Autonomous aeroplane sensors undergo first flight test

A project to develop autonomous sensors to monitor aircraft’s structural health has taken off, with EADS and Vienna University of Technology stating the first test flight to be a success.

Several factors cause stress on aircraft structure such as humidity, pressure, temperature, which could create corrosion, cracks and other structural failures.

There are several sensors that monitor the structural problems, but these are wired-based solutions, which though reliable, not only add to the overall weight of the aircraft, but also increase design complexity.

Vienna University of Technology’s Institute of Sensor and Actuator Systems professor Ulrich Schmid noted that conventional batteries are not designed for such large temperature difference an aircraft is continuously exposed to during operation.

"Nobody wants to regularly replace all the sensor batteries in the complete aircraft," Schmid adds.

To address these challenging issues, EADS Innovation Works and the Vienna Institute of Technology have been jointly developing a cost-effective wireless solution that uses thermoelectric Energy Harvesting Modules, which will supply enough energy to power the sensor node and wirelessly transmit data on health status of the aircraft.

The modules use the temperature difference that occur in fuselage, when the aircraft takes off and lands, to generate enough electrical energy required by the sensor.

Each module has a small water reservoir of 10cm³, which freezes during takeoff.

Explaining the procedure, Prof. Schmid’s doctoral student Alexandros Elefsiniotis said: "It cools down at a slower rate than the fuselage, thus a thermoelectric generator located between these components creates electricity from that temperature difference."

During landing of the aircraft, the fuselage temperature is warmer than that of the water tank, so energy is again generated.

A tailored low-power management system ensures that varying energy output is converted into levels appropriate to drive a sensor node efficiently.

Around two years ago, initial climate chamber simulations were conducted, with the first test flight then carried out.

Elefsiniotis added: "We have been able to obtain around 23 joules of energy per flight, which is sufficient to power up a wireless sensor node."

Research is ongoing over the use of alternatives to water that may be more suitable under extreme weather conditions such as for flight routes in cold regions.

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Image: The thermoelectric Energy Harvesting Module with just a few centimetres in outer diameter supplies enough energy to wireless sensor nodes in an aircraft. Photo: courtesy of Vienna University of Technology.