Smart screw connection – Fraunhofer CCIT presents wireless and energy-autonomous monitoring solution
Nuremberg: Loose screws at important connection points constitute a considerable safety risk. The research center IoT-COMMs – part of the Fraunhofer Cluster of Excellence Cognitive Internet Technologies CCIT – has developed an intelligent screw connection which enables wireless, energy-autonomous monitoring. A thin-film sensor thereby measures both the forces acting on the screw connection and changes in the ambient temperature at the installation site. Via the standardized mioty® wireless protocol, the screw regularly transmits load data for control purposes. The aim is the realization of an energy-autonomous monitoring of bridges, scaffolding, wind-power plants and similar structures through permanent long-term surveillance. The solution will be presented for the first time during the Fraunhofer Solution Days from 26th - 29th October 2020.
Despite sufficient pre-tensioning force, screws can nevertheless become loose of their own accord. Safe operation can then no longer be guaranteed for load-bearing elements which are exposed to heavy mechanical or thermal stresses. In the case of, for example, bridges, scaffolding, or fairground rides, this can have fatal consequences. Depending on the application, a drop in the pre-tensioning force of a bolted connection can jeopardize the operational safety of an entire facility or bring a complete production plant to a standstill. With the intelligent screw connection developed at the Research Center IoT-COMMs, this could be detected at an early stage. It permanently monitors even hard-to-reach points and areas.
Sensor reports loose screws
With the thin-film sensor system based on the DiaForce® film from the Fraunhofer Institute for Surface Engineering and Thin Films IST, the tightening force of the screw connection and the temperature at the installation site can be determined. The sensor structures measure pressure effects and temperature changes by altering their electrical resistance. A change in pressure can be used to determine whether the screw has become loose. The temperature measurement is necessary as an excessively high ambient temperature can influence the measurement data.
Wireless, secure data transmission with mioty®
With the aid of the wireless transmission technology mioty®, the sensor system regularly transmits measured values to a cloud-linked control body. By means of the mioty® LPWAN technology, the data can be sent over a range of several kilometers and with high transmission security. In addition, prior to assembly, the screws are configured in the manipulation-proof programming unit “FunkeyBox” from the Fraunhofer Institute for Applied and Integrated Security AISEC and receive their own spanner. As a result, the sensor data is tamper-proof during transmission to the base station or backend.
Special feature: Self-sufficient energy supply through energy harvesting
Due to the Fraunhofer IIS energy harvesting technology, the screw connection does not require an external power supply. The screw connection incorporates a thermogenerator which, when exposed to even the smallest amount of heat, generates electrical energy via the screw thread, thereby enabling the sensor to operate self-sufficiently as regards energy. Alternatively, the sensor and transmitter can be powered by a solar cell or battery.
This solution is being developed within the framework of the Fraunhofer research center IoT-COMMs in collaboration with the Fraunhofer institutes IIS, IST and AISEC. The FIoT-COMMs is part of the Cluster Initiative CCIT (Cluster of Excellence Cognitive Internet Technologies) of the Fraunhofer-Gesellschaft. This solution will be presented at the Fraunhofer Solution Days from the 26th - 29th October 2020.