
Further a base station is located in the bridge deck which collects the data from the wireless nodes and transmits the data into the Internet. Additionally the base station is equipped with a humidity and temperature sensor.
Image: Photo of the deployed base station.
Since energy resources are limited and data communication is an energy consuming task, the amount of transmitted data has to be optimised to extend the system lifetime. In this case, the acceleration time series is processed on the node and reduced to one min and max value per 1.6s . Only raw measurements which variation exceed a defined threshold are processed and transmitted. Following the Schematic overview of the system deployment.
Image: Schematic of IoT Bridge Pilot setup.
The bridge is meanwhile instruments with cabled and very precise instruments giving the project the opportunity to cross compare the measurements. The recorded data is sent to the project partners server and can be accessed through a web browser and the iPhone WebHybris.
WebHybris for iPhone is an application for monitoring bridges and tunnels in Sweden. The user interface presents a full screen map, which features clickable pins for bridges and tunnels. Once clicked, pictures and information about the selected infrastructure are displayed. The current version supports IoT sensors connected through DecentLabs. These sensors enable to monitor and display vibrations and anomalies through the iPhone app, thereby overseeing the overall health of a bridge in real time.
Currently there are a couple of sensors installed on the new Årsta-bridge (Årsta holmar) and from these sensors it is possible to see vibrations (e.g vertical acceleration) when trains pass as well as environmental conditions (e.g. temperature/humidity). These values can be monitored navigating the map. Infrastructures equipped with sensors are visually differentiated and are easy to spot. Activation of an icon of an infrastructure enables the user to see all collected values.