Wireless and Autonomous Sensor for Strut Load Monitoring

Abstract : In case of hard landings, engine mounts or landing gears can be damaged and must be inspected as the severity of landing is not well estimated based on aircraft inertial system and models. Such inspections can be time consuming and generate delays, cancellations and inappropriate maintenance actions that could be avoided if a sensor is able to measure the accurate load level sustained by the equipment. The aim of the project is to develop an autonomous wireless sensor with local intelligence and storage capacity that can be downloaded upon request. A micro-mechanic MEMS sensor (chronoMEMS), using cogwheels, has been implemented: when a predefined level of load is reached, the sensor increments a counter. To validate the discrete information given by this sensor, strain gauges have been added. Interrogating the sensor must be easy and fast so that a wireless interrogating system based on RFID has been chosen. An Energy Harvesting system transforming Thermal and Vibration into electric power has been developed to supply the strain gauges and the memory (chronoMEMS does not require power). Lab tests have been done on thermal and vibration energy harvesters. RFID transmission in the engine area is yet under studies and tests. The next step is to develop a prototype of a full sensor integrating all these parts working together in the engine harsh environment. This technology could be used to monitor any kind of load charge for which real time surveillance is not necessary. Snecma (Safran Group) is the leader of this project allied to SilMach and SKF Aerospace. SilMach develops the chronoMEMS load sensor. SKF Aerospace is in charge of strain gauges, energy harvesting, RFID modules and complete system assembly.