Design of Better Control Surface for MAVs in Gust

The compact size and challenging turbulence present at low altitudes means that all current stabilization technology is not sufficient to hold steady flight through urban canyons on wind days. The main issue is inadequate actuation rate of conventional fixed wing control surfaces which are located on the trailing edges of wings and tailplanes.

Free body diagram of trailing edge (top) and leading edge (bottom) control surface

We are investigating a potential solution for reducing the response time of the control system and increasing the control authority (control force) by using control surfaces that are hinged on the leading edges of wings (LECS). These provide an unstable hinge moment where the fluid is driving the actuator (forcing a passive moment), rather than resisting against it, contrary to the situation with conventional control surfaces.

Through flow visualization experiments it was found (surprisingly) that high actuation rates on leading edge hinged control surfaces promoted flow attachment on the airfoil, enhancing control forces. Higher actuation rates produced dominant unsteady vertical structures from the leading edge and hence a transient lift enhancement over the airfoil was found. These lift enhancements from increased actuations of LECS could thus be exploited to generate rapid and high control forces, just like small airborne creatures are believed to do when flying in gusts. Current research is focused on understanding the dynamics of LECS and the generation of these transient control forces for MAV flight in gusts.. The potential of this control methodology could serve micro flight applications well and improve handling / flight in gust.

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