Development of a Quad Shrouded Rotor Micro Air Vehicle and Performance Evaluation in Edgewise Flow

This paper describes the design and development of a quad shrouded rotor micro air vehicle (MAV) and experiments to evaluate performance in edgewise flow. The aerodynamic efficiency of a conventional micro quad rotor is improved by incorporating a shroud structure. Proof of concept studies were conducted on 1.3", 1.6" and 2.6" commercial ducted fan systems. Comparison of a 2.6" shrouded rotor with an optimized unshrouded rotor showed a 30% improvement in power loading at a power input of 2 W. The shroud structure consisted of a machined foam diffuser with carbon fiber inlets attached. The total weight of the MAV was 104 grams with the shroud structure weighing 12 grams. The vehicle had maximum dimensions of 6"x6". Successful hover flight testing of the vehicle was achieved using a proportional-derivative onboard feedback controller. Wind tunnel tests were conducted to assess thrust, drag and pitching moment of the vehicle in edgewise flight up to 4 m/s using a 6 component force transducer. For both the shrouded and unshrouded rotors, the thrust increased by 10% at 4 m/s, the drag had a quadratic variation with thrust and a linear variation with speed. The drag and pitching moment for the shrouded quad was up to 2-2.5 times greater than the unshrouded quad rotor. Control moment measurements suggested that the quad shrouded rotor had an edgewise gust tolerance of at least 4 m/s. The drag and thrust measurements were compared with data from another study (9.5" shrouded rotor) revealing that the performance of the shrouded rotor scales satisfactorily with size.