Design of Propeller-Assisted Flapping Wing Air Vehicles for Enhanced Aerodynamic Performance

Abstract

Flapping flight is impressive because aerodynamic performance increases whereas fixed wing aircraft performance declines in low Reynolds regimes. In order to achieve biologically-inspired flapping, motion in multiple degrees of freedom is required and power density requirements must be satisfied. Given the mass of high output actuators, weight is a key limitation as it must be offset for flight. In light of this, only recently, with developments in motor technology, has independent wing control been achieved with consumer available components. Due to power demands, motor bandwidth is used largely to sustain flight, limiting the effect of wing independence. An interesting paradigm is one where the aerodynamic flight advantages of propeller-driven flight are utilized in addition to those of flapping wings to allow hybrid vehicles that can occupy unique operational bandwidth. In this work, a propeller-assisted version of Robo Raven, a miniature independent wing flapping air vehicle developed at the University of Maryland College Park, is presented. Having successfully flown with propeller assistance and having demonstrated improved force generation for aerodynamic performance over flapping alone, this modified Robo Raven will constitute the next major iteration of the vehicle as Robo Raven V.

Characterizing and modeling the enhancement of lift and payload capacity resulting from thrust augmentation in a propeller-assisted flapping wing air vehicle

“…As an alternate means to changing the main servo motors for the flapping wings to augment thrust production in FWAVs, propeller assistance was investigated in Robo Raven V. The addition of propeller-motor assemblies will change the steady-state thrust in equation (4) to the sum of the two modes minus a loss term for anticipated coupling, Ψ (because of preliminary findings 50 ) where the thrust of the propellers can be modeled by the following expression 1,54–57 …”

“…The tail is operated as a rudder inclined such that it provides a static elevator functionality. In the initial presentation of Robo Raven V, 50 the tail also had elevator functionality. While it can be accommodated in the platform payload and used as an altitude control, it was removed for characterization simplicity and to increase payload capacity.…”

“…There have been different versions of Robo Raven for various research pursuits: platform wing sizing and motor performance (II), 4,24 harvesting solar energy (III), [43][44][45] and autonomous flight control (IV). [46][47][48] (an additional version exploring integrated flexible energy storage (VI) is also in development 49 which postdates the introduction of the concept for this work, 50 which is designated Robo Raven (V)). In these versions, continuously flapping, outside of brief periods of time, is required to sustain flight because of platform weight.…”

Design and Verification of a Large-Scaled Flapping-Wing Aircraft Named “Cloud Owl”

“…The Smart-bird [3,4] has a wingspan of 2 m, a weight of 0.48 kg, a flight speed of 5 m/s, and a flapping frequency of 2 Hz; however, even though it has good low-speed flight stability and gliding performance, its load-carrying capacity and endurance are currently unknown. The "Robo raven" [5,6] has a wingspan of 1.168 m, a weight of 290.3 g, a flight speed of about 6.7 m/s, and a flapping frequency of 4 Hz; the falcon [7] has a wingspan of 1.2 m, a total weight of 600 g, a flight speed of 8 m/s, a flapping frequency of 3.5 Hz, and can carry a total weight of 16.7% of the payload for a 20-min flight. The "HIT-Hawk" and the "Hit-phoenix" [8][9][10] had wingspans of 2.0 m and 2.3 m, weights of 792 g and 675 g, respectively, and maximum take-off weights of 1.15 kg and 0.86 kg, respectively, with no-load maximum stable flight endurances of 65 min and 8 min, respectively.…”

A simulation-based approach to modeling component interactions during design of flapping wing aerial vehicles

“…23 As a consequence of these research efforts, we have developed the Robo Raven FWAV, 5 which has since become a testbed for additional research in related fields. [24][25][26][27] Historically, the development of the Robo Raven platform has relied on a significant amount of experimental evaluation to establish feasible conditions for flight. This approach has resulted in a body of data that describes the flight envelope and subsystem parameters that lead to acceptable operation, but is a time-consuming strategy for exploring component interactions due to reliance on a huge number of experimental trials.…”