Today, wired sensors are used for monitoring the condition of aircraft engines, airframes, structures, gearboxes, etc. Wireless Sensor Networks (WSNs), i.e., smart sensors with radio interfaces, promise unprecedented operational benefits, such as reduced airplane sensor wiring costs and weight as cabling is limited to specific scenarios and the flexibility to be deployed on-board aircraft without requiring a redesign of the data wiring layout.
To this end, the FLITE-WISE project developed a platform including an autonomous wireless sensor node to which sensors, such as acoustic or pressure, can be connected. This platform was able to operate airborne on rotating blades in the long-term, thanks to the use of an embedded energy harvesting device. The same wireless technology can also be used for connecting rechargeable battery-operated sensors located on the aircraft outer skin.
The technical strategy was to build an integrated autonomous sensor platform from existing, already proofed hardware and software, and to bring innovations on energy harvesting, sensor interfaces, data processing and compression, and high performance communication parts, which are specifically tailored to meet the objectives of the call.
More precisely, the proposed concept was based on the results of the StrainWise project, which was retained for its appropriateness and efficiency in the targeted environment, most prominently by providing a wireless solution for aeronautic applications. The project developed innovative aspects that are essential to the achievement of the listed objectives: tight synchronization, high frequency data sampling, compactness, flexibility to connect several kinds of sensors (such as acoustic, pressure, strain, acceleration or vibration sensors), adaptability to different contexts (rotating blades and outer aircraft skin), robustness to the external RF environment with network self-healing capability, autonomy in energy and interconnection with the aircraft IT environment.
The consortium was made of three highly qualified complementary entities. CSEM brought its expertise in Wireless Sensor Networks and ultra-low power electronics. SERMA, an experienced actor in the aeronautics technology, brought expertise in harsh environment and constraints, as well as industrialisation, production and test facilities. Imperial College London, one of the world leading laboratories, provided the energy harvesting and management expertise. The participants were part of ISO 9001-2000 compliant organisations, which also have ISO14001:2004 certificates. They all have experience in aeronautics system development, including RTCA and/or MIL standards.
The Flite-Wise project consortium was coordinated by CSEM – Centre Suisse d’Électronique et de Microtechnique, a Swiss R&D centre dedicated to the transfer of cutting-edge micro/nano/bio and communications technologies into industrial products. The energy harvesting is developed by Imperial College London, the UK’s premier science and technology university. The system is industrialised by SERMA INGENIERIE, a French aeronautic equipment manufacturer.
The project was under the supervision of its topic manager Airbus Operations GmbH from Germany.
The Flite-Wise project developed an autonomous wireless sensor node platform for continuous acoustic or pressure measurements on aircraft frames. The project addresses two use cases. The first one, aka the “propeller use case”, concerns pressure measurements on rotating frames (propeller blades) using nodes powered by an energy harvester with multiple sensors.
The second use case, aka the “patch use case”, defines acoustic pressure measurements along the aircraft skin using an ultra-thin, battery powered and wirelessly rechargeable sensor node.
The result is an integrated autonomous wireless system from existing, already proofed hardware and software combined with innovative concepts in the domains of robust and high performance networking, energy harvesting, sensor interfaces and data acquisition.
The developed platform advances the state of the art in a number of aspects:
- energy harvesting and electronics capable of withstanding high accelerations and low temperatures;
- resilience to interferences and jamming;
- highly efficient and robust communication with ultra-low energy requirements;
- highly compact and slim design with fully wireless operations including charging;
- accurate synchronisation in WSN for the time-stamping of sensor data.
The evaluation done for both use cases demonstrated the good global performance of both sensor nodes. In particular, the nodes support 50 KHz sensor acquisition rate, logging in high-capacity SD card and deferred transmission at 40 KSamples/s. The power consumption of the devices in inactive state is as low as 27 µA. The total power consumption (active and inactive states) is compatible with the power supply capacity in both use cases. The network synchronisation accuracy is better than 40 µs. The patch use case batteries work at temperatures below -20°C and can be recharged by inductive coupling in about five hours.
Current flight test systems are wired and their installation is costly and cumbersome. The Flite-Wise project delivers a major contribution towards new wireless sensors with energy efficiency which allows them to be powered by batteries and energy harvesters. The wireless recharging feature helps reducing the thickness of the patch sensor by avoiding the need for connectors. Large on-board data storage allows high sensor sampling rates with deferred data transmission. The overall benefits of such sensors are reduced installation and maintenance costs.
From a short-term viewpoint, the Flite-Wise project allowed the consortium members to perform significant progress in their respective areas of expertise: ultra-low power communications and synchronisation (CSEM), energy harvesting and power regulation (Imperial College London) as well as electronics and industrialisation (Serma Ingénierie). The project partners wish to continue their collaboration and will keep in touch to monitor project opportunities.