Aerodynamics and Propulsion of Micro Air Vehicles

The research program on Micro Air Vehicles (MAV, unmanned aerial vehicles under 30 cm in any dimension) started in 2000 with a series of studies of fixed-wing MAVs and, more recently, of rotary-wing MAVs.

The purpose of the present research is to identify, understand and solve the technical bottlenecks related to the development of MAVs for urban reconnaissance missions. From a practical viewpoint, the success of a reconnaissance mission in a confined environment requires two remote constraints: on the one hand, a fast covert forward flight capability to escape enemy attention and fire, on the other hand, a low-speed or hovering capability to allow for adequate image transmission in real time. In view of obtaining a single versatile concept, two different strategies have been identified.

The first strategy consists of designing a fixed-wing MAV with low-speed capability according to the tilt-body concept. The propeller-wing interaction has been exploited to extend the flight envelope of existing fixed-wing MAVs. In particular, a fixed-wing configuration with a coaxial rotor in tractor position has been analyzed (see photograph of the MiniVertiGo) in collaboration with the University of Arizona (Prof. Sergey Shkarayev).

As opposed to the first strategy, the second strategy consists of starting with a ducted coaxial rotor with hovering capability and modifying it to allow for horizontal flight.

Two test benches for short-ducted and long-ducted coaxial birotors have been developed, allowing for local measurements of aerodynamic and propulsion effects induced by the duct and affecting the overall vehicle in forward flight. This research has been focused on the duct shape in order to increase the global efficiency of the propulsion set and to improve the behavior of the vehicle in the presence of lateral wind gusts.

Finally, a series of test benches dedicated to the measurement of outrunner brushless motors and nano- or micro-rotors have been developed. This development has made possible the design of nano air vehicles (maximum dimension under 10 cm) controlled by electro-active materials such as piezo-actuators for instance.