CGull: A Non-Flapping Bioinspired Composite Morphing Drone

Abstract

Despite the tremendous advances in aircraft design that led to successful powered flights of aircraft as heavy as the Antonov An-225 Mriya, which weighs 640 tons, or as fast as the NASA-X-43A, which reached a record of Mach 9.6, many characteristics of bird flight have yet to be utilized in aircraft designs. These characteristics enable various species of birds to fly efficiently in gusty environments and rapidly change their momentum in flight without having modern thrust vector control (TVC) systems. Vultures and seagulls, as examples of expert gliding birds, can fly for hours, covering more than 100 miles, without a single flap of their wings. Inspired by the Great Black-Backed Gull (GBBG), this paper presents "CGull", a non-flapping unmanned aerial vehicle (UAV) with wing and tail morphing capabilities. A coupled two degree-of-freedom (DOF) morphing mechanism is used in CGull's wings to sweep the middle wing forward and the outer feathered wing backward, replicating the GBBG's wing deformation. A modular two DOF mechanism enables CGull to pitch and tilt its tail. A computational model was first developed in MachUpX to study the effects of wing and tail morphing on the generated forces and moments. Following the biological construction of birds' feathers and bones, CGull's structure is mainly constructed from carbon-fiber composite shells. The successful flight test of the proof-of-concept physical model proved the effectiveness of the proposed morphing mechanisms in controlling the UAV's path.

Keywords: biomimetic designs; composite materials; morphing drones; sweep-morphing.

Figure 1

(a) CGull’s preliminary computational model in MachUpX; (b) airfoil distribution of the preliminary wing model.

Figure 2

Six considered morphing wing and tail configurations.

Figure 3

(a) Lift force, (b) drag force, and (c) L/D vs. AOA for four different configurations.

Figure 4

Effect of tail pitch on (a) lift coefficient and (b) pitching moment coefficient.

Figure 5

Effect of asymmetric wing morphing and tail tilt on roll moment coefficient.

Figure 6

(a) Effect of tail tilt on yaw moment coefficient; (b) effect of combing tail pitch and tilt on yaw moment coefficient.

Figure 7

CGull’s full CAD assembly.

Figure 8

(a) CGull’s wing design; (b) wing in extended and tucked configurations.

Figure 9

(a) CGull’s tail design; (b) tail in pitched up and down configurations.

Figure 10

(a) Fuselage outer composite shell; (b) CGull’s fuselage internal structure.

Figure 11

CGull’s avionics diagram.

Figure 12

CGull’s remote control mapping.

Figure 13

(a) Exploded and assembled views of the fuselage and inner-wing lower mold; (b) mid-wing and outer-wing skin molds.

Figure 14

3D-printed molds used for composite manufacturing.

Figure 15

Composite structures of the fuselage and wings.

Figure 16

Manufacturing of the final composite tail model.

Figure 17

Wing actuation: (a) extended wing, (b) tucked wing (the fuselage and inner-wing lower-skin structure are placed on its mold; the top skin is removed for demonstration; and the outer-wing composite skin is also removed to show the feather folding mechanism).

Figure 18

CGull prototype before the flight test (the top fuselage cover is removed, and the left wing is swept back in the bottom figure).

Figure 19

CGull’s flight test.