UAV anti-icing system based on conductive coating
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Icing on leading edge surfaces such as wings and propeller blades presents a major risk for UAVs operating in a cold and humid environment. Reducing or loss of manoeuvrability, loss of lift, increase in drag, reducing performance through increased weight and in worst case crashing, are phenomena that can occur in case of ice formation on a UAV surface. The use of UAVs has increased significantly the last years through surveillance and reconnaissance operations and they are able to perform operations where danger to people is present. Therefore, an appropriate and efficient method for protecting the UAVs against icing conditions is desirable.The objectives of the project were to use simulations and laboratory experiments to investigate the efficiency and design of such a system where electric heating is supplied to exposed leading edges of a UAV wing surfaces through a conductive coating material. Lightweight, easy-to-apply and robust equipment due to weight restrictions of UAVs and harsh weather conditions respectively should be emphasized during the design phase of the project. In this thesis, an experimental setup of a compact and independent anti-icing system to be installed on a UAV has been wired up and tested in a laboratory and in freezing conditions. The experimental setup consisted of an Arduino microcontroller capable of controlling the power delivered to the conductive coating through feedback from thermocouples and a humidity sensor, sensing the surface temperature of the UAV wing and humidity of the surroundings respectively.It was during the experiments discovered that the PI-controllers implemented for the two heating zones were able to adjust relative to the surroundings, and keep a steady reference surface temperature of the UAV's leading edge surface during icing conditions. However, with the speed of a UAV entering icing conditions in e.g. a cloud in mind, the heating-up period of the entire leading edge surface takes too long with the available battery capacity to prevent supercooled water droplets freezing on impact. Nevertheless, with the results presented, a proof of concept by using conductive coating for anti-icing UAV leading edges has been achieved. Through lab experiment results, with small patches made with Carbo E-Therm electrically conductive coating, the coating shows great potential with rapid temperature increase, uniform heat distribution, and resistance against external influences such as water, ice and rough treatment. Thermal images revealed that this material has the necessary properties needed to prevent ice formation on UAV leading edges. Through simulations in LEWICE and COMSOL, the ice accretion process has been investigated together with how ice accretion on an airfoil's leading edge affects UAVs' manoeuvrability.Continuation of this thesis should involve ice tunnel testing to examine icing effects and how the conductive coating performs with realistic icing conditions. It would be desirable to divide the wing into more and smaller heating zones with separate temperature sensors, resulting in a rapidly surface temperature rise. Finally, the system developed in this thesis should be integrated onto a UAV and evaluated through flight tests.